1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2022 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2022 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2022 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Debuginfod:: Download debugging resources with @code{debuginfod}
188 * Man Pages:: Manual pages
189 * Copying:: GNU General Public License says
190 how you can copy and share GDB
191 * GNU Free Documentation License:: The license for this documentation
192 * Concept Index:: Index of @value{GDBN} concepts
193 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
194 functions, and Python data types
202 @unnumbered Summary of @value{GDBN}
204 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
205 going on ``inside'' another program while it executes---or what another
206 program was doing at the moment it crashed.
208 @value{GDBN} can do four main kinds of things (plus other things in support of
209 these) to help you catch bugs in the act:
213 Start your program, specifying anything that might affect its behavior.
216 Make your program stop on specified conditions.
219 Examine what has happened, when your program has stopped.
222 Change things in your program, so you can experiment with correcting the
223 effects of one bug and go on to learn about another.
226 You can use @value{GDBN} to debug programs written in C and C@t{++}.
227 For more information, see @ref{Supported Languages,,Supported Languages}.
228 For more information, see @ref{C,,C and C++}.
230 Support for D is partial. For information on D, see
234 Support for Modula-2 is partial. For information on Modula-2, see
235 @ref{Modula-2,,Modula-2}.
237 Support for OpenCL C is partial. For information on OpenCL C, see
238 @ref{OpenCL C,,OpenCL C}.
241 Debugging Pascal programs which use sets, subranges, file variables, or
242 nested functions does not currently work. @value{GDBN} does not support
243 entering expressions, printing values, or similar features using Pascal
247 @value{GDBN} can be used to debug programs written in Fortran, although
248 it may be necessary to refer to some variables with a trailing
251 @value{GDBN} can be used to debug programs written in Objective-C,
252 using either the Apple/NeXT or the GNU Objective-C runtime.
255 * Free Software:: Freely redistributable software
256 * Free Documentation:: Free Software Needs Free Documentation
257 * Contributors:: Contributors to GDB
261 @unnumberedsec Free Software
263 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
264 General Public License
265 (GPL). The GPL gives you the freedom to copy or adapt a licensed
266 program---but every person getting a copy also gets with it the
267 freedom to modify that copy (which means that they must get access to
268 the source code), and the freedom to distribute further copies.
269 Typical software companies use copyrights to limit your freedoms; the
270 Free Software Foundation uses the GPL to preserve these freedoms.
272 Fundamentally, the General Public License is a license which says that
273 you have these freedoms and that you cannot take these freedoms away
276 @node Free Documentation
277 @unnumberedsec Free Software Needs Free Documentation
279 The biggest deficiency in the free software community today is not in
280 the software---it is the lack of good free documentation that we can
281 include with the free software. Many of our most important
282 programs do not come with free reference manuals and free introductory
283 texts. Documentation is an essential part of any software package;
284 when an important free software package does not come with a free
285 manual and a free tutorial, that is a major gap. We have many such
288 Consider Perl, for instance. The tutorial manuals that people
289 normally use are non-free. How did this come about? Because the
290 authors of those manuals published them with restrictive terms---no
291 copying, no modification, source files not available---which exclude
292 them from the free software world.
294 That wasn't the first time this sort of thing happened, and it was far
295 from the last. Many times we have heard a GNU user eagerly describe a
296 manual that he is writing, his intended contribution to the community,
297 only to learn that he had ruined everything by signing a publication
298 contract to make it non-free.
300 Free documentation, like free software, is a matter of freedom, not
301 price. The problem with the non-free manual is not that publishers
302 charge a price for printed copies---that in itself is fine. (The Free
303 Software Foundation sells printed copies of manuals, too.) The
304 problem is the restrictions on the use of the manual. Free manuals
305 are available in source code form, and give you permission to copy and
306 modify. Non-free manuals do not allow this.
308 The criteria of freedom for a free manual are roughly the same as for
309 free software. Redistribution (including the normal kinds of
310 commercial redistribution) must be permitted, so that the manual can
311 accompany every copy of the program, both on-line and on paper.
313 Permission for modification of the technical content is crucial too.
314 When people modify the software, adding or changing features, if they
315 are conscientious they will change the manual too---so they can
316 provide accurate and clear documentation for the modified program. A
317 manual that leaves you no choice but to write a new manual to document
318 a changed version of the program is not really available to our
321 Some kinds of limits on the way modification is handled are
322 acceptable. For example, requirements to preserve the original
323 author's copyright notice, the distribution terms, or the list of
324 authors, are ok. It is also no problem to require modified versions
325 to include notice that they were modified. Even entire sections that
326 may not be deleted or changed are acceptable, as long as they deal
327 with nontechnical topics (like this one). These kinds of restrictions
328 are acceptable because they don't obstruct the community's normal use
331 However, it must be possible to modify all the @emph{technical}
332 content of the manual, and then distribute the result in all the usual
333 media, through all the usual channels. Otherwise, the restrictions
334 obstruct the use of the manual, it is not free, and we need another
335 manual to replace it.
337 Please spread the word about this issue. Our community continues to
338 lose manuals to proprietary publishing. If we spread the word that
339 free software needs free reference manuals and free tutorials, perhaps
340 the next person who wants to contribute by writing documentation will
341 realize, before it is too late, that only free manuals contribute to
342 the free software community.
344 If you are writing documentation, please insist on publishing it under
345 the GNU Free Documentation License or another free documentation
346 license. Remember that this decision requires your approval---you
347 don't have to let the publisher decide. Some commercial publishers
348 will use a free license if you insist, but they will not propose the
349 option; it is up to you to raise the issue and say firmly that this is
350 what you want. If the publisher you are dealing with refuses, please
351 try other publishers. If you're not sure whether a proposed license
352 is free, write to @email{licensing@@gnu.org}.
354 You can encourage commercial publishers to sell more free, copylefted
355 manuals and tutorials by buying them, and particularly by buying
356 copies from the publishers that paid for their writing or for major
357 improvements. Meanwhile, try to avoid buying non-free documentation
358 at all. Check the distribution terms of a manual before you buy it,
359 and insist that whoever seeks your business must respect your freedom.
360 Check the history of the book, and try to reward the publishers that
361 have paid or pay the authors to work on it.
363 The Free Software Foundation maintains a list of free documentation
364 published by other publishers, at
365 @url{http://www.fsf.org/doc/other-free-books.html}.
368 @unnumberedsec Contributors to @value{GDBN}
370 Richard Stallman was the original author of @value{GDBN}, and of many
371 other @sc{gnu} programs. Many others have contributed to its
372 development. This section attempts to credit major contributors. One
373 of the virtues of free software is that everyone is free to contribute
374 to it; with regret, we cannot actually acknowledge everyone here. The
375 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
376 blow-by-blow account.
378 Changes much prior to version 2.0 are lost in the mists of time.
381 @emph{Plea:} Additions to this section are particularly welcome. If you
382 or your friends (or enemies, to be evenhanded) have been unfairly
383 omitted from this list, we would like to add your names!
386 So that they may not regard their many labors as thankless, we
387 particularly thank those who shepherded @value{GDBN} through major
389 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
390 Jim Blandy (release 4.18);
391 Jason Molenda (release 4.17);
392 Stan Shebs (release 4.14);
393 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
394 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
395 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
396 Jim Kingdon (releases 3.5, 3.4, and 3.3);
397 and Randy Smith (releases 3.2, 3.1, and 3.0).
399 Richard Stallman, assisted at various times by Peter TerMaat, Chris
400 Hanson, and Richard Mlynarik, handled releases through 2.8.
402 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
403 in @value{GDBN}, with significant additional contributions from Per
404 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
405 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
406 much general update work leading to release 3.0).
408 @value{GDBN} uses the BFD subroutine library to examine multiple
409 object-file formats; BFD was a joint project of David V.
410 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
412 David Johnson wrote the original COFF support; Pace Willison did
413 the original support for encapsulated COFF.
415 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
417 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
418 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
420 Jean-Daniel Fekete contributed Sun 386i support.
421 Chris Hanson improved the HP9000 support.
422 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
423 David Johnson contributed Encore Umax support.
424 Jyrki Kuoppala contributed Altos 3068 support.
425 Jeff Law contributed HP PA and SOM support.
426 Keith Packard contributed NS32K support.
427 Doug Rabson contributed Acorn Risc Machine support.
428 Bob Rusk contributed Harris Nighthawk CX-UX support.
429 Chris Smith contributed Convex support (and Fortran debugging).
430 Jonathan Stone contributed Pyramid support.
431 Michael Tiemann contributed SPARC support.
432 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
433 Pace Willison contributed Intel 386 support.
434 Jay Vosburgh contributed Symmetry support.
435 Marko Mlinar contributed OpenRISC 1000 support.
437 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
439 Rich Schaefer and Peter Schauer helped with support of SunOS shared
442 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
443 about several machine instruction sets.
445 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
446 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
447 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
448 and RDI targets, respectively.
450 Brian Fox is the author of the readline libraries providing
451 command-line editing and command history.
453 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
454 Modula-2 support, and contributed the Languages chapter of this manual.
456 Fred Fish wrote most of the support for Unix System Vr4.
457 He also enhanced the command-completion support to cover C@t{++} overloaded
460 Hitachi America (now Renesas America), Ltd. sponsored the support for
461 H8/300, H8/500, and Super-H processors.
463 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
465 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
468 Toshiba sponsored the support for the TX39 Mips processor.
470 Matsushita sponsored the support for the MN10200 and MN10300 processors.
472 Fujitsu sponsored the support for SPARClite and FR30 processors.
474 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
477 Michael Snyder added support for tracepoints.
479 Stu Grossman wrote gdbserver.
481 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
482 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
484 The following people at the Hewlett-Packard Company contributed
485 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
486 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
487 compiler, and the Text User Interface (nee Terminal User Interface):
488 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
489 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
490 provided HP-specific information in this manual.
492 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
493 Robert Hoehne made significant contributions to the DJGPP port.
495 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
496 development since 1991. Cygnus engineers who have worked on @value{GDBN}
497 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
498 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
499 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
500 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
501 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
502 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
503 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
504 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
505 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
506 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
507 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
508 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
509 Zuhn have made contributions both large and small.
511 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
512 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
514 Jim Blandy added support for preprocessor macros, while working for Red
517 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
518 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
519 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
520 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
521 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
522 with the migration of old architectures to this new framework.
524 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
525 unwinder framework, this consisting of a fresh new design featuring
526 frame IDs, independent frame sniffers, and the sentinel frame. Mark
527 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
528 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
529 trad unwinders. The architecture-specific changes, each involving a
530 complete rewrite of the architecture's frame code, were carried out by
531 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
532 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
533 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
534 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
537 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
538 Tensilica, Inc.@: contributed support for Xtensa processors. Others
539 who have worked on the Xtensa port of @value{GDBN} in the past include
540 Steve Tjiang, John Newlin, and Scott Foehner.
542 Michael Eager and staff of Xilinx, Inc., contributed support for the
543 Xilinx MicroBlaze architecture.
545 Initial support for the FreeBSD/mips target and native configuration
546 was developed by SRI International and the University of Cambridge
547 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
548 ("CTSRD"), as part of the DARPA CRASH research programme.
550 Initial support for the FreeBSD/riscv target and native configuration
551 was developed by SRI International and the University of Cambridge
552 Computer Laboratory (Department of Computer Science and Technology)
553 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
554 SSITH research programme.
556 The original port to the OpenRISC 1000 is believed to be due to
557 Alessandro Forin and Per Bothner. More recent ports have been the work
558 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 Weimin Pan, David Faust and Jose E. Marchesi contributed support for
562 the Linux kernel BPF virtual architecture. This work was sponsored by
566 @chapter A Sample @value{GDBN} Session
568 You can use this manual at your leisure to read all about @value{GDBN}.
569 However, a handful of commands are enough to get started using the
570 debugger. This chapter illustrates those commands.
573 In this sample session, we emphasize user input like this: @b{input},
574 to make it easier to pick out from the surrounding output.
577 @c FIXME: this example may not be appropriate for some configs, where
578 @c FIXME...primary interest is in remote use.
580 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
581 processor) exhibits the following bug: sometimes, when we change its
582 quote strings from the default, the commands used to capture one macro
583 definition within another stop working. In the following short @code{m4}
584 session, we define a macro @code{foo} which expands to @code{0000}; we
585 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
586 same thing. However, when we change the open quote string to
587 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
588 procedure fails to define a new synonym @code{baz}:
597 @b{define(bar,defn(`foo'))}
601 @b{changequote(<QUOTE>,<UNQUOTE>)}
603 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
606 m4: End of input: 0: fatal error: EOF in string
610 Let us use @value{GDBN} to try to see what is going on.
613 $ @b{@value{GDBP} m4}
614 @c FIXME: this falsifies the exact text played out, to permit smallbook
615 @c FIXME... format to come out better.
616 @value{GDBN} is free software and you are welcome to distribute copies
617 of it under certain conditions; type "show copying" to see
619 There is absolutely no warranty for @value{GDBN}; type "show warranty"
622 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
627 @value{GDBN} reads only enough symbol data to know where to find the
628 rest when needed; as a result, the first prompt comes up very quickly.
629 We now tell @value{GDBN} to use a narrower display width than usual, so
630 that examples fit in this manual.
633 (@value{GDBP}) @b{set width 70}
637 We need to see how the @code{m4} built-in @code{changequote} works.
638 Having looked at the source, we know the relevant subroutine is
639 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
640 @code{break} command.
643 (@value{GDBP}) @b{break m4_changequote}
644 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
648 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
649 control; as long as control does not reach the @code{m4_changequote}
650 subroutine, the program runs as usual:
653 (@value{GDBP}) @b{run}
654 Starting program: /work/Editorial/gdb/gnu/m4/m4
662 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
663 suspends execution of @code{m4}, displaying information about the
664 context where it stops.
667 @b{changequote(<QUOTE>,<UNQUOTE>)}
669 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
671 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
675 Now we use the command @code{n} (@code{next}) to advance execution to
676 the next line of the current function.
680 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
685 @code{set_quotes} looks like a promising subroutine. We can go into it
686 by using the command @code{s} (@code{step}) instead of @code{next}.
687 @code{step} goes to the next line to be executed in @emph{any}
688 subroutine, so it steps into @code{set_quotes}.
692 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
694 530 if (lquote != def_lquote)
698 The display that shows the subroutine where @code{m4} is now
699 suspended (and its arguments) is called a stack frame display. It
700 shows a summary of the stack. We can use the @code{backtrace}
701 command (which can also be spelled @code{bt}), to see where we are
702 in the stack as a whole: the @code{backtrace} command displays a
703 stack frame for each active subroutine.
706 (@value{GDBP}) @b{bt}
707 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
709 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
711 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
712 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
714 #4 0x79dc in expand_input () at macro.c:40
715 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
719 We step through a few more lines to see what happens. The first two
720 times, we can use @samp{s}; the next two times we use @code{n} to avoid
721 falling into the @code{xstrdup} subroutine.
725 0x3b5c 532 if (rquote != def_rquote)
727 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
728 def_lquote : xstrdup(lq);
730 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
733 538 len_lquote = strlen(rquote);
737 The last line displayed looks a little odd; we can examine the variables
738 @code{lquote} and @code{rquote} to see if they are in fact the new left
739 and right quotes we specified. We use the command @code{p}
740 (@code{print}) to see their values.
743 (@value{GDBP}) @b{p lquote}
744 $1 = 0x35d40 "<QUOTE>"
745 (@value{GDBP}) @b{p rquote}
746 $2 = 0x35d50 "<UNQUOTE>"
750 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
751 To look at some context, we can display ten lines of source
752 surrounding the current line with the @code{l} (@code{list}) command.
758 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
760 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
763 538 len_lquote = strlen(rquote);
764 539 len_rquote = strlen(lquote);
771 Let us step past the two lines that set @code{len_lquote} and
772 @code{len_rquote}, and then examine the values of those variables.
776 539 len_rquote = strlen(lquote);
779 (@value{GDBP}) @b{p len_lquote}
781 (@value{GDBP}) @b{p len_rquote}
786 That certainly looks wrong, assuming @code{len_lquote} and
787 @code{len_rquote} are meant to be the lengths of @code{lquote} and
788 @code{rquote} respectively. We can set them to better values using
789 the @code{p} command, since it can print the value of
790 any expression---and that expression can include subroutine calls and
794 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
796 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
801 Is that enough to fix the problem of using the new quotes with the
802 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
803 executing with the @code{c} (@code{continue}) command, and then try the
804 example that caused trouble initially:
810 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
817 Success! The new quotes now work just as well as the default ones. The
818 problem seems to have been just the two typos defining the wrong
819 lengths. We allow @code{m4} exit by giving it an EOF as input:
823 Program exited normally.
827 The message @samp{Program exited normally.} is from @value{GDBN}; it
828 indicates @code{m4} has finished executing. We can end our @value{GDBN}
829 session with the @value{GDBN} @code{quit} command.
832 (@value{GDBP}) @b{quit}
836 @chapter Getting In and Out of @value{GDBN}
838 This chapter discusses how to start @value{GDBN}, and how to get out of it.
842 type @samp{@value{GDBP}} to start @value{GDBN}.
844 type @kbd{quit}, @kbd{exit} or @kbd{Ctrl-d} to exit.
848 * Invoking GDB:: How to start @value{GDBN}
849 * Quitting GDB:: How to quit @value{GDBN}
850 * Shell Commands:: How to use shell commands inside @value{GDBN}
851 * Logging Output:: How to log @value{GDBN}'s output to a file
855 @section Invoking @value{GDBN}
857 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
858 @value{GDBN} reads commands from the terminal until you tell it to exit.
860 You can also run @code{@value{GDBP}} with a variety of arguments and options,
861 to specify more of your debugging environment at the outset.
863 The command-line options described here are designed
864 to cover a variety of situations; in some environments, some of these
865 options may effectively be unavailable.
867 The most usual way to start @value{GDBN} is with one argument,
868 specifying an executable program:
871 @value{GDBP} @var{program}
875 You can also start with both an executable program and a core file
879 @value{GDBP} @var{program} @var{core}
882 You can, instead, specify a process ID as a second argument or use option
883 @code{-p}, if you want to debug a running process:
886 @value{GDBP} @var{program} 1234
891 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
892 can omit the @var{program} filename.
894 Taking advantage of the second command-line argument requires a fairly
895 complete operating system; when you use @value{GDBN} as a remote
896 debugger attached to a bare board, there may not be any notion of
897 ``process'', and there is often no way to get a core dump. @value{GDBN}
898 will warn you if it is unable to attach or to read core dumps.
900 You can optionally have @code{@value{GDBP}} pass any arguments after the
901 executable file to the inferior using @code{--args}. This option stops
904 @value{GDBP} --args gcc -O2 -c foo.c
906 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
907 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
909 You can run @code{@value{GDBP}} without printing the front material, which describes
910 @value{GDBN}'s non-warranty, by specifying @code{--silent}
911 (or @code{-q}/@code{--quiet}):
914 @value{GDBP} --silent
918 You can further control how @value{GDBN} starts up by using command-line
919 options. @value{GDBN} itself can remind you of the options available.
929 to display all available options and briefly describe their use
930 (@samp{@value{GDBP} -h} is a shorter equivalent).
932 All options and command line arguments you give are processed
933 in sequential order. The order makes a difference when the
934 @samp{-x} option is used.
938 * File Options:: Choosing files
939 * Mode Options:: Choosing modes
940 * Startup:: What @value{GDBN} does during startup
941 * Initialization Files:: Initialization Files
945 @subsection Choosing Files
947 When @value{GDBN} starts, it reads any arguments other than options as
948 specifying an executable file and core file (or process ID). This is
949 the same as if the arguments were specified by the @samp{-se} and
950 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
951 first argument that does not have an associated option flag as
952 equivalent to the @samp{-se} option followed by that argument; and the
953 second argument that does not have an associated option flag, if any, as
954 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
955 If the second argument begins with a decimal digit, @value{GDBN} will
956 first attempt to attach to it as a process, and if that fails, attempt
957 to open it as a corefile. If you have a corefile whose name begins with
958 a digit, you can prevent @value{GDBN} from treating it as a pid by
959 prefixing it with @file{./}, e.g.@: @file{./12345}.
961 If @value{GDBN} has not been configured to included core file support,
962 such as for most embedded targets, then it will complain about a second
963 argument and ignore it.
965 For the @samp{-s}, @samp{-e}, and @samp{-se} options, and their long
966 form equivalents, the method used to search the file system for the
967 symbol and/or executable file is the same as that used by the
968 @code{file} command. @xref{Files, ,file}.
970 Many options have both long and short forms; both are shown in the
971 following list. @value{GDBN} also recognizes the long forms if you truncate
972 them, so long as enough of the option is present to be unambiguous.
973 (If you prefer, you can flag option arguments with @samp{--} rather
974 than @samp{-}, though we illustrate the more usual convention.)
976 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
977 @c way, both those who look for -foo and --foo in the index, will find
981 @item -symbols @var{file}
983 @cindex @code{--symbols}
985 Read symbol table from file @var{file}.
987 @item -exec @var{file}
989 @cindex @code{--exec}
991 Use file @var{file} as the executable file to execute when appropriate,
992 and for examining pure data in conjunction with a core dump.
996 Read symbol table from file @var{file} and use it as the executable
999 @item -core @var{file}
1000 @itemx -c @var{file}
1001 @cindex @code{--core}
1003 Use file @var{file} as a core dump to examine.
1005 @item -pid @var{number}
1006 @itemx -p @var{number}
1007 @cindex @code{--pid}
1009 Connect to process ID @var{number}, as with the @code{attach} command.
1011 @item -command @var{file}
1012 @itemx -x @var{file}
1013 @cindex @code{--command}
1015 Execute commands from file @var{file}. The contents of this file is
1016 evaluated exactly as the @code{source} command would.
1017 @xref{Command Files,, Command files}.
1019 @item -eval-command @var{command}
1020 @itemx -ex @var{command}
1021 @cindex @code{--eval-command}
1023 Execute a single @value{GDBN} command.
1025 This option may be used multiple times to call multiple commands. It may
1026 also be interleaved with @samp{-command} as required.
1029 @value{GDBP} -ex 'target sim' -ex 'load' \
1030 -x setbreakpoints -ex 'run' a.out
1033 @item -init-command @var{file}
1034 @itemx -ix @var{file}
1035 @cindex @code{--init-command}
1037 Execute commands from file @var{file} before loading the inferior (but
1038 after loading gdbinit files).
1041 @item -init-eval-command @var{command}
1042 @itemx -iex @var{command}
1043 @cindex @code{--init-eval-command}
1045 Execute a single @value{GDBN} command before loading the inferior (but
1046 after loading gdbinit files).
1049 @item -early-init-command @var{file}
1050 @itemx -eix @var{file}
1051 @cindex @code{--early-init-command}
1053 Execute commands from @var{file} very early in the initialization
1054 process, before any output is produced. @xref{Startup}.
1056 @item -early-init-eval-command @var{command}
1057 @itemx -eiex @var{command}
1058 @cindex @code{--early-init-eval-command}
1059 @cindex @code{-eiex}
1060 Execute a single @value{GDBN} command very early in the initialization
1061 process, before any output is produced.
1063 @item -directory @var{directory}
1064 @itemx -d @var{directory}
1065 @cindex @code{--directory}
1067 Add @var{directory} to the path to search for source and script files.
1071 @cindex @code{--readnow}
1073 Read each symbol file's entire symbol table immediately, rather than
1074 the default, which is to read it incrementally as it is needed.
1075 This makes startup slower, but makes future operations faster.
1078 @anchor{--readnever}
1079 @cindex @code{--readnever}, command-line option
1080 Do not read each symbol file's symbolic debug information. This makes
1081 startup faster but at the expense of not being able to perform
1082 symbolic debugging. DWARF unwind information is also not read,
1083 meaning backtraces may become incomplete or inaccurate. One use of
1084 this is when a user simply wants to do the following sequence: attach,
1085 dump core, detach. Loading the debugging information in this case is
1086 an unnecessary cause of delay.
1090 @subsection Choosing Modes
1092 You can run @value{GDBN} in various alternative modes---for example, in
1093 batch mode or quiet mode.
1101 Do not execute commands found in any initialization files
1102 (@pxref{Initialization Files}).
1107 Do not execute commands found in any home directory initialization
1108 file (@pxref{Initialization Files,,Home directory initialization
1109 file}). The system wide and current directory initialization files
1115 @cindex @code{--quiet}
1116 @cindex @code{--silent}
1118 ``Quiet''. Do not print the introductory and copyright messages. These
1119 messages are also suppressed in batch mode.
1121 @kindex set startup-quietly
1122 @kindex show startup-quietly
1123 This can also be enabled using @code{set startup-quietly on}. The
1124 default is @code{off}. Use @code{show startup-quietly} to see the
1125 current setting. Place @code{set startup-quietly on} into your early
1126 initialization file (@pxref{Initialization Files,,Initialization
1127 Files}) to have future @value{GDBN} sessions startup quietly.
1130 @cindex @code{--batch}
1131 Run in batch mode. Exit with status @code{0} after processing all the
1132 command files specified with @samp{-x} (and all commands from
1133 initialization files, if not inhibited with @samp{-n}). Exit with
1134 nonzero status if an error occurs in executing the @value{GDBN} commands
1135 in the command files. Batch mode also disables pagination, sets unlimited
1136 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1137 off} were in effect (@pxref{Messages/Warnings}).
1139 Batch mode may be useful for running @value{GDBN} as a filter, for
1140 example to download and run a program on another computer; in order to
1141 make this more useful, the message
1144 Program exited normally.
1148 (which is ordinarily issued whenever a program running under
1149 @value{GDBN} control terminates) is not issued when running in batch
1153 @cindex @code{--batch-silent}
1154 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1155 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1156 unaffected). This is much quieter than @samp{-silent} and would be useless
1157 for an interactive session.
1159 This is particularly useful when using targets that give @samp{Loading section}
1160 messages, for example.
1162 Note that targets that give their output via @value{GDBN}, as opposed to
1163 writing directly to @code{stdout}, will also be made silent.
1165 @item -return-child-result
1166 @cindex @code{--return-child-result}
1167 The return code from @value{GDBN} will be the return code from the child
1168 process (the process being debugged), with the following exceptions:
1172 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1173 internal error. In this case the exit code is the same as it would have been
1174 without @samp{-return-child-result}.
1176 The user quits with an explicit value. E.g., @samp{quit 1}.
1178 The child process never runs, or is not allowed to terminate, in which case
1179 the exit code will be -1.
1182 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1183 when @value{GDBN} is being used as a remote program loader or simulator
1188 @cindex @code{--nowindows}
1190 ``No windows''. If @value{GDBN} comes with a graphical user interface
1191 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1192 interface. If no GUI is available, this option has no effect.
1196 @cindex @code{--windows}
1198 If @value{GDBN} includes a GUI, then this option requires it to be
1201 @item -cd @var{directory}
1203 Run @value{GDBN} using @var{directory} as its working directory,
1204 instead of the current directory.
1206 @item -data-directory @var{directory}
1207 @itemx -D @var{directory}
1208 @cindex @code{--data-directory}
1210 Run @value{GDBN} using @var{directory} as its data directory.
1211 The data directory is where @value{GDBN} searches for its
1212 auxiliary files. @xref{Data Files}.
1216 @cindex @code{--fullname}
1218 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1219 subprocess. It tells @value{GDBN} to output the full file name and line
1220 number in a standard, recognizable fashion each time a stack frame is
1221 displayed (which includes each time your program stops). This
1222 recognizable format looks like two @samp{\032} characters, followed by
1223 the file name, line number and character position separated by colons,
1224 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1225 @samp{\032} characters as a signal to display the source code for the
1228 @item -annotate @var{level}
1229 @cindex @code{--annotate}
1230 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1231 effect is identical to using @samp{set annotate @var{level}}
1232 (@pxref{Annotations}). The annotation @var{level} controls how much
1233 information @value{GDBN} prints together with its prompt, values of
1234 expressions, source lines, and other types of output. Level 0 is the
1235 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1236 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1237 that control @value{GDBN}, and level 2 has been deprecated.
1239 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1243 @cindex @code{--args}
1244 Change interpretation of command line so that arguments following the
1245 executable file are passed as command line arguments to the inferior.
1246 This option stops option processing.
1248 @item -baud @var{bps}
1250 @cindex @code{--baud}
1252 Set the line speed (baud rate or bits per second) of any serial
1253 interface used by @value{GDBN} for remote debugging.
1255 @item -l @var{timeout}
1257 Set the timeout (in seconds) of any communication used by @value{GDBN}
1258 for remote debugging.
1260 @item -tty @var{device}
1261 @itemx -t @var{device}
1262 @cindex @code{--tty}
1264 Run using @var{device} for your program's standard input and output.
1265 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1267 @c resolve the situation of these eventually
1269 @cindex @code{--tui}
1270 Activate the @dfn{Text User Interface} when starting. The Text User
1271 Interface manages several text windows on the terminal, showing
1272 source, assembly, registers and @value{GDBN} command outputs
1273 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1274 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1275 Using @value{GDBN} under @sc{gnu} Emacs}).
1277 @item -interpreter @var{interp}
1278 @cindex @code{--interpreter}
1279 Use the interpreter @var{interp} for interface with the controlling
1280 program or device. This option is meant to be set by programs which
1281 communicate with @value{GDBN} using it as a back end.
1282 @xref{Interpreters, , Command Interpreters}.
1284 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1285 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1286 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1287 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1288 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1289 interfaces are no longer supported.
1292 @cindex @code{--write}
1293 Open the executable and core files for both reading and writing. This
1294 is equivalent to the @samp{set write on} command inside @value{GDBN}
1298 @cindex @code{--statistics}
1299 This option causes @value{GDBN} to print statistics about time and
1300 memory usage after it completes each command and returns to the prompt.
1303 @cindex @code{--version}
1304 This option causes @value{GDBN} to print its version number and
1305 no-warranty blurb, and exit.
1307 @item -configuration
1308 @cindex @code{--configuration}
1309 This option causes @value{GDBN} to print details about its build-time
1310 configuration parameters, and then exit. These details can be
1311 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1316 @subsection What @value{GDBN} Does During Startup
1317 @cindex @value{GDBN} startup
1319 Here's the description of what @value{GDBN} does during session startup:
1324 Performs minimal setup required to initialize basic internal state.
1327 @cindex early initialization file
1328 Reads commands from the early initialization file (if any) in your
1329 home directory. Only a restricted set of commands can be placed into
1330 an early initialization file, see @ref{Initialization Files}, for
1334 Executes commands and command files specified by the @samp{-eiex} and
1335 @samp{-eix} command line options in their specified order. Only a
1336 restricted set of commands can be used with @samp{-eiex} and
1337 @samp{eix}, see @ref{Initialization Files}, for details.
1340 Sets up the command interpreter as specified by the command line
1341 (@pxref{Mode Options, interpreter}).
1345 Reads the system wide initialization file and the files from the
1346 system wide initialization directory, @pxref{System Wide Init Files}.
1349 Reads the initialization file (if any) in your home directory and
1350 executes all the commands in that file, @pxref{Home Directory Init
1353 @anchor{Option -init-eval-command}
1355 Executes commands and command files specified by the @samp{-iex} and
1356 @samp{-ix} options in their specified order. Usually you should use the
1357 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1358 settings before @value{GDBN} init files get executed and before inferior
1362 Processes command line options and operands.
1365 Reads and executes the commands from the initialization file (if any)
1366 in the current working directory as long as @samp{set auto-load
1367 local-gdbinit} is set to @samp{on} (@pxref{Init File in the Current
1368 Directory}). This is only done if the current directory is different
1369 from your home directory. Thus, you can have more than one init file,
1370 one generic in your home directory, and another, specific to the
1371 program you are debugging, in the directory where you invoke
1372 @value{GDBN}. @xref{Init File in the Current Directory during
1376 If the command line specified a program to debug, or a process to
1377 attach to, or a core file, @value{GDBN} loads any auto-loaded
1378 scripts provided for the program or for its loaded shared libraries.
1379 @xref{Auto-loading}.
1381 If you wish to disable the auto-loading during startup,
1382 you must do something like the following:
1385 $ gdb -iex "set auto-load python-scripts off" myprogram
1388 Option @samp{-ex} does not work because the auto-loading is then turned
1392 Executes commands and command files specified by the @samp{-ex} and
1393 @samp{-x} options in their specified order. @xref{Command Files}, for
1394 more details about @value{GDBN} command files.
1397 Reads the command history recorded in the @dfn{history file}.
1398 @xref{Command History}, for more details about the command history and the
1399 files where @value{GDBN} records it.
1402 @node Initialization Files
1403 @subsection Initialization Files
1404 @cindex init file name
1406 During startup (@pxref{Startup}) @value{GDBN} will execute commands
1407 from several initialization files. These initialization files use the
1408 same syntax as @dfn{command files} (@pxref{Command Files}) and are
1409 processed by @value{GDBN} in the same way.
1411 To display the list of initialization files loaded by @value{GDBN} at
1412 startup, in the order they will be loaded, you can use @kbd{gdb
1415 @cindex early initialization
1416 The @dfn{early initialization} file is loaded very early in
1417 @value{GDBN}'s initialization process, before the interpreter
1418 (@pxref{Interpreters}) has been initialized, and before the default
1419 target (@pxref{Targets}) is initialized. Only @code{set} or
1420 @code{source} commands should be placed into an early initialization
1421 file, and the only @code{set} commands that can be used are those that
1422 control how @value{GDBN} starts up.
1424 Commands that can be placed into an early initialization file will be
1425 documented as such throughout this manual. Any command that is not
1426 documented as being suitable for an early initialization file should
1427 instead be placed into a general initialization file. Command files
1428 passed to @code{--early-init-command} or @code{-eix} are also early
1429 initialization files, with the same command restrictions. Only
1430 commands that can appear in an early initialization file should be
1431 passed to @code{--early-init-eval-command} or @code{-eiex}.
1433 @cindex general initialization
1434 In contrast, the @dfn{general initialization} files are processed
1435 later, after @value{GDBN} has finished its own internal initialization
1436 process, any valid command can be used in these files.
1438 @cindex initialization file
1439 Throughout the rest of this document the term @dfn{initialization
1440 file} refers to one of the general initialization files, not the early
1441 initialization file. Any discussion of the early initialization file
1442 will specifically mention that it is the early initialization file
1445 As the system wide and home directory initialization files are
1446 processed before most command line options, changes to settings
1447 (e.g.@: @samp{set complaints}) can affect subsequent processing of
1448 command line options and operands.
1450 The following sections describe where @value{GDBN} looks for the early
1451 initialization and initialization files, and the order that the files
1454 @subsubsection Home directory early initialization files
1456 @value{GDBN} initially looks for an early initialization file in the
1457 users home directory@footnote{On DOS/Windows systems, the home
1458 directory is the one pointed to by the @env{HOME} environment
1459 variable.}. There are a number of locations that @value{GDBN} will
1460 search in the home directory, these locations are searched in order
1461 and @value{GDBN} will load the first file that it finds, and
1462 subsequent locations will not be checked.
1464 On non-macOS hosts the locations searched are:
1467 The file @file{gdb/gdbearlyinit} within the directory pointed to by the
1468 environment variable @env{XDG_CONFIG_HOME}, if it is defined.
1470 The file @file{.config/gdb/gdbearlyinit} within the directory pointed to
1471 by the environment variable @env{HOME}, if it is defined.
1473 The file @file{.gdbearlyinit} within the directory pointed to by the
1474 environment variable @env{HOME}, if it is defined.
1477 By contrast, on macOS hosts the locations searched are:
1480 The file @file{Library/Preferences/gdb/gdbearlyinit} within the
1481 directory pointed to by the environment variable @env{HOME}, if it is
1484 The file @file{.gdbearlyinit} within the directory pointed to by the
1485 environment variable @env{HOME}, if it is defined.
1488 It is possible to prevent the home directory early initialization file
1489 from being loaded using the @samp{-nx} or @samp{-nh} command line
1490 options, @pxref{Mode Options,,Choosing Modes}.
1492 @anchor{System Wide Init Files}
1493 @subsubsection System wide initialization files
1495 There are two locations that are searched for system wide
1496 initialization files. Both of these locations are always checked:
1500 @item @file{system.gdbinit}
1501 This is a single system-wide initialization file. Its location is
1502 specified with the @code{--with-system-gdbinit} configure option
1503 (@pxref{System-wide configuration}). It is loaded first when
1504 @value{GDBN} starts, before command line options have been processed.
1506 @item @file{system.gdbinit.d}
1507 This is the system-wide initialization directory. Its location is
1508 specified with the @code{--with-system-gdbinit-dir} configure option
1509 (@pxref{System-wide configuration}). Files in this directory are
1510 loaded in alphabetical order immediately after @file{system.gdbinit}
1511 (if enabled) when @value{GDBN} starts, before command line options
1512 have been processed. Files need to have a recognized scripting
1513 language extension (@file{.py}/@file{.scm}) or be named with a
1514 @file{.gdb} extension to be interpreted as regular @value{GDBN}
1515 commands. @value{GDBN} will not recurse into any subdirectories of
1520 It is possible to prevent the system wide initialization files from
1521 being loaded using the @samp{-nx} command line option, @pxref{Mode
1522 Options,,Choosing Modes}.
1524 @anchor{Home Directory Init File}
1525 @subsubsection Home directory initialization file
1526 @cindex @file{gdbinit}
1527 @cindex @file{.gdbinit}
1528 @cindex @file{gdb.ini}
1530 After loading the system wide initialization files @value{GDBN} will
1531 look for an initialization file in the users home
1532 directory@footnote{On DOS/Windows systems, the home directory is the
1533 one pointed to by the @env{HOME} environment variable.}. There are a
1534 number of locations that @value{GDBN} will search in the home
1535 directory, these locations are searched in order and @value{GDBN} will
1536 load the first file that it finds, and subsequent locations will not
1539 On non-Apple hosts the locations searched are:
1541 @item $XDG_CONFIG_HOME/gdb/gdbinit
1542 @item $HOME/.config/gdb/gdbinit
1543 @item $HOME/.gdbinit
1546 While on Apple hosts the locations searched are:
1548 @item $HOME/Library/Preferences/gdb/gdbinit
1549 @item $HOME/.gdbinit
1552 It is possible to prevent the home directory initialization file from
1553 being loaded using the @samp{-nx} or @samp{-nh} command line options,
1554 @pxref{Mode Options,,Choosing Modes}.
1556 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini} instead of
1557 @file{.gdbinit} or @file{gdbinit}, due to the limitations of file
1558 names imposed by DOS filesystems. The Windows port of @value{GDBN}
1559 uses the standard name, but if it finds a @file{gdb.ini} file in your
1560 home directory, it warns you about that and suggests to rename the
1561 file to the standard name.
1563 @anchor{Init File in the Current Directory during Startup}
1564 @subsubsection Local directory initialization file
1566 @value{GDBN} will check the current directory for a file called
1567 @file{.gdbinit}. It is loaded last, after command line options
1568 other than @samp{-x} and @samp{-ex} have been processed. The command
1569 line options @samp{-x} and @samp{-ex} are processed last, after
1570 @file{.gdbinit} has been loaded, @pxref{File Options,,Choosing
1573 If the file in the current directory was already loaded as the home
1574 directory initialization file then it will not be loaded a second
1577 It is possible to prevent the local directory initialization file from
1578 being loaded using the @samp{-nx} command line option, @pxref{Mode
1579 Options,,Choosing Modes}.
1582 @section Quitting @value{GDBN}
1583 @cindex exiting @value{GDBN}
1584 @cindex leaving @value{GDBN}
1587 @kindex quit @r{[}@var{expression}@r{]}
1588 @kindex exit @r{[}@var{expression}@r{]}
1589 @kindex q @r{(@code{quit})}
1590 @item quit @r{[}@var{expression}@r{]}
1591 @itemx exit @r{[}@var{expression}@r{]}
1593 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1594 @code{q}), the @code{exit} command, or type an end-of-file
1595 character (usually @kbd{Ctrl-d}). If you do not supply @var{expression},
1596 @value{GDBN} will terminate normally; otherwise it will terminate using
1597 the result of @var{expression} as the error code.
1601 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1602 terminates the action of any @value{GDBN} command that is in progress and
1603 returns to @value{GDBN} command level. It is safe to type the interrupt
1604 character at any time because @value{GDBN} does not allow it to take effect
1605 until a time when it is safe.
1607 If you have been using @value{GDBN} to control an attached process or
1608 device, you can release it with the @code{detach} command
1609 (@pxref{Attach, ,Debugging an Already-running Process}).
1611 @node Shell Commands
1612 @section Shell Commands
1614 If you need to execute occasional shell commands during your
1615 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1616 just use the @code{shell} command.
1621 @cindex shell escape
1622 @item shell @var{command-string}
1623 @itemx !@var{command-string}
1624 Invoke a standard shell to execute @var{command-string}.
1625 Note that no space is needed between @code{!} and @var{command-string}.
1626 On GNU and Unix systems, the environment variable @env{SHELL}, if it
1627 exists, determines which shell to run. Otherwise @value{GDBN} uses
1628 the default shell (@file{/bin/sh} on GNU and Unix systems,
1629 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1632 The utility @code{make} is often needed in development environments.
1633 You do not have to use the @code{shell} command for this purpose in
1638 @cindex calling make
1639 @item make @var{make-args}
1640 Execute the @code{make} program with the specified
1641 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1647 @cindex send the output of a gdb command to a shell command
1649 @item pipe [@var{command}] | @var{shell_command}
1650 @itemx | [@var{command}] | @var{shell_command}
1651 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1652 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1653 Executes @var{command} and sends its output to @var{shell_command}.
1654 Note that no space is needed around @code{|}.
1655 If no @var{command} is provided, the last command executed is repeated.
1657 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1658 can be used to specify an alternate delimiter string @var{delim} that separates
1659 the @var{command} from the @var{shell_command}.
1692 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1693 this contains a PIPE char
1694 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1695 this contains a PIPE char!
1701 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1702 can be used to examine the exit status of the last shell command launched
1703 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1704 @xref{Convenience Vars,, Convenience Variables}.
1706 @node Logging Output
1707 @section Logging Output
1708 @cindex logging @value{GDBN} output
1709 @cindex save @value{GDBN} output to a file
1711 You may want to save the output of @value{GDBN} commands to a file.
1712 There are several commands to control @value{GDBN}'s logging.
1715 @kindex set logging enabled
1716 @item set logging enabled [on|off]
1717 Enable or disable logging.
1718 @cindex logging file name
1719 @item set logging file @var{file}
1720 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1721 @item set logging overwrite [on|off]
1722 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1723 you want @code{set logging enabled on} to overwrite the logfile instead.
1724 @item set logging redirect [on|off]
1725 By default, @value{GDBN} output will go to both the terminal and the logfile.
1726 Set @code{redirect} if you want output to go only to the log file.
1727 @item set logging debugredirect [on|off]
1728 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1729 Set @code{debugredirect} if you want debug output to go only to the log file.
1730 @kindex show logging
1732 Show the current values of the logging settings.
1735 You can also redirect the output of a @value{GDBN} command to a
1736 shell command. @xref{pipe}.
1738 @chapter @value{GDBN} Commands
1740 You can abbreviate a @value{GDBN} command to the first few letters of the command
1741 name, if that abbreviation is unambiguous; and you can repeat certain
1742 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1743 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1744 show you the alternatives available, if there is more than one possibility).
1747 * Command Syntax:: How to give commands to @value{GDBN}
1748 * Command Settings:: How to change default behavior of commands
1749 * Completion:: Command completion
1750 * Command Options:: Command options
1751 * Help:: How to ask @value{GDBN} for help
1754 @node Command Syntax
1755 @section Command Syntax
1757 A @value{GDBN} command is a single line of input. There is no limit on
1758 how long it can be. It starts with a command name, which is followed by
1759 arguments whose meaning depends on the command name. For example, the
1760 command @code{step} accepts an argument which is the number of times to
1761 step, as in @samp{step 5}. You can also use the @code{step} command
1762 with no arguments. Some commands do not allow any arguments.
1764 @cindex abbreviation
1765 @value{GDBN} command names may always be truncated if that abbreviation is
1766 unambiguous. Other possible command abbreviations are listed in the
1767 documentation for individual commands. In some cases, even ambiguous
1768 abbreviations are allowed; for example, @code{s} is specially defined as
1769 equivalent to @code{step} even though there are other commands whose
1770 names start with @code{s}. You can test abbreviations by using them as
1771 arguments to the @code{help} command.
1773 @cindex repeating commands
1774 @kindex RET @r{(repeat last command)}
1775 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1776 repeat the previous command. Certain commands (for example, @code{run})
1777 will not repeat this way; these are commands whose unintentional
1778 repetition might cause trouble and which you are unlikely to want to
1779 repeat. User-defined commands can disable this feature; see
1780 @ref{Define, dont-repeat}.
1782 The @code{list} and @code{x} commands, when you repeat them with
1783 @key{RET}, construct new arguments rather than repeating
1784 exactly as typed. This permits easy scanning of source or memory.
1786 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1787 output, in a way similar to the common utility @code{more}
1788 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1789 @key{RET} too many in this situation, @value{GDBN} disables command
1790 repetition after any command that generates this sort of display.
1792 @kindex # @r{(a comment)}
1794 Any text from a @kbd{#} to the end of the line is a comment; it does
1795 nothing. This is useful mainly in command files (@pxref{Command
1796 Files,,Command Files}).
1798 @cindex repeating command sequences
1799 @kindex Ctrl-o @r{(operate-and-get-next)}
1800 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1801 commands. This command accepts the current line, like @key{RET}, and
1802 then fetches the next line relative to the current line from the history
1806 @node Command Settings
1807 @section Command Settings
1808 @cindex default behavior of commands, changing
1809 @cindex default settings, changing
1811 Many commands change their behavior according to command-specific
1812 variables or settings. These settings can be changed with the
1813 @code{set} subcommands. For example, the @code{print} command
1814 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1815 settings changeable with the commands @code{set print elements
1816 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1818 You can change these settings to your preference in the gdbinit files
1819 loaded at @value{GDBN} startup. @xref{Startup}.
1821 The settings can also be changed interactively during the debugging
1822 session. For example, to change the limit of array elements to print,
1823 you can do the following:
1825 (@value{GDBN}) set print elements 10
1826 (@value{GDBN}) print some_array
1827 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1830 The above @code{set print elements 10} command changes the number of
1831 elements to print from the default of 200 to 10. If you only intend
1832 this limit of 10 to be used for printing @code{some_array}, then you
1833 must restore the limit back to 200, with @code{set print elements
1836 Some commands allow overriding settings with command options. For
1837 example, the @code{print} command supports a number of options that
1838 allow overriding relevant global print settings as set by @code{set
1839 print} subcommands. @xref{print options}. The example above could be
1842 (@value{GDBN}) print -elements 10 -- some_array
1843 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1846 Alternatively, you can use the @code{with} command to change a setting
1847 temporarily, for the duration of a command invocation.
1850 @kindex with command
1851 @kindex w @r{(@code{with})}
1853 @cindex temporarily change settings
1854 @item with @var{setting} [@var{value}] [-- @var{command}]
1855 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1856 Temporarily set @var{setting} to @var{value} for the duration of
1859 @var{setting} is any setting you can change with the @code{set}
1860 subcommands. @var{value} is the value to assign to @code{setting}
1861 while running @code{command}.
1863 If no @var{command} is provided, the last command executed is
1866 If a @var{command} is provided, it must be preceded by a double dash
1867 (@code{--}) separator. This is required because some settings accept
1868 free-form arguments, such as expressions or filenames.
1870 For example, the command
1872 (@value{GDBN}) with print array on -- print some_array
1875 is equivalent to the following 3 commands:
1877 (@value{GDBN}) set print array on
1878 (@value{GDBN}) print some_array
1879 (@value{GDBN}) set print array off
1882 The @code{with} command is particularly useful when you want to
1883 override a setting while running user-defined commands, or commands
1884 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1887 (@value{GDBN}) with print pretty on -- my_complex_command
1890 To change several settings for the same command, you can nest
1891 @code{with} commands. For example, @code{with language ada -- with
1892 print elements 10} temporarily changes the language to Ada and sets a
1893 limit of 10 elements to print for arrays and strings.
1898 @section Command Completion
1901 @cindex word completion
1902 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1903 only one possibility; it can also show you what the valid possibilities
1904 are for the next word in a command, at any time. This works for @value{GDBN}
1905 commands, @value{GDBN} subcommands, command options, and the names of symbols
1908 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1909 of a word. If there is only one possibility, @value{GDBN} fills in the
1910 word, and waits for you to finish the command (or press @key{RET} to
1911 enter it). For example, if you type
1913 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1914 @c complete accuracy in these examples; space introduced for clarity.
1915 @c If texinfo enhancements make it unnecessary, it would be nice to
1916 @c replace " @key" by "@key" in the following...
1918 (@value{GDBP}) info bre@key{TAB}
1922 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1923 the only @code{info} subcommand beginning with @samp{bre}:
1926 (@value{GDBP}) info breakpoints
1930 You can either press @key{RET} at this point, to run the @code{info
1931 breakpoints} command, or backspace and enter something else, if
1932 @samp{breakpoints} does not look like the command you expected. (If you
1933 were sure you wanted @code{info breakpoints} in the first place, you
1934 might as well just type @key{RET} immediately after @samp{info bre},
1935 to exploit command abbreviations rather than command completion).
1937 If there is more than one possibility for the next word when you press
1938 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1939 characters and try again, or just press @key{TAB} a second time;
1940 @value{GDBN} displays all the possible completions for that word. For
1941 example, you might want to set a breakpoint on a subroutine whose name
1942 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1943 just sounds the bell. Typing @key{TAB} again displays all the
1944 function names in your program that begin with those characters, for
1948 (@value{GDBP}) b make_@key{TAB}
1949 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1950 make_a_section_from_file make_environ
1951 make_abs_section make_function_type
1952 make_blockvector make_pointer_type
1953 make_cleanup make_reference_type
1954 make_command make_symbol_completion_list
1955 (@value{GDBP}) b make_
1959 After displaying the available possibilities, @value{GDBN} copies your
1960 partial input (@samp{b make_} in the example) so you can finish the
1963 If the command you are trying to complete expects either a keyword or a
1964 number to follow, then @samp{NUMBER} will be shown among the available
1965 completions, for example:
1968 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
1970 (@value{GDBP}) print -elements@tie{}
1974 Here, the option expects a number (e.g., @code{100}), not literal
1975 @code{NUMBER}. Such metasyntactical arguments are always presented in
1978 If you just want to see the list of alternatives in the first place, you
1979 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1980 means @kbd{@key{META} ?}. You can type this either by holding down a
1981 key designated as the @key{META} shift on your keyboard (if there is
1982 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1984 If the number of possible completions is large, @value{GDBN} will
1985 print as much of the list as it has collected, as well as a message
1986 indicating that the list may be truncated.
1989 (@value{GDBP}) b m@key{TAB}@key{TAB}
1991 <... the rest of the possible completions ...>
1992 *** List may be truncated, max-completions reached. ***
1997 This behavior can be controlled with the following commands:
2000 @kindex set max-completions
2001 @item set max-completions @var{limit}
2002 @itemx set max-completions unlimited
2003 Set the maximum number of completion candidates. @value{GDBN} will
2004 stop looking for more completions once it collects this many candidates.
2005 This is useful when completing on things like function names as collecting
2006 all the possible candidates can be time consuming.
2007 The default value is 200. A value of zero disables tab-completion.
2008 Note that setting either no limit or a very large limit can make
2010 @kindex show max-completions
2011 @item show max-completions
2012 Show the maximum number of candidates that @value{GDBN} will collect and show
2016 @cindex quotes in commands
2017 @cindex completion of quoted strings
2018 Sometimes the string you need, while logically a ``word'', may contain
2019 parentheses or other characters that @value{GDBN} normally excludes from
2020 its notion of a word. To permit word completion to work in this
2021 situation, you may enclose words in @code{'} (single quote marks) in
2022 @value{GDBN} commands.
2024 A likely situation where you might need this is in typing an
2025 expression that involves a C@t{++} symbol name with template
2026 parameters. This is because when completing expressions, GDB treats
2027 the @samp{<} character as word delimiter, assuming that it's the
2028 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
2031 For example, when you want to call a C@t{++} template function
2032 interactively using the @code{print} or @code{call} commands, you may
2033 need to distinguish whether you mean the version of @code{name} that
2034 was specialized for @code{int}, @code{name<int>()}, or the version
2035 that was specialized for @code{float}, @code{name<float>()}. To use
2036 the word-completion facilities in this situation, type a single quote
2037 @code{'} at the beginning of the function name. This alerts
2038 @value{GDBN} that it may need to consider more information than usual
2039 when you press @key{TAB} or @kbd{M-?} to request word completion:
2042 (@value{GDBP}) p 'func<@kbd{M-?}
2043 func<int>() func<float>()
2044 (@value{GDBP}) p 'func<
2047 When setting breakpoints however (@pxref{Location Specifications}), you don't
2048 usually need to type a quote before the function name, because
2049 @value{GDBN} understands that you want to set a breakpoint on a
2053 (@value{GDBP}) b func<@kbd{M-?}
2054 func<int>() func<float>()
2055 (@value{GDBP}) b func<
2058 This is true even in the case of typing the name of C@t{++} overloaded
2059 functions (multiple definitions of the same function, distinguished by
2060 argument type). For example, when you want to set a breakpoint you
2061 don't need to distinguish whether you mean the version of @code{name}
2062 that takes an @code{int} parameter, @code{name(int)}, or the version
2063 that takes a @code{float} parameter, @code{name(float)}.
2066 (@value{GDBP}) b bubble(@kbd{M-?}
2067 bubble(int) bubble(double)
2068 (@value{GDBP}) b bubble(dou@kbd{M-?}
2072 See @ref{quoting names} for a description of other scenarios that
2075 For more information about overloaded functions, see @ref{C Plus Plus
2076 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
2077 overload-resolution off} to disable overload resolution;
2078 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
2080 @cindex completion of structure field names
2081 @cindex structure field name completion
2082 @cindex completion of union field names
2083 @cindex union field name completion
2084 When completing in an expression which looks up a field in a
2085 structure, @value{GDBN} also tries@footnote{The completer can be
2086 confused by certain kinds of invalid expressions. Also, it only
2087 examines the static type of the expression, not the dynamic type.} to
2088 limit completions to the field names available in the type of the
2092 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
2093 magic to_fputs to_rewind
2094 to_data to_isatty to_write
2095 to_delete to_put to_write_async_safe
2100 This is because the @code{gdb_stdout} is a variable of the type
2101 @code{struct ui_file} that is defined in @value{GDBN} sources as
2108 ui_file_flush_ftype *to_flush;
2109 ui_file_write_ftype *to_write;
2110 ui_file_write_async_safe_ftype *to_write_async_safe;
2111 ui_file_fputs_ftype *to_fputs;
2112 ui_file_read_ftype *to_read;
2113 ui_file_delete_ftype *to_delete;
2114 ui_file_isatty_ftype *to_isatty;
2115 ui_file_rewind_ftype *to_rewind;
2116 ui_file_put_ftype *to_put;
2121 @node Command Options
2122 @section Command options
2124 @cindex command options
2125 Some commands accept options starting with a leading dash. For
2126 example, @code{print -pretty}. Similarly to command names, you can
2127 abbreviate a @value{GDBN} option to the first few letters of the
2128 option name, if that abbreviation is unambiguous, and you can also use
2129 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
2130 in an option (or to show you the alternatives available, if there is
2131 more than one possibility).
2133 @cindex command options, raw input
2134 Some commands take raw input as argument. For example, the print
2135 command processes arbitrary expressions in any of the languages
2136 supported by @value{GDBN}. With such commands, because raw input may
2137 start with a leading dash that would be confused with an option or any
2138 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
2139 -pretty} or printing negative @code{p}?), if you specify any command
2140 option, then you must use a double-dash (@code{--}) delimiter to
2141 indicate the end of options.
2143 @cindex command options, boolean
2145 Some options are described as accepting an argument which can be
2146 either @code{on} or @code{off}. These are known as @dfn{boolean
2147 options}. Similarly to boolean settings commands---@code{on} and
2148 @code{off} are the typical values, but any of @code{1}, @code{yes} and
2149 @code{enable} can also be used as ``true'' value, and any of @code{0},
2150 @code{no} and @code{disable} can also be used as ``false'' value. You
2151 can also omit a ``true'' value, as it is implied by default.
2153 For example, these are equivalent:
2156 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
2157 (@value{GDBP}) p -o -p 0 -e u -- *myptr
2160 You can discover the set of options some command accepts by completing
2161 on @code{-} after the command name. For example:
2164 (@value{GDBP}) print -@key{TAB}@key{TAB}
2165 -address -max-depth -object -static-members
2166 -array -memory-tag-violations -pretty -symbol
2167 -array-indexes -nibbles -raw-values -union
2168 -elements -null-stop -repeats -vtbl
2171 Completion will in some cases guide you with a suggestion of what kind
2172 of argument an option expects. For example:
2175 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
2180 Here, the option expects a number (e.g., @code{100}), not literal
2181 @code{NUMBER}. Such metasyntactical arguments are always presented in
2184 (For more on using the @code{print} command, see @ref{Data, ,Examining
2188 @section Getting Help
2189 @cindex online documentation
2192 You can always ask @value{GDBN} itself for information on its commands,
2193 using the command @code{help}.
2196 @kindex h @r{(@code{help})}
2199 You can use @code{help} (abbreviated @code{h}) with no arguments to
2200 display a short list of named classes of commands:
2204 List of classes of commands:
2206 aliases -- User-defined aliases of other commands
2207 breakpoints -- Making program stop at certain points
2208 data -- Examining data
2209 files -- Specifying and examining files
2210 internals -- Maintenance commands
2211 obscure -- Obscure features
2212 running -- Running the program
2213 stack -- Examining the stack
2214 status -- Status inquiries
2215 support -- Support facilities
2216 tracepoints -- Tracing of program execution without
2217 stopping the program
2218 user-defined -- User-defined commands
2220 Type "help" followed by a class name for a list of
2221 commands in that class.
2222 Type "help" followed by command name for full
2224 Command name abbreviations are allowed if unambiguous.
2227 @c the above line break eliminates huge line overfull...
2229 @item help @var{class}
2230 Using one of the general help classes as an argument, you can get a
2231 list of the individual commands in that class. If a command has
2232 aliases, the aliases are given after the command name, separated by
2233 commas. If an alias has default arguments, the full definition of
2234 the alias is given after the first line.
2235 For example, here is the help display for the class @code{status}:
2238 (@value{GDBP}) help status
2243 @c Line break in "show" line falsifies real output, but needed
2244 @c to fit in smallbook page size.
2245 info, inf, i -- Generic command for showing things
2246 about the program being debugged
2247 info address, iamain -- Describe where symbol SYM is stored.
2248 alias iamain = info address main
2249 info all-registers -- List of all registers and their contents,
2250 for selected stack frame.
2252 show, info set -- Generic command for showing things
2255 Type "help" followed by command name for full
2257 Command name abbreviations are allowed if unambiguous.
2261 @item help @var{command}
2262 With a command name as @code{help} argument, @value{GDBN} displays a
2263 short paragraph on how to use that command. If that command has
2264 one or more aliases, @value{GDBN} will display a first line with
2265 the command name and all its aliases separated by commas.
2266 This first line will be followed by the full definition of all aliases
2267 having default arguments.
2268 When asking the help for an alias, the documentation for the aliased
2271 A user-defined alias can optionally be documented using the
2272 @code{document} command (@pxref{Define, document}). @value{GDBN} then
2273 considers this alias as different from the aliased command: this alias
2274 is not listed in the aliased command help output, and asking help for
2275 this alias will show the documentation provided for the alias instead of
2276 the documentation of the aliased command.
2279 @item apropos [-v] @var{regexp}
2280 The @code{apropos} command searches through all of the @value{GDBN}
2281 commands and aliases, and their documentation, for the regular expression specified in
2282 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2283 which stands for @samp{verbose}, indicates to output the full documentation
2284 of the matching commands and highlight the parts of the documentation
2285 matching @var{regexp}. For example:
2296 alias -- Define a new command that is an alias of an existing command
2297 aliases -- User-defined aliases of other commands
2305 apropos -v cut.*thread apply
2309 results in the below output, where @samp{cut for 'thread apply}
2310 is highlighted if styling is enabled.
2314 taas -- Apply a command to all threads (ignoring errors
2317 shortcut for 'thread apply all -s COMMAND'
2319 tfaas -- Apply a command to all frames of all threads
2320 (ignoring errors and empty output).
2321 Usage: tfaas COMMAND
2322 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2327 @item complete @var{args}
2328 The @code{complete @var{args}} command lists all the possible completions
2329 for the beginning of a command. Use @var{args} to specify the beginning of the
2330 command you want completed. For example:
2336 @noindent results in:
2347 @noindent This is intended for use by @sc{gnu} Emacs.
2350 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2351 and @code{show} to inquire about the state of your program, or the state
2352 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2353 manual introduces each of them in the appropriate context. The listings
2354 under @code{info} and under @code{show} in the Command, Variable, and
2355 Function Index point to all the sub-commands. @xref{Command and Variable
2361 @kindex i @r{(@code{info})}
2363 This command (abbreviated @code{i}) is for describing the state of your
2364 program. For example, you can show the arguments passed to a function
2365 with @code{info args}, list the registers currently in use with @code{info
2366 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2367 You can get a complete list of the @code{info} sub-commands with
2368 @w{@code{help info}}.
2372 You can assign the result of an expression to an environment variable with
2373 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2374 @code{set prompt $}.
2378 In contrast to @code{info}, @code{show} is for describing the state of
2379 @value{GDBN} itself.
2380 You can change most of the things you can @code{show}, by using the
2381 related command @code{set}; for example, you can control what number
2382 system is used for displays with @code{set radix}, or simply inquire
2383 which is currently in use with @code{show radix}.
2386 To display all the settable parameters and their current
2387 values, you can use @code{show} with no arguments; you may also use
2388 @code{info set}. Both commands produce the same display.
2389 @c FIXME: "info set" violates the rule that "info" is for state of
2390 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2391 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2395 Here are several miscellaneous @code{show} subcommands, all of which are
2396 exceptional in lacking corresponding @code{set} commands:
2399 @kindex show version
2400 @cindex @value{GDBN} version number
2402 Show what version of @value{GDBN} is running. You should include this
2403 information in @value{GDBN} bug-reports. If multiple versions of
2404 @value{GDBN} are in use at your site, you may need to determine which
2405 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2406 commands are introduced, and old ones may wither away. Also, many
2407 system vendors ship variant versions of @value{GDBN}, and there are
2408 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2409 The version number is the same as the one announced when you start
2412 @kindex show copying
2413 @kindex info copying
2414 @cindex display @value{GDBN} copyright
2417 Display information about permission for copying @value{GDBN}.
2419 @kindex show warranty
2420 @kindex info warranty
2422 @itemx info warranty
2423 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2424 if your version of @value{GDBN} comes with one.
2426 @kindex show configuration
2427 @item show configuration
2428 Display detailed information about the way @value{GDBN} was configured
2429 when it was built. This displays the optional arguments passed to the
2430 @file{configure} script and also configuration parameters detected
2431 automatically by @command{configure}. When reporting a @value{GDBN}
2432 bug (@pxref{GDB Bugs}), it is important to include this information in
2438 @chapter Running Programs Under @value{GDBN}
2440 When you run a program under @value{GDBN}, you must first generate
2441 debugging information when you compile it.
2443 You may start @value{GDBN} with its arguments, if any, in an environment
2444 of your choice. If you are doing native debugging, you may redirect
2445 your program's input and output, debug an already running process, or
2446 kill a child process.
2449 * Compilation:: Compiling for debugging
2450 * Starting:: Starting your program
2451 * Arguments:: Your program's arguments
2452 * Environment:: Your program's environment
2454 * Working Directory:: Your program's working directory
2455 * Input/Output:: Your program's input and output
2456 * Attach:: Debugging an already-running process
2457 * Kill Process:: Killing the child process
2458 * Inferiors Connections and Programs:: Debugging multiple inferiors
2459 connections and programs
2460 * Threads:: Debugging programs with multiple threads
2461 * Forks:: Debugging forks
2462 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2466 @section Compiling for Debugging
2468 In order to debug a program effectively, you need to generate
2469 debugging information when you compile it. This debugging information
2470 is stored in the object file; it describes the data type of each
2471 variable or function and the correspondence between source line numbers
2472 and addresses in the executable code.
2474 To request debugging information, specify the @samp{-g} option when you run
2477 Programs that are to be shipped to your customers are compiled with
2478 optimizations, using the @samp{-O} compiler option. However, some
2479 compilers are unable to handle the @samp{-g} and @samp{-O} options
2480 together. Using those compilers, you cannot generate optimized
2481 executables containing debugging information.
2483 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2484 without @samp{-O}, making it possible to debug optimized code. We
2485 recommend that you @emph{always} use @samp{-g} whenever you compile a
2486 program. You may think your program is correct, but there is no sense
2487 in pushing your luck. For more information, see @ref{Optimized Code}.
2489 Older versions of the @sc{gnu} C compiler permitted a variant option
2490 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2491 format; if your @sc{gnu} C compiler has this option, do not use it.
2493 @value{GDBN} knows about preprocessor macros and can show you their
2494 expansion (@pxref{Macros}). Most compilers do not include information
2495 about preprocessor macros in the debugging information if you specify
2496 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2497 the @sc{gnu} C compiler, provides macro information if you are using
2498 the DWARF debugging format, and specify the option @option{-g3}.
2500 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2501 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2502 information on @value{NGCC} options affecting debug information.
2504 You will have the best debugging experience if you use the latest
2505 version of the DWARF debugging format that your compiler supports.
2506 DWARF is currently the most expressive and best supported debugging
2507 format in @value{GDBN}.
2511 @section Starting your Program
2517 @kindex r @r{(@code{run})}
2520 Use the @code{run} command to start your program under @value{GDBN}.
2521 You must first specify the program name with an argument to
2522 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2523 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2524 command (@pxref{Files, ,Commands to Specify Files}).
2528 If you are running your program in an execution environment that
2529 supports processes, @code{run} creates an inferior process and makes
2530 that process run your program. In some environments without processes,
2531 @code{run} jumps to the start of your program. Other targets,
2532 like @samp{remote}, are always running. If you get an error
2533 message like this one:
2536 The "remote" target does not support "run".
2537 Try "help target" or "continue".
2541 then use @code{continue} to run your program. You may need @code{load}
2542 first (@pxref{load}).
2544 The execution of a program is affected by certain information it
2545 receives from its superior. @value{GDBN} provides ways to specify this
2546 information, which you must do @emph{before} starting your program. (You
2547 can change it after starting your program, but such changes only affect
2548 your program the next time you start it.) This information may be
2549 divided into four categories:
2552 @item The @emph{arguments.}
2553 Specify the arguments to give your program as the arguments of the
2554 @code{run} command. If a shell is available on your target, the shell
2555 is used to pass the arguments, so that you may use normal conventions
2556 (such as wildcard expansion or variable substitution) in describing
2558 In Unix systems, you can control which shell is used with the
2559 @env{SHELL} environment variable. If you do not define @env{SHELL},
2560 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2561 use of any shell with the @code{set startup-with-shell} command (see
2564 @item The @emph{environment.}
2565 Your program normally inherits its environment from @value{GDBN}, but you can
2566 use the @value{GDBN} commands @code{set environment} and @code{unset
2567 environment} to change parts of the environment that affect
2568 your program. @xref{Environment, ,Your Program's Environment}.
2570 @item The @emph{working directory.}
2571 You can set your program's working directory with the command
2572 @kbd{set cwd}. If you do not set any working directory with this
2573 command, your program will inherit @value{GDBN}'s working directory if
2574 native debugging, or the remote server's working directory if remote
2575 debugging. @xref{Working Directory, ,Your Program's Working
2578 @item The @emph{standard input and output.}
2579 Your program normally uses the same device for standard input and
2580 standard output as @value{GDBN} is using. You can redirect input and output
2581 in the @code{run} command line, or you can use the @code{tty} command to
2582 set a different device for your program.
2583 @xref{Input/Output, ,Your Program's Input and Output}.
2586 @emph{Warning:} While input and output redirection work, you cannot use
2587 pipes to pass the output of the program you are debugging to another
2588 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2592 When you issue the @code{run} command, your program begins to execute
2593 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2594 of how to arrange for your program to stop. Once your program has
2595 stopped, you may call functions in your program, using the @code{print}
2596 or @code{call} commands. @xref{Data, ,Examining Data}.
2598 If the modification time of your symbol file has changed since the last
2599 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2600 table, and reads it again. When it does this, @value{GDBN} tries to retain
2601 your current breakpoints.
2606 @cindex run to main procedure
2607 The name of the main procedure can vary from language to language.
2608 With C or C@t{++}, the main procedure name is always @code{main}, but
2609 other languages such as Ada do not require a specific name for their
2610 main procedure. The debugger provides a convenient way to start the
2611 execution of the program and to stop at the beginning of the main
2612 procedure, depending on the language used.
2614 The @samp{start} command does the equivalent of setting a temporary
2615 breakpoint at the beginning of the main procedure and then invoking
2616 the @samp{run} command.
2618 @cindex elaboration phase
2619 Some programs contain an @dfn{elaboration} phase where some startup code is
2620 executed before the main procedure is called. This depends on the
2621 languages used to write your program. In C@t{++}, for instance,
2622 constructors for static and global objects are executed before
2623 @code{main} is called. It is therefore possible that the debugger stops
2624 before reaching the main procedure. However, the temporary breakpoint
2625 will remain to halt execution.
2627 Specify the arguments to give to your program as arguments to the
2628 @samp{start} command. These arguments will be given verbatim to the
2629 underlying @samp{run} command. Note that the same arguments will be
2630 reused if no argument is provided during subsequent calls to
2631 @samp{start} or @samp{run}.
2633 It is sometimes necessary to debug the program during elaboration. In
2634 these cases, using the @code{start} command would stop the execution
2635 of your program too late, as the program would have already completed
2636 the elaboration phase. Under these circumstances, either insert
2637 breakpoints in your elaboration code before running your program or
2638 use the @code{starti} command.
2642 @cindex run to first instruction
2643 The @samp{starti} command does the equivalent of setting a temporary
2644 breakpoint at the first instruction of a program's execution and then
2645 invoking the @samp{run} command. For programs containing an
2646 elaboration phase, the @code{starti} command will stop execution at
2647 the start of the elaboration phase.
2649 @anchor{set exec-wrapper}
2650 @kindex set exec-wrapper
2651 @item set exec-wrapper @var{wrapper}
2652 @itemx show exec-wrapper
2653 @itemx unset exec-wrapper
2654 When @samp{exec-wrapper} is set, the specified wrapper is used to
2655 launch programs for debugging. @value{GDBN} starts your program
2656 with a shell command of the form @kbd{exec @var{wrapper}
2657 @var{program}}. Quoting is added to @var{program} and its
2658 arguments, but not to @var{wrapper}, so you should add quotes if
2659 appropriate for your shell. The wrapper runs until it executes
2660 your program, and then @value{GDBN} takes control.
2662 You can use any program that eventually calls @code{execve} with
2663 its arguments as a wrapper. Several standard Unix utilities do
2664 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2665 with @code{exec "$@@"} will also work.
2667 For example, you can use @code{env} to pass an environment variable to
2668 the debugged program, without setting the variable in your shell's
2672 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2676 This command is available when debugging locally on most targets, excluding
2677 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2679 @kindex set startup-with-shell
2680 @anchor{set startup-with-shell}
2681 @item set startup-with-shell
2682 @itemx set startup-with-shell on
2683 @itemx set startup-with-shell off
2684 @itemx show startup-with-shell
2685 On Unix systems, by default, if a shell is available on your target,
2686 @value{GDBN}) uses it to start your program. Arguments of the
2687 @code{run} command are passed to the shell, which does variable
2688 substitution, expands wildcard characters and performs redirection of
2689 I/O. In some circumstances, it may be useful to disable such use of a
2690 shell, for example, when debugging the shell itself or diagnosing
2691 startup failures such as:
2695 Starting program: ./a.out
2696 During startup program terminated with signal SIGSEGV, Segmentation fault.
2700 which indicates the shell or the wrapper specified with
2701 @samp{exec-wrapper} crashed, not your program. Most often, this is
2702 caused by something odd in your shell's non-interactive mode
2703 initialization file---such as @file{.cshrc} for C-shell,
2704 $@file{.zshenv} for the Z shell, or the file specified in the
2705 @env{BASH_ENV} environment variable for BASH.
2707 @anchor{set auto-connect-native-target}
2708 @kindex set auto-connect-native-target
2709 @item set auto-connect-native-target
2710 @itemx set auto-connect-native-target on
2711 @itemx set auto-connect-native-target off
2712 @itemx show auto-connect-native-target
2714 By default, if the current inferior is not connected to any target yet
2715 (e.g., with @code{target remote}), the @code{run} command starts your
2716 program as a native process under @value{GDBN}, on your local machine.
2717 If you're sure you don't want to debug programs on your local machine,
2718 you can tell @value{GDBN} to not connect to the native target
2719 automatically with the @code{set auto-connect-native-target off}
2722 If @code{on}, which is the default, and if the current inferior is not
2723 connected to a target already, the @code{run} command automaticaly
2724 connects to the native target, if one is available.
2726 If @code{off}, and if the current inferior is not connected to a
2727 target already, the @code{run} command fails with an error:
2731 Don't know how to run. Try "help target".
2734 If the current inferior is already connected to a target, @value{GDBN}
2735 always uses it with the @code{run} command.
2737 In any case, you can explicitly connect to the native target with the
2738 @code{target native} command. For example,
2741 (@value{GDBP}) set auto-connect-native-target off
2743 Don't know how to run. Try "help target".
2744 (@value{GDBP}) target native
2746 Starting program: ./a.out
2747 [Inferior 1 (process 10421) exited normally]
2750 In case you connected explicitly to the @code{native} target,
2751 @value{GDBN} remains connected even if all inferiors exit, ready for
2752 the next @code{run} command. Use the @code{disconnect} command to
2755 Examples of other commands that likewise respect the
2756 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2757 proc}, @code{info os}.
2759 @kindex set disable-randomization
2760 @item set disable-randomization
2761 @itemx set disable-randomization on
2762 This option (enabled by default in @value{GDBN}) will turn off the native
2763 randomization of the virtual address space of the started program. This option
2764 is useful for multiple debugging sessions to make the execution better
2765 reproducible and memory addresses reusable across debugging sessions.
2767 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2768 On @sc{gnu}/Linux you can get the same behavior using
2771 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2774 @item set disable-randomization off
2775 Leave the behavior of the started executable unchanged. Some bugs rear their
2776 ugly heads only when the program is loaded at certain addresses. If your bug
2777 disappears when you run the program under @value{GDBN}, that might be because
2778 @value{GDBN} by default disables the address randomization on platforms, such
2779 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2780 disable-randomization off} to try to reproduce such elusive bugs.
2782 On targets where it is available, virtual address space randomization
2783 protects the programs against certain kinds of security attacks. In these
2784 cases the attacker needs to know the exact location of a concrete executable
2785 code. Randomizing its location makes it impossible to inject jumps misusing
2786 a code at its expected addresses.
2788 Prelinking shared libraries provides a startup performance advantage but it
2789 makes addresses in these libraries predictable for privileged processes by
2790 having just unprivileged access at the target system. Reading the shared
2791 library binary gives enough information for assembling the malicious code
2792 misusing it. Still even a prelinked shared library can get loaded at a new
2793 random address just requiring the regular relocation process during the
2794 startup. Shared libraries not already prelinked are always loaded at
2795 a randomly chosen address.
2797 Position independent executables (PIE) contain position independent code
2798 similar to the shared libraries and therefore such executables get loaded at
2799 a randomly chosen address upon startup. PIE executables always load even
2800 already prelinked shared libraries at a random address. You can build such
2801 executable using @command{gcc -fPIE -pie}.
2803 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2804 (as long as the randomization is enabled).
2806 @item show disable-randomization
2807 Show the current setting of the explicit disable of the native randomization of
2808 the virtual address space of the started program.
2813 @section Your Program's Arguments
2815 @cindex arguments (to your program)
2816 The arguments to your program can be specified by the arguments of the
2818 They are passed to a shell, which expands wildcard characters and
2819 performs redirection of I/O, and thence to your program. Your
2820 @env{SHELL} environment variable (if it exists) specifies what shell
2821 @value{GDBN} uses. If you do not define @env{SHELL}, @value{GDBN} uses
2822 the default shell (@file{/bin/sh} on Unix).
2824 On non-Unix systems, the program is usually invoked directly by
2825 @value{GDBN}, which emulates I/O redirection via the appropriate system
2826 calls, and the wildcard characters are expanded by the startup code of
2827 the program, not by the shell.
2829 @code{run} with no arguments uses the same arguments used by the previous
2830 @code{run}, or those set by the @code{set args} command.
2835 Specify the arguments to be used the next time your program is run. If
2836 @code{set args} has no arguments, @code{run} executes your program
2837 with no arguments. Once you have run your program with arguments,
2838 using @code{set args} before the next @code{run} is the only way to run
2839 it again without arguments.
2843 Show the arguments to give your program when it is started.
2847 @section Your Program's Environment
2849 @cindex environment (of your program)
2850 The @dfn{environment} consists of a set of environment variables and
2851 their values. Environment variables conventionally record such things as
2852 your user name, your home directory, your terminal type, and your search
2853 path for programs to run. Usually you set up environment variables with
2854 the shell and they are inherited by all the other programs you run. When
2855 debugging, it can be useful to try running your program with a modified
2856 environment without having to start @value{GDBN} over again.
2860 @item path @var{directory}
2861 Add @var{directory} to the front of the @env{PATH} environment variable
2862 (the search path for executables) that will be passed to your program.
2863 The value of @env{PATH} used by @value{GDBN} does not change.
2864 You may specify several directory names, separated by whitespace or by a
2865 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2866 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2867 is moved to the front, so it is searched sooner.
2869 You can use the string @samp{$cwd} to refer to whatever is the current
2870 working directory at the time @value{GDBN} searches the path. If you
2871 use @samp{.} instead, it refers to the directory where you executed the
2872 @code{path} command. @value{GDBN} replaces @samp{.} in the
2873 @var{directory} argument (with the current path) before adding
2874 @var{directory} to the search path.
2875 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2876 @c document that, since repeating it would be a no-op.
2880 Display the list of search paths for executables (the @env{PATH}
2881 environment variable).
2883 @kindex show environment
2884 @item show environment @r{[}@var{varname}@r{]}
2885 Print the value of environment variable @var{varname} to be given to
2886 your program when it starts. If you do not supply @var{varname},
2887 print the names and values of all environment variables to be given to
2888 your program. You can abbreviate @code{environment} as @code{env}.
2890 @kindex set environment
2891 @anchor{set environment}
2892 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2893 Set environment variable @var{varname} to @var{value}. The value
2894 changes for your program (and the shell @value{GDBN} uses to launch
2895 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2896 values of environment variables are just strings, and any
2897 interpretation is supplied by your program itself. The @var{value}
2898 parameter is optional; if it is eliminated, the variable is set to a
2900 @c "any string" here does not include leading, trailing
2901 @c blanks. Gnu asks: does anyone care?
2903 For example, this command:
2910 tells the debugged program, when subsequently run, that its user is named
2911 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2912 are not actually required.)
2914 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2915 which also inherits the environment set with @code{set environment}.
2916 If necessary, you can avoid that by using the @samp{env} program as a
2917 wrapper instead of using @code{set environment}. @xref{set
2918 exec-wrapper}, for an example doing just that.
2920 Environment variables that are set by the user are also transmitted to
2921 @command{gdbserver} to be used when starting the remote inferior.
2922 @pxref{QEnvironmentHexEncoded}.
2924 @kindex unset environment
2925 @anchor{unset environment}
2926 @item unset environment @var{varname}
2927 Remove variable @var{varname} from the environment to be passed to your
2928 program. This is different from @samp{set env @var{varname} =};
2929 @code{unset environment} removes the variable from the environment,
2930 rather than assigning it an empty value.
2932 Environment variables that are unset by the user are also unset on
2933 @command{gdbserver} when starting the remote inferior.
2934 @pxref{QEnvironmentUnset}.
2937 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2938 the shell indicated by your @env{SHELL} environment variable if it
2939 exists (or @code{/bin/sh} if not). If your @env{SHELL} variable
2940 names a shell that runs an initialization file when started
2941 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2942 for the Z shell, or the file specified in the @env{BASH_ENV}
2943 environment variable for BASH---any variables you set in that file
2944 affect your program. You may wish to move setting of environment
2945 variables to files that are only run when you sign on, such as
2946 @file{.login} or @file{.profile}.
2948 @node Working Directory
2949 @section Your Program's Working Directory
2951 @cindex working directory (of your program)
2952 Each time you start your program with @code{run}, the inferior will be
2953 initialized with the current working directory specified by the
2954 @kbd{set cwd} command. If no directory has been specified by this
2955 command, then the inferior will inherit @value{GDBN}'s current working
2956 directory as its working directory if native debugging, or it will
2957 inherit the remote server's current working directory if remote
2962 @cindex change inferior's working directory
2963 @anchor{set cwd command}
2964 @item set cwd @r{[}@var{directory}@r{]}
2965 Set the inferior's working directory to @var{directory}, which will be
2966 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2967 argument has been specified, the command clears the setting and resets
2968 it to an empty state. This setting has no effect on @value{GDBN}'s
2969 working directory, and it only takes effect the next time you start
2970 the inferior. The @file{~} in @var{directory} is a short for the
2971 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2972 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2973 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2976 You can also change @value{GDBN}'s current working directory by using
2977 the @code{cd} command.
2981 @cindex show inferior's working directory
2983 Show the inferior's working directory. If no directory has been
2984 specified by @kbd{set cwd}, then the default inferior's working
2985 directory is the same as @value{GDBN}'s working directory.
2988 @cindex change @value{GDBN}'s working directory
2990 @item cd @r{[}@var{directory}@r{]}
2991 Set the @value{GDBN} working directory to @var{directory}. If not
2992 given, @var{directory} uses @file{'~'}.
2994 The @value{GDBN} working directory serves as a default for the
2995 commands that specify files for @value{GDBN} to operate on.
2996 @xref{Files, ,Commands to Specify Files}.
2997 @xref{set cwd command}.
3001 Print the @value{GDBN} working directory.
3004 It is generally impossible to find the current working directory of
3005 the process being debugged (since a program can change its directory
3006 during its run). If you work on a system where @value{GDBN} supports
3007 the @code{info proc} command (@pxref{Process Information}), you can
3008 use the @code{info proc} command to find out the
3009 current working directory of the debuggee.
3012 @section Your Program's Input and Output
3017 By default, the program you run under @value{GDBN} does input and output to
3018 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
3019 to its own terminal modes to interact with you, but it records the terminal
3020 modes your program was using and switches back to them when you continue
3021 running your program.
3024 @kindex info terminal
3026 Displays information recorded by @value{GDBN} about the terminal modes your
3030 You can redirect your program's input and/or output using shell
3031 redirection with the @code{run} command. For example,
3038 starts your program, diverting its output to the file @file{outfile}.
3041 @cindex controlling terminal
3042 Another way to specify where your program should do input and output is
3043 with the @code{tty} command. This command accepts a file name as
3044 argument, and causes this file to be the default for future @code{run}
3045 commands. It also resets the controlling terminal for the child
3046 process, for future @code{run} commands. For example,
3053 directs that processes started with subsequent @code{run} commands
3054 default to do input and output on the terminal @file{/dev/ttyb} and have
3055 that as their controlling terminal.
3057 An explicit redirection in @code{run} overrides the @code{tty} command's
3058 effect on the input/output device, but not its effect on the controlling
3061 When you use the @code{tty} command or redirect input in the @code{run}
3062 command, only the input @emph{for your program} is affected. The input
3063 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
3064 for @code{set inferior-tty}.
3066 @cindex inferior tty
3067 @cindex set inferior controlling terminal
3068 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
3069 display the name of the terminal that will be used for future runs of your
3073 @item set inferior-tty [ @var{tty} ]
3074 @kindex set inferior-tty
3075 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
3076 restores the default behavior, which is to use the same terminal as
3079 @item show inferior-tty
3080 @kindex show inferior-tty
3081 Show the current tty for the program being debugged.
3085 @section Debugging an Already-running Process
3090 @item attach @var{process-id}
3091 This command attaches to a running process---one that was started
3092 outside @value{GDBN}. (@code{info files} shows your active
3093 targets.) The command takes as argument a process ID. The usual way to
3094 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
3095 or with the @samp{jobs -l} shell command.
3097 @code{attach} does not repeat if you press @key{RET} a second time after
3098 executing the command.
3101 To use @code{attach}, your program must be running in an environment
3102 which supports processes; for example, @code{attach} does not work for
3103 programs on bare-board targets that lack an operating system. You must
3104 also have permission to send the process a signal.
3106 When you use @code{attach}, the debugger finds the program running in
3107 the process first by looking in the current working directory, then (if
3108 the program is not found) by using the source file search path
3109 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
3110 the @code{file} command to load the program. @xref{Files, ,Commands to
3113 @anchor{set exec-file-mismatch}
3114 If the debugger can determine that the executable file running in the
3115 process it is attaching to does not match the current exec-file loaded
3116 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
3117 handle the mismatch. @value{GDBN} tries to compare the files by
3118 comparing their build IDs (@pxref{build ID}), if available.
3121 @kindex exec-file-mismatch
3122 @cindex set exec-file-mismatch
3123 @item set exec-file-mismatch @samp{ask|warn|off}
3125 Whether to detect mismatch between the current executable file loaded
3126 by @value{GDBN} and the executable file used to start the process. If
3127 @samp{ask}, the default, display a warning and ask the user whether to
3128 load the process executable file; if @samp{warn}, just display a
3129 warning; if @samp{off}, don't attempt to detect a mismatch.
3130 If the user confirms loading the process executable file, then its symbols
3131 will be loaded as well.
3133 @cindex show exec-file-mismatch
3134 @item show exec-file-mismatch
3135 Show the current value of @code{exec-file-mismatch}.
3139 The first thing @value{GDBN} does after arranging to debug the specified
3140 process is to stop it. You can examine and modify an attached process
3141 with all the @value{GDBN} commands that are ordinarily available when
3142 you start processes with @code{run}. You can insert breakpoints; you
3143 can step and continue; you can modify storage. If you would rather the
3144 process continue running, you may use the @code{continue} command after
3145 attaching @value{GDBN} to the process.
3150 When you have finished debugging the attached process, you can use the
3151 @code{detach} command to release it from @value{GDBN} control. Detaching
3152 the process continues its execution. After the @code{detach} command,
3153 that process and @value{GDBN} become completely independent once more, and you
3154 are ready to @code{attach} another process or start one with @code{run}.
3155 @code{detach} does not repeat if you press @key{RET} again after
3156 executing the command.
3159 If you exit @value{GDBN} while you have an attached process, you detach
3160 that process. If you use the @code{run} command, you kill that process.
3161 By default, @value{GDBN} asks for confirmation if you try to do either of these
3162 things; you can control whether or not you need to confirm by using the
3163 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3167 @section Killing the Child Process
3172 Kill the child process in which your program is running under @value{GDBN}.
3175 This command is useful if you wish to debug a core dump instead of a
3176 running process. @value{GDBN} ignores any core dump file while your program
3179 On some operating systems, a program cannot be executed outside @value{GDBN}
3180 while you have breakpoints set on it inside @value{GDBN}. You can use the
3181 @code{kill} command in this situation to permit running your program
3182 outside the debugger.
3184 The @code{kill} command is also useful if you wish to recompile and
3185 relink your program, since on many systems it is impossible to modify an
3186 executable file while it is running in a process. In this case, when you
3187 next type @code{run}, @value{GDBN} notices that the file has changed, and
3188 reads the symbol table again (while trying to preserve your current
3189 breakpoint settings).
3191 @node Inferiors Connections and Programs
3192 @section Debugging Multiple Inferiors Connections and Programs
3194 @value{GDBN} lets you run and debug multiple programs in a single
3195 session. In addition, @value{GDBN} on some systems may let you run
3196 several programs simultaneously (otherwise you have to exit from one
3197 before starting another). On some systems @value{GDBN} may even let
3198 you debug several programs simultaneously on different remote systems.
3199 In the most general case, you can have multiple threads of execution
3200 in each of multiple processes, launched from multiple executables,
3201 running on different machines.
3204 @value{GDBN} represents the state of each program execution with an
3205 object called an @dfn{inferior}. An inferior typically corresponds to
3206 a process, but is more general and applies also to targets that do not
3207 have processes. Inferiors may be created before a process runs, and
3208 may be retained after a process exits. Inferiors have unique
3209 identifiers that are different from process ids. Usually each
3210 inferior will also have its own distinct address space, although some
3211 embedded targets may have several inferiors running in different parts
3212 of a single address space. Each inferior may in turn have multiple
3213 threads running in it.
3215 To find out what inferiors exist at any moment, use @w{@code{info
3219 @kindex info inferiors [ @var{id}@dots{} ]
3220 @item info inferiors
3221 Print a list of all inferiors currently being managed by @value{GDBN}.
3222 By default all inferiors are printed, but the argument @var{id}@dots{}
3223 -- a space separated list of inferior numbers -- can be used to limit
3224 the display to just the requested inferiors.
3226 @value{GDBN} displays for each inferior (in this order):
3230 the inferior number assigned by @value{GDBN}
3233 the target system's inferior identifier
3236 the target connection the inferior is bound to, including the unique
3237 connection number assigned by @value{GDBN}, and the protocol used by
3241 the name of the executable the inferior is running.
3246 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3247 indicates the current inferior.
3251 @c end table here to get a little more width for example
3254 (@value{GDBP}) info inferiors
3255 Num Description Connection Executable
3256 * 1 process 3401 1 (native) goodbye
3257 2 process 2307 2 (extended-remote host:10000) hello
3260 To get informations about the current inferior, use @code{inferior}:
3265 Shows information about the current inferior.
3269 @c end table here to get a little more width for example
3272 (@value{GDBP}) inferior
3273 [Current inferior is 1 [process 3401] (helloworld)]
3276 To find out what open target connections exist at any moment, use
3277 @w{@code{info connections}}:
3280 @kindex info connections [ @var{id}@dots{} ]
3281 @item info connections
3282 Print a list of all open target connections currently being managed by
3283 @value{GDBN}. By default all connections are printed, but the
3284 argument @var{id}@dots{} -- a space separated list of connections
3285 numbers -- can be used to limit the display to just the requested
3288 @value{GDBN} displays for each connection (in this order):
3292 the connection number assigned by @value{GDBN}.
3295 the protocol used by the connection.
3298 a textual description of the protocol used by the connection.
3303 An asterisk @samp{*} preceding the connection number indicates the
3304 connection of the current inferior.
3308 @c end table here to get a little more width for example
3311 (@value{GDBP}) info connections
3312 Num What Description
3313 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3314 2 native Native process
3315 3 core Local core dump file
3318 To switch focus between inferiors, use the @code{inferior} command:
3321 @kindex inferior @var{infno}
3322 @item inferior @var{infno}
3323 Make inferior number @var{infno} the current inferior. The argument
3324 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3325 in the first field of the @samp{info inferiors} display.
3328 @vindex $_inferior@r{, convenience variable}
3329 The debugger convenience variable @samp{$_inferior} contains the
3330 number of the current inferior. You may find this useful in writing
3331 breakpoint conditional expressions, command scripts, and so forth.
3332 @xref{Convenience Vars,, Convenience Variables}, for general
3333 information on convenience variables.
3335 You can get multiple executables into a debugging session via the
3336 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3337 systems @value{GDBN} can add inferiors to the debug session
3338 automatically by following calls to @code{fork} and @code{exec}. To
3339 remove inferiors from the debugging session use the
3340 @w{@code{remove-inferiors}} command.
3343 @anchor{add_inferior_cli}
3344 @kindex add-inferior
3345 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3346 Adds @var{n} inferiors to be run using @var{executable} as the
3347 executable; @var{n} defaults to 1. If no executable is specified,
3348 the inferiors begins empty, with no program. You can still assign or
3349 change the program assigned to the inferior at any time by using the
3350 @code{file} command with the executable name as its argument.
3352 By default, the new inferior begins connected to the same target
3353 connection as the current inferior. For example, if the current
3354 inferior was connected to @code{gdbserver} with @code{target remote},
3355 then the new inferior will be connected to the same @code{gdbserver}
3356 instance. The @samp{-no-connection} option starts the new inferior
3357 with no connection yet. You can then for example use the @code{target
3358 remote} command to connect to some other @code{gdbserver} instance,
3359 use @code{run} to spawn a local program, etc.
3361 @kindex clone-inferior
3362 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3363 Adds @var{n} inferiors ready to execute the same program as inferior
3364 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3365 number of the current inferior. This command copies the values of the
3366 @var{args}, @w{@var{inferior-tty}} and @var{cwd} properties from the
3367 current inferior to the new one. It also propagates changes the user
3368 made to environment variables using the @w{@code{set environment}} and
3369 @w{@code{unset environment}} commands. This is a convenient command
3370 when you want to run another instance of the inferior you are debugging.
3373 (@value{GDBP}) info inferiors
3374 Num Description Connection Executable
3375 * 1 process 29964 1 (native) helloworld
3376 (@value{GDBP}) clone-inferior
3379 (@value{GDBP}) info inferiors
3380 Num Description Connection Executable
3381 * 1 process 29964 1 (native) helloworld
3382 2 <null> 1 (native) helloworld
3385 You can now simply switch focus to inferior 2 and run it.
3387 @kindex remove-inferiors
3388 @item remove-inferiors @var{infno}@dots{}
3389 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3390 possible to remove an inferior that is running with this command. For
3391 those, use the @code{kill} or @code{detach} command first.
3395 To quit debugging one of the running inferiors that is not the current
3396 inferior, you can either detach from it by using the @w{@code{detach
3397 inferior}} command (allowing it to run independently), or kill it
3398 using the @w{@code{kill inferiors}} command:
3401 @kindex detach inferiors @var{infno}@dots{}
3402 @item detach inferior @var{infno}@dots{}
3403 Detach from the inferior or inferiors identified by @value{GDBN}
3404 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3405 still stays on the list of inferiors shown by @code{info inferiors},
3406 but its Description will show @samp{<null>}.
3408 @kindex kill inferiors @var{infno}@dots{}
3409 @item kill inferiors @var{infno}@dots{}
3410 Kill the inferior or inferiors identified by @value{GDBN} inferior
3411 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3412 stays on the list of inferiors shown by @code{info inferiors}, but its
3413 Description will show @samp{<null>}.
3416 After the successful completion of a command such as @code{detach},
3417 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3418 a normal process exit, the inferior is still valid and listed with
3419 @code{info inferiors}, ready to be restarted.
3422 To be notified when inferiors are started or exit under @value{GDBN}'s
3423 control use @w{@code{set print inferior-events}}:
3426 @kindex set print inferior-events
3427 @cindex print messages on inferior start and exit
3428 @item set print inferior-events
3429 @itemx set print inferior-events on
3430 @itemx set print inferior-events off
3431 The @code{set print inferior-events} command allows you to enable or
3432 disable printing of messages when @value{GDBN} notices that new
3433 inferiors have started or that inferiors have exited or have been
3434 detached. By default, these messages will be printed.
3436 @kindex show print inferior-events
3437 @item show print inferior-events
3438 Show whether messages will be printed when @value{GDBN} detects that
3439 inferiors have started, exited or have been detached.
3442 Many commands will work the same with multiple programs as with a
3443 single program: e.g., @code{print myglobal} will simply display the
3444 value of @code{myglobal} in the current inferior.
3447 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3448 get more info about the relationship of inferiors, programs, address
3449 spaces in a debug session. You can do that with the @w{@code{maint
3450 info program-spaces}} command.
3453 @kindex maint info program-spaces
3454 @item maint info program-spaces
3455 Print a list of all program spaces currently being managed by
3458 @value{GDBN} displays for each program space (in this order):
3462 the program space number assigned by @value{GDBN}
3465 the name of the executable loaded into the program space, with e.g.,
3466 the @code{file} command.
3471 An asterisk @samp{*} preceding the @value{GDBN} program space number
3472 indicates the current program space.
3474 In addition, below each program space line, @value{GDBN} prints extra
3475 information that isn't suitable to display in tabular form. For
3476 example, the list of inferiors bound to the program space.
3479 (@value{GDBP}) maint info program-spaces
3483 Bound inferiors: ID 1 (process 21561)
3486 Here we can see that no inferior is running the program @code{hello},
3487 while @code{process 21561} is running the program @code{goodbye}. On
3488 some targets, it is possible that multiple inferiors are bound to the
3489 same program space. The most common example is that of debugging both
3490 the parent and child processes of a @code{vfork} call. For example,
3493 (@value{GDBP}) maint info program-spaces
3496 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3499 Here, both inferior 2 and inferior 1 are running in the same program
3500 space as a result of inferior 1 having executed a @code{vfork} call.
3504 @section Debugging Programs with Multiple Threads
3506 @cindex threads of execution
3507 @cindex multiple threads
3508 @cindex switching threads
3509 In some operating systems, such as GNU/Linux and Solaris, a single program
3510 may have more than one @dfn{thread} of execution. The precise semantics
3511 of threads differ from one operating system to another, but in general
3512 the threads of a single program are akin to multiple processes---except
3513 that they share one address space (that is, they can all examine and
3514 modify the same variables). On the other hand, each thread has its own
3515 registers and execution stack, and perhaps private memory.
3517 @value{GDBN} provides these facilities for debugging multi-thread
3521 @item automatic notification of new threads
3522 @item @samp{thread @var{thread-id}}, a command to switch among threads
3523 @item @samp{info threads}, a command to inquire about existing threads
3524 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3525 a command to apply a command to a list of threads
3526 @item thread-specific breakpoints
3527 @item @samp{set print thread-events}, which controls printing of
3528 messages on thread start and exit.
3529 @item @samp{set libthread-db-search-path @var{path}}, which lets
3530 the user specify which @code{libthread_db} to use if the default choice
3531 isn't compatible with the program.
3534 @cindex focus of debugging
3535 @cindex current thread
3536 The @value{GDBN} thread debugging facility allows you to observe all
3537 threads while your program runs---but whenever @value{GDBN} takes
3538 control, one thread in particular is always the focus of debugging.
3539 This thread is called the @dfn{current thread}. Debugging commands show
3540 program information from the perspective of the current thread.
3542 @cindex @code{New} @var{systag} message
3543 @cindex thread identifier (system)
3544 @c FIXME-implementors!! It would be more helpful if the [New...] message
3545 @c included GDB's numeric thread handle, so you could just go to that
3546 @c thread without first checking `info threads'.
3547 Whenever @value{GDBN} detects a new thread in your program, it displays
3548 the target system's identification for the thread with a message in the
3549 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3550 whose form varies depending on the particular system. For example, on
3551 @sc{gnu}/Linux, you might see
3554 [New Thread 0x41e02940 (LWP 25582)]
3558 when @value{GDBN} notices a new thread. In contrast, on other systems,
3559 the @var{systag} is simply something like @samp{process 368}, with no
3562 @c FIXME!! (1) Does the [New...] message appear even for the very first
3563 @c thread of a program, or does it only appear for the
3564 @c second---i.e.@: when it becomes obvious we have a multithread
3566 @c (2) *Is* there necessarily a first thread always? Or do some
3567 @c multithread systems permit starting a program with multiple
3568 @c threads ab initio?
3570 @anchor{thread numbers}
3571 @cindex thread number, per inferior
3572 @cindex thread identifier (GDB)
3573 For debugging purposes, @value{GDBN} associates its own thread number
3574 ---always a single integer---with each thread of an inferior. This
3575 number is unique between all threads of an inferior, but not unique
3576 between threads of different inferiors.
3578 @cindex qualified thread ID
3579 You can refer to a given thread in an inferior using the qualified
3580 @var{inferior-num}.@var{thread-num} syntax, also known as
3581 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3582 number and @var{thread-num} being the thread number of the given
3583 inferior. For example, thread @code{2.3} refers to thread number 3 of
3584 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3585 then @value{GDBN} infers you're referring to a thread of the current
3588 Until you create a second inferior, @value{GDBN} does not show the
3589 @var{inferior-num} part of thread IDs, even though you can always use
3590 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3591 of inferior 1, the initial inferior.
3593 @anchor{thread ID lists}
3594 @cindex thread ID lists
3595 Some commands accept a space-separated @dfn{thread ID list} as
3596 argument. A list element can be:
3600 A thread ID as shown in the first field of the @samp{info threads}
3601 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3605 A range of thread numbers, again with or without an inferior
3606 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3607 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3610 All threads of an inferior, specified with a star wildcard, with or
3611 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3612 @samp{1.*}) or @code{*}. The former refers to all threads of the
3613 given inferior, and the latter form without an inferior qualifier
3614 refers to all threads of the current inferior.
3618 For example, if the current inferior is 1, and inferior 7 has one
3619 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3620 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3621 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3622 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3626 @anchor{global thread numbers}
3627 @cindex global thread number
3628 @cindex global thread identifier (GDB)
3629 In addition to a @emph{per-inferior} number, each thread is also
3630 assigned a unique @emph{global} number, also known as @dfn{global
3631 thread ID}, a single integer. Unlike the thread number component of
3632 the thread ID, no two threads have the same global ID, even when
3633 you're debugging multiple inferiors.
3635 From @value{GDBN}'s perspective, a process always has at least one
3636 thread. In other words, @value{GDBN} assigns a thread number to the
3637 program's ``main thread'' even if the program is not multi-threaded.
3639 @vindex $_thread@r{, convenience variable}
3640 @vindex $_gthread@r{, convenience variable}
3641 The debugger convenience variables @samp{$_thread} and
3642 @samp{$_gthread} contain, respectively, the per-inferior thread number
3643 and the global thread number of the current thread. You may find this
3644 useful in writing breakpoint conditional expressions, command scripts,
3645 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3646 general information on convenience variables.
3648 If @value{GDBN} detects the program is multi-threaded, it augments the
3649 usual message about stopping at a breakpoint with the ID and name of
3650 the thread that hit the breakpoint.
3653 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3656 Likewise when the program receives a signal:
3659 Thread 1 "main" received signal SIGINT, Interrupt.
3663 @anchor{info_threads}
3664 @kindex info threads
3665 @item info threads @r{[}@var{thread-id-list}@r{]}
3667 Display information about one or more threads. With no arguments
3668 displays information about all threads. You can specify the list of
3669 threads that you want to display using the thread ID list syntax
3670 (@pxref{thread ID lists}).
3672 @value{GDBN} displays for each thread (in this order):
3676 the per-inferior thread number assigned by @value{GDBN}
3679 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3680 option was specified
3683 the target system's thread identifier (@var{systag})
3686 the thread's name, if one is known. A thread can either be named by
3687 the user (see @code{thread name}, below), or, in some cases, by the
3691 the current stack frame summary for that thread
3695 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3696 indicates the current thread.
3700 @c end table here to get a little more width for example
3703 (@value{GDBP}) info threads
3705 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3706 2 process 35 thread 23 0x34e5 in sigpause ()
3707 3 process 35 thread 27 0x34e5 in sigpause ()
3711 If you're debugging multiple inferiors, @value{GDBN} displays thread
3712 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3713 Otherwise, only @var{thread-num} is shown.
3715 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3716 indicating each thread's global thread ID:
3719 (@value{GDBP}) info threads
3720 Id GId Target Id Frame
3721 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3722 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3723 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3724 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3727 On Solaris, you can display more information about user threads with a
3728 Solaris-specific command:
3731 @item maint info sol-threads
3732 @kindex maint info sol-threads
3733 @cindex thread info (Solaris)
3734 Display info on Solaris user threads.
3738 @kindex thread @var{thread-id}
3739 @item thread @var{thread-id}
3740 Make thread ID @var{thread-id} the current thread. The command
3741 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3742 the first field of the @samp{info threads} display, with or without an
3743 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3745 @value{GDBN} responds by displaying the system identifier of the
3746 thread you selected, and its current stack frame summary:
3749 (@value{GDBP}) thread 2
3750 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3751 #0 some_function (ignore=0x0) at example.c:8
3752 8 printf ("hello\n");
3756 As with the @samp{[New @dots{}]} message, the form of the text after
3757 @samp{Switching to} depends on your system's conventions for identifying
3760 @anchor{thread apply all}
3761 @kindex thread apply
3762 @cindex apply command to several threads
3763 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3764 The @code{thread apply} command allows you to apply the named
3765 @var{command} to one or more threads. Specify the threads that you
3766 want affected using the thread ID list syntax (@pxref{thread ID
3767 lists}), or specify @code{all} to apply to all threads. To apply a
3768 command to all threads in descending order, type @kbd{thread apply all
3769 @var{command}}. To apply a command to all threads in ascending order,
3770 type @kbd{thread apply all -ascending @var{command}}.
3772 The @var{flag} arguments control what output to produce and how to handle
3773 errors raised when applying @var{command} to a thread. @var{flag}
3774 must start with a @code{-} directly followed by one letter in
3775 @code{qcs}. If several flags are provided, they must be given
3776 individually, such as @code{-c -q}.
3778 By default, @value{GDBN} displays some thread information before the
3779 output produced by @var{command}, and an error raised during the
3780 execution of a @var{command} will abort @code{thread apply}. The
3781 following flags can be used to fine-tune this behavior:
3785 The flag @code{-c}, which stands for @samp{continue}, causes any
3786 errors in @var{command} to be displayed, and the execution of
3787 @code{thread apply} then continues.
3789 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3790 or empty output produced by a @var{command} to be silently ignored.
3791 That is, the execution continues, but the thread information and errors
3794 The flag @code{-q} (@samp{quiet}) disables printing the thread
3798 Flags @code{-c} and @code{-s} cannot be used together.
3801 @cindex apply command to all threads (ignoring errors and empty output)
3802 @item taas [@var{option}]@dots{} @var{command}
3803 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3804 Applies @var{command} on all threads, ignoring errors and empty output.
3806 The @code{taas} command accepts the same options as the @code{thread
3807 apply all} command. @xref{thread apply all}.
3810 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3811 @item tfaas [@var{option}]@dots{} @var{command}
3812 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3813 Applies @var{command} on all frames of all threads, ignoring errors
3814 and empty output. Note that the flag @code{-s} is specified twice:
3815 The first @code{-s} ensures that @code{thread apply} only shows the thread
3816 information of the threads for which @code{frame apply} produces
3817 some output. The second @code{-s} is needed to ensure that @code{frame
3818 apply} shows the frame information of a frame only if the
3819 @var{command} successfully produced some output.
3821 It can for example be used to print a local variable or a function
3822 argument without knowing the thread or frame where this variable or argument
3825 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3828 The @code{tfaas} command accepts the same options as the @code{frame
3829 apply} command. @xref{Frame Apply,,frame apply}.
3832 @cindex name a thread
3833 @item thread name [@var{name}]
3834 This command assigns a name to the current thread. If no argument is
3835 given, any existing user-specified name is removed. The thread name
3836 appears in the @samp{info threads} display.
3838 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3839 determine the name of the thread as given by the OS. On these
3840 systems, a name specified with @samp{thread name} will override the
3841 system-give name, and removing the user-specified name will cause
3842 @value{GDBN} to once again display the system-specified name.
3845 @cindex search for a thread
3846 @item thread find [@var{regexp}]
3847 Search for and display thread ids whose name or @var{systag}
3848 matches the supplied regular expression.
3850 As well as being the complement to the @samp{thread name} command,
3851 this command also allows you to identify a thread by its target
3852 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3856 (@value{GDBN}) thread find 26688
3857 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3858 (@value{GDBN}) info thread 4
3860 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3863 @kindex set print thread-events
3864 @cindex print messages on thread start and exit
3865 @item set print thread-events
3866 @itemx set print thread-events on
3867 @itemx set print thread-events off
3868 The @code{set print thread-events} command allows you to enable or
3869 disable printing of messages when @value{GDBN} notices that new threads have
3870 started or that threads have exited. By default, these messages will
3871 be printed if detection of these events is supported by the target.
3872 Note that these messages cannot be disabled on all targets.
3874 @kindex show print thread-events
3875 @item show print thread-events
3876 Show whether messages will be printed when @value{GDBN} detects that threads
3877 have started and exited.
3880 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3881 more information about how @value{GDBN} behaves when you stop and start
3882 programs with multiple threads.
3884 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3885 watchpoints in programs with multiple threads.
3887 @anchor{set libthread-db-search-path}
3889 @kindex set libthread-db-search-path
3890 @cindex search path for @code{libthread_db}
3891 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3892 If this variable is set, @var{path} is a colon-separated list of
3893 directories @value{GDBN} will use to search for @code{libthread_db}.
3894 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3895 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3896 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3899 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3900 @code{libthread_db} library to obtain information about threads in the
3901 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3902 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3903 specific thread debugging library loading is enabled
3904 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3906 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3907 refers to the default system directories that are
3908 normally searched for loading shared libraries. The @samp{$sdir} entry
3909 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3910 (@pxref{libthread_db.so.1 file}).
3912 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3913 refers to the directory from which @code{libpthread}
3914 was loaded in the inferior process.
3916 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3917 @value{GDBN} attempts to initialize it with the current inferior process.
3918 If this initialization fails (which could happen because of a version
3919 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3920 will unload @code{libthread_db}, and continue with the next directory.
3921 If none of @code{libthread_db} libraries initialize successfully,
3922 @value{GDBN} will issue a warning and thread debugging will be disabled.
3924 Setting @code{libthread-db-search-path} is currently implemented
3925 only on some platforms.
3927 @kindex show libthread-db-search-path
3928 @item show libthread-db-search-path
3929 Display current libthread_db search path.
3931 @kindex set debug libthread-db
3932 @kindex show debug libthread-db
3933 @cindex debugging @code{libthread_db}
3934 @item set debug libthread-db
3935 @itemx show debug libthread-db
3936 Turns on or off display of @code{libthread_db}-related events.
3937 Use @code{1} to enable, @code{0} to disable.
3939 @kindex set debug threads
3940 @kindex show debug threads
3941 @cindex debugging @code{threads}
3942 @item set debug threads @r{[}on@r{|}off@r{]}
3943 @itemx show debug threads
3944 When @samp{on} @value{GDBN} will print additional messages when
3945 threads are created and deleted.
3949 @section Debugging Forks
3951 @cindex fork, debugging programs which call
3952 @cindex multiple processes
3953 @cindex processes, multiple
3954 On most systems, @value{GDBN} has no special support for debugging
3955 programs which create additional processes using the @code{fork}
3956 function. When a program forks, @value{GDBN} will continue to debug the
3957 parent process and the child process will run unimpeded. If you have
3958 set a breakpoint in any code which the child then executes, the child
3959 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3960 will cause it to terminate.
3962 However, if you want to debug the child process there is a workaround
3963 which isn't too painful. Put a call to @code{sleep} in the code which
3964 the child process executes after the fork. It may be useful to sleep
3965 only if a certain environment variable is set, or a certain file exists,
3966 so that the delay need not occur when you don't want to run @value{GDBN}
3967 on the child. While the child is sleeping, use the @code{ps} program to
3968 get its process ID. Then tell @value{GDBN} (a new invocation of
3969 @value{GDBN} if you are also debugging the parent process) to attach to
3970 the child process (@pxref{Attach}). From that point on you can debug
3971 the child process just like any other process which you attached to.
3973 On some systems, @value{GDBN} provides support for debugging programs
3974 that create additional processes using the @code{fork} or @code{vfork}
3975 functions. On @sc{gnu}/Linux platforms, this feature is supported
3976 with kernel version 2.5.46 and later.
3978 The fork debugging commands are supported in native mode and when
3979 connected to @code{gdbserver} in either @code{target remote} mode or
3980 @code{target extended-remote} mode.
3982 By default, when a program forks, @value{GDBN} will continue to debug
3983 the parent process and the child process will run unimpeded.
3985 If you want to follow the child process instead of the parent process,
3986 use the command @w{@code{set follow-fork-mode}}.
3989 @kindex set follow-fork-mode
3990 @item set follow-fork-mode @var{mode}
3991 Set the debugger response to a program call of @code{fork} or
3992 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3993 process. The @var{mode} argument can be:
3997 The original process is debugged after a fork. The child process runs
3998 unimpeded. This is the default.
4001 The new process is debugged after a fork. The parent process runs
4006 @kindex show follow-fork-mode
4007 @item show follow-fork-mode
4008 Display the current debugger response to a @code{fork} or @code{vfork} call.
4011 @cindex debugging multiple processes
4012 On Linux, if you want to debug both the parent and child processes, use the
4013 command @w{@code{set detach-on-fork}}.
4016 @kindex set detach-on-fork
4017 @item set detach-on-fork @var{mode}
4018 Tells gdb whether to detach one of the processes after a fork, or
4019 retain debugger control over them both.
4023 The child process (or parent process, depending on the value of
4024 @code{follow-fork-mode}) will be detached and allowed to run
4025 independently. This is the default.
4028 Both processes will be held under the control of @value{GDBN}.
4029 One process (child or parent, depending on the value of
4030 @code{follow-fork-mode}) is debugged as usual, while the other
4035 @kindex show detach-on-fork
4036 @item show detach-on-fork
4037 Show whether detach-on-fork mode is on/off.
4040 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
4041 will retain control of all forked processes (including nested forks).
4042 You can list the forked processes under the control of @value{GDBN} by
4043 using the @w{@code{info inferiors}} command, and switch from one fork
4044 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
4045 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
4047 To quit debugging one of the forked processes, you can either detach
4048 from it by using the @w{@code{detach inferiors}} command (allowing it
4049 to run independently), or kill it using the @w{@code{kill inferiors}}
4050 command. @xref{Inferiors Connections and Programs, ,Debugging
4051 Multiple Inferiors Connections and Programs}.
4053 If you ask to debug a child process and a @code{vfork} is followed by an
4054 @code{exec}, @value{GDBN} executes the new target up to the first
4055 breakpoint in the new target. If you have a breakpoint set on
4056 @code{main} in your original program, the breakpoint will also be set on
4057 the child process's @code{main}.
4059 On some systems, when a child process is spawned by @code{vfork}, you
4060 cannot debug the child or parent until an @code{exec} call completes.
4062 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
4063 call executes, the new target restarts. To restart the parent
4064 process, use the @code{file} command with the parent executable name
4065 as its argument. By default, after an @code{exec} call executes,
4066 @value{GDBN} discards the symbols of the previous executable image.
4067 You can change this behaviour with the @w{@code{set follow-exec-mode}}
4071 @kindex set follow-exec-mode
4072 @item set follow-exec-mode @var{mode}
4074 Set debugger response to a program call of @code{exec}. An
4075 @code{exec} call replaces the program image of a process.
4077 @code{follow-exec-mode} can be:
4081 @value{GDBN} creates a new inferior and rebinds the process to this
4082 new inferior. The program the process was running before the
4083 @code{exec} call can be restarted afterwards by restarting the
4089 (@value{GDBP}) info inferiors
4091 Id Description Executable
4094 process 12020 is executing new program: prog2
4095 Program exited normally.
4096 (@value{GDBP}) info inferiors
4097 Id Description Executable
4103 @value{GDBN} keeps the process bound to the same inferior. The new
4104 executable image replaces the previous executable loaded in the
4105 inferior. Restarting the inferior after the @code{exec} call, with
4106 e.g., the @code{run} command, restarts the executable the process was
4107 running after the @code{exec} call. This is the default mode.
4112 (@value{GDBP}) info inferiors
4113 Id Description Executable
4116 process 12020 is executing new program: prog2
4117 Program exited normally.
4118 (@value{GDBP}) info inferiors
4119 Id Description Executable
4126 @code{follow-exec-mode} is supported in native mode and
4127 @code{target extended-remote} mode.
4129 You can use the @code{catch} command to make @value{GDBN} stop whenever
4130 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
4131 Catchpoints, ,Setting Catchpoints}.
4133 @node Checkpoint/Restart
4134 @section Setting a @emph{Bookmark} to Return to Later
4139 @cindex snapshot of a process
4140 @cindex rewind program state
4142 On certain operating systems@footnote{Currently, only
4143 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4144 program's state, called a @dfn{checkpoint}, and come back to it
4147 Returning to a checkpoint effectively undoes everything that has
4148 happened in the program since the @code{checkpoint} was saved. This
4149 includes changes in memory, registers, and even (within some limits)
4150 system state. Effectively, it is like going back in time to the
4151 moment when the checkpoint was saved.
4153 Thus, if you're stepping thru a program and you think you're
4154 getting close to the point where things go wrong, you can save
4155 a checkpoint. Then, if you accidentally go too far and miss
4156 the critical statement, instead of having to restart your program
4157 from the beginning, you can just go back to the checkpoint and
4158 start again from there.
4160 This can be especially useful if it takes a lot of time or
4161 steps to reach the point where you think the bug occurs.
4163 To use the @code{checkpoint}/@code{restart} method of debugging:
4168 Save a snapshot of the debugged program's current execution state.
4169 The @code{checkpoint} command takes no arguments, but each checkpoint
4170 is assigned a small integer id, similar to a breakpoint id.
4172 @kindex info checkpoints
4173 @item info checkpoints
4174 List the checkpoints that have been saved in the current debugging
4175 session. For each checkpoint, the following information will be
4182 @item Source line, or label
4185 @kindex restart @var{checkpoint-id}
4186 @item restart @var{checkpoint-id}
4187 Restore the program state that was saved as checkpoint number
4188 @var{checkpoint-id}. All program variables, registers, stack frames
4189 etc.@: will be returned to the values that they had when the checkpoint
4190 was saved. In essence, gdb will ``wind back the clock'' to the point
4191 in time when the checkpoint was saved.
4193 Note that breakpoints, @value{GDBN} variables, command history etc.
4194 are not affected by restoring a checkpoint. In general, a checkpoint
4195 only restores things that reside in the program being debugged, not in
4198 @kindex delete checkpoint @var{checkpoint-id}
4199 @item delete checkpoint @var{checkpoint-id}
4200 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4204 Returning to a previously saved checkpoint will restore the user state
4205 of the program being debugged, plus a significant subset of the system
4206 (OS) state, including file pointers. It won't ``un-write'' data from
4207 a file, but it will rewind the file pointer to the previous location,
4208 so that the previously written data can be overwritten. For files
4209 opened in read mode, the pointer will also be restored so that the
4210 previously read data can be read again.
4212 Of course, characters that have been sent to a printer (or other
4213 external device) cannot be ``snatched back'', and characters received
4214 from eg.@: a serial device can be removed from internal program buffers,
4215 but they cannot be ``pushed back'' into the serial pipeline, ready to
4216 be received again. Similarly, the actual contents of files that have
4217 been changed cannot be restored (at this time).
4219 However, within those constraints, you actually can ``rewind'' your
4220 program to a previously saved point in time, and begin debugging it
4221 again --- and you can change the course of events so as to debug a
4222 different execution path this time.
4224 @cindex checkpoints and process id
4225 Finally, there is one bit of internal program state that will be
4226 different when you return to a checkpoint --- the program's process
4227 id. Each checkpoint will have a unique process id (or @var{pid}),
4228 and each will be different from the program's original @var{pid}.
4229 If your program has saved a local copy of its process id, this could
4230 potentially pose a problem.
4232 @subsection A Non-obvious Benefit of Using Checkpoints
4234 On some systems such as @sc{gnu}/Linux, address space randomization
4235 is performed on new processes for security reasons. This makes it
4236 difficult or impossible to set a breakpoint, or watchpoint, on an
4237 absolute address if you have to restart the program, since the
4238 absolute location of a symbol will change from one execution to the
4241 A checkpoint, however, is an @emph{identical} copy of a process.
4242 Therefore if you create a checkpoint at (eg.@:) the start of main,
4243 and simply return to that checkpoint instead of restarting the
4244 process, you can avoid the effects of address randomization and
4245 your symbols will all stay in the same place.
4248 @chapter Stopping and Continuing
4250 The principal purposes of using a debugger are so that you can stop your
4251 program before it terminates; or so that, if your program runs into
4252 trouble, you can investigate and find out why.
4254 Inside @value{GDBN}, your program may stop for any of several reasons,
4255 such as a signal, a breakpoint, or reaching a new line after a
4256 @value{GDBN} command such as @code{step}. You may then examine and
4257 change variables, set new breakpoints or remove old ones, and then
4258 continue execution. Usually, the messages shown by @value{GDBN} provide
4259 ample explanation of the status of your program---but you can also
4260 explicitly request this information at any time.
4263 @kindex info program
4265 Display information about the status of your program: whether it is
4266 running or not, what process it is, and why it stopped.
4270 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4271 * Continuing and Stepping:: Resuming execution
4272 * Skipping Over Functions and Files::
4273 Skipping over functions and files
4275 * Thread Stops:: Stopping and starting multi-thread programs
4279 @section Breakpoints, Watchpoints, and Catchpoints
4282 A @dfn{breakpoint} makes your program stop whenever a certain point in
4283 the program is reached. For each breakpoint, you can add conditions to
4284 control in finer detail whether your program stops. You can set
4285 breakpoints with the @code{break} command and its variants (@pxref{Set
4286 Breaks, ,Setting Breakpoints}), to specify the place where your program
4287 should stop by line number, function name or exact address in the
4290 On some systems, you can set breakpoints in shared libraries before
4291 the executable is run.
4294 @cindex data breakpoints
4295 @cindex memory tracing
4296 @cindex breakpoint on memory address
4297 @cindex breakpoint on variable modification
4298 A @dfn{watchpoint} is a special breakpoint that stops your program
4299 when the value of an expression changes. The expression may be a value
4300 of a variable, or it could involve values of one or more variables
4301 combined by operators, such as @samp{a + b}. This is sometimes called
4302 @dfn{data breakpoints}. You must use a different command to set
4303 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4304 from that, you can manage a watchpoint like any other breakpoint: you
4305 enable, disable, and delete both breakpoints and watchpoints using the
4308 You can arrange to have values from your program displayed automatically
4309 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4313 @cindex breakpoint on events
4314 A @dfn{catchpoint} is another special breakpoint that stops your program
4315 when a certain kind of event occurs, such as the throwing of a C@t{++}
4316 exception or the loading of a library. As with watchpoints, you use a
4317 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4318 Catchpoints}), but aside from that, you can manage a catchpoint like any
4319 other breakpoint. (To stop when your program receives a signal, use the
4320 @code{handle} command; see @ref{Signals, ,Signals}.)
4322 @cindex breakpoint numbers
4323 @cindex numbers for breakpoints
4324 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4325 catchpoint when you create it; these numbers are successive integers
4326 starting with one. In many of the commands for controlling various
4327 features of breakpoints you use the breakpoint number to say which
4328 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4329 @dfn{disabled}; if disabled, it has no effect on your program until you
4332 @cindex breakpoint ranges
4333 @cindex breakpoint lists
4334 @cindex ranges of breakpoints
4335 @cindex lists of breakpoints
4336 Some @value{GDBN} commands accept a space-separated list of breakpoints
4337 on which to operate. A list element can be either a single breakpoint number,
4338 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4339 When a breakpoint list is given to a command, all breakpoints in that list
4343 * Set Breaks:: Setting breakpoints
4344 * Set Watchpoints:: Setting watchpoints
4345 * Set Catchpoints:: Setting catchpoints
4346 * Delete Breaks:: Deleting breakpoints
4347 * Disabling:: Disabling breakpoints
4348 * Conditions:: Break conditions
4349 * Break Commands:: Breakpoint command lists
4350 * Dynamic Printf:: Dynamic printf
4351 * Save Breakpoints:: How to save breakpoints in a file
4352 * Static Probe Points:: Listing static probe points
4353 * Error in Breakpoints:: ``Cannot insert breakpoints''
4354 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4358 @subsection Setting Breakpoints
4360 @c FIXME LMB what does GDB do if no code on line of breakpt?
4361 @c consider in particular declaration with/without initialization.
4363 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4366 @kindex b @r{(@code{break})}
4367 @vindex $bpnum@r{, convenience variable}
4368 @cindex latest breakpoint
4369 Breakpoints are set with the @code{break} command (abbreviated
4370 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4371 number of the breakpoint you've set most recently; see @ref{Convenience
4372 Vars,, Convenience Variables}, for a discussion of what you can do with
4373 convenience variables.
4376 @item break @var{locspec}
4377 Set a breakpoint at all the code locations in your program that result
4378 from resolving the given @var{locspec}. @var{locspec} can specify a
4379 function name, a line number, an address of an instruction, and more.
4380 @xref{Location Specifications}, for the various forms of
4381 @var{locspec}. The breakpoint will stop your program just before it
4382 executes the instruction at the address of any of the breakpoint's
4385 When using source languages that permit overloading of symbols, such
4386 as C@t{++}, a function name may refer to more than one symbol, and
4387 thus more than one place to break. @xref{Ambiguous
4388 Expressions,,Ambiguous Expressions}, for a discussion of that
4391 It is also possible to insert a breakpoint that will stop the program
4392 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4393 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4396 When called without any arguments, @code{break} sets a breakpoint at
4397 the next instruction to be executed in the selected stack frame
4398 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4399 innermost, this makes your program stop as soon as control
4400 returns to that frame. This is similar to the effect of a
4401 @code{finish} command in the frame inside the selected frame---except
4402 that @code{finish} does not leave an active breakpoint. If you use
4403 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4404 the next time it reaches the current location; this may be useful
4407 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4408 least one instruction has been executed. If it did not do this, you
4409 would be unable to proceed past a breakpoint without first disabling the
4410 breakpoint. This rule applies whether or not the breakpoint already
4411 existed when your program stopped.
4413 @item break @dots{} if @var{cond}
4414 Set a breakpoint with condition @var{cond}; evaluate the expression
4415 @var{cond} each time the breakpoint is reached, and stop only if the
4416 value is nonzero---that is, if @var{cond} evaluates as true.
4417 @samp{@dots{}} stands for one of the possible arguments described
4418 above (or no argument) specifying where to break. @xref{Conditions,
4419 ,Break Conditions}, for more information on breakpoint conditions.
4421 The breakpoint may be mapped to multiple locations. If the breakpoint
4422 condition @var{cond} is invalid at some but not all of the locations,
4423 the locations for which the condition is invalid are disabled. For
4424 example, @value{GDBN} reports below that two of the three locations
4428 (@value{GDBP}) break func if a == 10
4429 warning: failed to validate condition at location 0x11ce, disabling:
4430 No symbol "a" in current context.
4431 warning: failed to validate condition at location 0x11b6, disabling:
4432 No symbol "a" in current context.
4433 Breakpoint 1 at 0x11b6: func. (3 locations)
4436 Locations that are disabled because of the condition are denoted by an
4437 uppercase @code{N} in the output of the @code{info breakpoints}
4441 (@value{GDBP}) info breakpoints
4442 Num Type Disp Enb Address What
4443 1 breakpoint keep y <MULTIPLE>
4444 stop only if a == 10
4445 1.1 N* 0x00000000000011b6 in ...
4446 1.2 y 0x00000000000011c2 in ...
4447 1.3 N* 0x00000000000011ce in ...
4448 (*): Breakpoint condition is invalid at this location.
4451 If the breakpoint condition @var{cond} is invalid in the context of
4452 @emph{all} the locations of the breakpoint, @value{GDBN} refuses to
4453 define the breakpoint. For example, if variable @code{foo} is an
4457 (@value{GDBP}) break func if foo
4458 No symbol "foo" in current context.
4461 @item break @dots{} -force-condition if @var{cond}
4462 There may be cases where the condition @var{cond} is invalid at all
4463 the current locations, but the user knows that it will be valid at a
4464 future location; for example, because of a library load. In such
4465 cases, by using the @code{-force-condition} keyword before @samp{if},
4466 @value{GDBN} can be forced to define the breakpoint with the given
4467 condition expression instead of refusing it.
4470 (@value{GDBP}) break func -force-condition if foo
4471 warning: failed to validate condition at location 1, disabling:
4472 No symbol "foo" in current context.
4473 warning: failed to validate condition at location 2, disabling:
4474 No symbol "foo" in current context.
4475 warning: failed to validate condition at location 3, disabling:
4476 No symbol "foo" in current context.
4477 Breakpoint 1 at 0x1158: test.c:18. (3 locations)
4480 This causes all the present locations where the breakpoint would
4481 otherwise be inserted, to be disabled, as seen in the example above.
4482 However, if there exist locations at which the condition is valid, the
4483 @code{-force-condition} keyword has no effect.
4486 @item tbreak @var{args}
4487 Set a breakpoint enabled only for one stop. The @var{args} are the
4488 same as for the @code{break} command, and the breakpoint is set in the same
4489 way, but the breakpoint is automatically deleted after the first time your
4490 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4493 @cindex hardware breakpoints
4494 @item hbreak @var{args}
4495 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4496 @code{break} command and the breakpoint is set in the same way, but the
4497 breakpoint requires hardware support and some target hardware may not
4498 have this support. The main purpose of this is EPROM/ROM code
4499 debugging, so you can set a breakpoint at an instruction without
4500 changing the instruction. This can be used with the new trap-generation
4501 provided by SPARClite DSU and most x86-based targets. These targets
4502 will generate traps when a program accesses some data or instruction
4503 address that is assigned to the debug registers. However the hardware
4504 breakpoint registers can take a limited number of breakpoints. For
4505 example, on the DSU, only two data breakpoints can be set at a time, and
4506 @value{GDBN} will reject this command if more than two are used. Delete
4507 or disable unused hardware breakpoints before setting new ones
4508 (@pxref{Disabling, ,Disabling Breakpoints}).
4509 @xref{Conditions, ,Break Conditions}.
4510 For remote targets, you can restrict the number of hardware
4511 breakpoints @value{GDBN} will use, see @ref{set remote
4512 hardware-breakpoint-limit}.
4515 @item thbreak @var{args}
4516 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4517 are the same as for the @code{hbreak} command and the breakpoint is set in
4518 the same way. However, like the @code{tbreak} command,
4519 the breakpoint is automatically deleted after the
4520 first time your program stops there. Also, like the @code{hbreak}
4521 command, the breakpoint requires hardware support and some target hardware
4522 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4523 See also @ref{Conditions, ,Break Conditions}.
4526 @cindex regular expression
4527 @cindex breakpoints at functions matching a regexp
4528 @cindex set breakpoints in many functions
4529 @item rbreak @var{regex}
4530 Set breakpoints on all functions matching the regular expression
4531 @var{regex}. This command sets an unconditional breakpoint on all
4532 matches, printing a list of all breakpoints it set. Once these
4533 breakpoints are set, they are treated just like the breakpoints set with
4534 the @code{break} command. You can delete them, disable them, or make
4535 them conditional the same way as any other breakpoint.
4537 In programs using different languages, @value{GDBN} chooses the syntax
4538 to print the list of all breakpoints it sets according to the
4539 @samp{set language} value: using @samp{set language auto}
4540 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4541 language of the breakpoint's function, other values mean to use
4542 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4544 The syntax of the regular expression is the standard one used with tools
4545 like @file{grep}. Note that this is different from the syntax used by
4546 shells, so for instance @code{foo*} matches all functions that include
4547 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4548 @code{.*} leading and trailing the regular expression you supply, so to
4549 match only functions that begin with @code{foo}, use @code{^foo}.
4551 @cindex non-member C@t{++} functions, set breakpoint in
4552 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4553 breakpoints on overloaded functions that are not members of any special
4556 @cindex set breakpoints on all functions
4557 The @code{rbreak} command can be used to set breakpoints in
4558 @strong{all} the functions in a program, like this:
4561 (@value{GDBP}) rbreak .
4564 @item rbreak @var{file}:@var{regex}
4565 If @code{rbreak} is called with a filename qualification, it limits
4566 the search for functions matching the given regular expression to the
4567 specified @var{file}. This can be used, for example, to set breakpoints on
4568 every function in a given file:
4571 (@value{GDBP}) rbreak file.c:.
4574 The colon separating the filename qualifier from the regex may
4575 optionally be surrounded by spaces.
4577 @kindex info breakpoints
4578 @cindex @code{$_} and @code{info breakpoints}
4579 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4580 @itemx info break @r{[}@var{list}@dots{}@r{]}
4581 Print a table of all breakpoints, watchpoints, and catchpoints set and
4582 not deleted. Optional argument @var{n} means print information only
4583 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4584 For each breakpoint, following columns are printed:
4587 @item Breakpoint Numbers
4589 Breakpoint, watchpoint, or catchpoint.
4591 Whether the breakpoint is marked to be disabled or deleted when hit.
4592 @item Enabled or Disabled
4593 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4594 that are not enabled.
4596 Where the breakpoint is in your program, as a memory address. For a
4597 pending breakpoint whose address is not yet known, this field will
4598 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4599 library that has the symbol or line referred by breakpoint is loaded.
4600 See below for details. A breakpoint with several locations will
4601 have @samp{<MULTIPLE>} in this field---see below for details.
4603 Where the breakpoint is in the source for your program, as a file and
4604 line number. For a pending breakpoint, the original string passed to
4605 the breakpoint command will be listed as it cannot be resolved until
4606 the appropriate shared library is loaded in the future.
4610 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4611 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4612 @value{GDBN} on the host's side. If it is ``target'', then the condition
4613 is evaluated by the target. The @code{info break} command shows
4614 the condition on the line following the affected breakpoint, together with
4615 its condition evaluation mode in between parentheses.
4617 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4618 allowed to have a condition specified for it. The condition is not parsed for
4619 validity until a shared library is loaded that allows the pending
4620 breakpoint to resolve to a valid location.
4623 @code{info break} with a breakpoint
4624 number @var{n} as argument lists only that breakpoint. The
4625 convenience variable @code{$_} and the default examining-address for
4626 the @code{x} command are set to the address of the last breakpoint
4627 listed (@pxref{Memory, ,Examining Memory}).
4630 @code{info break} displays a count of the number of times the breakpoint
4631 has been hit. This is especially useful in conjunction with the
4632 @code{ignore} command. You can ignore a large number of breakpoint
4633 hits, look at the breakpoint info to see how many times the breakpoint
4634 was hit, and then run again, ignoring one less than that number. This
4635 will get you quickly to the last hit of that breakpoint.
4638 For a breakpoints with an enable count (xref) greater than 1,
4639 @code{info break} also displays that count.
4643 @value{GDBN} allows you to set any number of breakpoints at the same place in
4644 your program. There is nothing silly or meaningless about this. When
4645 the breakpoints are conditional, this is even useful
4646 (@pxref{Conditions, ,Break Conditions}).
4648 @cindex multiple locations, breakpoints
4649 @cindex breakpoints, multiple locations
4650 It is possible that a single logical breakpoint is set at several code
4651 locations in your program. @xref{Location Specifications}, for
4654 A breakpoint with multiple code locations is displayed in the
4655 breakpoint table using several rows---one header row, followed by one
4656 row for each code location. The header row has @samp{<MULTIPLE>} in
4657 the address column. Each code location row contains the actual
4658 address, source file, source line and function of its code location.
4659 The number column for a code location is of the form
4660 @var{breakpoint-number}.@var{location-number}.
4665 Num Type Disp Enb Address What
4666 1 breakpoint keep y <MULTIPLE>
4668 breakpoint already hit 1 time
4669 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4670 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4673 You cannot delete the individual locations from a breakpoint. However,
4674 each location can be individually enabled or disabled by passing
4675 @var{breakpoint-number}.@var{location-number} as argument to the
4676 @code{enable} and @code{disable} commands. It's also possible to
4677 @code{enable} and @code{disable} a range of @var{location-number}
4678 locations using a @var{breakpoint-number} and two @var{location-number}s,
4679 in increasing order, separated by a hyphen, like
4680 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4681 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4682 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4683 all of the locations that belong to that breakpoint.
4685 Locations that are enabled while their parent breakpoint is disabled
4686 won't trigger a break, and are denoted by @code{y-} in the @code{Enb}
4687 column. For example:
4690 (@value{GDBP}) info breakpoints
4691 Num Type Disp Enb Address What
4692 1 breakpoint keep n <MULTIPLE>
4693 1.1 y- 0x00000000000011b6 in ...
4694 1.2 y- 0x00000000000011c2 in ...
4695 1.3 n 0x00000000000011ce in ...
4698 @cindex pending breakpoints
4699 It's quite common to have a breakpoint inside a shared library.
4700 Shared libraries can be loaded and unloaded explicitly,
4701 and possibly repeatedly, as the program is executed. To support
4702 this use case, @value{GDBN} updates breakpoint locations whenever
4703 any shared library is loaded or unloaded. Typically, you would
4704 set a breakpoint in a shared library at the beginning of your
4705 debugging session, when the library is not loaded, and when the
4706 symbols from the library are not available. When you try to set
4707 breakpoint, @value{GDBN} will ask you if you want to set
4708 a so called @dfn{pending breakpoint}---breakpoint whose address
4709 is not yet resolved.
4711 After the program is run, whenever a new shared library is loaded,
4712 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4713 shared library contains the symbol or line referred to by some
4714 pending breakpoint, that breakpoint is resolved and becomes an
4715 ordinary breakpoint. When a library is unloaded, all breakpoints
4716 that refer to its symbols or source lines become pending again.
4718 This logic works for breakpoints with multiple locations, too. For
4719 example, if you have a breakpoint in a C@t{++} template function, and
4720 a newly loaded shared library has an instantiation of that template,
4721 a new location is added to the list of locations for the breakpoint.
4723 Except for having unresolved address, pending breakpoints do not
4724 differ from regular breakpoints. You can set conditions or commands,
4725 enable and disable them and perform other breakpoint operations.
4727 @value{GDBN} provides some additional commands for controlling what
4728 happens when the @samp{break} command cannot resolve the location spec
4729 to any code location in your program (@pxref{Location
4732 @kindex set breakpoint pending
4733 @kindex show breakpoint pending
4735 @item set breakpoint pending auto
4736 This is the default behavior. When @value{GDBN} cannot resolve the
4737 location spec, it queries you whether a pending breakpoint should be
4740 @item set breakpoint pending on
4741 This indicates that when @value{GDBN} cannot resolve the location
4742 spec, it should create a pending breakpoint without confirmation.
4744 @item set breakpoint pending off
4745 This indicates that pending breakpoints are not to be created. If
4746 @value{GDBN} cannot resolve the location spec, it aborts the
4747 breakpoint creation with an error. This setting does not affect any
4748 pending breakpoints previously created.
4750 @item show breakpoint pending
4751 Show the current behavior setting for creating pending breakpoints.
4754 The settings above only affect the @code{break} command and its
4755 variants. Once a breakpoint is set, it will be automatically updated
4756 as shared libraries are loaded and unloaded.
4758 @cindex automatic hardware breakpoints
4759 For some targets, @value{GDBN} can automatically decide if hardware or
4760 software breakpoints should be used, depending on whether the
4761 breakpoint address is read-only or read-write. This applies to
4762 breakpoints set with the @code{break} command as well as to internal
4763 breakpoints set by commands like @code{next} and @code{finish}. For
4764 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4767 You can control this automatic behaviour with the following commands:
4769 @kindex set breakpoint auto-hw
4770 @kindex show breakpoint auto-hw
4772 @item set breakpoint auto-hw on
4773 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4774 will try to use the target memory map to decide if software or hardware
4775 breakpoint must be used.
4777 @item set breakpoint auto-hw off
4778 This indicates @value{GDBN} should not automatically select breakpoint
4779 type. If the target provides a memory map, @value{GDBN} will warn when
4780 trying to set software breakpoint at a read-only address.
4783 @value{GDBN} normally implements breakpoints by replacing the program code
4784 at the breakpoint address with a special instruction, which, when
4785 executed, given control to the debugger. By default, the program
4786 code is so modified only when the program is resumed. As soon as
4787 the program stops, @value{GDBN} restores the original instructions. This
4788 behaviour guards against leaving breakpoints inserted in the
4789 target should gdb abrubptly disconnect. However, with slow remote
4790 targets, inserting and removing breakpoint can reduce the performance.
4791 This behavior can be controlled with the following commands::
4793 @kindex set breakpoint always-inserted
4794 @kindex show breakpoint always-inserted
4796 @item set breakpoint always-inserted off
4797 All breakpoints, including newly added by the user, are inserted in
4798 the target only when the target is resumed. All breakpoints are
4799 removed from the target when it stops. This is the default mode.
4801 @item set breakpoint always-inserted on
4802 Causes all breakpoints to be inserted in the target at all times. If
4803 the user adds a new breakpoint, or changes an existing breakpoint, the
4804 breakpoints in the target are updated immediately. A breakpoint is
4805 removed from the target only when breakpoint itself is deleted.
4808 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4809 when a breakpoint breaks. If the condition is true, then the process being
4810 debugged stops, otherwise the process is resumed.
4812 If the target supports evaluating conditions on its end, @value{GDBN} may
4813 download the breakpoint, together with its conditions, to it.
4815 This feature can be controlled via the following commands:
4817 @kindex set breakpoint condition-evaluation
4818 @kindex show breakpoint condition-evaluation
4820 @item set breakpoint condition-evaluation host
4821 This option commands @value{GDBN} to evaluate the breakpoint
4822 conditions on the host's side. Unconditional breakpoints are sent to
4823 the target which in turn receives the triggers and reports them back to GDB
4824 for condition evaluation. This is the standard evaluation mode.
4826 @item set breakpoint condition-evaluation target
4827 This option commands @value{GDBN} to download breakpoint conditions
4828 to the target at the moment of their insertion. The target
4829 is responsible for evaluating the conditional expression and reporting
4830 breakpoint stop events back to @value{GDBN} whenever the condition
4831 is true. Due to limitations of target-side evaluation, some conditions
4832 cannot be evaluated there, e.g., conditions that depend on local data
4833 that is only known to the host. Examples include
4834 conditional expressions involving convenience variables, complex types
4835 that cannot be handled by the agent expression parser and expressions
4836 that are too long to be sent over to the target, specially when the
4837 target is a remote system. In these cases, the conditions will be
4838 evaluated by @value{GDBN}.
4840 @item set breakpoint condition-evaluation auto
4841 This is the default mode. If the target supports evaluating breakpoint
4842 conditions on its end, @value{GDBN} will download breakpoint conditions to
4843 the target (limitations mentioned previously apply). If the target does
4844 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4845 to evaluating all these conditions on the host's side.
4849 @cindex negative breakpoint numbers
4850 @cindex internal @value{GDBN} breakpoints
4851 @value{GDBN} itself sometimes sets breakpoints in your program for
4852 special purposes, such as proper handling of @code{longjmp} (in C
4853 programs). These internal breakpoints are assigned negative numbers,
4854 starting with @code{-1}; @samp{info breakpoints} does not display them.
4855 You can see these breakpoints with the @value{GDBN} maintenance command
4856 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4859 @node Set Watchpoints
4860 @subsection Setting Watchpoints
4862 @cindex setting watchpoints
4863 You can use a watchpoint to stop execution whenever the value of an
4864 expression changes, without having to predict a particular place where
4865 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4866 The expression may be as simple as the value of a single variable, or
4867 as complex as many variables combined by operators. Examples include:
4871 A reference to the value of a single variable.
4874 An address cast to an appropriate data type. For example,
4875 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4876 address (assuming an @code{int} occupies 4 bytes).
4879 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4880 expression can use any operators valid in the program's native
4881 language (@pxref{Languages}).
4884 You can set a watchpoint on an expression even if the expression can
4885 not be evaluated yet. For instance, you can set a watchpoint on
4886 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4887 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4888 the expression produces a valid value. If the expression becomes
4889 valid in some other way than changing a variable (e.g.@: if the memory
4890 pointed to by @samp{*global_ptr} becomes readable as the result of a
4891 @code{malloc} call), @value{GDBN} may not stop until the next time
4892 the expression changes.
4894 @cindex software watchpoints
4895 @cindex hardware watchpoints
4896 Depending on your system, watchpoints may be implemented in software or
4897 hardware. @value{GDBN} does software watchpointing by single-stepping your
4898 program and testing the variable's value each time, which is hundreds of
4899 times slower than normal execution. (But this may still be worth it, to
4900 catch errors where you have no clue what part of your program is the
4903 On some systems, such as most PowerPC or x86-based targets,
4904 @value{GDBN} includes support for hardware watchpoints, which do not
4905 slow down the running of your program.
4909 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]} @r{[}task @var{task-id}@r{]}
4910 Set a watchpoint for an expression. @value{GDBN} will break when the
4911 expression @var{expr} is written into by the program and its value
4912 changes. The simplest (and the most popular) use of this command is
4913 to watch the value of a single variable:
4916 (@value{GDBP}) watch foo
4919 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4920 argument, @value{GDBN} breaks only when the thread identified by
4921 @var{thread-id} changes the value of @var{expr}. If any other threads
4922 change the value of @var{expr}, @value{GDBN} will not break. Note
4923 that watchpoints restricted to a single thread in this way only work
4924 with Hardware Watchpoints.
4926 Similarly, if the @code{task} argument is given, then the watchpoint
4927 will be specific to the indicated Ada task (@pxref{Ada Tasks}).
4929 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4930 (see below). The @code{-location} argument tells @value{GDBN} to
4931 instead watch the memory referred to by @var{expr}. In this case,
4932 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4933 and watch the memory at that address. The type of the result is used
4934 to determine the size of the watched memory. If the expression's
4935 result does not have an address, then @value{GDBN} will print an
4938 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4939 of masked watchpoints, if the current architecture supports this
4940 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4941 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4942 to an address to watch. The mask specifies that some bits of an address
4943 (the bits which are reset in the mask) should be ignored when matching
4944 the address accessed by the inferior against the watchpoint address.
4945 Thus, a masked watchpoint watches many addresses simultaneously---those
4946 addresses whose unmasked bits are identical to the unmasked bits in the
4947 watchpoint address. The @code{mask} argument implies @code{-location}.
4951 (@value{GDBP}) watch foo mask 0xffff00ff
4952 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4956 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4957 Set a watchpoint that will break when the value of @var{expr} is read
4961 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4962 Set a watchpoint that will break when @var{expr} is either read from
4963 or written into by the program.
4965 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4966 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4967 This command prints a list of watchpoints, using the same format as
4968 @code{info break} (@pxref{Set Breaks}).
4971 If you watch for a change in a numerically entered address you need to
4972 dereference it, as the address itself is just a constant number which will
4973 never change. @value{GDBN} refuses to create a watchpoint that watches
4974 a never-changing value:
4977 (@value{GDBP}) watch 0x600850
4978 Cannot watch constant value 0x600850.
4979 (@value{GDBP}) watch *(int *) 0x600850
4980 Watchpoint 1: *(int *) 6293584
4983 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4984 watchpoints execute very quickly, and the debugger reports a change in
4985 value at the exact instruction where the change occurs. If @value{GDBN}
4986 cannot set a hardware watchpoint, it sets a software watchpoint, which
4987 executes more slowly and reports the change in value at the next
4988 @emph{statement}, not the instruction, after the change occurs.
4990 @cindex use only software watchpoints
4991 You can force @value{GDBN} to use only software watchpoints with the
4992 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4993 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4994 the underlying system supports them. (Note that hardware-assisted
4995 watchpoints that were set @emph{before} setting
4996 @code{can-use-hw-watchpoints} to zero will still use the hardware
4997 mechanism of watching expression values.)
5000 @item set can-use-hw-watchpoints
5001 @kindex set can-use-hw-watchpoints
5002 Set whether or not to use hardware watchpoints.
5004 @item show can-use-hw-watchpoints
5005 @kindex show can-use-hw-watchpoints
5006 Show the current mode of using hardware watchpoints.
5009 For remote targets, you can restrict the number of hardware
5010 watchpoints @value{GDBN} will use, see @ref{set remote
5011 hardware-breakpoint-limit}.
5013 When you issue the @code{watch} command, @value{GDBN} reports
5016 Hardware watchpoint @var{num}: @var{expr}
5020 if it was able to set a hardware watchpoint.
5022 Currently, the @code{awatch} and @code{rwatch} commands can only set
5023 hardware watchpoints, because accesses to data that don't change the
5024 value of the watched expression cannot be detected without examining
5025 every instruction as it is being executed, and @value{GDBN} does not do
5026 that currently. If @value{GDBN} finds that it is unable to set a
5027 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
5028 will print a message like this:
5031 Expression cannot be implemented with read/access watchpoint.
5034 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
5035 data type of the watched expression is wider than what a hardware
5036 watchpoint on the target machine can handle. For example, some systems
5037 can only watch regions that are up to 4 bytes wide; on such systems you
5038 cannot set hardware watchpoints for an expression that yields a
5039 double-precision floating-point number (which is typically 8 bytes
5040 wide). As a work-around, it might be possible to break the large region
5041 into a series of smaller ones and watch them with separate watchpoints.
5043 If you set too many hardware watchpoints, @value{GDBN} might be unable
5044 to insert all of them when you resume the execution of your program.
5045 Since the precise number of active watchpoints is unknown until such
5046 time as the program is about to be resumed, @value{GDBN} might not be
5047 able to warn you about this when you set the watchpoints, and the
5048 warning will be printed only when the program is resumed:
5051 Hardware watchpoint @var{num}: Could not insert watchpoint
5055 If this happens, delete or disable some of the watchpoints.
5057 Watching complex expressions that reference many variables can also
5058 exhaust the resources available for hardware-assisted watchpoints.
5059 That's because @value{GDBN} needs to watch every variable in the
5060 expression with separately allocated resources.
5062 If you call a function interactively using @code{print} or @code{call},
5063 any watchpoints you have set will be inactive until @value{GDBN} reaches another
5064 kind of breakpoint or the call completes.
5066 @value{GDBN} automatically deletes watchpoints that watch local
5067 (automatic) variables, or expressions that involve such variables, when
5068 they go out of scope, that is, when the execution leaves the block in
5069 which these variables were defined. In particular, when the program
5070 being debugged terminates, @emph{all} local variables go out of scope,
5071 and so only watchpoints that watch global variables remain set. If you
5072 rerun the program, you will need to set all such watchpoints again. One
5073 way of doing that would be to set a code breakpoint at the entry to the
5074 @code{main} function and when it breaks, set all the watchpoints.
5076 @cindex watchpoints and threads
5077 @cindex threads and watchpoints
5078 In multi-threaded programs, watchpoints will detect changes to the
5079 watched expression from every thread.
5082 @emph{Warning:} In multi-threaded programs, software watchpoints
5083 have only limited usefulness. If @value{GDBN} creates a software
5084 watchpoint, it can only watch the value of an expression @emph{in a
5085 single thread}. If you are confident that the expression can only
5086 change due to the current thread's activity (and if you are also
5087 confident that no other thread can become current), then you can use
5088 software watchpoints as usual. However, @value{GDBN} may not notice
5089 when a non-current thread's activity changes the expression. (Hardware
5090 watchpoints, in contrast, watch an expression in all threads.)
5093 @xref{set remote hardware-watchpoint-limit}.
5095 @node Set Catchpoints
5096 @subsection Setting Catchpoints
5097 @cindex catchpoints, setting
5098 @cindex exception handlers
5099 @cindex event handling
5101 You can use @dfn{catchpoints} to cause the debugger to stop for certain
5102 kinds of program events, such as C@t{++} exceptions or the loading of a
5103 shared library. Use the @code{catch} command to set a catchpoint.
5107 @item catch @var{event}
5108 Stop when @var{event} occurs. The @var{event} can be any of the following:
5111 @item throw @r{[}@var{regexp}@r{]}
5112 @itemx rethrow @r{[}@var{regexp}@r{]}
5113 @itemx catch @r{[}@var{regexp}@r{]}
5115 @kindex catch rethrow
5117 @cindex stop on C@t{++} exceptions
5118 The throwing, re-throwing, or catching of a C@t{++} exception.
5120 If @var{regexp} is given, then only exceptions whose type matches the
5121 regular expression will be caught.
5123 @vindex $_exception@r{, convenience variable}
5124 The convenience variable @code{$_exception} is available at an
5125 exception-related catchpoint, on some systems. This holds the
5126 exception being thrown.
5128 There are currently some limitations to C@t{++} exception handling in
5133 The support for these commands is system-dependent. Currently, only
5134 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
5138 The regular expression feature and the @code{$_exception} convenience
5139 variable rely on the presence of some SDT probes in @code{libstdc++}.
5140 If these probes are not present, then these features cannot be used.
5141 These probes were first available in the GCC 4.8 release, but whether
5142 or not they are available in your GCC also depends on how it was
5146 The @code{$_exception} convenience variable is only valid at the
5147 instruction at which an exception-related catchpoint is set.
5150 When an exception-related catchpoint is hit, @value{GDBN} stops at a
5151 location in the system library which implements runtime exception
5152 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
5153 (@pxref{Selection}) to get to your code.
5156 If you call a function interactively, @value{GDBN} normally returns
5157 control to you when the function has finished executing. If the call
5158 raises an exception, however, the call may bypass the mechanism that
5159 returns control to you and cause your program either to abort or to
5160 simply continue running until it hits a breakpoint, catches a signal
5161 that @value{GDBN} is listening for, or exits. This is the case even if
5162 you set a catchpoint for the exception; catchpoints on exceptions are
5163 disabled within interactive calls. @xref{Calling}, for information on
5164 controlling this with @code{set unwind-on-terminating-exception}.
5167 You cannot raise an exception interactively.
5170 You cannot install an exception handler interactively.
5173 @item exception @r{[}@var{name}@r{]}
5174 @kindex catch exception
5175 @cindex Ada exception catching
5176 @cindex catch Ada exceptions
5177 An Ada exception being raised. If an exception name is specified
5178 at the end of the command (eg @code{catch exception Program_Error}),
5179 the debugger will stop only when this specific exception is raised.
5180 Otherwise, the debugger stops execution when any Ada exception is raised.
5182 When inserting an exception catchpoint on a user-defined exception whose
5183 name is identical to one of the exceptions defined by the language, the
5184 fully qualified name must be used as the exception name. Otherwise,
5185 @value{GDBN} will assume that it should stop on the pre-defined exception
5186 rather than the user-defined one. For instance, assuming an exception
5187 called @code{Constraint_Error} is defined in package @code{Pck}, then
5188 the command to use to catch such exceptions is @kbd{catch exception
5189 Pck.Constraint_Error}.
5191 @vindex $_ada_exception@r{, convenience variable}
5192 The convenience variable @code{$_ada_exception} holds the address of
5193 the exception being thrown. This can be useful when setting a
5194 condition for such a catchpoint.
5196 @item exception unhandled
5197 @kindex catch exception unhandled
5198 An exception that was raised but is not handled by the program. The
5199 convenience variable @code{$_ada_exception} is set as for @code{catch
5202 @item handlers @r{[}@var{name}@r{]}
5203 @kindex catch handlers
5204 @cindex Ada exception handlers catching
5205 @cindex catch Ada exceptions when handled
5206 An Ada exception being handled. If an exception name is
5207 specified at the end of the command
5208 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5209 only when this specific exception is handled.
5210 Otherwise, the debugger stops execution when any Ada exception is handled.
5212 When inserting a handlers catchpoint on a user-defined
5213 exception whose name is identical to one of the exceptions
5214 defined by the language, the fully qualified name must be used
5215 as the exception name. Otherwise, @value{GDBN} will assume that it
5216 should stop on the pre-defined exception rather than the
5217 user-defined one. For instance, assuming an exception called
5218 @code{Constraint_Error} is defined in package @code{Pck}, then the
5219 command to use to catch such exceptions handling is
5220 @kbd{catch handlers Pck.Constraint_Error}.
5222 The convenience variable @code{$_ada_exception} is set as for
5223 @code{catch exception}.
5226 @kindex catch assert
5227 A failed Ada assertion. Note that the convenience variable
5228 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5232 @cindex break on fork/exec
5233 A call to @code{exec}.
5235 @anchor{catch syscall}
5237 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5238 @kindex catch syscall
5239 @cindex break on a system call.
5240 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5241 syscall is a mechanism for application programs to request a service
5242 from the operating system (OS) or one of the OS system services.
5243 @value{GDBN} can catch some or all of the syscalls issued by the
5244 debuggee, and show the related information for each syscall. If no
5245 argument is specified, calls to and returns from all system calls
5248 @var{name} can be any system call name that is valid for the
5249 underlying OS. Just what syscalls are valid depends on the OS. On
5250 GNU and Unix systems, you can find the full list of valid syscall
5251 names on @file{/usr/include/asm/unistd.h}.
5253 @c For MS-Windows, the syscall names and the corresponding numbers
5254 @c can be found, e.g., on this URL:
5255 @c http://www.metasploit.com/users/opcode/syscalls.html
5256 @c but we don't support Windows syscalls yet.
5258 Normally, @value{GDBN} knows in advance which syscalls are valid for
5259 each OS, so you can use the @value{GDBN} command-line completion
5260 facilities (@pxref{Completion,, command completion}) to list the
5263 You may also specify the system call numerically. A syscall's
5264 number is the value passed to the OS's syscall dispatcher to
5265 identify the requested service. When you specify the syscall by its
5266 name, @value{GDBN} uses its database of syscalls to convert the name
5267 into the corresponding numeric code, but using the number directly
5268 may be useful if @value{GDBN}'s database does not have the complete
5269 list of syscalls on your system (e.g., because @value{GDBN} lags
5270 behind the OS upgrades).
5272 You may specify a group of related syscalls to be caught at once using
5273 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5274 instance, on some platforms @value{GDBN} allows you to catch all
5275 network related syscalls, by passing the argument @code{group:network}
5276 to @code{catch syscall}. Note that not all syscall groups are
5277 available in every system. You can use the command completion
5278 facilities (@pxref{Completion,, command completion}) to list the
5279 syscall groups available on your environment.
5281 The example below illustrates how this command works if you don't provide
5285 (@value{GDBP}) catch syscall
5286 Catchpoint 1 (syscall)
5288 Starting program: /tmp/catch-syscall
5290 Catchpoint 1 (call to syscall 'close'), \
5291 0xffffe424 in __kernel_vsyscall ()
5295 Catchpoint 1 (returned from syscall 'close'), \
5296 0xffffe424 in __kernel_vsyscall ()
5300 Here is an example of catching a system call by name:
5303 (@value{GDBP}) catch syscall chroot
5304 Catchpoint 1 (syscall 'chroot' [61])
5306 Starting program: /tmp/catch-syscall
5308 Catchpoint 1 (call to syscall 'chroot'), \
5309 0xffffe424 in __kernel_vsyscall ()
5313 Catchpoint 1 (returned from syscall 'chroot'), \
5314 0xffffe424 in __kernel_vsyscall ()
5318 An example of specifying a system call numerically. In the case
5319 below, the syscall number has a corresponding entry in the XML
5320 file, so @value{GDBN} finds its name and prints it:
5323 (@value{GDBP}) catch syscall 252
5324 Catchpoint 1 (syscall(s) 'exit_group')
5326 Starting program: /tmp/catch-syscall
5328 Catchpoint 1 (call to syscall 'exit_group'), \
5329 0xffffe424 in __kernel_vsyscall ()
5333 Program exited normally.
5337 Here is an example of catching a syscall group:
5340 (@value{GDBP}) catch syscall group:process
5341 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5342 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5343 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5345 Starting program: /tmp/catch-syscall
5347 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5348 from /lib64/ld-linux-x86-64.so.2
5354 However, there can be situations when there is no corresponding name
5355 in XML file for that syscall number. In this case, @value{GDBN} prints
5356 a warning message saying that it was not able to find the syscall name,
5357 but the catchpoint will be set anyway. See the example below:
5360 (@value{GDBP}) catch syscall 764
5361 warning: The number '764' does not represent a known syscall.
5362 Catchpoint 2 (syscall 764)
5366 If you configure @value{GDBN} using the @samp{--without-expat} option,
5367 it will not be able to display syscall names. Also, if your
5368 architecture does not have an XML file describing its system calls,
5369 you will not be able to see the syscall names. It is important to
5370 notice that these two features are used for accessing the syscall
5371 name database. In either case, you will see a warning like this:
5374 (@value{GDBP}) catch syscall
5375 warning: Could not open "syscalls/i386-linux.xml"
5376 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5377 GDB will not be able to display syscall names.
5378 Catchpoint 1 (syscall)
5382 Of course, the file name will change depending on your architecture and system.
5384 Still using the example above, you can also try to catch a syscall by its
5385 number. In this case, you would see something like:
5388 (@value{GDBP}) catch syscall 252
5389 Catchpoint 1 (syscall(s) 252)
5392 Again, in this case @value{GDBN} would not be able to display syscall's names.
5396 A call to @code{fork}.
5400 A call to @code{vfork}.
5402 @item load @r{[}@var{regexp}@r{]}
5403 @itemx unload @r{[}@var{regexp}@r{]}
5405 @kindex catch unload
5406 The loading or unloading of a shared library. If @var{regexp} is
5407 given, then the catchpoint will stop only if the regular expression
5408 matches one of the affected libraries.
5410 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5411 @kindex catch signal
5412 The delivery of a signal.
5414 With no arguments, this catchpoint will catch any signal that is not
5415 used internally by @value{GDBN}, specifically, all signals except
5416 @samp{SIGTRAP} and @samp{SIGINT}.
5418 With the argument @samp{all}, all signals, including those used by
5419 @value{GDBN}, will be caught. This argument cannot be used with other
5422 Otherwise, the arguments are a list of signal names as given to
5423 @code{handle} (@pxref{Signals}). Only signals specified in this list
5426 One reason that @code{catch signal} can be more useful than
5427 @code{handle} is that you can attach commands and conditions to the
5430 When a signal is caught by a catchpoint, the signal's @code{stop} and
5431 @code{print} settings, as specified by @code{handle}, are ignored.
5432 However, whether the signal is still delivered to the inferior depends
5433 on the @code{pass} setting; this can be changed in the catchpoint's
5438 @item tcatch @var{event}
5440 Set a catchpoint that is enabled only for one stop. The catchpoint is
5441 automatically deleted after the first time the event is caught.
5445 Use the @code{info break} command to list the current catchpoints.
5449 @subsection Deleting Breakpoints
5451 @cindex clearing breakpoints, watchpoints, catchpoints
5452 @cindex deleting breakpoints, watchpoints, catchpoints
5453 It is often necessary to eliminate a breakpoint, watchpoint, or
5454 catchpoint once it has done its job and you no longer want your program
5455 to stop there. This is called @dfn{deleting} the breakpoint. A
5456 breakpoint that has been deleted no longer exists; it is forgotten.
5458 With the @code{clear} command you can delete breakpoints according to
5459 where they are in your program. With the @code{delete} command you can
5460 delete individual breakpoints, watchpoints, or catchpoints by specifying
5461 their breakpoint numbers.
5463 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5464 automatically ignores breakpoints on the first instruction to be executed
5465 when you continue execution without changing the execution address.
5470 Delete any breakpoints at the next instruction to be executed in the
5471 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5472 the innermost frame is selected, this is a good way to delete a
5473 breakpoint where your program just stopped.
5475 @item clear @var{locspec}
5476 Delete any breakpoint with a code location that corresponds to
5477 @var{locspec}. @xref{Location Specifications}, for the various forms
5478 of @var{locspec}. Which code locations correspond to @var{locspec}
5479 depends on the form used in the location specification @var{locspec}:
5483 @itemx @var{filename}:@var{linenum}
5484 @itemx -line @var{linenum}
5485 @itemx -source @var{filename} -line @var{linenum}
5486 If @var{locspec} specifies a line number, with or without a file name,
5487 the command deletes any breakpoint with a code location that is at or
5488 within the specified line @var{linenum} in files that match the
5489 specified @var{filename}. If @var{filename} is omitted, it defaults
5490 to the current source file.
5492 @item *@var{address}
5493 If @var{locspec} specifies an address, the command deletes any
5494 breakpoint with a code location that is at the given @var{address}.
5496 @item @var{function}
5497 @itemx -function @var{function}
5498 If @var{locspec} specifies a function, the command deletes any
5499 breakpoint with a code location that is at the entry to any function
5500 whose name matches @var{function}.
5503 Ambiguity in names of files and functions can be resolved as described
5504 in @ref{Location Specifications}.
5506 @cindex delete breakpoints
5508 @kindex d @r{(@code{delete})}
5509 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5510 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5511 list specified as argument. If no argument is specified, delete all
5512 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5513 confirm off}). You can abbreviate this command as @code{d}.
5517 @subsection Disabling Breakpoints
5519 @cindex enable/disable a breakpoint
5520 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5521 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5522 it had been deleted, but remembers the information on the breakpoint so
5523 that you can @dfn{enable} it again later.
5525 You disable and enable breakpoints, watchpoints, and catchpoints with
5526 the @code{enable} and @code{disable} commands, optionally specifying
5527 one or more breakpoint numbers as arguments. Use @code{info break} to
5528 print a list of all breakpoints, watchpoints, and catchpoints if you
5529 do not know which numbers to use.
5531 Disabling and enabling a breakpoint that has multiple locations
5532 affects all of its locations.
5534 A breakpoint, watchpoint, or catchpoint can have any of several
5535 different states of enablement:
5539 Enabled. The breakpoint stops your program. A breakpoint set
5540 with the @code{break} command starts out in this state.
5542 Disabled. The breakpoint has no effect on your program.
5544 Enabled once. The breakpoint stops your program, but then becomes
5547 Enabled for a count. The breakpoint stops your program for the next
5548 N times, then becomes disabled.
5550 Enabled for deletion. The breakpoint stops your program, but
5551 immediately after it does so it is deleted permanently. A breakpoint
5552 set with the @code{tbreak} command starts out in this state.
5555 You can use the following commands to enable or disable breakpoints,
5556 watchpoints, and catchpoints:
5560 @kindex dis @r{(@code{disable})}
5561 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5562 Disable the specified breakpoints---or all breakpoints, if none are
5563 listed. A disabled breakpoint has no effect but is not forgotten. All
5564 options such as ignore-counts, conditions and commands are remembered in
5565 case the breakpoint is enabled again later. You may abbreviate
5566 @code{disable} as @code{dis}.
5569 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5570 Enable the specified breakpoints (or all defined breakpoints). They
5571 become effective once again in stopping your program.
5573 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5574 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5575 of these breakpoints immediately after stopping your program.
5577 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5578 Enable the specified breakpoints temporarily. @value{GDBN} records
5579 @var{count} with each of the specified breakpoints, and decrements a
5580 breakpoint's count when it is hit. When any count reaches 0,
5581 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5582 count (@pxref{Conditions, ,Break Conditions}), that will be
5583 decremented to 0 before @var{count} is affected.
5585 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5586 Enable the specified breakpoints to work once, then die. @value{GDBN}
5587 deletes any of these breakpoints as soon as your program stops there.
5588 Breakpoints set by the @code{tbreak} command start out in this state.
5591 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5592 @c confusing: tbreak is also initially enabled.
5593 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5594 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5595 subsequently, they become disabled or enabled only when you use one of
5596 the commands above. (The command @code{until} can set and delete a
5597 breakpoint of its own, but it does not change the state of your other
5598 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5602 @subsection Break Conditions
5603 @cindex conditional breakpoints
5604 @cindex breakpoint conditions
5606 @c FIXME what is scope of break condition expr? Context where wanted?
5607 @c in particular for a watchpoint?
5608 The simplest sort of breakpoint breaks every time your program reaches a
5609 specified place. You can also specify a @dfn{condition} for a
5610 breakpoint. A condition is just a Boolean expression in your
5611 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5612 a condition evaluates the expression each time your program reaches it,
5613 and your program stops only if the condition is @emph{true}.
5615 This is the converse of using assertions for program validation; in that
5616 situation, you want to stop when the assertion is violated---that is,
5617 when the condition is false. In C, if you want to test an assertion expressed
5618 by the condition @var{assert}, you should set the condition
5619 @samp{! @var{assert}} on the appropriate breakpoint.
5621 Conditions are also accepted for watchpoints; you may not need them,
5622 since a watchpoint is inspecting the value of an expression anyhow---but
5623 it might be simpler, say, to just set a watchpoint on a variable name,
5624 and specify a condition that tests whether the new value is an interesting
5627 Break conditions can have side effects, and may even call functions in
5628 your program. This can be useful, for example, to activate functions
5629 that log program progress, or to use your own print functions to
5630 format special data structures. The effects are completely predictable
5631 unless there is another enabled breakpoint at the same address. (In
5632 that case, @value{GDBN} might see the other breakpoint first and stop your
5633 program without checking the condition of this one.) Note that
5634 breakpoint commands are usually more convenient and flexible than break
5636 purpose of performing side effects when a breakpoint is reached
5637 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5639 Breakpoint conditions can also be evaluated on the target's side if
5640 the target supports it. Instead of evaluating the conditions locally,
5641 @value{GDBN} encodes the expression into an agent expression
5642 (@pxref{Agent Expressions}) suitable for execution on the target,
5643 independently of @value{GDBN}. Global variables become raw memory
5644 locations, locals become stack accesses, and so forth.
5646 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5647 when its condition evaluates to true. This mechanism may provide faster
5648 response times depending on the performance characteristics of the target
5649 since it does not need to keep @value{GDBN} informed about
5650 every breakpoint trigger, even those with false conditions.
5652 Break conditions can be specified when a breakpoint is set, by using
5653 @samp{if} in the arguments to the @code{break} command. @xref{Set
5654 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5655 with the @code{condition} command.
5657 You can also use the @code{if} keyword with the @code{watch} command.
5658 The @code{catch} command does not recognize the @code{if} keyword;
5659 @code{condition} is the only way to impose a further condition on a
5664 @item condition @var{bnum} @var{expression}
5665 Specify @var{expression} as the break condition for breakpoint,
5666 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5667 breakpoint @var{bnum} stops your program only if the value of
5668 @var{expression} is true (nonzero, in C). When you use
5669 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5670 syntactic correctness, and to determine whether symbols in it have
5671 referents in the context of your breakpoint. If @var{expression} uses
5672 symbols not referenced in the context of the breakpoint, @value{GDBN}
5673 prints an error message:
5676 No symbol "foo" in current context.
5681 not actually evaluate @var{expression} at the time the @code{condition}
5682 command (or a command that sets a breakpoint with a condition, like
5683 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5685 @item condition -force @var{bnum} @var{expression}
5686 When the @code{-force} flag is used, define the condition even if
5687 @var{expression} is invalid at all the current locations of breakpoint
5688 @var{bnum}. This is similar to the @code{-force-condition} option
5689 of the @code{break} command.
5691 @item condition @var{bnum}
5692 Remove the condition from breakpoint number @var{bnum}. It becomes
5693 an ordinary unconditional breakpoint.
5696 @cindex ignore count (of breakpoint)
5697 A special case of a breakpoint condition is to stop only when the
5698 breakpoint has been reached a certain number of times. This is so
5699 useful that there is a special way to do it, using the @dfn{ignore
5700 count} of the breakpoint. Every breakpoint has an ignore count, which
5701 is an integer. Most of the time, the ignore count is zero, and
5702 therefore has no effect. But if your program reaches a breakpoint whose
5703 ignore count is positive, then instead of stopping, it just decrements
5704 the ignore count by one and continues. As a result, if the ignore count
5705 value is @var{n}, the breakpoint does not stop the next @var{n} times
5706 your program reaches it.
5710 @item ignore @var{bnum} @var{count}
5711 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5712 The next @var{count} times the breakpoint is reached, your program's
5713 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5716 To make the breakpoint stop the next time it is reached, specify
5719 When you use @code{continue} to resume execution of your program from a
5720 breakpoint, you can specify an ignore count directly as an argument to
5721 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5722 Stepping,,Continuing and Stepping}.
5724 If a breakpoint has a positive ignore count and a condition, the
5725 condition is not checked. Once the ignore count reaches zero,
5726 @value{GDBN} resumes checking the condition.
5728 You could achieve the effect of the ignore count with a condition such
5729 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5730 is decremented each time. @xref{Convenience Vars, ,Convenience
5734 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5737 @node Break Commands
5738 @subsection Breakpoint Command Lists
5740 @cindex breakpoint commands
5741 You can give any breakpoint (or watchpoint or catchpoint) a series of
5742 commands to execute when your program stops due to that breakpoint. For
5743 example, you might want to print the values of certain expressions, or
5744 enable other breakpoints.
5748 @kindex end@r{ (breakpoint commands)}
5749 @item commands @r{[}@var{list}@dots{}@r{]}
5750 @itemx @dots{} @var{command-list} @dots{}
5752 Specify a list of commands for the given breakpoints. The commands
5753 themselves appear on the following lines. Type a line containing just
5754 @code{end} to terminate the commands.
5756 To remove all commands from a breakpoint, type @code{commands} and
5757 follow it immediately with @code{end}; that is, give no commands.
5759 With no argument, @code{commands} refers to the last breakpoint,
5760 watchpoint, or catchpoint set (not to the breakpoint most recently
5761 encountered). If the most recent breakpoints were set with a single
5762 command, then the @code{commands} will apply to all the breakpoints
5763 set by that command. This applies to breakpoints set by
5764 @code{rbreak}, and also applies when a single @code{break} command
5765 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5769 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5770 disabled within a @var{command-list}.
5772 You can use breakpoint commands to start your program up again. Simply
5773 use the @code{continue} command, or @code{step}, or any other command
5774 that resumes execution.
5776 Any other commands in the command list, after a command that resumes
5777 execution, are ignored. This is because any time you resume execution
5778 (even with a simple @code{next} or @code{step}), you may encounter
5779 another breakpoint---which could have its own command list, leading to
5780 ambiguities about which list to execute.
5783 If the first command you specify in a command list is @code{silent}, the
5784 usual message about stopping at a breakpoint is not printed. This may
5785 be desirable for breakpoints that are to print a specific message and
5786 then continue. If none of the remaining commands print anything, you
5787 see no sign that the breakpoint was reached. @code{silent} is
5788 meaningful only at the beginning of a breakpoint command list.
5790 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5791 print precisely controlled output, and are often useful in silent
5792 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5794 For example, here is how you could use breakpoint commands to print the
5795 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5801 printf "x is %d\n",x
5806 One application for breakpoint commands is to compensate for one bug so
5807 you can test for another. Put a breakpoint just after the erroneous line
5808 of code, give it a condition to detect the case in which something
5809 erroneous has been done, and give it commands to assign correct values
5810 to any variables that need them. End with the @code{continue} command
5811 so that your program does not stop, and start with the @code{silent}
5812 command so that no output is produced. Here is an example:
5823 @node Dynamic Printf
5824 @subsection Dynamic Printf
5826 @cindex dynamic printf
5828 The dynamic printf command @code{dprintf} combines a breakpoint with
5829 formatted printing of your program's data to give you the effect of
5830 inserting @code{printf} calls into your program on-the-fly, without
5831 having to recompile it.
5833 In its most basic form, the output goes to the GDB console. However,
5834 you can set the variable @code{dprintf-style} for alternate handling.
5835 For instance, you can ask to format the output by calling your
5836 program's @code{printf} function. This has the advantage that the
5837 characters go to the program's output device, so they can recorded in
5838 redirects to files and so forth.
5840 If you are doing remote debugging with a stub or agent, you can also
5841 ask to have the printf handled by the remote agent. In addition to
5842 ensuring that the output goes to the remote program's device along
5843 with any other output the program might produce, you can also ask that
5844 the dprintf remain active even after disconnecting from the remote
5845 target. Using the stub/agent is also more efficient, as it can do
5846 everything without needing to communicate with @value{GDBN}.
5850 @item dprintf @var{locspec},@var{template},@var{expression}[,@var{expression}@dots{}]
5851 Whenever execution reaches a code location that results from resolving
5852 @var{locspec}, print the values of one or more @var{expressions} under
5853 the control of the string @var{template}. To print several values,
5854 separate them with commas.
5856 @item set dprintf-style @var{style}
5857 Set the dprintf output to be handled in one of several different
5858 styles enumerated below. A change of style affects all existing
5859 dynamic printfs immediately. (If you need individual control over the
5860 print commands, simply define normal breakpoints with
5861 explicitly-supplied command lists.)
5865 @kindex dprintf-style gdb
5866 Handle the output using the @value{GDBN} @code{printf} command.
5869 @kindex dprintf-style call
5870 Handle the output by calling a function in your program (normally
5874 @kindex dprintf-style agent
5875 Have the remote debugging agent (such as @code{gdbserver}) handle
5876 the output itself. This style is only available for agents that
5877 support running commands on the target.
5880 @item set dprintf-function @var{function}
5881 Set the function to call if the dprintf style is @code{call}. By
5882 default its value is @code{printf}. You may set it to any expression.
5883 that @value{GDBN} can evaluate to a function, as per the @code{call}
5886 @item set dprintf-channel @var{channel}
5887 Set a ``channel'' for dprintf. If set to a non-empty value,
5888 @value{GDBN} will evaluate it as an expression and pass the result as
5889 a first argument to the @code{dprintf-function}, in the manner of
5890 @code{fprintf} and similar functions. Otherwise, the dprintf format
5891 string will be the first argument, in the manner of @code{printf}.
5893 As an example, if you wanted @code{dprintf} output to go to a logfile
5894 that is a standard I/O stream assigned to the variable @code{mylog},
5895 you could do the following:
5898 (gdb) set dprintf-style call
5899 (gdb) set dprintf-function fprintf
5900 (gdb) set dprintf-channel mylog
5901 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5902 Dprintf 1 at 0x123456: file main.c, line 25.
5904 1 dprintf keep y 0x00123456 in main at main.c:25
5905 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5910 Note that the @code{info break} displays the dynamic printf commands
5911 as normal breakpoint commands; you can thus easily see the effect of
5912 the variable settings.
5914 @item set disconnected-dprintf on
5915 @itemx set disconnected-dprintf off
5916 @kindex set disconnected-dprintf
5917 Choose whether @code{dprintf} commands should continue to run if
5918 @value{GDBN} has disconnected from the target. This only applies
5919 if the @code{dprintf-style} is @code{agent}.
5921 @item show disconnected-dprintf off
5922 @kindex show disconnected-dprintf
5923 Show the current choice for disconnected @code{dprintf}.
5927 @value{GDBN} does not check the validity of function and channel,
5928 relying on you to supply values that are meaningful for the contexts
5929 in which they are being used. For instance, the function and channel
5930 may be the values of local variables, but if that is the case, then
5931 all enabled dynamic prints must be at locations within the scope of
5932 those locals. If evaluation fails, @value{GDBN} will report an error.
5934 @node Save Breakpoints
5935 @subsection How to save breakpoints to a file
5937 To save breakpoint definitions to a file use the @w{@code{save
5938 breakpoints}} command.
5941 @kindex save breakpoints
5942 @cindex save breakpoints to a file for future sessions
5943 @item save breakpoints [@var{filename}]
5944 This command saves all current breakpoint definitions together with
5945 their commands and ignore counts, into a file @file{@var{filename}}
5946 suitable for use in a later debugging session. This includes all
5947 types of breakpoints (breakpoints, watchpoints, catchpoints,
5948 tracepoints). To read the saved breakpoint definitions, use the
5949 @code{source} command (@pxref{Command Files}). Note that watchpoints
5950 with expressions involving local variables may fail to be recreated
5951 because it may not be possible to access the context where the
5952 watchpoint is valid anymore. Because the saved breakpoint definitions
5953 are simply a sequence of @value{GDBN} commands that recreate the
5954 breakpoints, you can edit the file in your favorite editing program,
5955 and remove the breakpoint definitions you're not interested in, or
5956 that can no longer be recreated.
5959 @node Static Probe Points
5960 @subsection Static Probe Points
5962 @cindex static probe point, SystemTap
5963 @cindex static probe point, DTrace
5964 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5965 for Statically Defined Tracing, and the probes are designed to have a tiny
5966 runtime code and data footprint, and no dynamic relocations.
5968 Currently, the following types of probes are supported on
5969 ELF-compatible systems:
5973 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5974 @acronym{SDT} probes@footnote{See
5975 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5976 for more information on how to add @code{SystemTap} @acronym{SDT}
5977 probes in your applications.}. @code{SystemTap} probes are usable
5978 from assembly, C and C@t{++} languages@footnote{See
5979 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5980 for a good reference on how the @acronym{SDT} probes are implemented.}.
5982 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5983 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5987 @cindex semaphores on static probe points
5988 Some @code{SystemTap} probes have an associated semaphore variable;
5989 for instance, this happens automatically if you defined your probe
5990 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5991 @value{GDBN} will automatically enable it when you specify a
5992 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5993 breakpoint at a probe's location by some other method (e.g.,
5994 @code{break file:line}), then @value{GDBN} will not automatically set
5995 the semaphore. @code{DTrace} probes do not support semaphores.
5997 You can examine the available static static probes using @code{info
5998 probes}, with optional arguments:
6002 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6003 If given, @var{type} is either @code{stap} for listing
6004 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
6005 probes. If omitted all probes are listed regardless of their types.
6007 If given, @var{provider} is a regular expression used to match against provider
6008 names when selecting which probes to list. If omitted, probes by all
6009 probes from all providers are listed.
6011 If given, @var{name} is a regular expression to match against probe names
6012 when selecting which probes to list. If omitted, probe names are not
6013 considered when deciding whether to display them.
6015 If given, @var{objfile} is a regular expression used to select which
6016 object files (executable or shared libraries) to examine. If not
6017 given, all object files are considered.
6019 @item info probes all
6020 List the available static probes, from all types.
6023 @cindex enabling and disabling probes
6024 Some probe points can be enabled and/or disabled. The effect of
6025 enabling or disabling a probe depends on the type of probe being
6026 handled. Some @code{DTrace} probes can be enabled or
6027 disabled, but @code{SystemTap} probes cannot be disabled.
6029 You can enable (or disable) one or more probes using the following
6030 commands, with optional arguments:
6033 @kindex enable probes
6034 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6035 If given, @var{provider} is a regular expression used to match against
6036 provider names when selecting which probes to enable. If omitted,
6037 all probes from all providers are enabled.
6039 If given, @var{name} is a regular expression to match against probe
6040 names when selecting which probes to enable. If omitted, probe names
6041 are not considered when deciding whether to enable them.
6043 If given, @var{objfile} is a regular expression used to select which
6044 object files (executable or shared libraries) to examine. If not
6045 given, all object files are considered.
6047 @kindex disable probes
6048 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6049 See the @code{enable probes} command above for a description of the
6050 optional arguments accepted by this command.
6053 @vindex $_probe_arg@r{, convenience variable}
6054 A probe may specify up to twelve arguments. These are available at the
6055 point at which the probe is defined---that is, when the current PC is
6056 at the probe's location. The arguments are available using the
6057 convenience variables (@pxref{Convenience Vars})
6058 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
6059 probes each probe argument is an integer of the appropriate size;
6060 types are not preserved. In @code{DTrace} probes types are preserved
6061 provided that they are recognized as such by @value{GDBN}; otherwise
6062 the value of the probe argument will be a long integer. The
6063 convenience variable @code{$_probe_argc} holds the number of arguments
6064 at the current probe point.
6066 These variables are always available, but attempts to access them at
6067 any location other than a probe point will cause @value{GDBN} to give
6071 @c @ifclear BARETARGET
6072 @node Error in Breakpoints
6073 @subsection ``Cannot insert breakpoints''
6075 If you request too many active hardware-assisted breakpoints and
6076 watchpoints, you will see this error message:
6078 @c FIXME: the precise wording of this message may change; the relevant
6079 @c source change is not committed yet (Sep 3, 1999).
6081 Stopped; cannot insert breakpoints.
6082 You may have requested too many hardware breakpoints and watchpoints.
6086 This message is printed when you attempt to resume the program, since
6087 only then @value{GDBN} knows exactly how many hardware breakpoints and
6088 watchpoints it needs to insert.
6090 When this message is printed, you need to disable or remove some of the
6091 hardware-assisted breakpoints and watchpoints, and then continue.
6093 @node Breakpoint-related Warnings
6094 @subsection ``Breakpoint address adjusted...''
6095 @cindex breakpoint address adjusted
6097 Some processor architectures place constraints on the addresses at
6098 which breakpoints may be placed. For architectures thus constrained,
6099 @value{GDBN} will attempt to adjust the breakpoint's address to comply
6100 with the constraints dictated by the architecture.
6102 One example of such an architecture is the Fujitsu FR-V. The FR-V is
6103 a VLIW architecture in which a number of RISC-like instructions may be
6104 bundled together for parallel execution. The FR-V architecture
6105 constrains the location of a breakpoint instruction within such a
6106 bundle to the instruction with the lowest address. @value{GDBN}
6107 honors this constraint by adjusting a breakpoint's address to the
6108 first in the bundle.
6110 It is not uncommon for optimized code to have bundles which contain
6111 instructions from different source statements, thus it may happen that
6112 a breakpoint's address will be adjusted from one source statement to
6113 another. Since this adjustment may significantly alter @value{GDBN}'s
6114 breakpoint related behavior from what the user expects, a warning is
6115 printed when the breakpoint is first set and also when the breakpoint
6118 A warning like the one below is printed when setting a breakpoint
6119 that's been subject to address adjustment:
6122 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
6125 Such warnings are printed both for user settable and @value{GDBN}'s
6126 internal breakpoints. If you see one of these warnings, you should
6127 verify that a breakpoint set at the adjusted address will have the
6128 desired affect. If not, the breakpoint in question may be removed and
6129 other breakpoints may be set which will have the desired behavior.
6130 E.g., it may be sufficient to place the breakpoint at a later
6131 instruction. A conditional breakpoint may also be useful in some
6132 cases to prevent the breakpoint from triggering too often.
6134 @value{GDBN} will also issue a warning when stopping at one of these
6135 adjusted breakpoints:
6138 warning: Breakpoint 1 address previously adjusted from 0x00010414
6142 When this warning is encountered, it may be too late to take remedial
6143 action except in cases where the breakpoint is hit earlier or more
6144 frequently than expected.
6146 @node Continuing and Stepping
6147 @section Continuing and Stepping
6151 @cindex resuming execution
6152 @dfn{Continuing} means resuming program execution until your program
6153 completes normally. In contrast, @dfn{stepping} means executing just
6154 one more ``step'' of your program, where ``step'' may mean either one
6155 line of source code, or one machine instruction (depending on what
6156 particular command you use). Either when continuing or when stepping,
6157 your program may stop even sooner, due to a breakpoint or a signal. (If
6158 it stops due to a signal, you may want to use @code{handle}, or use
6159 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
6160 or you may step into the signal's handler (@pxref{stepping and signal
6165 @kindex c @r{(@code{continue})}
6166 @kindex fg @r{(resume foreground execution)}
6167 @item continue @r{[}@var{ignore-count}@r{]}
6168 @itemx c @r{[}@var{ignore-count}@r{]}
6169 @itemx fg @r{[}@var{ignore-count}@r{]}
6170 Resume program execution, at the address where your program last stopped;
6171 any breakpoints set at that address are bypassed. The optional argument
6172 @var{ignore-count} allows you to specify a further number of times to
6173 ignore a breakpoint at this location; its effect is like that of
6174 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
6176 The argument @var{ignore-count} is meaningful only when your program
6177 stopped due to a breakpoint. At other times, the argument to
6178 @code{continue} is ignored.
6180 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
6181 debugged program is deemed to be the foreground program) are provided
6182 purely for convenience, and have exactly the same behavior as
6186 To resume execution at a different place, you can use @code{return}
6187 (@pxref{Returning, ,Returning from a Function}) to go back to the
6188 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
6189 Different Address}) to go to an arbitrary location in your program.
6191 A typical technique for using stepping is to set a breakpoint
6192 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
6193 beginning of the function or the section of your program where a problem
6194 is believed to lie, run your program until it stops at that breakpoint,
6195 and then step through the suspect area, examining the variables that are
6196 interesting, until you see the problem happen.
6200 @kindex s @r{(@code{step})}
6202 Continue running your program until control reaches a different source
6203 line, then stop it and return control to @value{GDBN}. This command is
6204 abbreviated @code{s}.
6207 @c "without debugging information" is imprecise; actually "without line
6208 @c numbers in the debugging information". (gcc -g1 has debugging info but
6209 @c not line numbers). But it seems complex to try to make that
6210 @c distinction here.
6211 @emph{Warning:} If you use the @code{step} command while control is
6212 within a function that was compiled without debugging information,
6213 execution proceeds until control reaches a function that does have
6214 debugging information. Likewise, it will not step into a function which
6215 is compiled without debugging information. To step through functions
6216 without debugging information, use the @code{stepi} command, described
6220 The @code{step} command only stops at the first instruction of a source
6221 line. This prevents the multiple stops that could otherwise occur in
6222 @code{switch} statements, @code{for} loops, etc. @code{step} continues
6223 to stop if a function that has debugging information is called within
6224 the line. In other words, @code{step} @emph{steps inside} any functions
6225 called within the line.
6227 Also, the @code{step} command only enters a function if there is line
6228 number information for the function. Otherwise it acts like the
6229 @code{next} command. This avoids problems when using @code{cc -gl}
6230 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6231 was any debugging information about the routine.
6233 @item step @var{count}
6234 Continue running as in @code{step}, but do so @var{count} times. If a
6235 breakpoint is reached, or a signal not related to stepping occurs before
6236 @var{count} steps, stepping stops right away.
6239 @kindex n @r{(@code{next})}
6240 @item next @r{[}@var{count}@r{]}
6241 Continue to the next source line in the current (innermost) stack frame.
6242 This is similar to @code{step}, but function calls that appear within
6243 the line of code are executed without stopping. Execution stops when
6244 control reaches a different line of code at the original stack level
6245 that was executing when you gave the @code{next} command. This command
6246 is abbreviated @code{n}.
6248 An argument @var{count} is a repeat count, as for @code{step}.
6251 @c FIX ME!! Do we delete this, or is there a way it fits in with
6252 @c the following paragraph? --- Vctoria
6254 @c @code{next} within a function that lacks debugging information acts like
6255 @c @code{step}, but any function calls appearing within the code of the
6256 @c function are executed without stopping.
6258 The @code{next} command only stops at the first instruction of a
6259 source line. This prevents multiple stops that could otherwise occur in
6260 @code{switch} statements, @code{for} loops, etc.
6262 @kindex set step-mode
6264 @cindex functions without line info, and stepping
6265 @cindex stepping into functions with no line info
6266 @itemx set step-mode on
6267 The @code{set step-mode on} command causes the @code{step} command to
6268 stop at the first instruction of a function which contains no debug line
6269 information rather than stepping over it.
6271 This is useful in cases where you may be interested in inspecting the
6272 machine instructions of a function which has no symbolic info and do not
6273 want @value{GDBN} to automatically skip over this function.
6275 @item set step-mode off
6276 Causes the @code{step} command to step over any functions which contains no
6277 debug information. This is the default.
6279 @item show step-mode
6280 Show whether @value{GDBN} will stop in or step over functions without
6281 source line debug information.
6284 @kindex fin @r{(@code{finish})}
6286 Continue running until just after function in the selected stack frame
6287 returns. Print the returned value (if any). This command can be
6288 abbreviated as @code{fin}.
6290 Contrast this with the @code{return} command (@pxref{Returning,
6291 ,Returning from a Function}).
6293 @kindex set print finish
6294 @kindex show print finish
6295 @item set print finish @r{[}on|off@r{]}
6296 @itemx show print finish
6297 By default the @code{finish} command will show the value that is
6298 returned by the function. This can be disabled using @code{set print
6299 finish off}. When disabled, the value is still entered into the value
6300 history (@pxref{Value History}), but not displayed.
6303 @kindex u @r{(@code{until})}
6304 @cindex run until specified location
6307 Continue running until a source line past the current line, in the
6308 current stack frame, is reached. This command is used to avoid single
6309 stepping through a loop more than once. It is like the @code{next}
6310 command, except that when @code{until} encounters a jump, it
6311 automatically continues execution until the program counter is greater
6312 than the address of the jump.
6314 This means that when you reach the end of a loop after single stepping
6315 though it, @code{until} makes your program continue execution until it
6316 exits the loop. In contrast, a @code{next} command at the end of a loop
6317 simply steps back to the beginning of the loop, which forces you to step
6318 through the next iteration.
6320 @code{until} always stops your program if it attempts to exit the current
6323 @code{until} may produce somewhat counterintuitive results if the order
6324 of machine code does not match the order of the source lines. For
6325 example, in the following excerpt from a debugging session, the @code{f}
6326 (@code{frame}) command shows that execution is stopped at line
6327 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6331 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6333 (@value{GDBP}) until
6334 195 for ( ; argc > 0; NEXTARG) @{
6337 This happened because, for execution efficiency, the compiler had
6338 generated code for the loop closure test at the end, rather than the
6339 start, of the loop---even though the test in a C @code{for}-loop is
6340 written before the body of the loop. The @code{until} command appeared
6341 to step back to the beginning of the loop when it advanced to this
6342 expression; however, it has not really gone to an earlier
6343 statement---not in terms of the actual machine code.
6345 @code{until} with no argument works by means of single
6346 instruction stepping, and hence is slower than @code{until} with an
6349 @item until @var{locspec}
6350 @itemx u @var{locspec}
6351 Continue running your program until either it reaches a code location
6352 that results from resolving @var{locspec}, or the current stack frame
6353 returns. @var{locspec} is any of the forms described in @ref{Location
6355 This form of the command uses temporary breakpoints, and
6356 hence is quicker than @code{until} without an argument. The specified
6357 location is actually reached only if it is in the current frame. This
6358 implies that @code{until} can be used to skip over recursive function
6359 invocations. For instance in the code below, if the current location is
6360 line @code{96}, issuing @code{until 99} will execute the program up to
6361 line @code{99} in the same invocation of factorial, i.e., after the inner
6362 invocations have returned.
6365 94 int factorial (int value)
6367 96 if (value > 1) @{
6368 97 value *= factorial (value - 1);
6375 @kindex advance @var{locspec}
6376 @item advance @var{locspec}
6377 Continue running your program until either it reaches a code location
6378 that results from resolving @var{locspec}, or the current stack frame
6379 returns. @var{locspec} is any of the forms described in @ref{Location
6380 Specifications}. This command is similar to @code{until}, but
6381 @code{advance} will not skip over recursive function calls, and the
6382 target code location doesn't have to be in the same frame as the
6387 @kindex si @r{(@code{stepi})}
6389 @itemx stepi @var{arg}
6391 Execute one machine instruction, then stop and return to the debugger.
6393 It is often useful to do @samp{display/i $pc} when stepping by machine
6394 instructions. This makes @value{GDBN} automatically display the next
6395 instruction to be executed, each time your program stops. @xref{Auto
6396 Display,, Automatic Display}.
6398 An argument is a repeat count, as in @code{step}.
6402 @kindex ni @r{(@code{nexti})}
6404 @itemx nexti @var{arg}
6406 Execute one machine instruction, but if it is a function call,
6407 proceed until the function returns.
6409 An argument is a repeat count, as in @code{next}.
6413 @anchor{range stepping}
6414 @cindex range stepping
6415 @cindex target-assisted range stepping
6416 By default, and if available, @value{GDBN} makes use of
6417 target-assisted @dfn{range stepping}. In other words, whenever you
6418 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6419 tells the target to step the corresponding range of instruction
6420 addresses instead of issuing multiple single-steps. This speeds up
6421 line stepping, particularly for remote targets. Ideally, there should
6422 be no reason you would want to turn range stepping off. However, it's
6423 possible that a bug in the debug info, a bug in the remote stub (for
6424 remote targets), or even a bug in @value{GDBN} could make line
6425 stepping behave incorrectly when target-assisted range stepping is
6426 enabled. You can use the following command to turn off range stepping
6430 @kindex set range-stepping
6431 @kindex show range-stepping
6432 @item set range-stepping
6433 @itemx show range-stepping
6434 Control whether range stepping is enabled.
6436 If @code{on}, and the target supports it, @value{GDBN} tells the
6437 target to step a range of addresses itself, instead of issuing
6438 multiple single-steps. If @code{off}, @value{GDBN} always issues
6439 single-steps, even if range stepping is supported by the target. The
6440 default is @code{on}.
6444 @node Skipping Over Functions and Files
6445 @section Skipping Over Functions and Files
6446 @cindex skipping over functions and files
6448 The program you are debugging may contain some functions which are
6449 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6450 skip a function, all functions in a file or a particular function in
6451 a particular file when stepping.
6453 For example, consider the following C function:
6464 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6465 are not interested in stepping through @code{boring}. If you run @code{step}
6466 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6467 step over both @code{foo} and @code{boring}!
6469 One solution is to @code{step} into @code{boring} and use the @code{finish}
6470 command to immediately exit it. But this can become tedious if @code{boring}
6471 is called from many places.
6473 A more flexible solution is to execute @kbd{skip boring}. This instructs
6474 @value{GDBN} never to step into @code{boring}. Now when you execute
6475 @code{step} at line 103, you'll step over @code{boring} and directly into
6478 Functions may be skipped by providing either a function name, linespec
6479 (@pxref{Location Specifications}), regular expression that matches the function's
6480 name, file name or a @code{glob}-style pattern that matches the file name.
6482 On Posix systems the form of the regular expression is
6483 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6484 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6485 expression is whatever is provided by the @code{regcomp} function of
6486 the underlying system.
6487 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6488 description of @code{glob}-style patterns.
6492 @item skip @r{[}@var{options}@r{]}
6493 The basic form of the @code{skip} command takes zero or more options
6494 that specify what to skip.
6495 The @var{options} argument is any useful combination of the following:
6498 @item -file @var{file}
6499 @itemx -fi @var{file}
6500 Functions in @var{file} will be skipped over when stepping.
6502 @item -gfile @var{file-glob-pattern}
6503 @itemx -gfi @var{file-glob-pattern}
6504 @cindex skipping over files via glob-style patterns
6505 Functions in files matching @var{file-glob-pattern} will be skipped
6509 (gdb) skip -gfi utils/*.c
6512 @item -function @var{linespec}
6513 @itemx -fu @var{linespec}
6514 Functions named by @var{linespec} or the function containing the line
6515 named by @var{linespec} will be skipped over when stepping.
6516 @xref{Location Specifications}.
6518 @item -rfunction @var{regexp}
6519 @itemx -rfu @var{regexp}
6520 @cindex skipping over functions via regular expressions
6521 Functions whose name matches @var{regexp} will be skipped over when stepping.
6523 This form is useful for complex function names.
6524 For example, there is generally no need to step into C@t{++} @code{std::string}
6525 constructors or destructors. Plus with C@t{++} templates it can be hard to
6526 write out the full name of the function, and often it doesn't matter what
6527 the template arguments are. Specifying the function to be skipped as a
6528 regular expression makes this easier.
6531 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6534 If you want to skip every templated C@t{++} constructor and destructor
6535 in the @code{std} namespace you can do:
6538 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6542 If no options are specified, the function you're currently debugging
6545 @kindex skip function
6546 @item skip function @r{[}@var{linespec}@r{]}
6547 After running this command, the function named by @var{linespec} or the
6548 function containing the line named by @var{linespec} will be skipped over when
6549 stepping. @xref{Location Specifications}.
6551 If you do not specify @var{linespec}, the function you're currently debugging
6554 (If you have a function called @code{file} that you want to skip, use
6555 @kbd{skip function file}.)
6558 @item skip file @r{[}@var{filename}@r{]}
6559 After running this command, any function whose source lives in @var{filename}
6560 will be skipped over when stepping.
6563 (gdb) skip file boring.c
6564 File boring.c will be skipped when stepping.
6567 If you do not specify @var{filename}, functions whose source lives in the file
6568 you're currently debugging will be skipped.
6571 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6572 These are the commands for managing your list of skips:
6576 @item info skip @r{[}@var{range}@r{]}
6577 Print details about the specified skip(s). If @var{range} is not specified,
6578 print a table with details about all functions and files marked for skipping.
6579 @code{info skip} prints the following information about each skip:
6583 A number identifying this skip.
6584 @item Enabled or Disabled
6585 Enabled skips are marked with @samp{y}.
6586 Disabled skips are marked with @samp{n}.
6588 If the file name is a @samp{glob} pattern this is @samp{y}.
6589 Otherwise it is @samp{n}.
6591 The name or @samp{glob} pattern of the file to be skipped.
6592 If no file is specified this is @samp{<none>}.
6594 If the function name is a @samp{regular expression} this is @samp{y}.
6595 Otherwise it is @samp{n}.
6597 The name or regular expression of the function to skip.
6598 If no function is specified this is @samp{<none>}.
6602 @item skip delete @r{[}@var{range}@r{]}
6603 Delete the specified skip(s). If @var{range} is not specified, delete all
6607 @item skip enable @r{[}@var{range}@r{]}
6608 Enable the specified skip(s). If @var{range} is not specified, enable all
6611 @kindex skip disable
6612 @item skip disable @r{[}@var{range}@r{]}
6613 Disable the specified skip(s). If @var{range} is not specified, disable all
6616 @kindex set debug skip
6617 @item set debug skip @r{[}on|off@r{]}
6618 Set whether to print the debug output about skipping files and functions.
6620 @kindex show debug skip
6621 @item show debug skip
6622 Show whether the debug output about skipping files and functions is printed.
6630 A signal is an asynchronous event that can happen in a program. The
6631 operating system defines the possible kinds of signals, and gives each
6632 kind a name and a number. For example, in Unix @code{SIGINT} is the
6633 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6634 @code{SIGSEGV} is the signal a program gets from referencing a place in
6635 memory far away from all the areas in use; @code{SIGALRM} occurs when
6636 the alarm clock timer goes off (which happens only if your program has
6637 requested an alarm).
6639 @cindex fatal signals
6640 Some signals, including @code{SIGALRM}, are a normal part of the
6641 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6642 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6643 program has not specified in advance some other way to handle the signal.
6644 @code{SIGINT} does not indicate an error in your program, but it is normally
6645 fatal so it can carry out the purpose of the interrupt: to kill the program.
6647 @value{GDBN} has the ability to detect any occurrence of a signal in your
6648 program. You can tell @value{GDBN} in advance what to do for each kind of
6651 @cindex handling signals
6652 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6653 @code{SIGALRM} be silently passed to your program
6654 (so as not to interfere with their role in the program's functioning)
6655 but to stop your program immediately whenever an error signal happens.
6656 You can change these settings with the @code{handle} command.
6659 @kindex info signals
6663 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6664 handle each one. You can use this to see the signal numbers of all
6665 the defined types of signals.
6667 @item info signals @var{sig}
6668 Similar, but print information only about the specified signal number.
6670 @code{info handle} is an alias for @code{info signals}.
6672 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6673 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6674 for details about this command.
6677 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6678 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6679 can be the number of a signal or its name (with or without the
6680 @samp{SIG} at the beginning); a list of signal numbers of the form
6681 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6682 known signals. Optional arguments @var{keywords}, described below,
6683 say what change to make.
6687 The keywords allowed by the @code{handle} command can be abbreviated.
6688 Their full names are:
6692 @value{GDBN} should not stop your program when this signal happens. It may
6693 still print a message telling you that the signal has come in.
6696 @value{GDBN} should stop your program when this signal happens. This implies
6697 the @code{print} keyword as well.
6700 @value{GDBN} should print a message when this signal happens.
6703 @value{GDBN} should not mention the occurrence of the signal at all. This
6704 implies the @code{nostop} keyword as well.
6708 @value{GDBN} should allow your program to see this signal; your program
6709 can handle the signal, or else it may terminate if the signal is fatal
6710 and not handled. @code{pass} and @code{noignore} are synonyms.
6714 @value{GDBN} should not allow your program to see this signal.
6715 @code{nopass} and @code{ignore} are synonyms.
6719 When a signal stops your program, the signal is not visible to the
6721 continue. Your program sees the signal then, if @code{pass} is in
6722 effect for the signal in question @emph{at that time}. In other words,
6723 after @value{GDBN} reports a signal, you can use the @code{handle}
6724 command with @code{pass} or @code{nopass} to control whether your
6725 program sees that signal when you continue.
6727 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6728 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6729 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6732 You can also use the @code{signal} command to prevent your program from
6733 seeing a signal, or cause it to see a signal it normally would not see,
6734 or to give it any signal at any time. For example, if your program stopped
6735 due to some sort of memory reference error, you might store correct
6736 values into the erroneous variables and continue, hoping to see more
6737 execution; but your program would probably terminate immediately as
6738 a result of the fatal signal once it saw the signal. To prevent this,
6739 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6742 @cindex stepping and signal handlers
6743 @anchor{stepping and signal handlers}
6745 @value{GDBN} optimizes for stepping the mainline code. If a signal
6746 that has @code{handle nostop} and @code{handle pass} set arrives while
6747 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6748 in progress, @value{GDBN} lets the signal handler run and then resumes
6749 stepping the mainline code once the signal handler returns. In other
6750 words, @value{GDBN} steps over the signal handler. This prevents
6751 signals that you've specified as not interesting (with @code{handle
6752 nostop}) from changing the focus of debugging unexpectedly. Note that
6753 the signal handler itself may still hit a breakpoint, stop for another
6754 signal that has @code{handle stop} in effect, or for any other event
6755 that normally results in stopping the stepping command sooner. Also
6756 note that @value{GDBN} still informs you that the program received a
6757 signal if @code{handle print} is set.
6759 @anchor{stepping into signal handlers}
6761 If you set @code{handle pass} for a signal, and your program sets up a
6762 handler for it, then issuing a stepping command, such as @code{step}
6763 or @code{stepi}, when your program is stopped due to the signal will
6764 step @emph{into} the signal handler (if the target supports that).
6766 Likewise, if you use the @code{queue-signal} command to queue a signal
6767 to be delivered to the current thread when execution of the thread
6768 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6769 stepping command will step into the signal handler.
6771 Here's an example, using @code{stepi} to step to the first instruction
6772 of @code{SIGUSR1}'s handler:
6775 (@value{GDBP}) handle SIGUSR1
6776 Signal Stop Print Pass to program Description
6777 SIGUSR1 Yes Yes Yes User defined signal 1
6781 Program received signal SIGUSR1, User defined signal 1.
6782 main () sigusr1.c:28
6785 sigusr1_handler () at sigusr1.c:9
6789 The same, but using @code{queue-signal} instead of waiting for the
6790 program to receive the signal first:
6795 (@value{GDBP}) queue-signal SIGUSR1
6797 sigusr1_handler () at sigusr1.c:9
6802 @cindex extra signal information
6803 @anchor{extra signal information}
6805 On some targets, @value{GDBN} can inspect extra signal information
6806 associated with the intercepted signal, before it is actually
6807 delivered to the program being debugged. This information is exported
6808 by the convenience variable @code{$_siginfo}, and consists of data
6809 that is passed by the kernel to the signal handler at the time of the
6810 receipt of a signal. The data type of the information itself is
6811 target dependent. You can see the data type using the @code{ptype
6812 $_siginfo} command. On Unix systems, it typically corresponds to the
6813 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6816 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6817 referenced address that raised a segmentation fault.
6821 (@value{GDBP}) continue
6822 Program received signal SIGSEGV, Segmentation fault.
6823 0x0000000000400766 in main ()
6825 (@value{GDBP}) ptype $_siginfo
6832 struct @{...@} _kill;
6833 struct @{...@} _timer;
6835 struct @{...@} _sigchld;
6836 struct @{...@} _sigfault;
6837 struct @{...@} _sigpoll;
6840 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6844 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6845 $1 = (void *) 0x7ffff7ff7000
6849 Depending on target support, @code{$_siginfo} may also be writable.
6851 @cindex Intel MPX boundary violations
6852 @cindex boundary violations, Intel MPX
6853 On some targets, a @code{SIGSEGV} can be caused by a boundary
6854 violation, i.e., accessing an address outside of the allowed range.
6855 In those cases @value{GDBN} may displays additional information,
6856 depending on how @value{GDBN} has been told to handle the signal.
6857 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6858 kind: "Upper" or "Lower", the memory address accessed and the
6859 bounds, while with @code{handle nostop SIGSEGV} no additional
6860 information is displayed.
6862 The usual output of a segfault is:
6864 Program received signal SIGSEGV, Segmentation fault
6865 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6866 68 value = *(p + len);
6869 While a bound violation is presented as:
6871 Program received signal SIGSEGV, Segmentation fault
6872 Upper bound violation while accessing address 0x7fffffffc3b3
6873 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6874 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6875 68 value = *(p + len);
6879 @section Stopping and Starting Multi-thread Programs
6881 @cindex stopped threads
6882 @cindex threads, stopped
6884 @cindex continuing threads
6885 @cindex threads, continuing
6887 @value{GDBN} supports debugging programs with multiple threads
6888 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6889 are two modes of controlling execution of your program within the
6890 debugger. In the default mode, referred to as @dfn{all-stop mode},
6891 when any thread in your program stops (for example, at a breakpoint
6892 or while being stepped), all other threads in the program are also stopped by
6893 @value{GDBN}. On some targets, @value{GDBN} also supports
6894 @dfn{non-stop mode}, in which other threads can continue to run freely while
6895 you examine the stopped thread in the debugger.
6898 * All-Stop Mode:: All threads stop when GDB takes control
6899 * Non-Stop Mode:: Other threads continue to execute
6900 * Background Execution:: Running your program asynchronously
6901 * Thread-Specific Breakpoints:: Controlling breakpoints
6902 * Interrupted System Calls:: GDB may interfere with system calls
6903 * Observer Mode:: GDB does not alter program behavior
6907 @subsection All-Stop Mode
6909 @cindex all-stop mode
6911 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6912 @emph{all} threads of execution stop, not just the current thread. This
6913 allows you to examine the overall state of the program, including
6914 switching between threads, without worrying that things may change
6917 Conversely, whenever you restart the program, @emph{all} threads start
6918 executing. @emph{This is true even when single-stepping} with commands
6919 like @code{step} or @code{next}.
6921 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6922 Since thread scheduling is up to your debugging target's operating
6923 system (not controlled by @value{GDBN}), other threads may
6924 execute more than one statement while the current thread completes a
6925 single step. Moreover, in general other threads stop in the middle of a
6926 statement, rather than at a clean statement boundary, when the program
6929 You might even find your program stopped in another thread after
6930 continuing or even single-stepping. This happens whenever some other
6931 thread runs into a breakpoint, a signal, or an exception before the
6932 first thread completes whatever you requested.
6934 @cindex automatic thread selection
6935 @cindex switching threads automatically
6936 @cindex threads, automatic switching
6937 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6938 signal, it automatically selects the thread where that breakpoint or
6939 signal happened. @value{GDBN} alerts you to the context switch with a
6940 message such as @samp{[Switching to Thread @var{n}]} to identify the
6943 On some OSes, you can modify @value{GDBN}'s default behavior by
6944 locking the OS scheduler to allow only a single thread to run.
6947 @item set scheduler-locking @var{mode}
6948 @cindex scheduler locking mode
6949 @cindex lock scheduler
6950 Set the scheduler locking mode. It applies to normal execution,
6951 record mode, and replay mode. @var{mode} can be one of
6956 There is no locking and any thread may run at any time.
6959 Only the current thread may run when the inferior is resumed.
6962 Behaves like @code{on} when stepping, and @code{off} otherwise.
6963 Threads other than the current never get a chance to run when you
6964 step, and they are completely free to run when you use commands like
6965 @samp{continue}, @samp{until}, or @samp{finish}.
6967 This mode optimizes for single-stepping; it prevents other threads
6968 from preempting the current thread while you are stepping, so that the
6969 focus of debugging does not change unexpectedly. However, unless
6970 another thread hits a breakpoint during its timeslice, @value{GDBN}
6971 does not change the current thread away from the thread that you are
6975 Behaves like @code{on} in replay mode, and @code{off} in either record
6976 mode or during normal execution. This is the default mode.
6979 @item show scheduler-locking
6980 Display the current scheduler locking mode.
6983 @cindex resume threads of multiple processes simultaneously
6984 By default, when you issue one of the execution commands such as
6985 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6986 threads of the current inferior to run. For example, if @value{GDBN}
6987 is attached to two inferiors, each with two threads, the
6988 @code{continue} command resumes only the two threads of the current
6989 inferior. This is useful, for example, when you debug a program that
6990 forks and you want to hold the parent stopped (so that, for instance,
6991 it doesn't run to exit), while you debug the child. In other
6992 situations, you may not be interested in inspecting the current state
6993 of any of the processes @value{GDBN} is attached to, and you may want
6994 to resume them all until some breakpoint is hit. In the latter case,
6995 you can instruct @value{GDBN} to allow all threads of all the
6996 inferiors to run with the @w{@code{set schedule-multiple}} command.
6999 @kindex set schedule-multiple
7000 @item set schedule-multiple
7001 Set the mode for allowing threads of multiple processes to be resumed
7002 when an execution command is issued. When @code{on}, all threads of
7003 all processes are allowed to run. When @code{off}, only the threads
7004 of the current process are resumed. The default is @code{off}. The
7005 @code{scheduler-locking} mode takes precedence when set to @code{on},
7006 or while you are stepping and set to @code{step}.
7008 @item show schedule-multiple
7009 Display the current mode for resuming the execution of threads of
7014 @subsection Non-Stop Mode
7016 @cindex non-stop mode
7018 @c This section is really only a place-holder, and needs to be expanded
7019 @c with more details.
7021 For some multi-threaded targets, @value{GDBN} supports an optional
7022 mode of operation in which you can examine stopped program threads in
7023 the debugger while other threads continue to execute freely. This
7024 minimizes intrusion when debugging live systems, such as programs
7025 where some threads have real-time constraints or must continue to
7026 respond to external events. This is referred to as @dfn{non-stop} mode.
7028 In non-stop mode, when a thread stops to report a debugging event,
7029 @emph{only} that thread is stopped; @value{GDBN} does not stop other
7030 threads as well, in contrast to the all-stop mode behavior. Additionally,
7031 execution commands such as @code{continue} and @code{step} apply by default
7032 only to the current thread in non-stop mode, rather than all threads as
7033 in all-stop mode. This allows you to control threads explicitly in
7034 ways that are not possible in all-stop mode --- for example, stepping
7035 one thread while allowing others to run freely, stepping
7036 one thread while holding all others stopped, or stepping several threads
7037 independently and simultaneously.
7039 To enter non-stop mode, use this sequence of commands before you run
7040 or attach to your program:
7043 # If using the CLI, pagination breaks non-stop.
7046 # Finally, turn it on!
7050 You can use these commands to manipulate the non-stop mode setting:
7053 @kindex set non-stop
7054 @item set non-stop on
7055 Enable selection of non-stop mode.
7056 @item set non-stop off
7057 Disable selection of non-stop mode.
7058 @kindex show non-stop
7060 Show the current non-stop enablement setting.
7063 Note these commands only reflect whether non-stop mode is enabled,
7064 not whether the currently-executing program is being run in non-stop mode.
7065 In particular, the @code{set non-stop} preference is only consulted when
7066 @value{GDBN} starts or connects to the target program, and it is generally
7067 not possible to switch modes once debugging has started. Furthermore,
7068 since not all targets support non-stop mode, even when you have enabled
7069 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
7072 In non-stop mode, all execution commands apply only to the current thread
7073 by default. That is, @code{continue} only continues one thread.
7074 To continue all threads, issue @code{continue -a} or @code{c -a}.
7076 You can use @value{GDBN}'s background execution commands
7077 (@pxref{Background Execution}) to run some threads in the background
7078 while you continue to examine or step others from @value{GDBN}.
7079 The MI execution commands (@pxref{GDB/MI Program Execution}) are
7080 always executed asynchronously in non-stop mode.
7082 Suspending execution is done with the @code{interrupt} command when
7083 running in the background, or @kbd{Ctrl-c} during foreground execution.
7084 In all-stop mode, this stops the whole process;
7085 but in non-stop mode the interrupt applies only to the current thread.
7086 To stop the whole program, use @code{interrupt -a}.
7088 Other execution commands do not currently support the @code{-a} option.
7090 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
7091 that thread current, as it does in all-stop mode. This is because the
7092 thread stop notifications are asynchronous with respect to @value{GDBN}'s
7093 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
7094 changed to a different thread just as you entered a command to operate on the
7095 previously current thread.
7097 @node Background Execution
7098 @subsection Background Execution
7100 @cindex foreground execution
7101 @cindex background execution
7102 @cindex asynchronous execution
7103 @cindex execution, foreground, background and asynchronous
7105 @value{GDBN}'s execution commands have two variants: the normal
7106 foreground (synchronous) behavior, and a background
7107 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
7108 the program to report that some thread has stopped before prompting for
7109 another command. In background execution, @value{GDBN} immediately gives
7110 a command prompt so that you can issue other commands while your program runs.
7112 If the target doesn't support async mode, @value{GDBN} issues an error
7113 message if you attempt to use the background execution commands.
7115 @cindex @code{&}, background execution of commands
7116 To specify background execution, add a @code{&} to the command. For example,
7117 the background form of the @code{continue} command is @code{continue&}, or
7118 just @code{c&}. The execution commands that accept background execution
7124 @xref{Starting, , Starting your Program}.
7128 @xref{Attach, , Debugging an Already-running Process}.
7132 @xref{Continuing and Stepping, step}.
7136 @xref{Continuing and Stepping, stepi}.
7140 @xref{Continuing and Stepping, next}.
7144 @xref{Continuing and Stepping, nexti}.
7148 @xref{Continuing and Stepping, continue}.
7152 @xref{Continuing and Stepping, finish}.
7156 @xref{Continuing and Stepping, until}.
7160 Background execution is especially useful in conjunction with non-stop
7161 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
7162 However, you can also use these commands in the normal all-stop mode with
7163 the restriction that you cannot issue another execution command until the
7164 previous one finishes. Examples of commands that are valid in all-stop
7165 mode while the program is running include @code{help} and @code{info break}.
7167 You can interrupt your program while it is running in the background by
7168 using the @code{interrupt} command.
7175 Suspend execution of the running program. In all-stop mode,
7176 @code{interrupt} stops the whole process, but in non-stop mode, it stops
7177 only the current thread. To stop the whole program in non-stop mode,
7178 use @code{interrupt -a}.
7181 @node Thread-Specific Breakpoints
7182 @subsection Thread-Specific Breakpoints
7184 When your program has multiple threads (@pxref{Threads,, Debugging
7185 Programs with Multiple Threads}), you can choose whether to set
7186 breakpoints on all threads, or on a particular thread.
7189 @cindex breakpoints and threads
7190 @cindex thread breakpoints
7191 @kindex break @dots{} thread @var{thread-id}
7192 @item break @var{locspec} thread @var{thread-id}
7193 @itemx break @var{locspec} thread @var{thread-id} if @dots{}
7194 @var{locspec} specifies a code location or locations in your program.
7195 @xref{Location Specifications}, for details.
7197 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
7198 to specify that you only want @value{GDBN} to stop the program when a
7199 particular thread reaches this breakpoint. The @var{thread-id} specifier
7200 is one of the thread identifiers assigned by @value{GDBN}, shown
7201 in the first column of the @samp{info threads} display.
7203 If you do not specify @samp{thread @var{thread-id}} when you set a
7204 breakpoint, the breakpoint applies to @emph{all} threads of your
7207 You can use the @code{thread} qualifier on conditional breakpoints as
7208 well; in this case, place @samp{thread @var{thread-id}} before or
7209 after the breakpoint condition, like this:
7212 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
7217 Thread-specific breakpoints are automatically deleted when
7218 @value{GDBN} detects the corresponding thread is no longer in the
7219 thread list. For example:
7223 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
7226 There are several ways for a thread to disappear, such as a regular
7227 thread exit, but also when you detach from the process with the
7228 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
7229 Process}), or if @value{GDBN} loses the remote connection
7230 (@pxref{Remote Debugging}), etc. Note that with some targets,
7231 @value{GDBN} is only able to detect a thread has exited when the user
7232 explictly asks for the thread list with the @code{info threads}
7235 @node Interrupted System Calls
7236 @subsection Interrupted System Calls
7238 @cindex thread breakpoints and system calls
7239 @cindex system calls and thread breakpoints
7240 @cindex premature return from system calls
7241 There is an unfortunate side effect when using @value{GDBN} to debug
7242 multi-threaded programs. If one thread stops for a
7243 breakpoint, or for some other reason, and another thread is blocked in a
7244 system call, then the system call may return prematurely. This is a
7245 consequence of the interaction between multiple threads and the signals
7246 that @value{GDBN} uses to implement breakpoints and other events that
7249 To handle this problem, your program should check the return value of
7250 each system call and react appropriately. This is good programming
7253 For example, do not write code like this:
7259 The call to @code{sleep} will return early if a different thread stops
7260 at a breakpoint or for some other reason.
7262 Instead, write this:
7267 unslept = sleep (unslept);
7270 A system call is allowed to return early, so the system is still
7271 conforming to its specification. But @value{GDBN} does cause your
7272 multi-threaded program to behave differently than it would without
7275 Also, @value{GDBN} uses internal breakpoints in the thread library to
7276 monitor certain events such as thread creation and thread destruction.
7277 When such an event happens, a system call in another thread may return
7278 prematurely, even though your program does not appear to stop.
7281 @subsection Observer Mode
7283 If you want to build on non-stop mode and observe program behavior
7284 without any chance of disruption by @value{GDBN}, you can set
7285 variables to disable all of the debugger's attempts to modify state,
7286 whether by writing memory, inserting breakpoints, etc. These operate
7287 at a low level, intercepting operations from all commands.
7289 When all of these are set to @code{off}, then @value{GDBN} is said to
7290 be @dfn{observer mode}. As a convenience, the variable
7291 @code{observer} can be set to disable these, plus enable non-stop
7294 Note that @value{GDBN} will not prevent you from making nonsensical
7295 combinations of these settings. For instance, if you have enabled
7296 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7297 then breakpoints that work by writing trap instructions into the code
7298 stream will still not be able to be placed.
7303 @item set observer on
7304 @itemx set observer off
7305 When set to @code{on}, this disables all the permission variables
7306 below (except for @code{insert-fast-tracepoints}), plus enables
7307 non-stop debugging. Setting this to @code{off} switches back to
7308 normal debugging, though remaining in non-stop mode.
7311 Show whether observer mode is on or off.
7313 @kindex may-write-registers
7314 @item set may-write-registers on
7315 @itemx set may-write-registers off
7316 This controls whether @value{GDBN} will attempt to alter the values of
7317 registers, such as with assignment expressions in @code{print}, or the
7318 @code{jump} command. It defaults to @code{on}.
7320 @item show may-write-registers
7321 Show the current permission to write registers.
7323 @kindex may-write-memory
7324 @item set may-write-memory on
7325 @itemx set may-write-memory off
7326 This controls whether @value{GDBN} will attempt to alter the contents
7327 of memory, such as with assignment expressions in @code{print}. It
7328 defaults to @code{on}.
7330 @item show may-write-memory
7331 Show the current permission to write memory.
7333 @kindex may-insert-breakpoints
7334 @item set may-insert-breakpoints on
7335 @itemx set may-insert-breakpoints off
7336 This controls whether @value{GDBN} will attempt to insert breakpoints.
7337 This affects all breakpoints, including internal breakpoints defined
7338 by @value{GDBN}. It defaults to @code{on}.
7340 @item show may-insert-breakpoints
7341 Show the current permission to insert breakpoints.
7343 @kindex may-insert-tracepoints
7344 @item set may-insert-tracepoints on
7345 @itemx set may-insert-tracepoints off
7346 This controls whether @value{GDBN} will attempt to insert (regular)
7347 tracepoints at the beginning of a tracing experiment. It affects only
7348 non-fast tracepoints, fast tracepoints being under the control of
7349 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7351 @item show may-insert-tracepoints
7352 Show the current permission to insert tracepoints.
7354 @kindex may-insert-fast-tracepoints
7355 @item set may-insert-fast-tracepoints on
7356 @itemx set may-insert-fast-tracepoints off
7357 This controls whether @value{GDBN} will attempt to insert fast
7358 tracepoints at the beginning of a tracing experiment. It affects only
7359 fast tracepoints, regular (non-fast) tracepoints being under the
7360 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7362 @item show may-insert-fast-tracepoints
7363 Show the current permission to insert fast tracepoints.
7365 @kindex may-interrupt
7366 @item set may-interrupt on
7367 @itemx set may-interrupt off
7368 This controls whether @value{GDBN} will attempt to interrupt or stop
7369 program execution. When this variable is @code{off}, the
7370 @code{interrupt} command will have no effect, nor will
7371 @kbd{Ctrl-c}. It defaults to @code{on}.
7373 @item show may-interrupt
7374 Show the current permission to interrupt or stop the program.
7378 @node Reverse Execution
7379 @chapter Running programs backward
7380 @cindex reverse execution
7381 @cindex running programs backward
7383 When you are debugging a program, it is not unusual to realize that
7384 you have gone too far, and some event of interest has already happened.
7385 If the target environment supports it, @value{GDBN} can allow you to
7386 ``rewind'' the program by running it backward.
7388 A target environment that supports reverse execution should be able
7389 to ``undo'' the changes in machine state that have taken place as the
7390 program was executing normally. Variables, registers etc.@: should
7391 revert to their previous values. Obviously this requires a great
7392 deal of sophistication on the part of the target environment; not
7393 all target environments can support reverse execution.
7395 When a program is executed in reverse, the instructions that
7396 have most recently been executed are ``un-executed'', in reverse
7397 order. The program counter runs backward, following the previous
7398 thread of execution in reverse. As each instruction is ``un-executed'',
7399 the values of memory and/or registers that were changed by that
7400 instruction are reverted to their previous states. After executing
7401 a piece of source code in reverse, all side effects of that code
7402 should be ``undone'', and all variables should be returned to their
7403 prior values@footnote{
7404 Note that some side effects are easier to undo than others. For instance,
7405 memory and registers are relatively easy, but device I/O is hard. Some
7406 targets may be able undo things like device I/O, and some may not.
7408 The contract between @value{GDBN} and the reverse executing target
7409 requires only that the target do something reasonable when
7410 @value{GDBN} tells it to execute backwards, and then report the
7411 results back to @value{GDBN}. Whatever the target reports back to
7412 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7413 assumes that the memory and registers that the target reports are in a
7414 consistent state, but @value{GDBN} accepts whatever it is given.
7417 On some platforms, @value{GDBN} has built-in support for reverse
7418 execution, activated with the @code{record} or @code{record btrace}
7419 commands. @xref{Process Record and Replay}. Some remote targets,
7420 typically full system emulators, support reverse execution directly
7421 without requiring any special command.
7423 If you are debugging in a target environment that supports
7424 reverse execution, @value{GDBN} provides the following commands.
7427 @kindex reverse-continue
7428 @kindex rc @r{(@code{reverse-continue})}
7429 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7430 @itemx rc @r{[}@var{ignore-count}@r{]}
7431 Beginning at the point where your program last stopped, start executing
7432 in reverse. Reverse execution will stop for breakpoints and synchronous
7433 exceptions (signals), just like normal execution. Behavior of
7434 asynchronous signals depends on the target environment.
7436 @kindex reverse-step
7437 @kindex rs @r{(@code{step})}
7438 @item reverse-step @r{[}@var{count}@r{]}
7439 Run the program backward until control reaches the start of a
7440 different source line; then stop it, and return control to @value{GDBN}.
7442 Like the @code{step} command, @code{reverse-step} will only stop
7443 at the beginning of a source line. It ``un-executes'' the previously
7444 executed source line. If the previous source line included calls to
7445 debuggable functions, @code{reverse-step} will step (backward) into
7446 the called function, stopping at the beginning of the @emph{last}
7447 statement in the called function (typically a return statement).
7449 Also, as with the @code{step} command, if non-debuggable functions are
7450 called, @code{reverse-step} will run thru them backward without stopping.
7452 @kindex reverse-stepi
7453 @kindex rsi @r{(@code{reverse-stepi})}
7454 @item reverse-stepi @r{[}@var{count}@r{]}
7455 Reverse-execute one machine instruction. Note that the instruction
7456 to be reverse-executed is @emph{not} the one pointed to by the program
7457 counter, but the instruction executed prior to that one. For instance,
7458 if the last instruction was a jump, @code{reverse-stepi} will take you
7459 back from the destination of the jump to the jump instruction itself.
7461 @kindex reverse-next
7462 @kindex rn @r{(@code{reverse-next})}
7463 @item reverse-next @r{[}@var{count}@r{]}
7464 Run backward to the beginning of the previous line executed in
7465 the current (innermost) stack frame. If the line contains function
7466 calls, they will be ``un-executed'' without stopping. Starting from
7467 the first line of a function, @code{reverse-next} will take you back
7468 to the caller of that function, @emph{before} the function was called,
7469 just as the normal @code{next} command would take you from the last
7470 line of a function back to its return to its caller
7471 @footnote{Unless the code is too heavily optimized.}.
7473 @kindex reverse-nexti
7474 @kindex rni @r{(@code{reverse-nexti})}
7475 @item reverse-nexti @r{[}@var{count}@r{]}
7476 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7477 in reverse, except that called functions are ``un-executed'' atomically.
7478 That is, if the previously executed instruction was a return from
7479 another function, @code{reverse-nexti} will continue to execute
7480 in reverse until the call to that function (from the current stack
7483 @kindex reverse-finish
7484 @item reverse-finish
7485 Just as the @code{finish} command takes you to the point where the
7486 current function returns, @code{reverse-finish} takes you to the point
7487 where it was called. Instead of ending up at the end of the current
7488 function invocation, you end up at the beginning.
7490 @kindex set exec-direction
7491 @item set exec-direction
7492 Set the direction of target execution.
7493 @item set exec-direction reverse
7494 @cindex execute forward or backward in time
7495 @value{GDBN} will perform all execution commands in reverse, until the
7496 exec-direction mode is changed to ``forward''. Affected commands include
7497 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7498 command cannot be used in reverse mode.
7499 @item set exec-direction forward
7500 @value{GDBN} will perform all execution commands in the normal fashion.
7501 This is the default.
7505 @node Process Record and Replay
7506 @chapter Recording Inferior's Execution and Replaying It
7507 @cindex process record and replay
7508 @cindex recording inferior's execution and replaying it
7510 On some platforms, @value{GDBN} provides a special @dfn{process record
7511 and replay} target that can record a log of the process execution, and
7512 replay it later with both forward and reverse execution commands.
7515 When this target is in use, if the execution log includes the record
7516 for the next instruction, @value{GDBN} will debug in @dfn{replay
7517 mode}. In the replay mode, the inferior does not really execute code
7518 instructions. Instead, all the events that normally happen during
7519 code execution are taken from the execution log. While code is not
7520 really executed in replay mode, the values of registers (including the
7521 program counter register) and the memory of the inferior are still
7522 changed as they normally would. Their contents are taken from the
7526 If the record for the next instruction is not in the execution log,
7527 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7528 inferior executes normally, and @value{GDBN} records the execution log
7531 The process record and replay target supports reverse execution
7532 (@pxref{Reverse Execution}), even if the platform on which the
7533 inferior runs does not. However, the reverse execution is limited in
7534 this case by the range of the instructions recorded in the execution
7535 log. In other words, reverse execution on platforms that don't
7536 support it directly can only be done in the replay mode.
7538 When debugging in the reverse direction, @value{GDBN} will work in
7539 replay mode as long as the execution log includes the record for the
7540 previous instruction; otherwise, it will work in record mode, if the
7541 platform supports reverse execution, or stop if not.
7543 Currently, process record and replay is supported on ARM, Aarch64,
7544 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7545 GNU/Linux. Process record and replay can be used both when native
7546 debugging, and when remote debugging via @code{gdbserver}.
7548 For architecture environments that support process record and replay,
7549 @value{GDBN} provides the following commands:
7552 @kindex target record
7553 @kindex target record-full
7554 @kindex target record-btrace
7557 @kindex record btrace
7558 @kindex record btrace bts
7559 @kindex record btrace pt
7565 @kindex rec btrace bts
7566 @kindex rec btrace pt
7569 @item record @var{method}
7570 This command starts the process record and replay target. The
7571 recording method can be specified as parameter. Without a parameter
7572 the command uses the @code{full} recording method. The following
7573 recording methods are available:
7577 Full record/replay recording using @value{GDBN}'s software record and
7578 replay implementation. This method allows replaying and reverse
7581 @item btrace @var{format}
7582 Hardware-supported instruction recording, supported on Intel
7583 processors. This method does not record data. Further, the data is
7584 collected in a ring buffer so old data will be overwritten when the
7585 buffer is full. It allows limited reverse execution. Variables and
7586 registers are not available during reverse execution. In remote
7587 debugging, recording continues on disconnect. Recorded data can be
7588 inspected after reconnecting. The recording may be stopped using
7591 The recording format can be specified as parameter. Without a parameter
7592 the command chooses the recording format. The following recording
7593 formats are available:
7597 @cindex branch trace store
7598 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7599 this format, the processor stores a from/to record for each executed
7600 branch in the btrace ring buffer.
7603 @cindex Intel Processor Trace
7604 Use the @dfn{Intel Processor Trace} recording format. In this
7605 format, the processor stores the execution trace in a compressed form
7606 that is afterwards decoded by @value{GDBN}.
7608 The trace can be recorded with very low overhead. The compressed
7609 trace format also allows small trace buffers to already contain a big
7610 number of instructions compared to @acronym{BTS}.
7612 Decoding the recorded execution trace, on the other hand, is more
7613 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7614 increased number of instructions to process. You should increase the
7615 buffer-size with care.
7618 Not all recording formats may be available on all processors.
7621 The process record and replay target can only debug a process that is
7622 already running. Therefore, you need first to start the process with
7623 the @kbd{run} or @kbd{start} commands, and then start the recording
7624 with the @kbd{record @var{method}} command.
7626 @cindex displaced stepping, and process record and replay
7627 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7628 will be automatically disabled when process record and replay target
7629 is started. That's because the process record and replay target
7630 doesn't support displaced stepping.
7632 @cindex non-stop mode, and process record and replay
7633 @cindex asynchronous execution, and process record and replay
7634 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7635 the asynchronous execution mode (@pxref{Background Execution}), not
7636 all recording methods are available. The @code{full} recording method
7637 does not support these two modes.
7642 Stop the process record and replay target. When process record and
7643 replay target stops, the entire execution log will be deleted and the
7644 inferior will either be terminated, or will remain in its final state.
7646 When you stop the process record and replay target in record mode (at
7647 the end of the execution log), the inferior will be stopped at the
7648 next instruction that would have been recorded. In other words, if
7649 you record for a while and then stop recording, the inferior process
7650 will be left in the same state as if the recording never happened.
7652 On the other hand, if the process record and replay target is stopped
7653 while in replay mode (that is, not at the end of the execution log,
7654 but at some earlier point), the inferior process will become ``live''
7655 at that earlier state, and it will then be possible to continue the
7656 usual ``live'' debugging of the process from that state.
7658 When the inferior process exits, or @value{GDBN} detaches from it,
7659 process record and replay target will automatically stop itself.
7663 Go to a specific location in the execution log. There are several
7664 ways to specify the location to go to:
7667 @item record goto begin
7668 @itemx record goto start
7669 Go to the beginning of the execution log.
7671 @item record goto end
7672 Go to the end of the execution log.
7674 @item record goto @var{n}
7675 Go to instruction number @var{n} in the execution log.
7679 @item record save @var{filename}
7680 Save the execution log to a file @file{@var{filename}}.
7681 Default filename is @file{gdb_record.@var{process_id}}, where
7682 @var{process_id} is the process ID of the inferior.
7684 This command may not be available for all recording methods.
7686 @kindex record restore
7687 @item record restore @var{filename}
7688 Restore the execution log from a file @file{@var{filename}}.
7689 File must have been created with @code{record save}.
7691 @kindex set record full
7692 @item set record full insn-number-max @var{limit}
7693 @itemx set record full insn-number-max unlimited
7694 Set the limit of instructions to be recorded for the @code{full}
7695 recording method. Default value is 200000.
7697 If @var{limit} is a positive number, then @value{GDBN} will start
7698 deleting instructions from the log once the number of the record
7699 instructions becomes greater than @var{limit}. For every new recorded
7700 instruction, @value{GDBN} will delete the earliest recorded
7701 instruction to keep the number of recorded instructions at the limit.
7702 (Since deleting recorded instructions loses information, @value{GDBN}
7703 lets you control what happens when the limit is reached, by means of
7704 the @code{stop-at-limit} option, described below.)
7706 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7707 delete recorded instructions from the execution log. The number of
7708 recorded instructions is limited only by the available memory.
7710 @kindex show record full
7711 @item show record full insn-number-max
7712 Show the limit of instructions to be recorded with the @code{full}
7715 @item set record full stop-at-limit
7716 Control the behavior of the @code{full} recording method when the
7717 number of recorded instructions reaches the limit. If ON (the
7718 default), @value{GDBN} will stop when the limit is reached for the
7719 first time and ask you whether you want to stop the inferior or
7720 continue running it and recording the execution log. If you decide
7721 to continue recording, each new recorded instruction will cause the
7722 oldest one to be deleted.
7724 If this option is OFF, @value{GDBN} will automatically delete the
7725 oldest record to make room for each new one, without asking.
7727 @item show record full stop-at-limit
7728 Show the current setting of @code{stop-at-limit}.
7730 @item set record full memory-query
7731 Control the behavior when @value{GDBN} is unable to record memory
7732 changes caused by an instruction for the @code{full} recording method.
7733 If ON, @value{GDBN} will query whether to stop the inferior in that
7736 If this option is OFF (the default), @value{GDBN} will automatically
7737 ignore the effect of such instructions on memory. Later, when
7738 @value{GDBN} replays this execution log, it will mark the log of this
7739 instruction as not accessible, and it will not affect the replay
7742 @item show record full memory-query
7743 Show the current setting of @code{memory-query}.
7745 @kindex set record btrace
7746 The @code{btrace} record target does not trace data. As a
7747 convenience, when replaying, @value{GDBN} reads read-only memory off
7748 the live program directly, assuming that the addresses of the
7749 read-only areas don't change. This for example makes it possible to
7750 disassemble code while replaying, but not to print variables.
7751 In some cases, being able to inspect variables might be useful.
7752 You can use the following command for that:
7754 @item set record btrace replay-memory-access
7755 Control the behavior of the @code{btrace} recording method when
7756 accessing memory during replay. If @code{read-only} (the default),
7757 @value{GDBN} will only allow accesses to read-only memory.
7758 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7759 and to read-write memory. Beware that the accessed memory corresponds
7760 to the live target and not necessarily to the current replay
7763 @item set record btrace cpu @var{identifier}
7764 Set the processor to be used for enabling workarounds for processor
7765 errata when decoding the trace.
7767 Processor errata are defects in processor operation, caused by its
7768 design or manufacture. They can cause a trace not to match the
7769 specification. This, in turn, may cause trace decode to fail.
7770 @value{GDBN} can detect erroneous trace packets and correct them, thus
7771 avoiding the decoding failures. These corrections are known as
7772 @dfn{errata workarounds}, and are enabled based on the processor on
7773 which the trace was recorded.
7775 By default, @value{GDBN} attempts to detect the processor
7776 automatically, and apply the necessary workarounds for it. However,
7777 you may need to specify the processor if @value{GDBN} does not yet
7778 support it. This command allows you to do that, and also allows to
7779 disable the workarounds.
7781 The argument @var{identifier} identifies the @sc{cpu} and is of the
7782 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7783 there are two special identifiers, @code{none} and @code{auto}
7786 The following vendor identifiers and corresponding processor
7787 identifiers are currently supported:
7789 @multitable @columnfractions .1 .9
7792 @tab @var{family}/@var{model}[/@var{stepping}]
7796 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7797 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7799 If @var{identifier} is @code{auto}, enable errata workarounds for the
7800 processor on which the trace was recorded. If @var{identifier} is
7801 @code{none}, errata workarounds are disabled.
7803 For example, when using an old @value{GDBN} on a new system, decode
7804 may fail because @value{GDBN} does not support the new processor. It
7805 often suffices to specify an older processor that @value{GDBN}
7810 Active record target: record-btrace
7811 Recording format: Intel Processor Trace.
7813 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7814 (gdb) set record btrace cpu intel:6/158
7816 Active record target: record-btrace
7817 Recording format: Intel Processor Trace.
7819 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7822 @kindex show record btrace
7823 @item show record btrace replay-memory-access
7824 Show the current setting of @code{replay-memory-access}.
7826 @item show record btrace cpu
7827 Show the processor to be used for enabling trace decode errata
7830 @kindex set record btrace bts
7831 @item set record btrace bts buffer-size @var{size}
7832 @itemx set record btrace bts buffer-size unlimited
7833 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7834 format. Default is 64KB.
7836 If @var{size} is a positive number, then @value{GDBN} will try to
7837 allocate a buffer of at least @var{size} bytes for each new thread
7838 that uses the btrace recording method and the @acronym{BTS} format.
7839 The actually obtained buffer size may differ from the requested
7840 @var{size}. Use the @code{info record} command to see the actual
7841 buffer size for each thread that uses the btrace recording method and
7842 the @acronym{BTS} format.
7844 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7845 allocate a buffer of 4MB.
7847 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7848 also need longer to process the branch trace data before it can be used.
7850 @item show record btrace bts buffer-size @var{size}
7851 Show the current setting of the requested ring buffer size for branch
7852 tracing in @acronym{BTS} format.
7854 @kindex set record btrace pt
7855 @item set record btrace pt buffer-size @var{size}
7856 @itemx set record btrace pt buffer-size unlimited
7857 Set the requested ring buffer size for branch tracing in Intel
7858 Processor Trace format. Default is 16KB.
7860 If @var{size} is a positive number, then @value{GDBN} will try to
7861 allocate a buffer of at least @var{size} bytes for each new thread
7862 that uses the btrace recording method and the Intel Processor Trace
7863 format. The actually obtained buffer size may differ from the
7864 requested @var{size}. Use the @code{info record} command to see the
7865 actual buffer size for each thread.
7867 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7868 allocate a buffer of 4MB.
7870 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7871 also need longer to process the branch trace data before it can be used.
7873 @item show record btrace pt buffer-size @var{size}
7874 Show the current setting of the requested ring buffer size for branch
7875 tracing in Intel Processor Trace format.
7879 Show various statistics about the recording depending on the recording
7884 For the @code{full} recording method, it shows the state of process
7885 record and its in-memory execution log buffer, including:
7889 Whether in record mode or replay mode.
7891 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7893 Highest recorded instruction number.
7895 Current instruction about to be replayed (if in replay mode).
7897 Number of instructions contained in the execution log.
7899 Maximum number of instructions that may be contained in the execution log.
7903 For the @code{btrace} recording method, it shows:
7909 Number of instructions that have been recorded.
7911 Number of blocks of sequential control-flow formed by the recorded
7914 Whether in record mode or replay mode.
7917 For the @code{bts} recording format, it also shows:
7920 Size of the perf ring buffer.
7923 For the @code{pt} recording format, it also shows:
7926 Size of the perf ring buffer.
7930 @kindex record delete
7933 When record target runs in replay mode (``in the past''), delete the
7934 subsequent execution log and begin to record a new execution log starting
7935 from the current address. This means you will abandon the previously
7936 recorded ``future'' and begin recording a new ``future''.
7938 @kindex record instruction-history
7939 @kindex rec instruction-history
7940 @item record instruction-history
7941 Disassembles instructions from the recorded execution log. By
7942 default, ten instructions are disassembled. This can be changed using
7943 the @code{set record instruction-history-size} command. Instructions
7944 are printed in execution order.
7946 It can also print mixed source+disassembly if you specify the the
7947 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7948 as well as in symbolic form by specifying the @code{/r} or @code{/b}
7949 modifier. The behaviour of the @code{/m}, @code{/s}, @code{/r}, and
7950 @code{/b} modifiers are the same as for the @kbd{disassemble} command
7951 (@pxref{disassemble,,@kbd{disassemble}}).
7953 The current position marker is printed for the instruction at the
7954 current program counter value. This instruction can appear multiple
7955 times in the trace and the current position marker will be printed
7956 every time. To omit the current position marker, specify the
7959 To better align the printed instructions when the trace contains
7960 instructions from more than one function, the function name may be
7961 omitted by specifying the @code{/f} modifier.
7963 Speculatively executed instructions are prefixed with @samp{?}. This
7964 feature is not available for all recording formats.
7966 There are several ways to specify what part of the execution log to
7970 @item record instruction-history @var{insn}
7971 Disassembles ten instructions starting from instruction number
7974 @item record instruction-history @var{insn}, +/-@var{n}
7975 Disassembles @var{n} instructions around instruction number
7976 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7977 @var{n} instructions after instruction number @var{insn}. If
7978 @var{n} is preceded with @code{-}, disassembles @var{n}
7979 instructions before instruction number @var{insn}.
7981 @item record instruction-history
7982 Disassembles ten more instructions after the last disassembly.
7984 @item record instruction-history -
7985 Disassembles ten more instructions before the last disassembly.
7987 @item record instruction-history @var{begin}, @var{end}
7988 Disassembles instructions beginning with instruction number
7989 @var{begin} until instruction number @var{end}. The instruction
7990 number @var{end} is included.
7993 This command may not be available for all recording methods.
7996 @item set record instruction-history-size @var{size}
7997 @itemx set record instruction-history-size unlimited
7998 Define how many instructions to disassemble in the @code{record
7999 instruction-history} command. The default value is 10.
8000 A @var{size} of @code{unlimited} means unlimited instructions.
8003 @item show record instruction-history-size
8004 Show how many instructions to disassemble in the @code{record
8005 instruction-history} command.
8007 @kindex record function-call-history
8008 @kindex rec function-call-history
8009 @item record function-call-history
8010 Prints the execution history at function granularity. For each sequence
8011 of instructions that belong to the same function, it prints the name of
8012 that function, the source lines for this instruction sequence (if the
8013 @code{/l} modifier is specified), and the instructions numbers that form
8014 the sequence (if the @code{/i} modifier is specified). The function names
8015 are indented to reflect the call stack depth if the @code{/c} modifier is
8016 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be given
8020 (@value{GDBP}) @b{list 1, 10}
8031 (@value{GDBP}) @b{record function-call-history /ilc}
8032 1 bar inst 1,4 at foo.c:6,8
8033 2 foo inst 5,10 at foo.c:2,3
8034 3 bar inst 11,13 at foo.c:9,10
8037 By default, ten functions are printed. This can be changed using the
8038 @code{set record function-call-history-size} command. Functions are
8039 printed in execution order. There are several ways to specify what
8043 @item record function-call-history @var{func}
8044 Prints ten functions starting from function number @var{func}.
8046 @item record function-call-history @var{func}, +/-@var{n}
8047 Prints @var{n} functions around function number @var{func}. If
8048 @var{n} is preceded with @code{+}, prints @var{n} functions after
8049 function number @var{func}. If @var{n} is preceded with @code{-},
8050 prints @var{n} functions before function number @var{func}.
8052 @item record function-call-history
8053 Prints ten more functions after the last ten-function print.
8055 @item record function-call-history -
8056 Prints ten more functions before the last ten-function print.
8058 @item record function-call-history @var{begin}, @var{end}
8059 Prints functions beginning with function number @var{begin} until
8060 function number @var{end}. The function number @var{end} is included.
8063 This command may not be available for all recording methods.
8065 @item set record function-call-history-size @var{size}
8066 @itemx set record function-call-history-size unlimited
8067 Define how many functions to print in the
8068 @code{record function-call-history} command. The default value is 10.
8069 A size of @code{unlimited} means unlimited functions.
8071 @item show record function-call-history-size
8072 Show how many functions to print in the
8073 @code{record function-call-history} command.
8078 @chapter Examining the Stack
8080 When your program has stopped, the first thing you need to know is where it
8081 stopped and how it got there.
8084 Each time your program performs a function call, information about the call
8086 That information includes the location of the call in your program,
8087 the arguments of the call,
8088 and the local variables of the function being called.
8089 The information is saved in a block of data called a @dfn{stack frame}.
8090 The stack frames are allocated in a region of memory called the @dfn{call
8093 When your program stops, the @value{GDBN} commands for examining the
8094 stack allow you to see all of this information.
8096 @cindex selected frame
8097 One of the stack frames is @dfn{selected} by @value{GDBN} and many
8098 @value{GDBN} commands refer implicitly to the selected frame. In
8099 particular, whenever you ask @value{GDBN} for the value of a variable in
8100 your program, the value is found in the selected frame. There are
8101 special @value{GDBN} commands to select whichever frame you are
8102 interested in. @xref{Selection, ,Selecting a Frame}.
8104 When your program stops, @value{GDBN} automatically selects the
8105 currently executing frame and describes it briefly, similar to the
8106 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
8109 * Frames:: Stack frames
8110 * Backtrace:: Backtraces
8111 * Selection:: Selecting a frame
8112 * Frame Info:: Information on a frame
8113 * Frame Apply:: Applying a command to several frames
8114 * Frame Filter Management:: Managing frame filters
8119 @section Stack Frames
8121 @cindex frame, definition
8123 The call stack is divided up into contiguous pieces called @dfn{stack
8124 frames}, or @dfn{frames} for short; each frame is the data associated
8125 with one call to one function. The frame contains the arguments given
8126 to the function, the function's local variables, and the address at
8127 which the function is executing.
8129 @cindex initial frame
8130 @cindex outermost frame
8131 @cindex innermost frame
8132 When your program is started, the stack has only one frame, that of the
8133 function @code{main}. This is called the @dfn{initial} frame or the
8134 @dfn{outermost} frame. Each time a function is called, a new frame is
8135 made. Each time a function returns, the frame for that function invocation
8136 is eliminated. If a function is recursive, there can be many frames for
8137 the same function. The frame for the function in which execution is
8138 actually occurring is called the @dfn{innermost} frame. This is the most
8139 recently created of all the stack frames that still exist.
8141 @cindex frame pointer
8142 Inside your program, stack frames are identified by their addresses. A
8143 stack frame consists of many bytes, each of which has its own address; each
8144 kind of computer has a convention for choosing one byte whose
8145 address serves as the address of the frame. Usually this address is kept
8146 in a register called the @dfn{frame pointer register}
8147 (@pxref{Registers, $fp}) while execution is going on in that frame.
8150 @cindex frame number
8151 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
8152 number that is zero for the innermost frame, one for the frame that
8153 called it, and so on upward. These level numbers give you a way of
8154 designating stack frames in @value{GDBN} commands. The terms
8155 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
8156 describe this number.
8158 @c The -fomit-frame-pointer below perennially causes hbox overflow
8159 @c underflow problems.
8160 @cindex frameless execution
8161 Some compilers provide a way to compile functions so that they operate
8162 without stack frames. (For example, the @value{NGCC} option
8164 @samp{-fomit-frame-pointer}
8166 generates functions without a frame.)
8167 This is occasionally done with heavily used library functions to save
8168 the frame setup time. @value{GDBN} has limited facilities for dealing
8169 with these function invocations. If the innermost function invocation
8170 has no stack frame, @value{GDBN} nevertheless regards it as though
8171 it had a separate frame, which is numbered zero as usual, allowing
8172 correct tracing of the function call chain. However, @value{GDBN} has
8173 no provision for frameless functions elsewhere in the stack.
8179 @cindex call stack traces
8180 A backtrace is a summary of how your program got where it is. It shows one
8181 line per frame, for many frames, starting with the currently executing
8182 frame (frame zero), followed by its caller (frame one), and on up the
8185 @anchor{backtrace-command}
8187 @kindex bt @r{(@code{backtrace})}
8188 To print a backtrace of the entire stack, use the @code{backtrace}
8189 command, or its alias @code{bt}. This command will print one line per
8190 frame for frames in the stack. By default, all stack frames are
8191 printed. You can stop the backtrace at any time by typing the system
8192 interrupt character, normally @kbd{Ctrl-c}.
8195 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8196 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8197 Print the backtrace of the entire stack.
8199 The optional @var{count} can be one of the following:
8204 Print only the innermost @var{n} frames, where @var{n} is a positive
8209 Print only the outermost @var{n} frames, where @var{n} is a positive
8217 Print the values of the local variables also. This can be combined
8218 with the optional @var{count} to limit the number of frames shown.
8221 Do not run Python frame filters on this backtrace. @xref{Frame
8222 Filter API}, for more information. Additionally use @ref{disable
8223 frame-filter all} to turn off all frame filters. This is only
8224 relevant when @value{GDBN} has been configured with @code{Python}
8228 A Python frame filter might decide to ``elide'' some frames. Normally
8229 such elided frames are still printed, but they are indented relative
8230 to the filtered frames that cause them to be elided. The @code{-hide}
8231 option causes elided frames to not be printed at all.
8234 The @code{backtrace} command also supports a number of options that
8235 allow overriding relevant global print settings as set by @code{set
8236 backtrace} and @code{set print} subcommands:
8239 @item -past-main [@code{on}|@code{off}]
8240 Set whether backtraces should continue past @code{main}. Related setting:
8241 @ref{set backtrace past-main}.
8243 @item -past-entry [@code{on}|@code{off}]
8244 Set whether backtraces should continue past the entry point of a program.
8245 Related setting: @ref{set backtrace past-entry}.
8247 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8248 Set printing of function arguments at function entry.
8249 Related setting: @ref{set print entry-values}.
8251 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8252 Set printing of non-scalar frame arguments.
8253 Related setting: @ref{set print frame-arguments}.
8255 @item -raw-frame-arguments [@code{on}|@code{off}]
8256 Set whether to print frame arguments in raw form.
8257 Related setting: @ref{set print raw-frame-arguments}.
8259 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8260 Set printing of frame information.
8261 Related setting: @ref{set print frame-info}.
8264 The optional @var{qualifier} is maintained for backward compatibility.
8265 It can be one of the following:
8269 Equivalent to the @code{-full} option.
8272 Equivalent to the @code{-no-filters} option.
8275 Equivalent to the @code{-hide} option.
8282 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8283 are additional aliases for @code{backtrace}.
8285 @cindex multiple threads, backtrace
8286 In a multi-threaded program, @value{GDBN} by default shows the
8287 backtrace only for the current thread. To display the backtrace for
8288 several or all of the threads, use the command @code{thread apply}
8289 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8290 apply all backtrace}, @value{GDBN} will display the backtrace for all
8291 the threads; this is handy when you debug a core dump of a
8292 multi-threaded program.
8294 Each line in the backtrace shows the frame number and the function name.
8295 The program counter value is also shown---unless you use @code{set
8296 print address off}. The backtrace also shows the source file name and
8297 line number, as well as the arguments to the function. The program
8298 counter value is omitted if it is at the beginning of the code for that
8301 Here is an example of a backtrace. It was made with the command
8302 @samp{bt 3}, so it shows the innermost three frames.
8306 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8308 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8309 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8311 (More stack frames follow...)
8316 The display for frame zero does not begin with a program counter
8317 value, indicating that your program has stopped at the beginning of the
8318 code for line @code{993} of @code{builtin.c}.
8321 The value of parameter @code{data} in frame 1 has been replaced by
8322 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8323 only if it is a scalar (integer, pointer, enumeration, etc). See command
8324 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8325 on how to configure the way function parameter values are printed.
8326 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8327 what frame information is printed.
8329 @cindex optimized out, in backtrace
8330 @cindex function call arguments, optimized out
8331 If your program was compiled with optimizations, some compilers will
8332 optimize away arguments passed to functions if those arguments are
8333 never used after the call. Such optimizations generate code that
8334 passes arguments through registers, but doesn't store those arguments
8335 in the stack frame. @value{GDBN} has no way of displaying such
8336 arguments in stack frames other than the innermost one. Here's what
8337 such a backtrace might look like:
8341 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8343 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8344 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8346 (More stack frames follow...)
8351 The values of arguments that were not saved in their stack frames are
8352 shown as @samp{<optimized out>}.
8354 If you need to display the values of such optimized-out arguments,
8355 either deduce that from other variables whose values depend on the one
8356 you are interested in, or recompile without optimizations.
8358 @cindex backtrace beyond @code{main} function
8359 @cindex program entry point
8360 @cindex startup code, and backtrace
8361 Most programs have a standard user entry point---a place where system
8362 libraries and startup code transition into user code. For C this is
8363 @code{main}@footnote{
8364 Note that embedded programs (the so-called ``free-standing''
8365 environment) are not required to have a @code{main} function as the
8366 entry point. They could even have multiple entry points.}.
8367 When @value{GDBN} finds the entry function in a backtrace
8368 it will terminate the backtrace, to avoid tracing into highly
8369 system-specific (and generally uninteresting) code.
8371 If you need to examine the startup code, or limit the number of levels
8372 in a backtrace, you can change this behavior:
8375 @item set backtrace past-main
8376 @itemx set backtrace past-main on
8377 @anchor{set backtrace past-main}
8378 @kindex set backtrace
8379 Backtraces will continue past the user entry point.
8381 @item set backtrace past-main off
8382 Backtraces will stop when they encounter the user entry point. This is the
8385 @item show backtrace past-main
8386 @kindex show backtrace
8387 Display the current user entry point backtrace policy.
8389 @item set backtrace past-entry
8390 @itemx set backtrace past-entry on
8391 @anchor{set backtrace past-entry}
8392 Backtraces will continue past the internal entry point of an application.
8393 This entry point is encoded by the linker when the application is built,
8394 and is likely before the user entry point @code{main} (or equivalent) is called.
8396 @item set backtrace past-entry off
8397 Backtraces will stop when they encounter the internal entry point of an
8398 application. This is the default.
8400 @item show backtrace past-entry
8401 Display the current internal entry point backtrace policy.
8403 @item set backtrace limit @var{n}
8404 @itemx set backtrace limit 0
8405 @itemx set backtrace limit unlimited
8406 @anchor{set backtrace limit}
8407 @cindex backtrace limit
8408 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8409 or zero means unlimited levels.
8411 @item show backtrace limit
8412 Display the current limit on backtrace levels.
8415 You can control how file names are displayed.
8418 @item set filename-display
8419 @itemx set filename-display relative
8420 @cindex filename-display
8421 Display file names relative to the compilation directory. This is the default.
8423 @item set filename-display basename
8424 Display only basename of a filename.
8426 @item set filename-display absolute
8427 Display an absolute filename.
8429 @item show filename-display
8430 Show the current way to display filenames.
8434 @section Selecting a Frame
8436 Most commands for examining the stack and other data in your program work on
8437 whichever stack frame is selected at the moment. Here are the commands for
8438 selecting a stack frame; all of them finish by printing a brief description
8439 of the stack frame just selected.
8442 @kindex frame@r{, selecting}
8443 @kindex f @r{(@code{frame})}
8444 @item frame @r{[} @var{frame-selection-spec} @r{]}
8445 @item f @r{[} @var{frame-selection-spec} @r{]}
8446 The @command{frame} command allows different stack frames to be
8447 selected. The @var{frame-selection-spec} can be any of the following:
8452 @item level @var{num}
8453 Select frame level @var{num}. Recall that frame zero is the innermost
8454 (currently executing) frame, frame one is the frame that called the
8455 innermost one, and so on. The highest level frame is usually the one
8458 As this is the most common method of navigating the frame stack, the
8459 string @command{level} can be omitted. For example, the following two
8460 commands are equivalent:
8463 (@value{GDBP}) frame 3
8464 (@value{GDBP}) frame level 3
8467 @kindex frame address
8468 @item address @var{stack-address}
8469 Select the frame with stack address @var{stack-address}. The
8470 @var{stack-address} for a frame can be seen in the output of
8471 @command{info frame}, for example:
8475 Stack level 1, frame at 0x7fffffffda30:
8476 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8477 tail call frame, caller of frame at 0x7fffffffda30
8478 source language c++.
8479 Arglist at unknown address.
8480 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8483 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8484 indicated by the line:
8487 Stack level 1, frame at 0x7fffffffda30:
8490 @kindex frame function
8491 @item function @var{function-name}
8492 Select the stack frame for function @var{function-name}. If there are
8493 multiple stack frames for function @var{function-name} then the inner
8494 most stack frame is selected.
8497 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8498 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8499 viewed has stack address @var{stack-addr}, and optionally, a program
8500 counter address of @var{pc-addr}.
8502 This is useful mainly if the chaining of stack frames has been
8503 damaged by a bug, making it impossible for @value{GDBN} to assign
8504 numbers properly to all frames. In addition, this can be useful
8505 when your program has multiple stacks and switches between them.
8507 When viewing a frame outside the current backtrace using
8508 @command{frame view} then you can always return to the original
8509 stack using one of the previous stack frame selection instructions,
8510 for example @command{frame level 0}.
8516 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8517 numbers @var{n}, this advances toward the outermost frame, to higher
8518 frame numbers, to frames that have existed longer.
8521 @kindex do @r{(@code{down})}
8523 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8524 positive numbers @var{n}, this advances toward the innermost frame, to
8525 lower frame numbers, to frames that were created more recently.
8526 You may abbreviate @code{down} as @code{do}.
8529 All of these commands end by printing two lines of output describing the
8530 frame. The first line shows the frame number, the function name, the
8531 arguments, and the source file and line number of execution in that
8532 frame. The second line shows the text of that source line.
8540 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8542 10 read_input_file (argv[i]);
8546 After such a printout, the @code{list} command with no arguments
8547 prints ten lines centered on the point of execution in the frame.
8548 You can also edit the program at the point of execution with your favorite
8549 editing program by typing @code{edit}.
8550 @xref{List, ,Printing Source Lines},
8554 @kindex select-frame
8555 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8556 The @code{select-frame} command is a variant of @code{frame} that does
8557 not display the new frame after selecting it. This command is
8558 intended primarily for use in @value{GDBN} command scripts, where the
8559 output might be unnecessary and distracting. The
8560 @var{frame-selection-spec} is as for the @command{frame} command
8561 described in @ref{Selection, ,Selecting a Frame}.
8563 @kindex down-silently
8565 @item up-silently @var{n}
8566 @itemx down-silently @var{n}
8567 These two commands are variants of @code{up} and @code{down},
8568 respectively; they differ in that they do their work silently, without
8569 causing display of the new frame. They are intended primarily for use
8570 in @value{GDBN} command scripts, where the output might be unnecessary and
8575 @section Information About a Frame
8577 There are several other commands to print information about the selected
8583 When used without any argument, this command does not change which
8584 frame is selected, but prints a brief description of the currently
8585 selected stack frame. It can be abbreviated @code{f}. With an
8586 argument, this command is used to select a stack frame.
8587 @xref{Selection, ,Selecting a Frame}.
8590 @kindex info f @r{(@code{info frame})}
8593 This command prints a verbose description of the selected stack frame,
8598 the address of the frame
8600 the address of the next frame down (called by this frame)
8602 the address of the next frame up (caller of this frame)
8604 the language in which the source code corresponding to this frame is written
8606 the address of the frame's arguments
8608 the address of the frame's local variables
8610 the program counter saved in it (the address of execution in the caller frame)
8612 which registers were saved in the frame
8615 @noindent The verbose description is useful when
8616 something has gone wrong that has made the stack format fail to fit
8617 the usual conventions.
8619 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8620 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8621 Print a verbose description of the frame selected by
8622 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8623 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8624 a Frame}). The selected frame remains unchanged by this command.
8627 @item info args [-q]
8628 Print the arguments of the selected frame, each on a separate line.
8630 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8631 printing header information and messages explaining why no argument
8634 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8635 Like @kbd{info args}, but only print the arguments selected
8636 with the provided regexp(s).
8638 If @var{regexp} is provided, print only the arguments whose names
8639 match the regular expression @var{regexp}.
8641 If @var{type_regexp} is provided, print only the arguments whose
8642 types, as printed by the @code{whatis} command, match
8643 the regular expression @var{type_regexp}.
8644 If @var{type_regexp} contains space(s), it should be enclosed in
8645 quote characters. If needed, use backslash to escape the meaning
8646 of special characters or quotes.
8648 If both @var{regexp} and @var{type_regexp} are provided, an argument
8649 is printed only if its name matches @var{regexp} and its type matches
8652 @item info locals [-q]
8654 Print the local variables of the selected frame, each on a separate
8655 line. These are all variables (declared either static or automatic)
8656 accessible at the point of execution of the selected frame.
8658 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8659 printing header information and messages explaining why no local variables
8662 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8663 Like @kbd{info locals}, but only print the local variables selected
8664 with the provided regexp(s).
8666 If @var{regexp} is provided, print only the local variables whose names
8667 match the regular expression @var{regexp}.
8669 If @var{type_regexp} is provided, print only the local variables whose
8670 types, as printed by the @code{whatis} command, match
8671 the regular expression @var{type_regexp}.
8672 If @var{type_regexp} contains space(s), it should be enclosed in
8673 quote characters. If needed, use backslash to escape the meaning
8674 of special characters or quotes.
8676 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8677 is printed only if its name matches @var{regexp} and its type matches
8680 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8681 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8682 For example, your program might use Resource Acquisition Is
8683 Initialization types (RAII) such as @code{lock_something_t}: each
8684 local variable of type @code{lock_something_t} automatically places a
8685 lock that is destroyed when the variable goes out of scope. You can
8686 then list all acquired locks in your program by doing
8688 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8691 or the equivalent shorter form
8693 tfaas i lo -q -t lock_something_t
8699 @section Applying a Command to Several Frames.
8701 @cindex apply command to several frames
8703 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8704 The @code{frame apply} command allows you to apply the named
8705 @var{command} to one or more frames.
8709 Specify @code{all} to apply @var{command} to all frames.
8712 Use @var{count} to apply @var{command} to the innermost @var{count}
8713 frames, where @var{count} is a positive number.
8716 Use @var{-count} to apply @var{command} to the outermost @var{count}
8717 frames, where @var{count} is a positive number.
8720 Use @code{level} to apply @var{command} to the set of frames identified
8721 by the @var{level} list. @var{level} is a frame level or a range of frame
8722 levels as @var{level1}-@var{level2}. The frame level is the number shown
8723 in the first field of the @samp{backtrace} command output.
8724 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8725 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8729 Note that the frames on which @code{frame apply} applies a command are
8730 also influenced by the @code{set backtrace} settings such as @code{set
8731 backtrace past-main} and @code{set backtrace limit N}.
8732 @xref{Backtrace,,Backtraces}.
8734 The @code{frame apply} command also supports a number of options that
8735 allow overriding relevant @code{set backtrace} settings:
8738 @item -past-main [@code{on}|@code{off}]
8739 Whether backtraces should continue past @code{main}.
8740 Related setting: @ref{set backtrace past-main}.
8742 @item -past-entry [@code{on}|@code{off}]
8743 Whether backtraces should continue past the entry point of a program.
8744 Related setting: @ref{set backtrace past-entry}.
8747 By default, @value{GDBN} displays some frame information before the
8748 output produced by @var{command}, and an error raised during the
8749 execution of a @var{command} will abort @code{frame apply}. The
8750 following options can be used to fine-tune these behaviors:
8754 The flag @code{-c}, which stands for @samp{continue}, causes any
8755 errors in @var{command} to be displayed, and the execution of
8756 @code{frame apply} then continues.
8758 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8759 or empty output produced by a @var{command} to be silently ignored.
8760 That is, the execution continues, but the frame information and errors
8763 The flag @code{-q} (@samp{quiet}) disables printing the frame
8767 The following example shows how the flags @code{-c} and @code{-s} are
8768 working when applying the command @code{p j} to all frames, where
8769 variable @code{j} can only be successfully printed in the outermost
8770 @code{#1 main} frame.
8774 (gdb) frame apply all p j
8775 #0 some_function (i=5) at fun.c:4
8776 No symbol "j" in current context.
8777 (gdb) frame apply all -c p j
8778 #0 some_function (i=5) at fun.c:4
8779 No symbol "j" in current context.
8780 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8782 (gdb) frame apply all -s p j
8783 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8789 By default, @samp{frame apply}, prints the frame location
8790 information before the command output:
8794 (gdb) frame apply all p $sp
8795 #0 some_function (i=5) at fun.c:4
8796 $4 = (void *) 0xffffd1e0
8797 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8798 $5 = (void *) 0xffffd1f0
8803 If the flag @code{-q} is given, no frame information is printed:
8806 (gdb) frame apply all -q p $sp
8807 $12 = (void *) 0xffffd1e0
8808 $13 = (void *) 0xffffd1f0
8818 @cindex apply a command to all frames (ignoring errors and empty output)
8819 @item faas @var{command}
8820 Shortcut for @code{frame apply all -s @var{command}}.
8821 Applies @var{command} on all frames, ignoring errors and empty output.
8823 It can for example be used to print a local variable or a function
8824 argument without knowing the frame where this variable or argument
8827 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8830 The @code{faas} command accepts the same options as the @code{frame
8831 apply} command. @xref{Frame Apply,,frame apply}.
8833 Note that the command @code{tfaas @var{command}} applies @var{command}
8834 on all frames of all threads. See @xref{Threads,,Threads}.
8838 @node Frame Filter Management
8839 @section Management of Frame Filters.
8840 @cindex managing frame filters
8842 Frame filters are Python based utilities to manage and decorate the
8843 output of frames. @xref{Frame Filter API}, for further information.
8845 Managing frame filters is performed by several commands available
8846 within @value{GDBN}, detailed here.
8849 @kindex info frame-filter
8850 @item info frame-filter
8851 Print a list of installed frame filters from all dictionaries, showing
8852 their name, priority and enabled status.
8854 @kindex disable frame-filter
8855 @anchor{disable frame-filter all}
8856 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8857 Disable a frame filter in the dictionary matching
8858 @var{filter-dictionary} and @var{filter-name}. The
8859 @var{filter-dictionary} may be @code{all}, @code{global},
8860 @code{progspace}, or the name of the object file where the frame filter
8861 dictionary resides. When @code{all} is specified, all frame filters
8862 across all dictionaries are disabled. The @var{filter-name} is the name
8863 of the frame filter and is used when @code{all} is not the option for
8864 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8865 may be enabled again later.
8867 @kindex enable frame-filter
8868 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8869 Enable a frame filter in the dictionary matching
8870 @var{filter-dictionary} and @var{filter-name}. The
8871 @var{filter-dictionary} may be @code{all}, @code{global},
8872 @code{progspace} or the name of the object file where the frame filter
8873 dictionary resides. When @code{all} is specified, all frame filters across
8874 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8875 filter and is used when @code{all} is not the option for
8876 @var{filter-dictionary}.
8881 (gdb) info frame-filter
8883 global frame-filters:
8884 Priority Enabled Name
8885 1000 No PrimaryFunctionFilter
8888 progspace /build/test frame-filters:
8889 Priority Enabled Name
8890 100 Yes ProgspaceFilter
8892 objfile /build/test frame-filters:
8893 Priority Enabled Name
8894 999 Yes BuildProgramFilter
8896 (gdb) disable frame-filter /build/test BuildProgramFilter
8897 (gdb) info frame-filter
8899 global frame-filters:
8900 Priority Enabled Name
8901 1000 No PrimaryFunctionFilter
8904 progspace /build/test frame-filters:
8905 Priority Enabled Name
8906 100 Yes ProgspaceFilter
8908 objfile /build/test frame-filters:
8909 Priority Enabled Name
8910 999 No BuildProgramFilter
8912 (gdb) enable frame-filter global PrimaryFunctionFilter
8913 (gdb) info frame-filter
8915 global frame-filters:
8916 Priority Enabled Name
8917 1000 Yes PrimaryFunctionFilter
8920 progspace /build/test frame-filters:
8921 Priority Enabled Name
8922 100 Yes ProgspaceFilter
8924 objfile /build/test frame-filters:
8925 Priority Enabled Name
8926 999 No BuildProgramFilter
8929 @kindex set frame-filter priority
8930 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8931 Set the @var{priority} of a frame filter in the dictionary matching
8932 @var{filter-dictionary}, and the frame filter name matching
8933 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8934 @code{progspace} or the name of the object file where the frame filter
8935 dictionary resides. The @var{priority} is an integer.
8937 @kindex show frame-filter priority
8938 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8939 Show the @var{priority} of a frame filter in the dictionary matching
8940 @var{filter-dictionary}, and the frame filter name matching
8941 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8942 @code{progspace} or the name of the object file where the frame filter
8948 (gdb) info frame-filter
8950 global frame-filters:
8951 Priority Enabled Name
8952 1000 Yes PrimaryFunctionFilter
8955 progspace /build/test frame-filters:
8956 Priority Enabled Name
8957 100 Yes ProgspaceFilter
8959 objfile /build/test frame-filters:
8960 Priority Enabled Name
8961 999 No BuildProgramFilter
8963 (gdb) set frame-filter priority global Reverse 50
8964 (gdb) info frame-filter
8966 global frame-filters:
8967 Priority Enabled Name
8968 1000 Yes PrimaryFunctionFilter
8971 progspace /build/test frame-filters:
8972 Priority Enabled Name
8973 100 Yes ProgspaceFilter
8975 objfile /build/test frame-filters:
8976 Priority Enabled Name
8977 999 No BuildProgramFilter
8982 @chapter Examining Source Files
8984 @value{GDBN} can print parts of your program's source, since the debugging
8985 information recorded in the program tells @value{GDBN} what source files were
8986 used to build it. When your program stops, @value{GDBN} spontaneously prints
8987 the line where it stopped. Likewise, when you select a stack frame
8988 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8989 execution in that frame has stopped. You can print other portions of
8990 source files by explicit command.
8992 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8993 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8994 @value{GDBN} under @sc{gnu} Emacs}.
8997 * List:: Printing source lines
8998 * Location Specifications:: How to specify code locations
8999 * Edit:: Editing source files
9000 * Search:: Searching source files
9001 * Source Path:: Specifying source directories
9002 * Machine Code:: Source and machine code
9003 * Disable Reading Source:: Disable Reading Source Code
9007 @section Printing Source Lines
9010 @kindex l @r{(@code{list})}
9011 To print lines from a source file, use the @code{list} command
9012 (abbreviated @code{l}). By default, ten lines are printed.
9013 There are several ways to specify what part of the file you want to
9014 print; see @ref{Location Specifications}, for the full list.
9016 Here are the forms of the @code{list} command most commonly used:
9019 @item list @var{linenum}
9020 Print lines centered around line number @var{linenum} in the
9021 current source file.
9023 @item list @var{function}
9024 Print lines centered around the beginning of function
9028 Print more lines. If the last lines printed were printed with a
9029 @code{list} command, this prints lines following the last lines
9030 printed; however, if the last line printed was a solitary line printed
9031 as part of displaying a stack frame (@pxref{Stack, ,Examining the
9032 Stack}), this prints lines centered around that line.
9035 Print lines just before the lines last printed.
9038 @cindex @code{list}, how many lines to display
9039 By default, @value{GDBN} prints ten source lines with any of these forms of
9040 the @code{list} command. You can change this using @code{set listsize}:
9043 @kindex set listsize
9044 @item set listsize @var{count}
9045 @itemx set listsize unlimited
9046 Make the @code{list} command display @var{count} source lines (unless
9047 the @code{list} argument explicitly specifies some other number).
9048 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
9050 @kindex show listsize
9052 Display the number of lines that @code{list} prints.
9055 Repeating a @code{list} command with @key{RET} discards the argument,
9056 so it is equivalent to typing just @code{list}. This is more useful
9057 than listing the same lines again. An exception is made for an
9058 argument of @samp{-}; that argument is preserved in repetition so that
9059 each repetition moves up in the source file.
9061 In general, the @code{list} command expects you to supply zero, one or
9062 two location specs. These location specs are interpreted to resolve
9063 to source code lines; there are several ways of writing them
9064 (@pxref{Location Specifications}), but the effect is always to resolve
9065 to some source lines to display.
9067 Here is a complete description of the possible arguments for @code{list}:
9070 @item list @var{locspec}
9071 Print lines centered around the line or lines of all the code
9072 locations that result from resolving @var{locspec}.
9074 @item list @var{first},@var{last}
9075 Print lines from @var{first} to @var{last}. Both arguments are
9076 location specs. When a @code{list} command has two location specs,
9077 and the source file of the second location spec is omitted, this
9078 refers to the same source file as the first location spec. If either
9079 @var{first} or @var{last} resolve to more than one source line in the
9080 program, then the list command shows the list of resolved source
9081 lines and does not proceed with the source code listing.
9083 @item list ,@var{last}
9084 Print lines ending with @var{last}.
9086 Likewise, if @var{last} resolves to more than one source line in the
9087 program, then the list command prints the list of resolved source
9088 lines and does not proceed with the source code listing.
9090 @item list @var{first},
9091 Print lines starting with @var{first}.
9094 Print lines just after the lines last printed.
9097 Print lines just before the lines last printed.
9100 As described in the preceding table.
9103 @node Location Specifications
9104 @section Location Specifications
9105 @cindex specifying location
9107 @cindex source location
9108 @cindex code location
9110 @cindex location spec
9111 Several @value{GDBN} commands accept arguments that specify a location
9112 or locations of your program's code. Many times locations are
9113 specified using a source line number, but they can also be specified
9114 by a function name, an address, a label, etc. The different
9115 forms of specifying a location that @value{GDBN} recognizes are
9116 collectively known as forms of @dfn{location specification}, or
9117 @dfn{location spec}. This section documents the forms of specifying
9118 locations that @value{GDBN} recognizes.
9120 @cindex location resolution
9121 @cindex resolution of location spec
9122 When you specify a location, @value{GDBN} needs to find the place in
9123 your program, known as @dfn{code location}, that corresponds to the
9124 given location spec. We call this process of finding actual code
9125 locations corresponding to a location spec @dfn{location resolution}.
9127 A concrete code location in your program is uniquely identifiable by a
9128 set of several attributes: its source line number, the name of its
9129 source file, the fully-qualified and prototyped function in which it
9130 is defined, and an instruction address. Because each inferior has its
9131 own address space, the inferior number is also a necessary part of
9134 By contrast, location specs you type will many times omit some of
9135 these attributes. For example, it is customary to specify just the
9136 source line number to mean a line in the current source file, or
9137 specify just the basename of the file, omitting its directories. In
9138 other words, a location spec is usually incomplete, a kind of
9139 blueprint, and @value{GDBN} needs to complete the missing attributes
9140 by using the implied defaults, and by considering the source code and
9141 the debug information available to it. This is what location
9142 resolution is about.
9144 The resolution of an incomplete location spec can produce more than a
9145 single code location, if the spec doesn't allow distinguishing between
9146 them. Here are some examples of situations that result in a location
9147 spec matching multiple code locations in your program:
9151 The location spec specifies a function name, and there are several
9152 functions in the program which have that name. (To distinguish
9153 between them, you can specify a fully-qualified and prototyped
9154 function name, such as @code{A::func(int)} instead of just
9158 The location spec specifies a source file name, and there are several
9159 source files in the program that share the same name, for example
9160 several files with the same basename in different subdirectories. (To
9161 distinguish between them, specify enough leading directories with the
9165 For a C@t{++} constructor, the @value{NGCC} compiler generates several
9166 instances of the function body, used in different cases, but their
9167 source-level names are identical.
9170 For a C@t{++} template function, a given line in the function can
9171 correspond to any number of instantiations.
9174 For an inlined function, a given source line can correspond to several
9175 actual code locations with that function's inlined code.
9178 Resolution of a location spec can also fail to produce a complete code
9179 location, or even fail to produce any code location. Here are some
9180 examples of such situations:
9184 Some parts of the program lack detailed enough debug info, so the
9185 resolved code location lacks some attributes, like source file name
9186 and line number, leaving just the instruction address and perhaps also
9187 a function name. Such an incomplete code location is only usable in
9188 contexts that work with addresses and/or function names. Some
9189 commands can only work with complete code locations.
9192 The location spec specifies a function name, and there are no
9193 functions in the program by that name, or they only exist in a
9194 yet-unloaded shared library.
9197 The location spec specifies a source file name, and there are no
9198 source files in the program by that name, or they only exist in a
9199 yet-unloaded shared library.
9202 The location spec specifies both a source file name and a source line
9203 number, and even though there are source files in the program that
9204 match the file name, none of those files has the specified line
9208 Locations may be specified using three different formats: linespec
9209 locations, explicit locations, or address locations. The following
9210 subsections describe these formats.
9213 * Linespec Locations:: Linespec locations
9214 * Explicit Locations:: Explicit locations
9215 * Address Locations:: Address locations
9218 @node Linespec Locations
9219 @subsection Linespec Locations
9220 @cindex linespec locations
9222 A @dfn{linespec} is a colon-separated list of source location parameters such
9223 as file name, function name, etc. Here are all the different ways of
9224 specifying a linespec:
9228 Specifies the line number @var{linenum} of the current source file.
9231 @itemx +@var{offset}
9232 Specifies the line @var{offset} lines before or after the @dfn{current
9233 line}. For the @code{list} command, the current line is the last one
9234 printed; for the breakpoint commands, this is the line at which
9235 execution stopped in the currently selected @dfn{stack frame}
9236 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
9237 used as the second of the two linespecs in a @code{list} command,
9238 this specifies the line @var{offset} lines up or down from the first
9241 @item @var{filename}:@var{linenum}
9242 Specifies the line @var{linenum} in the source file @var{filename}.
9243 If @var{filename} is a relative file name, then it will match any
9244 source file name with the same trailing components. For example, if
9245 @var{filename} is @samp{gcc/expr.c}, then it will match source file
9246 name of @file{/build/trunk/gcc/expr.c}, but not
9247 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
9249 @item @var{function}
9250 Specifies the line that begins the body of the function @var{function}.
9251 For example, in C, this is the line with the open brace.
9253 By default, in C@t{++} and Ada, @var{function} is interpreted as
9254 specifying all functions named @var{function} in all scopes. For
9255 C@t{++}, this means in all namespaces and classes. For Ada, this
9256 means in all packages.
9258 For example, assuming a program with C@t{++} symbols named
9259 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9260 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
9262 Commands that accept a linespec let you override this with the
9263 @code{-qualified} option. For example, @w{@kbd{break -qualified
9264 func}} sets a breakpoint on a free-function named @code{func} ignoring
9265 any C@t{++} class methods and namespace functions called @code{func}.
9267 @xref{Explicit Locations}.
9269 @item @var{function}:@var{label}
9270 Specifies the line where @var{label} appears in @var{function}.
9272 @item @var{filename}:@var{function}
9273 Specifies the line that begins the body of the function @var{function}
9274 in the file @var{filename}. You only need the file name with a
9275 function name to avoid ambiguity when there are identically named
9276 functions in different source files.
9279 Specifies the line at which the label named @var{label} appears
9280 in the function corresponding to the currently selected stack frame.
9281 If there is no current selected stack frame (for instance, if the inferior
9282 is not running), then @value{GDBN} will not search for a label.
9284 @cindex breakpoint at static probe point
9285 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
9286 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
9287 applications to embed static probes. @xref{Static Probe Points}, for more
9288 information on finding and using static probes. This form of linespec
9289 specifies the location of such a static probe.
9291 If @var{objfile} is given, only probes coming from that shared library
9292 or executable matching @var{objfile} as a regular expression are considered.
9293 If @var{provider} is given, then only probes from that provider are considered.
9294 If several probes match the spec, @value{GDBN} will insert a breakpoint at
9295 each one of those probes.
9298 @node Explicit Locations
9299 @subsection Explicit Locations
9300 @cindex explicit locations
9302 @dfn{Explicit locations} allow the user to directly specify the source
9303 location's parameters using option-value pairs.
9305 Explicit locations are useful when several functions, labels, or
9306 file names have the same name (base name for files) in the program's
9307 sources. In these cases, explicit locations point to the source
9308 line you meant more accurately and unambiguously. Also, using
9309 explicit locations might be faster in large programs.
9311 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
9312 defined in the file named @file{foo} or the label @code{bar} in a function
9313 named @code{foo}. @value{GDBN} must search either the file system or
9314 the symbol table to know.
9316 The list of valid explicit location options is summarized in the
9320 @item -source @var{filename}
9321 The value specifies the source file name. To differentiate between
9322 files with the same base name, prepend as many directories as is necessary
9323 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
9324 @value{GDBN} will use the first file it finds with the given base
9325 name. This option requires the use of either @code{-function} or @code{-line}.
9327 @item -function @var{function}
9328 The value specifies the name of a function. Operations
9329 on function locations unmodified by other options (such as @code{-label}
9330 or @code{-line}) refer to the line that begins the body of the function.
9331 In C, for example, this is the line with the open brace.
9333 By default, in C@t{++} and Ada, @var{function} is interpreted as
9334 specifying all functions named @var{function} in all scopes. For
9335 C@t{++}, this means in all namespaces and classes. For Ada, this
9336 means in all packages.
9338 For example, assuming a program with C@t{++} symbols named
9339 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9340 -function func}} and @w{@kbd{break -function B::func}} set a
9341 breakpoint on both symbols.
9343 You can use the @kbd{-qualified} flag to override this (see below).
9347 This flag makes @value{GDBN} interpret a function name specified with
9348 @kbd{-function} as a complete fully-qualified name.
9350 For example, assuming a C@t{++} program with symbols named
9351 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9352 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9354 (Note: the @kbd{-qualified} option can precede a linespec as well
9355 (@pxref{Linespec Locations}), so the particular example above could be
9356 simplified as @w{@kbd{break -qualified B::func}}.)
9358 @item -label @var{label}
9359 The value specifies the name of a label. When the function
9360 name is not specified, the label is searched in the function of the currently
9361 selected stack frame.
9363 @item -line @var{number}
9364 The value specifies a line offset for the location. The offset may either
9365 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9366 the command. When specified without any other options, the line offset is
9367 relative to the current line.
9370 Explicit location options may be abbreviated by omitting any non-unique
9371 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9373 @node Address Locations
9374 @subsection Address Locations
9375 @cindex address locations
9377 @dfn{Address locations} indicate a specific program address. They have
9378 the generalized form *@var{address}.
9380 For line-oriented commands, such as @code{list} and @code{edit}, this
9381 specifies a source line that contains @var{address}. For @code{break} and
9382 other breakpoint-oriented commands, this can be used to set breakpoints in
9383 parts of your program which do not have debugging information or
9386 Here @var{address} may be any expression valid in the current working
9387 language (@pxref{Languages, working language}) that specifies a code
9388 address. In addition, as a convenience, @value{GDBN} extends the
9389 semantics of expressions used in locations to cover several situations
9390 that frequently occur during debugging. Here are the various forms
9394 @item @var{expression}
9395 Any expression valid in the current working language.
9397 @item @var{funcaddr}
9398 An address of a function or procedure derived from its name. In C,
9399 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9400 simply the function's name @var{function} (and actually a special case
9401 of a valid expression). In Pascal and Modula-2, this is
9402 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9403 (although the Pascal form also works).
9405 This form specifies the address of the function's first instruction,
9406 before the stack frame and arguments have been set up.
9408 @item '@var{filename}':@var{funcaddr}
9409 Like @var{funcaddr} above, but also specifies the name of the source
9410 file explicitly. This is useful if the name of the function does not
9411 specify the function unambiguously, e.g., if there are several
9412 functions with identical names in different source files.
9416 @section Editing Source Files
9417 @cindex editing source files
9420 @kindex e @r{(@code{edit})}
9421 To edit the lines in a source file, use the @code{edit} command.
9422 The editing program of your choice
9423 is invoked with the current line set to
9424 the active line in the program.
9425 Alternatively, there are several ways to specify what part of the file you
9426 want to print if you want to see other parts of the program:
9429 @item edit @var{locspec}
9430 Edit the source file of the code location that results from resolving
9431 @code{locspec}. Editing starts at the source file and source line
9432 @code{locspec} resolves to.
9433 @xref{Location Specifications}, for all the possible forms of the
9434 @var{locspec} argument.
9436 If @code{locspec} resolves to more than one source line in your
9437 program, then the command prints the list of resolved source lines and
9438 does not proceed with the editing.
9440 Here are the forms of the @code{edit} command most commonly used:
9443 @item edit @var{number}
9444 Edit the current source file with @var{number} as the active line number.
9446 @item edit @var{function}
9447 Edit the file containing @var{function} at the beginning of its definition.
9452 @subsection Choosing your Editor
9453 You can customize @value{GDBN} to use any editor you want
9455 The only restriction is that your editor (say @code{ex}), recognizes the
9456 following command-line syntax:
9458 ex +@var{number} file
9460 The optional numeric value +@var{number} specifies the number of the line in
9461 the file where to start editing.}.
9462 By default, it is @file{@value{EDITOR}}, but you can change this
9463 by setting the environment variable @env{EDITOR} before using
9464 @value{GDBN}. For example, to configure @value{GDBN} to use the
9465 @code{vi} editor, you could use these commands with the @code{sh} shell:
9471 or in the @code{csh} shell,
9473 setenv EDITOR /usr/bin/vi
9478 @section Searching Source Files
9479 @cindex searching source files
9481 There are two commands for searching through the current source file for a
9486 @kindex forward-search
9487 @kindex fo @r{(@code{forward-search})}
9488 @item forward-search @var{regexp}
9489 @itemx search @var{regexp}
9490 The command @samp{forward-search @var{regexp}} checks each line,
9491 starting with the one following the last line listed, for a match for
9492 @var{regexp}. It lists the line that is found. You can use the
9493 synonym @samp{search @var{regexp}} or abbreviate the command name as
9496 @kindex reverse-search
9497 @item reverse-search @var{regexp}
9498 The command @samp{reverse-search @var{regexp}} checks each line, starting
9499 with the one before the last line listed and going backward, for a match
9500 for @var{regexp}. It lists the line that is found. You can abbreviate
9501 this command as @code{rev}.
9505 @section Specifying Source Directories
9508 @cindex directories for source files
9509 Executable programs sometimes do not record the directories of the source
9510 files from which they were compiled, just the names. Even when they do,
9511 the directories could be moved between the compilation and your debugging
9512 session. @value{GDBN} has a list of directories to search for source files;
9513 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9514 it tries all the directories in the list, in the order they are present
9515 in the list, until it finds a file with the desired name.
9517 For example, suppose an executable references the file
9518 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9519 directory, and the @dfn{source path} is @file{/mnt/cross}.
9520 @value{GDBN} would look for the source file in the following
9525 @item @file{/usr/src/foo-1.0/lib/foo.c}
9526 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9527 @item @file{/mnt/cross/foo.c}
9531 If the source file is not present at any of the above locations then
9532 an error is printed. @value{GDBN} does not look up the parts of the
9533 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9534 Likewise, the subdirectories of the source path are not searched: if
9535 the source path is @file{/mnt/cross}, and the binary refers to
9536 @file{foo.c}, @value{GDBN} would not find it under
9537 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9539 Plain file names, relative file names with leading directories, file
9540 names containing dots, etc.@: are all treated as described above,
9541 except that non-absolute file names are not looked up literally. If
9542 the @dfn{source path} is @file{/mnt/cross}, the source file is
9543 recorded as @file{../lib/foo.c}, and no compilation directory is
9544 recorded, then @value{GDBN} will search in the following locations:
9548 @item @file{/mnt/cross/../lib/foo.c}
9549 @item @file{/mnt/cross/foo.c}
9555 @vindex $cdir@r{, convenience variable}
9556 @vindex $cwd@r{, convenience variable}
9557 @cindex compilation directory
9558 @cindex current directory
9559 @cindex working directory
9560 @cindex directory, current
9561 @cindex directory, compilation
9562 The @dfn{source path} will always include two special entries
9563 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9564 (if one is recorded) and the current working directory respectively.
9566 @samp{$cdir} causes @value{GDBN} to search within the compilation
9567 directory, if one is recorded in the debug information. If no
9568 compilation directory is recorded in the debug information then
9569 @samp{$cdir} is ignored.
9571 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9572 current working directory as it changes during your @value{GDBN}
9573 session, while the latter is immediately expanded to the current
9574 directory at the time you add an entry to the source path.
9576 If a compilation directory is recorded in the debug information, and
9577 @value{GDBN} has not found the source file after the first search
9578 using @dfn{source path}, then @value{GDBN} will combine the
9579 compilation directory and the filename, and then search for the source
9580 file again using the @dfn{source path}.
9582 For example, if the executable records the source file as
9583 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9584 recorded as @file{/project/build}, and the @dfn{source path} is
9585 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9586 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9587 search for the source file in the following locations:
9591 @item @file{/usr/src/foo-1.0/lib/foo.c}
9592 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9593 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9594 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9595 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9596 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9597 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9598 @item @file{/mnt/cross/foo.c}
9599 @item @file{/project/build/foo.c}
9600 @item @file{/home/user/foo.c}
9604 If the file name in the previous example had been recorded in the
9605 executable as a relative path rather than an absolute path, then the
9606 first look up would not have occurred, but all of the remaining steps
9609 When searching for source files on MS-DOS and MS-Windows, where
9610 absolute paths start with a drive letter (e.g.@:
9611 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9612 from the file name before appending it to a search directory from
9613 @dfn{source path}; for instance if the executable references the
9614 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9615 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9616 locations for the source file:
9620 @item @file{C:/project/foo.c}
9621 @item @file{D:/mnt/cross/project/foo.c}
9622 @item @file{D:/mnt/cross/foo.c}
9626 Note that the executable search path is @emph{not} used to locate the
9629 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9630 any information it has cached about where source files are found and where
9631 each line is in the file.
9635 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9636 and @samp{$cwd}, in that order.
9637 To add other directories, use the @code{directory} command.
9639 The search path is used to find both program source files and @value{GDBN}
9640 script files (read using the @samp{-command} option and @samp{source} command).
9642 In addition to the source path, @value{GDBN} provides a set of commands
9643 that manage a list of source path substitution rules. A @dfn{substitution
9644 rule} specifies how to rewrite source directories stored in the program's
9645 debug information in case the sources were moved to a different
9646 directory between compilation and debugging. A rule is made of
9647 two strings, the first specifying what needs to be rewritten in
9648 the path, and the second specifying how it should be rewritten.
9649 In @ref{set substitute-path}, we name these two parts @var{from} and
9650 @var{to} respectively. @value{GDBN} does a simple string replacement
9651 of @var{from} with @var{to} at the start of the directory part of the
9652 source file name, and uses that result instead of the original file
9653 name to look up the sources.
9655 Using the previous example, suppose the @file{foo-1.0} tree has been
9656 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9657 @value{GDBN} to replace @file{/usr/src} in all source path names with
9658 @file{/mnt/cross}. The first lookup will then be
9659 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9660 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9661 substitution rule, use the @code{set substitute-path} command
9662 (@pxref{set substitute-path}).
9664 To avoid unexpected substitution results, a rule is applied only if the
9665 @var{from} part of the directory name ends at a directory separator.
9666 For instance, a rule substituting @file{/usr/source} into
9667 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9668 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9669 is applied only at the beginning of the directory name, this rule will
9670 not be applied to @file{/root/usr/source/baz.c} either.
9672 In many cases, you can achieve the same result using the @code{directory}
9673 command. However, @code{set substitute-path} can be more efficient in
9674 the case where the sources are organized in a complex tree with multiple
9675 subdirectories. With the @code{directory} command, you need to add each
9676 subdirectory of your project. If you moved the entire tree while
9677 preserving its internal organization, then @code{set substitute-path}
9678 allows you to direct the debugger to all the sources with one single
9681 @code{set substitute-path} is also more than just a shortcut command.
9682 The source path is only used if the file at the original location no
9683 longer exists. On the other hand, @code{set substitute-path} modifies
9684 the debugger behavior to look at the rewritten location instead. So, if
9685 for any reason a source file that is not relevant to your executable is
9686 located at the original location, a substitution rule is the only
9687 method available to point @value{GDBN} at the new location.
9689 @cindex @samp{--with-relocated-sources}
9690 @cindex default source path substitution
9691 You can configure a default source path substitution rule by
9692 configuring @value{GDBN} with the
9693 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9694 should be the name of a directory under @value{GDBN}'s configured
9695 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9696 directory names in debug information under @var{dir} will be adjusted
9697 automatically if the installed @value{GDBN} is moved to a new
9698 location. This is useful if @value{GDBN}, libraries or executables
9699 with debug information and corresponding source code are being moved
9703 @item directory @var{dirname} @dots{}
9704 @item dir @var{dirname} @dots{}
9705 Add directory @var{dirname} to the front of the source path. Several
9706 directory names may be given to this command, separated by @samp{:}
9707 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9708 part of absolute file names) or
9709 whitespace. You may specify a directory that is already in the source
9710 path; this moves it forward, so @value{GDBN} searches it sooner.
9712 The special strings @samp{$cdir} (to refer to the compilation
9713 directory, if one is recorded), and @samp{$cwd} (to refer to the
9714 current working directory) can also be included in the list of
9715 directories @var{dirname}. Though these will already be in the source
9716 path they will be moved forward in the list so @value{GDBN} searches
9720 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9722 @c RET-repeat for @code{directory} is explicitly disabled, but since
9723 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9725 @item set directories @var{path-list}
9726 @kindex set directories
9727 Set the source path to @var{path-list}.
9728 @samp{$cdir:$cwd} are added if missing.
9730 @item show directories
9731 @kindex show directories
9732 Print the source path: show which directories it contains.
9734 @anchor{set substitute-path}
9735 @item set substitute-path @var{from} @var{to}
9736 @kindex set substitute-path
9737 Define a source path substitution rule, and add it at the end of the
9738 current list of existing substitution rules. If a rule with the same
9739 @var{from} was already defined, then the old rule is also deleted.
9741 For example, if the file @file{/foo/bar/baz.c} was moved to
9742 @file{/mnt/cross/baz.c}, then the command
9745 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9749 will tell @value{GDBN} to replace @samp{/foo/bar} with
9750 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9751 @file{baz.c} even though it was moved.
9753 In the case when more than one substitution rule have been defined,
9754 the rules are evaluated one by one in the order where they have been
9755 defined. The first one matching, if any, is selected to perform
9758 For instance, if we had entered the following commands:
9761 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9762 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9766 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9767 @file{/mnt/include/defs.h} by using the first rule. However, it would
9768 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9769 @file{/mnt/src/lib/foo.c}.
9772 @item unset substitute-path [path]
9773 @kindex unset substitute-path
9774 If a path is specified, search the current list of substitution rules
9775 for a rule that would rewrite that path. Delete that rule if found.
9776 A warning is emitted by the debugger if no rule could be found.
9778 If no path is specified, then all substitution rules are deleted.
9780 @item show substitute-path [path]
9781 @kindex show substitute-path
9782 If a path is specified, then print the source path substitution rule
9783 which would rewrite that path, if any.
9785 If no path is specified, then print all existing source path substitution
9790 If your source path is cluttered with directories that are no longer of
9791 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9792 versions of source. You can correct the situation as follows:
9796 Use @code{directory} with no argument to reset the source path to its default value.
9799 Use @code{directory} with suitable arguments to reinstall the
9800 directories you want in the source path. You can add all the
9801 directories in one command.
9805 @section Source and Machine Code
9806 @cindex source line and its code address
9808 You can use the command @code{info line} to map source lines to program
9809 addresses (and vice versa), and the command @code{disassemble} to display
9810 a range of addresses as machine instructions. You can use the command
9811 @code{set disassemble-next-line} to set whether to disassemble next
9812 source line when execution stops. When run under @sc{gnu} Emacs
9813 mode, the @code{info line} command causes the arrow to point to the
9814 line specified. Also, @code{info line} prints addresses in symbolic form as
9820 @itemx info line @var{locspec}
9821 Print the starting and ending addresses of the compiled code for the
9822 source lines of the code locations that result from resolving
9823 @var{locspec}. @xref{Location Specifications}, for the various forms
9825 With no @var{locspec}, information about the current source line is
9829 For example, we can use @code{info line} to discover the location of
9830 the object code for the first line of function
9831 @code{m4_changequote}:
9834 (@value{GDBP}) info line m4_changequote
9835 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9836 ends at 0x6350 <m4_changequote+4>.
9840 @cindex code address and its source line
9841 We can also inquire, using @code{*@var{addr}} as the form for
9842 @var{locspec}, what source line covers a particular address
9845 (@value{GDBP}) info line *0x63ff
9846 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9847 ends at 0x6404 <m4_changequote+184>.
9850 @cindex @code{$_} and @code{info line}
9851 @cindex @code{x} command, default address
9852 @kindex x@r{(examine), and} info line
9853 After @code{info line}, the default address for the @code{x} command
9854 is changed to the starting address of the line, so that @samp{x/i} is
9855 sufficient to begin examining the machine code (@pxref{Memory,
9856 ,Examining Memory}). Also, this address is saved as the value of the
9857 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9860 @cindex info line, repeated calls
9861 After @code{info line}, using @code{info line} again without
9862 specifying a location will display information about the next source
9865 @anchor{disassemble}
9868 @cindex assembly instructions
9869 @cindex instructions, assembly
9870 @cindex machine instructions
9871 @cindex listing machine instructions
9873 @itemx disassemble /m
9874 @itemx disassemble /s
9875 @itemx disassemble /r
9876 @itemx disassemble /b
9877 This specialized command dumps a range of memory as machine
9878 instructions. It can also print mixed source+disassembly by specifying
9879 the @code{/m} or @code{/s} modifier and print the raw instructions in
9880 hex as well as in symbolic form by specifying the @code{/r} or @code{/b}
9881 modifier. The default memory range is the function surrounding the
9882 program counter of the selected frame. A single argument to this
9883 command is a program counter value; @value{GDBN} dumps the function
9884 surrounding this value. When two arguments are given, they should be
9885 separated by a comma, possibly surrounded by whitespace. The arguments
9886 specify a range of addresses to dump, in one of two forms:
9889 @item @var{start},@var{end}
9890 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9891 @item @var{start},+@var{length}
9892 the addresses from @var{start} (inclusive) to
9893 @code{@var{start}+@var{length}} (exclusive).
9897 When 2 arguments are specified, the name of the function is also
9898 printed (since there could be several functions in the given range).
9900 The argument(s) can be any expression yielding a numeric value, such as
9901 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9903 If the range of memory being disassembled contains current program counter,
9904 the instruction at that location is shown with a @code{=>} marker.
9907 The following example shows the disassembly of a range of addresses of
9908 HP PA-RISC 2.0 code:
9911 (@value{GDBP}) disas 0x32c4, 0x32e4
9912 Dump of assembler code from 0x32c4 to 0x32e4:
9913 0x32c4 <main+204>: addil 0,dp
9914 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9915 0x32cc <main+212>: ldil 0x3000,r31
9916 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9917 0x32d4 <main+220>: ldo 0(r31),rp
9918 0x32d8 <main+224>: addil -0x800,dp
9919 0x32dc <main+228>: ldo 0x588(r1),r26
9920 0x32e0 <main+232>: ldil 0x3000,r31
9921 End of assembler dump.
9924 The following two examples are for RISC-V, and demonstrates the
9925 difference between the @code{/r} and @code{/b} modifiers. First with
9926 @code{/b}, the bytes of the instruction are printed, in hex, in memory
9930 (@value{GDBP}) disassemble /b 0x00010150,0x0001015c
9931 Dump of assembler code from 0x10150 to 0x1015c:
9932 0x00010150 <call_me+4>: 22 dc sw s0,56(sp)
9933 0x00010152 <call_me+6>: 80 00 addi s0,sp,64
9934 0x00010154 <call_me+8>: 23 26 a4 fe sw a0,-20(s0)
9935 0x00010158 <call_me+12>: 23 24 b4 fe sw a1,-24(s0)
9936 End of assembler dump.
9939 In contrast, with @code{/r} the bytes of the instruction are displayed
9940 in the instruction order, for RISC-V this means that the bytes have been
9941 swapped to little-endian order:
9944 (@value{GDBP}) disassemble /r 0x00010150,0x0001015c
9945 Dump of assembler code from 0x10150 to 0x1015c:
9946 0x00010150 <call_me+4>: dc22 sw s0,56(sp)
9947 0x00010152 <call_me+6>: 0080 addi s0,sp,64
9948 0x00010154 <call_me+8>: fea42623 sw a0,-20(s0)
9949 0x00010158 <call_me+12>: feb42423 sw a1,-24(s0)
9950 End of assembler dump.
9953 Here is an example showing mixed source+assembly for Intel x86
9954 with @code{/m} or @code{/s}, when the program is stopped just after
9955 function prologue in a non-optimized function with no inline code.
9958 (@value{GDBP}) disas /m main
9959 Dump of assembler code for function main:
9961 0x08048330 <+0>: push %ebp
9962 0x08048331 <+1>: mov %esp,%ebp
9963 0x08048333 <+3>: sub $0x8,%esp
9964 0x08048336 <+6>: and $0xfffffff0,%esp
9965 0x08048339 <+9>: sub $0x10,%esp
9967 6 printf ("Hello.\n");
9968 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9969 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9973 0x08048348 <+24>: mov $0x0,%eax
9974 0x0804834d <+29>: leave
9975 0x0804834e <+30>: ret
9977 End of assembler dump.
9980 The @code{/m} option is deprecated as its output is not useful when
9981 there is either inlined code or re-ordered code.
9982 The @code{/s} option is the preferred choice.
9983 Here is an example for AMD x86-64 showing the difference between
9984 @code{/m} output and @code{/s} output.
9985 This example has one inline function defined in a header file,
9986 and the code is compiled with @samp{-O2} optimization.
9987 Note how the @code{/m} output is missing the disassembly of
9988 several instructions that are present in the @code{/s} output.
10018 (@value{GDBP}) disas /m main
10019 Dump of assembler code for function main:
10023 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
10024 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
10028 0x000000000040041d <+29>: xor %eax,%eax
10029 0x000000000040041f <+31>: retq
10030 0x0000000000400420 <+32>: add %eax,%eax
10031 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
10033 End of assembler dump.
10034 (@value{GDBP}) disas /s main
10035 Dump of assembler code for function main:
10039 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
10043 0x0000000000400406 <+6>: test %eax,%eax
10044 0x0000000000400408 <+8>: js 0x400420 <main+32>
10049 0x000000000040040a <+10>: lea 0xa(%rax),%edx
10050 0x000000000040040d <+13>: test %eax,%eax
10051 0x000000000040040f <+15>: mov $0x1,%eax
10052 0x0000000000400414 <+20>: cmovne %edx,%eax
10056 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
10060 0x000000000040041d <+29>: xor %eax,%eax
10061 0x000000000040041f <+31>: retq
10065 0x0000000000400420 <+32>: add %eax,%eax
10066 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
10067 End of assembler dump.
10070 Here is another example showing raw instructions in hex for AMD x86-64,
10073 (gdb) disas /r 0x400281,+10
10074 Dump of assembler code from 0x400281 to 0x40028b:
10075 0x0000000000400281: 38 36 cmp %dh,(%rsi)
10076 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
10077 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
10078 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
10079 End of assembler dump.
10082 Note that the @samp{disassemble} command's address arguments are
10083 specified using expressions in your programming language
10084 (@pxref{Expressions, ,Expressions}), not location specs
10085 (@pxref{Location Specifications}). So, for example, if you want to
10086 disassemble function @code{bar} in file @file{foo.c}, you must type
10087 @samp{disassemble 'foo.c'::bar} and not @samp{disassemble foo.c:bar}.
10089 Some architectures have more than one commonly-used set of instruction
10090 mnemonics or other syntax.
10092 For programs that were dynamically linked and use shared libraries,
10093 instructions that call functions or branch to locations in the shared
10094 libraries might show a seemingly bogus location---it's actually a
10095 location of the relocation table. On some architectures, @value{GDBN}
10096 might be able to resolve these to actual function names.
10099 @kindex set disassembler-options
10100 @cindex disassembler options
10101 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
10102 This command controls the passing of target specific information to
10103 the disassembler. For a list of valid options, please refer to the
10104 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
10105 manual and/or the output of @kbd{objdump --help}
10106 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
10107 The default value is the empty string.
10109 If it is necessary to specify more than one disassembler option, then
10110 multiple options can be placed together into a comma separated list.
10111 Currently this command is only supported on targets ARC, ARM, MIPS,
10114 @kindex show disassembler-options
10115 @item show disassembler-options
10116 Show the current setting of the disassembler options.
10120 @kindex set disassembly-flavor
10121 @cindex Intel disassembly flavor
10122 @cindex AT&T disassembly flavor
10123 @item set disassembly-flavor @var{instruction-set}
10124 Select the instruction set to use when disassembling the
10125 program via the @code{disassemble} or @code{x/i} commands.
10127 Currently this command is only defined for the Intel x86 family. You
10128 can set @var{instruction-set} to either @code{intel} or @code{att}.
10129 The default is @code{att}, the AT&T flavor used by default by Unix
10130 assemblers for x86-based targets.
10132 @kindex show disassembly-flavor
10133 @item show disassembly-flavor
10134 Show the current setting of the disassembly flavor.
10138 @kindex set disassemble-next-line
10139 @kindex show disassemble-next-line
10140 @item set disassemble-next-line
10141 @itemx show disassemble-next-line
10142 Control whether or not @value{GDBN} will disassemble the next source
10143 line or instruction when execution stops. If ON, @value{GDBN} will
10144 display disassembly of the next source line when execution of the
10145 program being debugged stops. This is @emph{in addition} to
10146 displaying the source line itself, which @value{GDBN} always does if
10147 possible. If the next source line cannot be displayed for some reason
10148 (e.g., if @value{GDBN} cannot find the source file, or there's no line
10149 info in the debug info), @value{GDBN} will display disassembly of the
10150 next @emph{instruction} instead of showing the next source line. If
10151 AUTO, @value{GDBN} will display disassembly of next instruction only
10152 if the source line cannot be displayed. This setting causes
10153 @value{GDBN} to display some feedback when you step through a function
10154 with no line info or whose source file is unavailable. The default is
10155 OFF, which means never display the disassembly of the next line or
10159 @node Disable Reading Source
10160 @section Disable Reading Source Code
10161 @cindex source code, disable access
10163 In some cases it can be desirable to prevent @value{GDBN} from
10164 accessing source code files. One case where this might be desirable
10165 is if the source code files are located over a slow network
10168 The following command can be used to control whether @value{GDBN}
10169 should access source code files or not:
10172 @kindex set source open
10173 @kindex show source open
10174 @item set source open @r{[}on@r{|}off@r{]}
10175 @itemx show source open
10176 When this option is @code{on}, which is the default, @value{GDBN} will
10177 access source code files when needed, for example to print source
10178 lines when @value{GDBN} stops, or in response to the @code{list}
10181 When this option is @code{off}, @value{GDBN} will not access source
10186 @chapter Examining Data
10188 @cindex printing data
10189 @cindex examining data
10192 The usual way to examine data in your program is with the @code{print}
10193 command (abbreviated @code{p}), or its synonym @code{inspect}. It
10194 evaluates and prints the value of an expression of the language your
10195 program is written in (@pxref{Languages, ,Using @value{GDBN} with
10196 Different Languages}). It may also print the expression using a
10197 Python-based pretty-printer (@pxref{Pretty Printing}).
10200 @item print [[@var{options}] --] @var{expr}
10201 @itemx print [[@var{options}] --] /@var{f} @var{expr}
10202 @var{expr} is an expression (in the source language). By default the
10203 value of @var{expr} is printed in a format appropriate to its data type;
10204 you can choose a different format by specifying @samp{/@var{f}}, where
10205 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
10208 @anchor{print options}
10209 The @code{print} command supports a number of options that allow
10210 overriding relevant global print settings as set by @code{set print}
10214 @item -address [@code{on}|@code{off}]
10215 Set printing of addresses.
10216 Related setting: @ref{set print address}.
10218 @item -array [@code{on}|@code{off}]
10219 Pretty formatting of arrays.
10220 Related setting: @ref{set print array}.
10222 @item -array-indexes [@code{on}|@code{off}]
10223 Set printing of array indexes.
10224 Related setting: @ref{set print array-indexes}.
10226 @item -elements @var{number-of-elements}|@code{unlimited}
10227 Set limit on string chars or array elements to print. The value
10228 @code{unlimited} causes there to be no limit. Related setting:
10229 @ref{set print elements}.
10231 @item -max-depth @var{depth}|@code{unlimited}
10232 Set the threshold after which nested structures are replaced with
10233 ellipsis. Related setting: @ref{set print max-depth}.
10235 @item -nibbles [@code{on}|@code{off}]
10236 Set whether to print binary values in groups of four bits, known
10237 as ``nibbles''. @xref{set print nibbles}.
10239 @item -memory-tag-violations [@code{on}|@code{off}]
10240 Set printing of additional information about memory tag violations.
10241 @xref{set print memory-tag-violations}.
10243 @item -null-stop [@code{on}|@code{off}]
10244 Set printing of char arrays to stop at first null char. Related
10245 setting: @ref{set print null-stop}.
10247 @item -object [@code{on}|@code{off}]
10248 Set printing C@t{++} virtual function tables. Related setting:
10249 @ref{set print object}.
10251 @item -pretty [@code{on}|@code{off}]
10252 Set pretty formatting of structures. Related setting: @ref{set print
10255 @item -raw-values [@code{on}|@code{off}]
10256 Set whether to print values in raw form, bypassing any
10257 pretty-printers for that value. Related setting: @ref{set print
10260 @item -repeats @var{number-of-repeats}|@code{unlimited}
10261 Set threshold for repeated print elements. @code{unlimited} causes
10262 all elements to be individually printed. Related setting: @ref{set
10265 @item -static-members [@code{on}|@code{off}]
10266 Set printing C@t{++} static members. Related setting: @ref{set print
10269 @item -symbol [@code{on}|@code{off}]
10270 Set printing of symbol names when printing pointers. Related setting:
10271 @ref{set print symbol}.
10273 @item -union [@code{on}|@code{off}]
10274 Set printing of unions interior to structures. Related setting:
10275 @ref{set print union}.
10277 @item -vtbl [@code{on}|@code{off}]
10278 Set printing of C++ virtual function tables. Related setting:
10279 @ref{set print vtbl}.
10282 Because the @code{print} command accepts arbitrary expressions which
10283 may look like options (including abbreviations), if you specify any
10284 command option, then you must use a double dash (@code{--}) to mark
10285 the end of option processing.
10287 For example, this prints the value of the @code{-p} expression:
10290 (@value{GDBP}) print -p
10293 While this repeats the last value in the value history (see below)
10294 with the @code{-pretty} option in effect:
10297 (@value{GDBP}) print -p --
10300 Here is an example including both on option and an expression:
10304 (@value{GDBP}) print -pretty -- *myptr
10316 @item print [@var{options}]
10317 @itemx print [@var{options}] /@var{f}
10318 @cindex reprint the last value
10319 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
10320 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
10321 conveniently inspect the same value in an alternative format.
10324 If the architecture supports memory tagging, the @code{print} command will
10325 display pointer/memory tag mismatches if what is being printed is a pointer
10326 or reference type. @xref{Memory Tagging}.
10328 A more low-level way of examining data is with the @code{x} command.
10329 It examines data in memory at a specified address and prints it in a
10330 specified format. @xref{Memory, ,Examining Memory}.
10332 If you are interested in information about types, or about how the
10333 fields of a struct or a class are declared, use the @code{ptype @var{expr}}
10334 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
10337 @cindex exploring hierarchical data structures
10339 Another way of examining values of expressions and type information is
10340 through the Python extension command @code{explore} (available only if
10341 the @value{GDBN} build is configured with @code{--with-python}). It
10342 offers an interactive way to start at the highest level (or, the most
10343 abstract level) of the data type of an expression (or, the data type
10344 itself) and explore all the way down to leaf scalar values/fields
10345 embedded in the higher level data types.
10348 @item explore @var{arg}
10349 @var{arg} is either an expression (in the source language), or a type
10350 visible in the current context of the program being debugged.
10353 The working of the @code{explore} command can be illustrated with an
10354 example. If a data type @code{struct ComplexStruct} is defined in your
10358 struct SimpleStruct
10364 struct ComplexStruct
10366 struct SimpleStruct *ss_p;
10372 followed by variable declarations as
10375 struct SimpleStruct ss = @{ 10, 1.11 @};
10376 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
10380 then, the value of the variable @code{cs} can be explored using the
10381 @code{explore} command as follows.
10385 The value of `cs' is a struct/class of type `struct ComplexStruct' with
10386 the following fields:
10388 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
10389 arr = <Enter 1 to explore this field of type `int [10]'>
10391 Enter the field number of choice:
10395 Since the fields of @code{cs} are not scalar values, you are being
10396 prompted to chose the field you want to explore. Let's say you choose
10397 the field @code{ss_p} by entering @code{0}. Then, since this field is a
10398 pointer, you will be asked if it is pointing to a single value. From
10399 the declaration of @code{cs} above, it is indeed pointing to a single
10400 value, hence you enter @code{y}. If you enter @code{n}, then you will
10401 be asked if it were pointing to an array of values, in which case this
10402 field will be explored as if it were an array.
10405 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
10406 Continue exploring it as a pointer to a single value [y/n]: y
10407 The value of `*(cs.ss_p)' is a struct/class of type `struct
10408 SimpleStruct' with the following fields:
10410 i = 10 .. (Value of type `int')
10411 d = 1.1100000000000001 .. (Value of type `double')
10413 Press enter to return to parent value:
10417 If the field @code{arr} of @code{cs} was chosen for exploration by
10418 entering @code{1} earlier, then since it is as array, you will be
10419 prompted to enter the index of the element in the array that you want
10423 `cs.arr' is an array of `int'.
10424 Enter the index of the element you want to explore in `cs.arr': 5
10426 `(cs.arr)[5]' is a scalar value of type `int'.
10430 Press enter to return to parent value:
10433 In general, at any stage of exploration, you can go deeper towards the
10434 leaf values by responding to the prompts appropriately, or hit the
10435 return key to return to the enclosing data structure (the @i{higher}
10436 level data structure).
10438 Similar to exploring values, you can use the @code{explore} command to
10439 explore types. Instead of specifying a value (which is typically a
10440 variable name or an expression valid in the current context of the
10441 program being debugged), you specify a type name. If you consider the
10442 same example as above, your can explore the type
10443 @code{struct ComplexStruct} by passing the argument
10444 @code{struct ComplexStruct} to the @code{explore} command.
10447 (gdb) explore struct ComplexStruct
10451 By responding to the prompts appropriately in the subsequent interactive
10452 session, you can explore the type @code{struct ComplexStruct} in a
10453 manner similar to how the value @code{cs} was explored in the above
10456 The @code{explore} command also has two sub-commands,
10457 @code{explore value} and @code{explore type}. The former sub-command is
10458 a way to explicitly specify that value exploration of the argument is
10459 being invoked, while the latter is a way to explicitly specify that type
10460 exploration of the argument is being invoked.
10463 @item explore value @var{expr}
10464 @cindex explore value
10465 This sub-command of @code{explore} explores the value of the
10466 expression @var{expr} (if @var{expr} is an expression valid in the
10467 current context of the program being debugged). The behavior of this
10468 command is identical to that of the behavior of the @code{explore}
10469 command being passed the argument @var{expr}.
10471 @item explore type @var{arg}
10472 @cindex explore type
10473 This sub-command of @code{explore} explores the type of @var{arg} (if
10474 @var{arg} is a type visible in the current context of program being
10475 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10476 is an expression valid in the current context of the program being
10477 debugged). If @var{arg} is a type, then the behavior of this command is
10478 identical to that of the @code{explore} command being passed the
10479 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10480 this command will be identical to that of the @code{explore} command
10481 being passed the type of @var{arg} as the argument.
10485 * Expressions:: Expressions
10486 * Ambiguous Expressions:: Ambiguous Expressions
10487 * Variables:: Program variables
10488 * Arrays:: Artificial arrays
10489 * Output Formats:: Output formats
10490 * Memory:: Examining memory
10491 * Memory Tagging:: Memory Tagging
10492 * Auto Display:: Automatic display
10493 * Print Settings:: Print settings
10494 * Pretty Printing:: Python pretty printing
10495 * Value History:: Value history
10496 * Convenience Vars:: Convenience variables
10497 * Convenience Funs:: Convenience functions
10498 * Registers:: Registers
10499 * Floating Point Hardware:: Floating point hardware
10500 * Vector Unit:: Vector Unit
10501 * OS Information:: Auxiliary data provided by operating system
10502 * Memory Region Attributes:: Memory region attributes
10503 * Dump/Restore Files:: Copy between memory and a file
10504 * Core File Generation:: Cause a program dump its core
10505 * Character Sets:: Debugging programs that use a different
10506 character set than GDB does
10507 * Caching Target Data:: Data caching for targets
10508 * Searching Memory:: Searching memory for a sequence of bytes
10509 * Value Sizes:: Managing memory allocated for values
10513 @section Expressions
10515 @cindex expressions
10516 @code{print} and many other @value{GDBN} commands accept an expression and
10517 compute its value. Any kind of constant, variable or operator defined
10518 by the programming language you are using is valid in an expression in
10519 @value{GDBN}. This includes conditional expressions, function calls,
10520 casts, and string constants. It also includes preprocessor macros, if
10521 you compiled your program to include this information; see
10524 @cindex arrays in expressions
10525 @value{GDBN} supports array constants in expressions input by
10526 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10527 you can use the command @code{print @{1, 2, 3@}} to create an array
10528 of three integers. If you pass an array to a function or assign it
10529 to a program variable, @value{GDBN} copies the array to memory that
10530 is @code{malloc}ed in the target program.
10532 Because C is so widespread, most of the expressions shown in examples in
10533 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10534 Languages}, for information on how to use expressions in other
10537 In this section, we discuss operators that you can use in @value{GDBN}
10538 expressions regardless of your programming language.
10540 @cindex casts, in expressions
10541 Casts are supported in all languages, not just in C, because it is so
10542 useful to cast a number into a pointer in order to examine a structure
10543 at that address in memory.
10544 @c FIXME: casts supported---Mod2 true?
10546 @value{GDBN} supports these operators, in addition to those common
10547 to programming languages:
10551 @samp{@@} is a binary operator for treating parts of memory as arrays.
10552 @xref{Arrays, ,Artificial Arrays}, for more information.
10555 @samp{::} allows you to specify a variable in terms of the file or
10556 function where it is defined. @xref{Variables, ,Program Variables}.
10558 @cindex @{@var{type}@}
10559 @cindex type casting memory
10560 @cindex memory, viewing as typed object
10561 @cindex casts, to view memory
10562 @item @{@var{type}@} @var{addr}
10563 Refers to an object of type @var{type} stored at address @var{addr} in
10564 memory. The address @var{addr} may be any expression whose value is
10565 an integer or pointer (but parentheses are required around binary
10566 operators, just as in a cast). This construct is allowed regardless
10567 of what kind of data is normally supposed to reside at @var{addr}.
10570 @node Ambiguous Expressions
10571 @section Ambiguous Expressions
10572 @cindex ambiguous expressions
10574 Expressions can sometimes contain some ambiguous elements. For instance,
10575 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10576 a single function name to be defined several times, for application in
10577 different contexts. This is called @dfn{overloading}. Another example
10578 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10579 templates and is typically instantiated several times, resulting in
10580 the same function name being defined in different contexts.
10582 In some cases and depending on the language, it is possible to adjust
10583 the expression to remove the ambiguity. For instance in C@t{++}, you
10584 can specify the signature of the function you want to break on, as in
10585 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10586 qualified name of your function often makes the expression unambiguous
10589 When an ambiguity that needs to be resolved is detected, the debugger
10590 has the capability to display a menu of numbered choices for each
10591 possibility, and then waits for the selection with the prompt @samp{>}.
10592 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10593 aborts the current command. If the command in which the expression was
10594 used allows more than one choice to be selected, the next option in the
10595 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10598 For example, the following session excerpt shows an attempt to set a
10599 breakpoint at the overloaded symbol @code{String::after}.
10600 We choose three particular definitions of that function name:
10602 @c FIXME! This is likely to change to show arg type lists, at least
10605 (@value{GDBP}) b String::after
10608 [2] file:String.cc; line number:867
10609 [3] file:String.cc; line number:860
10610 [4] file:String.cc; line number:875
10611 [5] file:String.cc; line number:853
10612 [6] file:String.cc; line number:846
10613 [7] file:String.cc; line number:735
10615 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10616 Breakpoint 2 at 0xb344: file String.cc, line 875.
10617 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10618 Multiple breakpoints were set.
10619 Use the "delete" command to delete unwanted
10626 @kindex set multiple-symbols
10627 @item set multiple-symbols @var{mode}
10628 @cindex multiple-symbols menu
10630 This option allows you to adjust the debugger behavior when an expression
10633 By default, @var{mode} is set to @code{all}. If the command with which
10634 the expression is used allows more than one choice, then @value{GDBN}
10635 automatically selects all possible choices. For instance, inserting
10636 a breakpoint on a function using an ambiguous name results in a breakpoint
10637 inserted on each possible match. However, if a unique choice must be made,
10638 then @value{GDBN} uses the menu to help you disambiguate the expression.
10639 For instance, printing the address of an overloaded function will result
10640 in the use of the menu.
10642 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10643 when an ambiguity is detected.
10645 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10646 an error due to the ambiguity and the command is aborted.
10648 @kindex show multiple-symbols
10649 @item show multiple-symbols
10650 Show the current value of the @code{multiple-symbols} setting.
10654 @section Program Variables
10656 The most common kind of expression to use is the name of a variable
10659 Variables in expressions are understood in the selected stack frame
10660 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10664 global (or file-static)
10671 visible according to the scope rules of the
10672 programming language from the point of execution in that frame
10675 @noindent This means that in the function
10690 you can examine and use the variable @code{a} whenever your program is
10691 executing within the function @code{foo}, but you can only use or
10692 examine the variable @code{b} while your program is executing inside
10693 the block where @code{b} is declared.
10695 @cindex variable name conflict
10696 There is an exception: you can refer to a variable or function whose
10697 scope is a single source file even if the current execution point is not
10698 in this file. But it is possible to have more than one such variable or
10699 function with the same name (in different source files). If that
10700 happens, referring to that name has unpredictable effects. If you wish,
10701 you can specify a static variable in a particular function or file by
10702 using the colon-colon (@code{::}) notation:
10704 @cindex colon-colon, context for variables/functions
10706 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10707 @cindex @code{::}, context for variables/functions
10710 @var{file}::@var{variable}
10711 @var{function}::@var{variable}
10715 Here @var{file} or @var{function} is the name of the context for the
10716 static @var{variable}. In the case of file names, you can use quotes to
10717 make sure @value{GDBN} parses the file name as a single word---for example,
10718 to print a global value of @code{x} defined in @file{f2.c}:
10721 (@value{GDBP}) p 'f2.c'::x
10724 The @code{::} notation is normally used for referring to
10725 static variables, since you typically disambiguate uses of local variables
10726 in functions by selecting the appropriate frame and using the
10727 simple name of the variable. However, you may also use this notation
10728 to refer to local variables in frames enclosing the selected frame:
10737 process (a); /* Stop here */
10748 For example, if there is a breakpoint at the commented line,
10749 here is what you might see
10750 when the program stops after executing the call @code{bar(0)}:
10755 (@value{GDBP}) p bar::a
10757 (@value{GDBP}) up 2
10758 #2 0x080483d0 in foo (a=5) at foobar.c:12
10761 (@value{GDBP}) p bar::a
10765 @cindex C@t{++} scope resolution
10766 These uses of @samp{::} are very rarely in conflict with the very
10767 similar use of the same notation in C@t{++}. When they are in
10768 conflict, the C@t{++} meaning takes precedence; however, this can be
10769 overridden by quoting the file or function name with single quotes.
10771 For example, suppose the program is stopped in a method of a class
10772 that has a field named @code{includefile}, and there is also an
10773 include file named @file{includefile} that defines a variable,
10774 @code{some_global}.
10777 (@value{GDBP}) p includefile
10779 (@value{GDBP}) p includefile::some_global
10780 A syntax error in expression, near `'.
10781 (@value{GDBP}) p 'includefile'::some_global
10785 @cindex wrong values
10786 @cindex variable values, wrong
10787 @cindex function entry/exit, wrong values of variables
10788 @cindex optimized code, wrong values of variables
10790 @emph{Warning:} Occasionally, a local variable may appear to have the
10791 wrong value at certain points in a function---just after entry to a new
10792 scope, and just before exit.
10794 You may see this problem when you are stepping by machine instructions.
10795 This is because, on most machines, it takes more than one instruction to
10796 set up a stack frame (including local variable definitions); if you are
10797 stepping by machine instructions, variables may appear to have the wrong
10798 values until the stack frame is completely built. On exit, it usually
10799 also takes more than one machine instruction to destroy a stack frame;
10800 after you begin stepping through that group of instructions, local
10801 variable definitions may be gone.
10803 This may also happen when the compiler does significant optimizations.
10804 To be sure of always seeing accurate values, turn off all optimization
10807 @cindex ``No symbol "foo" in current context''
10808 Another possible effect of compiler optimizations is to optimize
10809 unused variables out of existence, or assign variables to registers (as
10810 opposed to memory addresses). Depending on the support for such cases
10811 offered by the debug info format used by the compiler, @value{GDBN}
10812 might not be able to display values for such local variables. If that
10813 happens, @value{GDBN} will print a message like this:
10816 No symbol "foo" in current context.
10819 To solve such problems, either recompile without optimizations, or use a
10820 different debug info format, if the compiler supports several such
10821 formats. @xref{Compilation}, for more information on choosing compiler
10822 options. @xref{C, ,C and C@t{++}}, for more information about debug
10823 info formats that are best suited to C@t{++} programs.
10825 If you ask to print an object whose contents are unknown to
10826 @value{GDBN}, e.g., because its data type is not completely specified
10827 by the debug information, @value{GDBN} will say @samp{<incomplete
10828 type>}. @xref{Symbols, incomplete type}, for more about this.
10830 @cindex no debug info variables
10831 If you try to examine or use the value of a (global) variable for
10832 which @value{GDBN} has no type information, e.g., because the program
10833 includes no debug information, @value{GDBN} displays an error message.
10834 @xref{Symbols, unknown type}, for more about unknown types. If you
10835 cast the variable to its declared type, @value{GDBN} gets the
10836 variable's value using the cast-to type as the variable's type. For
10837 example, in a C program:
10840 (@value{GDBP}) p var
10841 'var' has unknown type; cast it to its declared type
10842 (@value{GDBP}) p (float) var
10846 If you append @kbd{@@entry} string to a function parameter name you get its
10847 value at the time the function got called. If the value is not available an
10848 error message is printed. Entry values are available only with some compilers.
10849 Entry values are normally also printed at the function parameter list according
10850 to @ref{set print entry-values}.
10853 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10859 (gdb) print i@@entry
10863 Strings are identified as arrays of @code{char} values without specified
10864 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10865 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10866 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10867 defines literal string type @code{"char"} as @code{char} without a sign.
10872 signed char var1[] = "A";
10875 You get during debugging
10880 $2 = @{65 'A', 0 '\0'@}
10884 @section Artificial Arrays
10886 @cindex artificial array
10888 @kindex @@@r{, referencing memory as an array}
10889 It is often useful to print out several successive objects of the
10890 same type in memory; a section of an array, or an array of
10891 dynamically determined size for which only a pointer exists in the
10894 You can do this by referring to a contiguous span of memory as an
10895 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10896 operand of @samp{@@} should be the first element of the desired array
10897 and be an individual object. The right operand should be the desired length
10898 of the array. The result is an array value whose elements are all of
10899 the type of the left argument. The first element is actually the left
10900 argument; the second element comes from bytes of memory immediately
10901 following those that hold the first element, and so on. Here is an
10902 example. If a program says
10905 int *array = (int *) malloc (len * sizeof (int));
10909 you can print the contents of @code{array} with
10915 The left operand of @samp{@@} must reside in memory. Array values made
10916 with @samp{@@} in this way behave just like other arrays in terms of
10917 subscripting, and are coerced to pointers when used in expressions.
10918 Artificial arrays most often appear in expressions via the value history
10919 (@pxref{Value History, ,Value History}), after printing one out.
10921 Another way to create an artificial array is to use a cast.
10922 This re-interprets a value as if it were an array.
10923 The value need not be in memory:
10925 (@value{GDBP}) p/x (short[2])0x12345678
10926 $1 = @{0x1234, 0x5678@}
10929 As a convenience, if you leave the array length out (as in
10930 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10931 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10933 (@value{GDBP}) p/x (short[])0x12345678
10934 $2 = @{0x1234, 0x5678@}
10937 Sometimes the artificial array mechanism is not quite enough; in
10938 moderately complex data structures, the elements of interest may not
10939 actually be adjacent---for example, if you are interested in the values
10940 of pointers in an array. One useful work-around in this situation is
10941 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10942 Variables}) as a counter in an expression that prints the first
10943 interesting value, and then repeat that expression via @key{RET}. For
10944 instance, suppose you have an array @code{dtab} of pointers to
10945 structures, and you are interested in the values of a field @code{fv}
10946 in each structure. Here is an example of what you might type:
10956 @node Output Formats
10957 @section Output Formats
10959 @cindex formatted output
10960 @cindex output formats
10961 By default, @value{GDBN} prints a value according to its data type. Sometimes
10962 this is not what you want. For example, you might want to print a number
10963 in hex, or a pointer in decimal. Or you might want to view data in memory
10964 at a certain address as a character string or as an instruction. To do
10965 these things, specify an @dfn{output format} when you print a value.
10967 The simplest use of output formats is to say how to print a value
10968 already computed. This is done by starting the arguments of the
10969 @code{print} command with a slash and a format letter. The format
10970 letters supported are:
10974 Print the binary representation of the value in hexadecimal.
10977 Print the binary representation of the value in decimal.
10980 Print the binary representation of the value as an decimal, as if it
10984 Print the binary representation of the value in octal.
10987 Print the binary representation of the value in binary. The letter
10988 @samp{t} stands for ``two''. @footnote{@samp{b} cannot be used
10989 because these format letters are also used with the @code{x} command,
10990 where @samp{b} stands for ``byte''; see @ref{Memory,,Examining
10994 @cindex unknown address, locating
10995 @cindex locate address
10996 Print as an address, both absolute in hexadecimal and as an offset from
10997 the nearest preceding symbol. You can use this format used to discover
10998 where (in what function) an unknown address is located:
11001 (@value{GDBP}) p/a 0x54320
11002 $3 = 0x54320 <_initialize_vx+396>
11006 The command @code{info symbol 0x54320} yields similar results.
11007 @xref{Symbols, info symbol}.
11010 Cast the value to an integer (unlike other formats, this does not just
11011 reinterpret the underlying bits) and print it as a character constant.
11012 This prints both the numerical value and its character representation.
11013 The character representation is replaced with the octal escape
11014 @samp{\nnn} for characters outside the 7-bit @sc{ascii} range.
11016 Without this format, @value{GDBN} displays @code{char},
11017 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
11018 constants. Single-byte members of vectors are displayed as integer
11022 Regard the bits of the value as a floating point number and print
11023 using typical floating point syntax.
11026 @cindex printing strings
11027 @cindex printing byte arrays
11028 Regard as a string, if possible. With this format, pointers to single-byte
11029 data are displayed as null-terminated strings and arrays of single-byte data
11030 are displayed as fixed-length strings. Other values are displayed in their
11033 Without this format, @value{GDBN} displays pointers to and arrays of
11034 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
11035 strings. Single-byte members of a vector are displayed as an integer
11039 Like @samp{x} formatting, the value is treated as an integer and
11040 printed as hexadecimal, but leading zeros are printed to pad the value
11041 to the size of the integer type.
11044 @cindex raw printing
11045 Print using the @samp{raw} formatting. By default, @value{GDBN} will
11046 use a Python-based pretty-printer, if one is available (@pxref{Pretty
11047 Printing}). This typically results in a higher-level display of the
11048 value's contents. The @samp{r} format bypasses any Python
11049 pretty-printer which might exist.
11052 For example, to print the program counter in hex (@pxref{Registers}), type
11059 Note that no space is required before the slash; this is because command
11060 names in @value{GDBN} cannot contain a slash.
11062 To reprint the last value in the value history with a different format,
11063 you can use the @code{print} command with just a format and no
11064 expression. For example, @samp{p/x} reprints the last value in hex.
11067 @section Examining Memory
11069 You can use the command @code{x} (for ``examine'') to examine memory in
11070 any of several formats, independently of your program's data types.
11072 @cindex examining memory
11074 @kindex x @r{(examine memory)}
11075 @item x/@var{nfu} @var{addr}
11076 @itemx x @var{addr}
11078 Use the @code{x} command to examine memory.
11081 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
11082 much memory to display and how to format it; @var{addr} is an
11083 expression giving the address where you want to start displaying memory.
11084 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
11085 Several commands set convenient defaults for @var{addr}.
11088 @item @var{n}, the repeat count
11089 The repeat count is a decimal integer; the default is 1. It specifies
11090 how much memory (counting by units @var{u}) to display. If a negative
11091 number is specified, memory is examined backward from @var{addr}.
11092 @c This really is **decimal**; unaffected by 'set radix' as of GDB
11095 @item @var{f}, the display format
11096 The display format is one of the formats used by @code{print}
11097 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
11098 @samp{f}, @samp{s}), @samp{i} (for machine instructions) and
11099 @samp{m} (for displaying memory tags).
11100 The default is @samp{x} (hexadecimal) initially. The default changes
11101 each time you use either @code{x} or @code{print}.
11103 @item @var{u}, the unit size
11104 The unit size is any of
11110 Halfwords (two bytes).
11112 Words (four bytes). This is the initial default.
11114 Giant words (eight bytes).
11117 Each time you specify a unit size with @code{x}, that size becomes the
11118 default unit the next time you use @code{x}. For the @samp{i} format,
11119 the unit size is ignored and is normally not written. For the @samp{s} format,
11120 the unit size defaults to @samp{b}, unless it is explicitly given.
11121 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
11122 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
11123 Note that the results depend on the programming language of the
11124 current compilation unit. If the language is C, the @samp{s}
11125 modifier will use the UTF-16 encoding while @samp{w} will use
11126 UTF-32. The encoding is set by the programming language and cannot
11129 @item @var{addr}, starting display address
11130 @var{addr} is the address where you want @value{GDBN} to begin displaying
11131 memory. The expression need not have a pointer value (though it may);
11132 it is always interpreted as an integer address of a byte of memory.
11133 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
11134 @var{addr} is usually just after the last address examined---but several
11135 other commands also set the default address: @code{info breakpoints} (to
11136 the address of the last breakpoint listed), @code{info line} (to the
11137 starting address of a line), and @code{print} (if you use it to display
11138 a value from memory).
11141 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
11142 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
11143 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
11144 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
11145 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
11147 You can also specify a negative repeat count to examine memory backward
11148 from the given address. For example, @samp{x/-3uh 0x54320} prints three
11149 halfwords (@code{h}) at @code{0x5431a}, @code{0x5431c}, and @code{0x5431e}.
11151 Since the letters indicating unit sizes are all distinct from the
11152 letters specifying output formats, you do not have to remember whether
11153 unit size or format comes first; either order works. The output
11154 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
11155 (However, the count @var{n} must come first; @samp{wx4} does not work.)
11157 Even though the unit size @var{u} is ignored for the formats @samp{s}
11158 and @samp{i}, you might still want to use a count @var{n}; for example,
11159 @samp{3i} specifies that you want to see three machine instructions,
11160 including any operands. For convenience, especially when used with
11161 the @code{display} command, the @samp{i} format also prints branch delay
11162 slot instructions, if any, beyond the count specified, which immediately
11163 follow the last instruction that is within the count. The command
11164 @code{disassemble} gives an alternative way of inspecting machine
11165 instructions; see @ref{Machine Code,,Source and Machine Code}.
11167 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
11168 the command displays null-terminated strings or instructions before the given
11169 address as many as the absolute value of the given number. For the @samp{i}
11170 format, we use line number information in the debug info to accurately locate
11171 instruction boundaries while disassembling backward. If line info is not
11172 available, the command stops examining memory with an error message.
11174 All the defaults for the arguments to @code{x} are designed to make it
11175 easy to continue scanning memory with minimal specifications each time
11176 you use @code{x}. For example, after you have inspected three machine
11177 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
11178 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
11179 the repeat count @var{n} is used again; the other arguments default as
11180 for successive uses of @code{x}.
11182 When examining machine instructions, the instruction at current program
11183 counter is shown with a @code{=>} marker. For example:
11186 (@value{GDBP}) x/5i $pc-6
11187 0x804837f <main+11>: mov %esp,%ebp
11188 0x8048381 <main+13>: push %ecx
11189 0x8048382 <main+14>: sub $0x4,%esp
11190 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
11191 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
11194 If the architecture supports memory tagging, the tags can be displayed by
11195 using @samp{m}. @xref{Memory Tagging}.
11197 The information will be displayed once per granule size
11198 (the amount of bytes a particular memory tag covers). For example, AArch64
11199 has a granule size of 16 bytes, so it will display a tag every 16 bytes.
11201 Due to the way @value{GDBN} prints information with the @code{x} command (not
11202 aligned to a particular boundary), the tag information will refer to the
11203 initial address displayed on a particular line. If a memory tag boundary
11204 is crossed in the middle of a line displayed by the @code{x} command, it
11205 will be displayed on the next line.
11207 The @samp{m} format doesn't affect any other specified formats that were
11208 passed to the @code{x} command.
11210 @cindex @code{$_}, @code{$__}, and value history
11211 The addresses and contents printed by the @code{x} command are not saved
11212 in the value history because there is often too much of them and they
11213 would get in the way. Instead, @value{GDBN} makes these values available for
11214 subsequent use in expressions as values of the convenience variables
11215 @code{$_} and @code{$__}. After an @code{x} command, the last address
11216 examined is available for use in expressions in the convenience variable
11217 @code{$_}. The contents of that address, as examined, are available in
11218 the convenience variable @code{$__}.
11220 If the @code{x} command has a repeat count, the address and contents saved
11221 are from the last memory unit printed; this is not the same as the last
11222 address printed if several units were printed on the last line of output.
11224 @anchor{addressable memory unit}
11225 @cindex addressable memory unit
11226 Most targets have an addressable memory unit size of 8 bits. This means
11227 that to each memory address are associated 8 bits of data. Some
11228 targets, however, have other addressable memory unit sizes.
11229 Within @value{GDBN} and this document, the term
11230 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
11231 when explicitly referring to a chunk of data of that size. The word
11232 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
11233 the addressable memory unit size of the target. For most systems,
11234 addressable memory unit is a synonym of byte.
11236 @cindex remote memory comparison
11237 @cindex target memory comparison
11238 @cindex verify remote memory image
11239 @cindex verify target memory image
11240 When you are debugging a program running on a remote target machine
11241 (@pxref{Remote Debugging}), you may wish to verify the program's image
11242 in the remote machine's memory against the executable file you
11243 downloaded to the target. Or, on any target, you may want to check
11244 whether the program has corrupted its own read-only sections. The
11245 @code{compare-sections} command is provided for such situations.
11248 @kindex compare-sections
11249 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
11250 Compare the data of a loadable section @var{section-name} in the
11251 executable file of the program being debugged with the same section in
11252 the target machine's memory, and report any mismatches. With no
11253 arguments, compares all loadable sections. With an argument of
11254 @code{-r}, compares all loadable read-only sections.
11256 Note: for remote targets, this command can be accelerated if the
11257 target supports computing the CRC checksum of a block of memory
11258 (@pxref{qCRC packet}).
11261 @node Memory Tagging
11262 @section Memory Tagging
11264 Memory tagging is a memory protection technology that uses a pair of tags to
11265 validate memory accesses through pointers. The tags are integer values
11266 usually comprised of a few bits, depending on the architecture.
11268 There are two types of tags that are used in this setup: logical and
11269 allocation. A logical tag is stored in the pointers themselves, usually at the
11270 higher bits of the pointers. An allocation tag is the tag associated
11271 with particular ranges of memory in the physical address space, against which
11272 the logical tags from pointers are compared.
11274 The pointer tag (logical tag) must match the memory tag (allocation tag)
11275 for the memory access to be valid. If the logical tag does not match the
11276 allocation tag, that will raise a memory violation.
11278 Allocation tags cover multiple contiguous bytes of physical memory. This
11279 range of bytes is called a memory tag granule and is architecture-specific.
11280 For example, AArch64 has a tag granule of 16 bytes, meaning each allocation
11281 tag spans 16 bytes of memory.
11283 If the underlying architecture supports memory tagging, like AArch64 MTE
11284 or SPARC ADI do, @value{GDBN} can make use of it to validate pointers
11285 against memory allocation tags.
11287 The @code{print} (@pxref{Data}) and @code{x} (@pxref{Memory}) commands will
11288 display tag information when appropriate, and a command prefix of
11289 @code{memory-tag} gives access to the various memory tagging commands.
11291 The @code{memory-tag} commands are the following:
11294 @kindex memory-tag print-logical-tag
11295 @item memory-tag print-logical-tag @var{pointer_expression}
11296 Print the logical tag stored in @var{pointer_expression}.
11297 @kindex memory-tag with-logical-tag
11298 @item memory-tag with-logical-tag @var{pointer_expression} @var{tag_bytes}
11299 Print the pointer given by @var{pointer_expression}, augmented with a logical
11300 tag of @var{tag_bytes}.
11301 @kindex memory-tag print-allocation-tag
11302 @item memory-tag print-allocation-tag @var{address_expression}
11303 Print the allocation tag associated with the memory address given by
11304 @var{address_expression}.
11305 @kindex memory-tag setatag
11306 @item memory-tag setatag @var{starting_address} @var{length} @var{tag_bytes}
11307 Set the allocation tag(s) for memory range @r{[}@var{starting_address},
11308 @var{starting_address} + @var{length}@r{)} to @var{tag_bytes}.
11309 @kindex memory-tag check
11310 @item memory-tag check @var{pointer_expression}
11311 Check if the logical tag in the pointer given by @var{pointer_expression}
11312 matches the allocation tag for the memory referenced by the pointer.
11314 This essentially emulates the hardware validation that is done when tagged
11315 memory is accessed through a pointer, but does not cause a memory fault as
11316 it would during hardware validation.
11318 It can be used to inspect potential memory tagging violations in the running
11319 process, before any faults get triggered.
11323 @section Automatic Display
11324 @cindex automatic display
11325 @cindex display of expressions
11327 If you find that you want to print the value of an expression frequently
11328 (to see how it changes), you might want to add it to the @dfn{automatic
11329 display list} so that @value{GDBN} prints its value each time your program stops.
11330 Each expression added to the list is given a number to identify it;
11331 to remove an expression from the list, you specify that number.
11332 The automatic display looks like this:
11336 3: bar[5] = (struct hack *) 0x3804
11340 This display shows item numbers, expressions and their current values. As with
11341 displays you request manually using @code{x} or @code{print}, you can
11342 specify the output format you prefer; in fact, @code{display} decides
11343 whether to use @code{print} or @code{x} depending your format
11344 specification---it uses @code{x} if you specify either the @samp{i}
11345 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
11349 @item display @var{expr}
11350 Add the expression @var{expr} to the list of expressions to display
11351 each time your program stops. @xref{Expressions, ,Expressions}.
11353 @code{display} does not repeat if you press @key{RET} again after using it.
11355 @item display/@var{fmt} @var{expr}
11356 For @var{fmt} specifying only a display format and not a size or
11357 count, add the expression @var{expr} to the auto-display list but
11358 arrange to display it each time in the specified format @var{fmt}.
11359 @xref{Output Formats,,Output Formats}.
11361 @item display/@var{fmt} @var{addr}
11362 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
11363 number of units, add the expression @var{addr} as a memory address to
11364 be examined each time your program stops. Examining means in effect
11365 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
11368 For example, @samp{display/i $pc} can be helpful, to see the machine
11369 instruction about to be executed each time execution stops (@samp{$pc}
11370 is a common name for the program counter; @pxref{Registers, ,Registers}).
11373 @kindex delete display
11375 @item undisplay @var{dnums}@dots{}
11376 @itemx delete display @var{dnums}@dots{}
11377 Remove items from the list of expressions to display. Specify the
11378 numbers of the displays that you want affected with the command
11379 argument @var{dnums}. It can be a single display number, one of the
11380 numbers shown in the first field of the @samp{info display} display;
11381 or it could be a range of display numbers, as in @code{2-4}.
11383 @code{undisplay} does not repeat if you press @key{RET} after using it.
11384 (Otherwise you would just get the error @samp{No display number @dots{}}.)
11386 @kindex disable display
11387 @item disable display @var{dnums}@dots{}
11388 Disable the display of item numbers @var{dnums}. A disabled display
11389 item is not printed automatically, but is not forgotten. It may be
11390 enabled again later. Specify the numbers of the displays that you
11391 want affected with the command argument @var{dnums}. It can be a
11392 single display number, one of the numbers shown in the first field of
11393 the @samp{info display} display; or it could be a range of display
11394 numbers, as in @code{2-4}.
11396 @kindex enable display
11397 @item enable display @var{dnums}@dots{}
11398 Enable display of item numbers @var{dnums}. It becomes effective once
11399 again in auto display of its expression, until you specify otherwise.
11400 Specify the numbers of the displays that you want affected with the
11401 command argument @var{dnums}. It can be a single display number, one
11402 of the numbers shown in the first field of the @samp{info display}
11403 display; or it could be a range of display numbers, as in @code{2-4}.
11406 Display the current values of the expressions on the list, just as is
11407 done when your program stops.
11409 @kindex info display
11411 Print the list of expressions previously set up to display
11412 automatically, each one with its item number, but without showing the
11413 values. This includes disabled expressions, which are marked as such.
11414 It also includes expressions which would not be displayed right now
11415 because they refer to automatic variables not currently available.
11418 @cindex display disabled out of scope
11419 If a display expression refers to local variables, then it does not make
11420 sense outside the lexical context for which it was set up. Such an
11421 expression is disabled when execution enters a context where one of its
11422 variables is not defined. For example, if you give the command
11423 @code{display last_char} while inside a function with an argument
11424 @code{last_char}, @value{GDBN} displays this argument while your program
11425 continues to stop inside that function. When it stops elsewhere---where
11426 there is no variable @code{last_char}---the display is disabled
11427 automatically. The next time your program stops where @code{last_char}
11428 is meaningful, you can enable the display expression once again.
11430 @node Print Settings
11431 @section Print Settings
11433 @cindex format options
11434 @cindex print settings
11435 @value{GDBN} provides the following ways to control how arrays, structures,
11436 and symbols are printed.
11439 These settings are useful for debugging programs in any language:
11443 @anchor{set print address}
11444 @item set print address
11445 @itemx set print address on
11446 @cindex print/don't print memory addresses
11447 @value{GDBN} prints memory addresses showing the location of stack
11448 traces, structure values, pointer values, breakpoints, and so forth,
11449 even when it also displays the contents of those addresses. The default
11450 is @code{on}. For example, this is what a stack frame display looks like with
11451 @code{set print address on}:
11456 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
11458 530 if (lquote != def_lquote)
11462 @item set print address off
11463 Do not print addresses when displaying their contents. For example,
11464 this is the same stack frame displayed with @code{set print address off}:
11468 (@value{GDBP}) set print addr off
11470 #0 set_quotes (lq="<<", rq=">>") at input.c:530
11471 530 if (lquote != def_lquote)
11475 You can use @samp{set print address off} to eliminate all machine
11476 dependent displays from the @value{GDBN} interface. For example, with
11477 @code{print address off}, you should get the same text for backtraces on
11478 all machines---whether or not they involve pointer arguments.
11481 @item show print address
11482 Show whether or not addresses are to be printed.
11485 When @value{GDBN} prints a symbolic address, it normally prints the
11486 closest earlier symbol plus an offset. If that symbol does not uniquely
11487 identify the address (for example, it is a name whose scope is a single
11488 source file), you may need to clarify. One way to do this is with
11489 @code{info line}, for example @samp{info line *0x4537}. Alternately,
11490 you can set @value{GDBN} to print the source file and line number when
11491 it prints a symbolic address:
11494 @item set print symbol-filename on
11495 @cindex source file and line of a symbol
11496 @cindex symbol, source file and line
11497 Tell @value{GDBN} to print the source file name and line number of a
11498 symbol in the symbolic form of an address.
11500 @item set print symbol-filename off
11501 Do not print source file name and line number of a symbol. This is the
11504 @item show print symbol-filename
11505 Show whether or not @value{GDBN} will print the source file name and
11506 line number of a symbol in the symbolic form of an address.
11509 Another situation where it is helpful to show symbol filenames and line
11510 numbers is when disassembling code; @value{GDBN} shows you the line
11511 number and source file that corresponds to each instruction.
11513 Also, you may wish to see the symbolic form only if the address being
11514 printed is reasonably close to the closest earlier symbol:
11517 @item set print max-symbolic-offset @var{max-offset}
11518 @itemx set print max-symbolic-offset unlimited
11519 @cindex maximum value for offset of closest symbol
11520 Tell @value{GDBN} to only display the symbolic form of an address if the
11521 offset between the closest earlier symbol and the address is less than
11522 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11523 to always print the symbolic form of an address if any symbol precedes
11524 it. Zero is equivalent to @code{unlimited}.
11526 @item show print max-symbolic-offset
11527 Ask how large the maximum offset is that @value{GDBN} prints in a
11531 @cindex wild pointer, interpreting
11532 @cindex pointer, finding referent
11533 If you have a pointer and you are not sure where it points, try
11534 @samp{set print symbol-filename on}. Then you can determine the name
11535 and source file location of the variable where it points, using
11536 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11537 For example, here @value{GDBN} shows that a variable @code{ptt} points
11538 at another variable @code{t}, defined in @file{hi2.c}:
11541 (@value{GDBP}) set print symbol-filename on
11542 (@value{GDBP}) p/a ptt
11543 $4 = 0xe008 <t in hi2.c>
11547 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11548 does not show the symbol name and filename of the referent, even with
11549 the appropriate @code{set print} options turned on.
11552 You can also enable @samp{/a}-like formatting all the time using
11553 @samp{set print symbol on}:
11555 @anchor{set print symbol}
11557 @item set print symbol on
11558 Tell @value{GDBN} to print the symbol corresponding to an address, if
11561 @item set print symbol off
11562 Tell @value{GDBN} not to print the symbol corresponding to an
11563 address. In this mode, @value{GDBN} will still print the symbol
11564 corresponding to pointers to functions. This is the default.
11566 @item show print symbol
11567 Show whether @value{GDBN} will display the symbol corresponding to an
11571 Other settings control how different kinds of objects are printed:
11574 @anchor{set print array}
11575 @item set print array
11576 @itemx set print array on
11577 @cindex pretty print arrays
11578 Pretty print arrays. This format is more convenient to read,
11579 but uses more space. The default is off.
11581 @item set print array off
11582 Return to compressed format for arrays.
11584 @item show print array
11585 Show whether compressed or pretty format is selected for displaying
11588 @cindex print array indexes
11589 @anchor{set print array-indexes}
11590 @item set print array-indexes
11591 @itemx set print array-indexes on
11592 Print the index of each element when displaying arrays. May be more
11593 convenient to locate a given element in the array or quickly find the
11594 index of a given element in that printed array. The default is off.
11596 @item set print array-indexes off
11597 Stop printing element indexes when displaying arrays.
11599 @item show print array-indexes
11600 Show whether the index of each element is printed when displaying
11603 @anchor{set print nibbles}
11604 @item set print nibbles
11605 @itemx set print nibbles on
11606 @cindex print binary values in groups of four bits
11607 Print binary values in groups of four bits, known as @dfn{nibbles},
11608 when using the print command of @value{GDBN} with the option @samp{/t}.
11609 For example, this is what it looks like with @code{set print nibbles on}:
11613 (@value{GDBP}) print val_flags
11615 (@value{GDBP}) print/t val_flags
11616 $2 = 0100 1100 1110
11620 @item set print nibbles off
11621 Don't printing binary values in groups. This is the default.
11623 @item show print nibbles
11624 Show whether to print binary values in groups of four bits.
11626 @anchor{set print elements}
11627 @item set print elements @var{number-of-elements}
11628 @itemx set print elements unlimited
11629 @cindex number of array elements to print
11630 @cindex limit on number of printed array elements
11631 Set a limit on how many elements of an array @value{GDBN} will print.
11632 If @value{GDBN} is printing a large array, it stops printing after it has
11633 printed the number of elements set by the @code{set print elements} command.
11634 This limit also applies to the display of strings.
11635 When @value{GDBN} starts, this limit is set to 200.
11636 Setting @var{number-of-elements} to @code{unlimited} or zero means
11637 that the number of elements to print is unlimited.
11639 @item show print elements
11640 Display the number of elements of a large array that @value{GDBN} will print.
11642 @anchor{set print frame-arguments}
11643 @item set print frame-arguments @var{value}
11644 @kindex set print frame-arguments
11645 @cindex printing frame argument values
11646 @cindex print all frame argument values
11647 @cindex print frame argument values for scalars only
11648 @cindex do not print frame arguments
11649 This command allows to control how the values of arguments are printed
11650 when the debugger prints a frame (@pxref{Frames}). The possible
11655 The values of all arguments are printed.
11658 Print the value of an argument only if it is a scalar. The value of more
11659 complex arguments such as arrays, structures, unions, etc, is replaced
11660 by @code{@dots{}}. This is the default. Here is an example where
11661 only scalar arguments are shown:
11664 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11669 None of the argument values are printed. Instead, the value of each argument
11670 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11673 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11678 Only the presence of arguments is indicated by @code{@dots{}}.
11679 The @code{@dots{}} are not printed for function without any arguments.
11680 None of the argument names and values are printed.
11681 In this case, the example above now becomes:
11684 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11689 By default, only scalar arguments are printed. This command can be used
11690 to configure the debugger to print the value of all arguments, regardless
11691 of their type. However, it is often advantageous to not print the value
11692 of more complex parameters. For instance, it reduces the amount of
11693 information printed in each frame, making the backtrace more readable.
11694 Also, it improves performance when displaying Ada frames, because
11695 the computation of large arguments can sometimes be CPU-intensive,
11696 especially in large applications. Setting @code{print frame-arguments}
11697 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11698 this computation, thus speeding up the display of each Ada frame.
11700 @item show print frame-arguments
11701 Show how the value of arguments should be displayed when printing a frame.
11703 @anchor{set print raw-frame-arguments}
11704 @item set print raw-frame-arguments on
11705 Print frame arguments in raw, non pretty-printed, form.
11707 @item set print raw-frame-arguments off
11708 Print frame arguments in pretty-printed form, if there is a pretty-printer
11709 for the value (@pxref{Pretty Printing}),
11710 otherwise print the value in raw form.
11711 This is the default.
11713 @item show print raw-frame-arguments
11714 Show whether to print frame arguments in raw form.
11716 @anchor{set print entry-values}
11717 @item set print entry-values @var{value}
11718 @kindex set print entry-values
11719 Set printing of frame argument values at function entry. In some cases
11720 @value{GDBN} can determine the value of function argument which was passed by
11721 the function caller, even if the value was modified inside the called function
11722 and therefore is different. With optimized code, the current value could be
11723 unavailable, but the entry value may still be known.
11725 The default value is @code{default} (see below for its description). Older
11726 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11727 this feature will behave in the @code{default} setting the same way as with the
11730 This functionality is currently supported only by DWARF 2 debugging format and
11731 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11732 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11735 The @var{value} parameter can be one of the following:
11739 Print only actual parameter values, never print values from function entry
11743 #0 different (val=6)
11744 #0 lost (val=<optimized out>)
11746 #0 invalid (val=<optimized out>)
11750 Print only parameter values from function entry point. The actual parameter
11751 values are never printed.
11753 #0 equal (val@@entry=5)
11754 #0 different (val@@entry=5)
11755 #0 lost (val@@entry=5)
11756 #0 born (val@@entry=<optimized out>)
11757 #0 invalid (val@@entry=<optimized out>)
11761 Print only parameter values from function entry point. If value from function
11762 entry point is not known while the actual value is known, print the actual
11763 value for such parameter.
11765 #0 equal (val@@entry=5)
11766 #0 different (val@@entry=5)
11767 #0 lost (val@@entry=5)
11769 #0 invalid (val@@entry=<optimized out>)
11773 Print actual parameter values. If actual parameter value is not known while
11774 value from function entry point is known, print the entry point value for such
11778 #0 different (val=6)
11779 #0 lost (val@@entry=5)
11781 #0 invalid (val=<optimized out>)
11785 Always print both the actual parameter value and its value from function entry
11786 point, even if values of one or both are not available due to compiler
11789 #0 equal (val=5, val@@entry=5)
11790 #0 different (val=6, val@@entry=5)
11791 #0 lost (val=<optimized out>, val@@entry=5)
11792 #0 born (val=10, val@@entry=<optimized out>)
11793 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11797 Print the actual parameter value if it is known and also its value from
11798 function entry point if it is known. If neither is known, print for the actual
11799 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11800 values are known and identical, print the shortened
11801 @code{param=param@@entry=VALUE} notation.
11803 #0 equal (val=val@@entry=5)
11804 #0 different (val=6, val@@entry=5)
11805 #0 lost (val@@entry=5)
11807 #0 invalid (val=<optimized out>)
11811 Always print the actual parameter value. Print also its value from function
11812 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11813 if both values are known and identical, print the shortened
11814 @code{param=param@@entry=VALUE} notation.
11816 #0 equal (val=val@@entry=5)
11817 #0 different (val=6, val@@entry=5)
11818 #0 lost (val=<optimized out>, val@@entry=5)
11820 #0 invalid (val=<optimized out>)
11824 For analysis messages on possible failures of frame argument values at function
11825 entry resolution see @ref{set debug entry-values}.
11827 @item show print entry-values
11828 Show the method being used for printing of frame argument values at function
11831 @anchor{set print frame-info}
11832 @item set print frame-info @var{value}
11833 @kindex set print frame-info
11834 @cindex printing frame information
11835 @cindex frame information, printing
11836 This command allows to control the information printed when
11837 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11838 for a general explanation about frames and frame information.
11839 Note that some other settings (such as @code{set print frame-arguments}
11840 and @code{set print address}) are also influencing if and how some frame
11841 information is displayed. In particular, the frame program counter is never
11842 printed if @code{set print address} is off.
11844 The possible values for @code{set print frame-info} are:
11846 @item short-location
11847 Print the frame level, the program counter (if not at the
11848 beginning of the location source line), the function, the function
11851 Same as @code{short-location} but also print the source file and source line
11853 @item location-and-address
11854 Same as @code{location} but print the program counter even if located at the
11855 beginning of the location source line.
11857 Print the program counter (if not at the beginning of the location
11858 source line), the line number and the source line.
11859 @item source-and-location
11860 Print what @code{location} and @code{source-line} are printing.
11862 The information printed for a frame is decided automatically
11863 by the @value{GDBN} command that prints a frame.
11864 For example, @code{frame} prints the information printed by
11865 @code{source-and-location} while @code{stepi} will switch between
11866 @code{source-line} and @code{source-and-location} depending on the program
11868 The default value is @code{auto}.
11871 @anchor{set print repeats}
11872 @item set print repeats @var{number-of-repeats}
11873 @itemx set print repeats unlimited
11874 @cindex repeated array elements
11875 Set the threshold for suppressing display of repeated array
11876 elements. When the number of consecutive identical elements of an
11877 array exceeds the threshold, @value{GDBN} prints the string
11878 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11879 identical repetitions, instead of displaying the identical elements
11880 themselves. Setting the threshold to @code{unlimited} or zero will
11881 cause all elements to be individually printed. The default threshold
11884 @item show print repeats
11885 Display the current threshold for printing repeated identical
11888 @anchor{set print max-depth}
11889 @item set print max-depth @var{depth}
11890 @item set print max-depth unlimited
11891 @cindex printing nested structures
11892 Set the threshold after which nested structures are replaced with
11893 ellipsis, this can make visualising deeply nested structures easier.
11895 For example, given this C code
11898 typedef struct s1 @{ int a; @} s1;
11899 typedef struct s2 @{ s1 b; @} s2;
11900 typedef struct s3 @{ s2 c; @} s3;
11901 typedef struct s4 @{ s3 d; @} s4;
11903 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11906 The following table shows how different values of @var{depth} will
11907 effect how @code{var} is printed by @value{GDBN}:
11909 @multitable @columnfractions .3 .7
11910 @headitem @var{depth} setting @tab Result of @samp{p var}
11912 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11914 @tab @code{$1 = @{...@}}
11916 @tab @code{$1 = @{d = @{...@}@}}
11918 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11920 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11922 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11925 To see the contents of structures that have been hidden the user can
11926 either increase the print max-depth, or they can print the elements of
11927 the structure that are visible, for example
11930 (gdb) set print max-depth 2
11932 $1 = @{d = @{c = @{...@}@}@}
11934 $2 = @{c = @{b = @{...@}@}@}
11936 $3 = @{b = @{a = 3@}@}
11939 The pattern used to replace nested structures varies based on
11940 language, for most languages @code{@{...@}} is used, but Fortran uses
11943 @item show print max-depth
11944 Display the current threshold after which nested structures are
11945 replaces with ellipsis.
11947 @anchor{set print memory-tag-violations}
11948 @cindex printing memory tag violation information
11949 @item set print memory-tag-violations
11950 @itemx set print memory-tag-violations on
11951 Cause @value{GDBN} to display additional information about memory tag violations
11952 when printing pointers and addresses.
11954 @item set print memory-tag-violations off
11955 Stop printing memory tag violation information.
11957 @item show print memory-tag-violations
11958 Show whether memory tag violation information is displayed when printing
11959 pointers and addresses.
11961 @anchor{set print null-stop}
11962 @item set print null-stop
11963 @cindex @sc{null} elements in arrays
11964 Cause @value{GDBN} to stop printing the characters of an array when the first
11965 @sc{null} is encountered. This is useful when large arrays actually
11966 contain only short strings.
11967 The default is off.
11969 @item show print null-stop
11970 Show whether @value{GDBN} stops printing an array on the first
11971 @sc{null} character.
11973 @anchor{set print pretty}
11974 @item set print pretty on
11975 @cindex print structures in indented form
11976 @cindex indentation in structure display
11977 Cause @value{GDBN} to print structures in an indented format with one member
11978 per line, like this:
11993 @item set print pretty off
11994 Cause @value{GDBN} to print structures in a compact format, like this:
11998 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11999 meat = 0x54 "Pork"@}
12004 This is the default format.
12006 @item show print pretty
12007 Show which format @value{GDBN} is using to print structures.
12009 @anchor{set print raw-values}
12010 @item set print raw-values on
12011 Print values in raw form, without applying the pretty
12012 printers for the value.
12014 @item set print raw-values off
12015 Print values in pretty-printed form, if there is a pretty-printer
12016 for the value (@pxref{Pretty Printing}),
12017 otherwise print the value in raw form.
12019 The default setting is ``off''.
12021 @item show print raw-values
12022 Show whether to print values in raw form.
12024 @item set print sevenbit-strings on
12025 @cindex eight-bit characters in strings
12026 @cindex octal escapes in strings
12027 Print using only seven-bit characters; if this option is set,
12028 @value{GDBN} displays any eight-bit characters (in strings or
12029 character values) using the notation @code{\}@var{nnn}. This setting is
12030 best if you are working in English (@sc{ascii}) and you use the
12031 high-order bit of characters as a marker or ``meta'' bit.
12033 @item set print sevenbit-strings off
12034 Print full eight-bit characters. This allows the use of more
12035 international character sets, and is the default.
12037 @item show print sevenbit-strings
12038 Show whether or not @value{GDBN} is printing only seven-bit characters.
12040 @anchor{set print union}
12041 @item set print union on
12042 @cindex unions in structures, printing
12043 Tell @value{GDBN} to print unions which are contained in structures
12044 and other unions. This is the default setting.
12046 @item set print union off
12047 Tell @value{GDBN} not to print unions which are contained in
12048 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
12051 @item show print union
12052 Ask @value{GDBN} whether or not it will print unions which are contained in
12053 structures and other unions.
12055 For example, given the declarations
12058 typedef enum @{Tree, Bug@} Species;
12059 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
12060 typedef enum @{Caterpillar, Cocoon, Butterfly@}
12071 struct thing foo = @{Tree, @{Acorn@}@};
12075 with @code{set print union on} in effect @samp{p foo} would print
12078 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
12082 and with @code{set print union off} in effect it would print
12085 $1 = @{it = Tree, form = @{...@}@}
12089 @code{set print union} affects programs written in C-like languages
12095 These settings are of interest when debugging C@t{++} programs:
12098 @cindex demangling C@t{++} names
12099 @item set print demangle
12100 @itemx set print demangle on
12101 Print C@t{++} names in their source form rather than in the encoded
12102 (``mangled'') form passed to the assembler and linker for type-safe
12103 linkage. The default is on.
12105 @item show print demangle
12106 Show whether C@t{++} names are printed in mangled or demangled form.
12108 @item set print asm-demangle
12109 @itemx set print asm-demangle on
12110 Print C@t{++} names in their source form rather than their mangled form, even
12111 in assembler code printouts such as instruction disassemblies.
12112 The default is off.
12114 @item show print asm-demangle
12115 Show whether C@t{++} names in assembly listings are printed in mangled
12118 @cindex C@t{++} symbol decoding style
12119 @cindex symbol decoding style, C@t{++}
12120 @kindex set demangle-style
12121 @item set demangle-style @var{style}
12122 Choose among several encoding schemes used by different compilers to represent
12123 C@t{++} names. If you omit @var{style}, you will see a list of possible
12124 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
12125 decoding style by inspecting your program.
12127 @item show demangle-style
12128 Display the encoding style currently in use for decoding C@t{++} symbols.
12130 @anchor{set print object}
12131 @item set print object
12132 @itemx set print object on
12133 @cindex derived type of an object, printing
12134 @cindex display derived types
12135 When displaying a pointer to an object, identify the @emph{actual}
12136 (derived) type of the object rather than the @emph{declared} type, using
12137 the virtual function table. Note that the virtual function table is
12138 required---this feature can only work for objects that have run-time
12139 type identification; a single virtual method in the object's declared
12140 type is sufficient. Note that this setting is also taken into account when
12141 working with variable objects via MI (@pxref{GDB/MI}).
12143 @item set print object off
12144 Display only the declared type of objects, without reference to the
12145 virtual function table. This is the default setting.
12147 @item show print object
12148 Show whether actual, or declared, object types are displayed.
12150 @anchor{set print static-members}
12151 @item set print static-members
12152 @itemx set print static-members on
12153 @cindex static members of C@t{++} objects
12154 Print static members when displaying a C@t{++} object. The default is on.
12156 @item set print static-members off
12157 Do not print static members when displaying a C@t{++} object.
12159 @item show print static-members
12160 Show whether C@t{++} static members are printed or not.
12162 @item set print pascal_static-members
12163 @itemx set print pascal_static-members on
12164 @cindex static members of Pascal objects
12165 @cindex Pascal objects, static members display
12166 Print static members when displaying a Pascal object. The default is on.
12168 @item set print pascal_static-members off
12169 Do not print static members when displaying a Pascal object.
12171 @item show print pascal_static-members
12172 Show whether Pascal static members are printed or not.
12174 @c These don't work with HP ANSI C++ yet.
12175 @anchor{set print vtbl}
12176 @item set print vtbl
12177 @itemx set print vtbl on
12178 @cindex pretty print C@t{++} virtual function tables
12179 @cindex virtual functions (C@t{++}) display
12180 @cindex VTBL display
12181 Pretty print C@t{++} virtual function tables. The default is off.
12182 (The @code{vtbl} commands do not work on programs compiled with the HP
12183 ANSI C@t{++} compiler (@code{aCC}).)
12185 @item set print vtbl off
12186 Do not pretty print C@t{++} virtual function tables.
12188 @item show print vtbl
12189 Show whether C@t{++} virtual function tables are pretty printed, or not.
12192 @node Pretty Printing
12193 @section Pretty Printing
12195 @value{GDBN} provides a mechanism to allow pretty-printing of values using
12196 Python code. It greatly simplifies the display of complex objects. This
12197 mechanism works for both MI and the CLI.
12200 * Pretty-Printer Introduction:: Introduction to pretty-printers
12201 * Pretty-Printer Example:: An example pretty-printer
12202 * Pretty-Printer Commands:: Pretty-printer commands
12205 @node Pretty-Printer Introduction
12206 @subsection Pretty-Printer Introduction
12208 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
12209 registered for the value. If there is then @value{GDBN} invokes the
12210 pretty-printer to print the value. Otherwise the value is printed normally.
12212 Pretty-printers are normally named. This makes them easy to manage.
12213 The @samp{info pretty-printer} command will list all the installed
12214 pretty-printers with their names.
12215 If a pretty-printer can handle multiple data types, then its
12216 @dfn{subprinters} are the printers for the individual data types.
12217 Each such subprinter has its own name.
12218 The format of the name is @var{printer-name};@var{subprinter-name}.
12220 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
12221 Typically they are automatically loaded and registered when the corresponding
12222 debug information is loaded, thus making them available without having to
12223 do anything special.
12225 There are three places where a pretty-printer can be registered.
12229 Pretty-printers registered globally are available when debugging
12233 Pretty-printers registered with a program space are available only
12234 when debugging that program.
12235 @xref{Progspaces In Python}, for more details on program spaces in Python.
12238 Pretty-printers registered with an objfile are loaded and unloaded
12239 with the corresponding objfile (e.g., shared library).
12240 @xref{Objfiles In Python}, for more details on objfiles in Python.
12243 @xref{Selecting Pretty-Printers}, for further information on how
12244 pretty-printers are selected,
12246 @xref{Writing a Pretty-Printer}, for implementing pretty printers
12249 @node Pretty-Printer Example
12250 @subsection Pretty-Printer Example
12252 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
12255 (@value{GDBP}) print s
12257 static npos = 4294967295,
12259 <std::allocator<char>> = @{
12260 <__gnu_cxx::new_allocator<char>> = @{
12261 <No data fields>@}, <No data fields>
12263 members of std::basic_string<char, std::char_traits<char>,
12264 std::allocator<char> >::_Alloc_hider:
12265 _M_p = 0x804a014 "abcd"
12270 With a pretty-printer for @code{std::string} only the contents are printed:
12273 (@value{GDBP}) print s
12277 @node Pretty-Printer Commands
12278 @subsection Pretty-Printer Commands
12279 @cindex pretty-printer commands
12282 @kindex info pretty-printer
12283 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12284 Print the list of installed pretty-printers.
12285 This includes disabled pretty-printers, which are marked as such.
12287 @var{object-regexp} is a regular expression matching the objects
12288 whose pretty-printers to list.
12289 Objects can be @code{global}, the program space's file
12290 (@pxref{Progspaces In Python}),
12291 and the object files within that program space (@pxref{Objfiles In Python}).
12292 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
12293 looks up a printer from these three objects.
12295 @var{name-regexp} is a regular expression matching the name of the printers
12298 @kindex disable pretty-printer
12299 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12300 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12301 A disabled pretty-printer is not forgotten, it may be enabled again later.
12303 @kindex enable pretty-printer
12304 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12305 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12310 Suppose we have three pretty-printers installed: one from library1.so
12311 named @code{foo} that prints objects of type @code{foo}, and
12312 another from library2.so named @code{bar} that prints two types of objects,
12313 @code{bar1} and @code{bar2}.
12317 (@value{GDBP}) info pretty-printer
12326 (@value{GDBP}) info pretty-printer library2
12333 (@value{GDBP}) disable pretty-printer library1
12335 2 of 3 printers enabled
12336 (@value{GDBP}) info pretty-printer
12345 (@value{GDBP}) disable pretty-printer library2 bar;bar1
12347 1 of 3 printers enabled
12348 (@value{GDBP}) info pretty-printer library2
12355 (@value{GDBP}) disable pretty-printer library2 bar
12357 0 of 3 printers enabled
12358 (@value{GDBP}) info pretty-printer
12368 Note that for @code{bar} the entire printer can be disabled,
12369 as can each individual subprinter.
12371 Printing values and frame arguments is done by default using
12372 the enabled pretty printers.
12374 The print option @code{-raw-values} and @value{GDBN} setting
12375 @code{set print raw-values} (@pxref{set print raw-values}) can be
12376 used to print values without applying the enabled pretty printers.
12378 Similarly, the backtrace option @code{-raw-frame-arguments} and
12379 @value{GDBN} setting @code{set print raw-frame-arguments}
12380 (@pxref{set print raw-frame-arguments}) can be used to ignore the
12381 enabled pretty printers when printing frame argument values.
12383 @node Value History
12384 @section Value History
12386 @cindex value history
12387 @cindex history of values printed by @value{GDBN}
12388 Values printed by the @code{print} command are saved in the @value{GDBN}
12389 @dfn{value history}. This allows you to refer to them in other expressions.
12390 Values are kept until the symbol table is re-read or discarded
12391 (for example with the @code{file} or @code{symbol-file} commands).
12392 When the symbol table changes, the value history is discarded,
12393 since the values may contain pointers back to the types defined in the
12398 @cindex history number
12399 The values printed are given @dfn{history numbers} by which you can
12400 refer to them. These are successive integers starting with one.
12401 @code{print} shows you the history number assigned to a value by
12402 printing @samp{$@var{num} = } before the value; here @var{num} is the
12405 To refer to any previous value, use @samp{$} followed by the value's
12406 history number. The way @code{print} labels its output is designed to
12407 remind you of this. Just @code{$} refers to the most recent value in
12408 the history, and @code{$$} refers to the value before that.
12409 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
12410 is the value just prior to @code{$$}, @code{$$1} is equivalent to
12411 @code{$$}, and @code{$$0} is equivalent to @code{$}.
12413 For example, suppose you have just printed a pointer to a structure and
12414 want to see the contents of the structure. It suffices to type
12420 If you have a chain of structures where the component @code{next} points
12421 to the next one, you can print the contents of the next one with this:
12428 You can print successive links in the chain by repeating this
12429 command---which you can do by just typing @key{RET}.
12431 Note that the history records values, not expressions. If the value of
12432 @code{x} is 4 and you type these commands:
12440 then the value recorded in the value history by the @code{print} command
12441 remains 4 even though the value of @code{x} has changed.
12444 @kindex show values
12446 Print the last ten values in the value history, with their item numbers.
12447 This is like @samp{p@ $$9} repeated ten times, except that @code{show
12448 values} does not change the history.
12450 @item show values @var{n}
12451 Print ten history values centered on history item number @var{n}.
12453 @item show values +
12454 Print ten history values just after the values last printed. If no more
12455 values are available, @code{show values +} produces no display.
12458 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
12459 same effect as @samp{show values +}.
12461 @node Convenience Vars
12462 @section Convenience Variables
12464 @cindex convenience variables
12465 @cindex user-defined variables
12466 @value{GDBN} provides @dfn{convenience variables} that you can use within
12467 @value{GDBN} to hold on to a value and refer to it later. These variables
12468 exist entirely within @value{GDBN}; they are not part of your program, and
12469 setting a convenience variable has no direct effect on further execution
12470 of your program. That is why you can use them freely.
12472 Convenience variables are prefixed with @samp{$}. Any name preceded by
12473 @samp{$} can be used for a convenience variable, unless it is one of
12474 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
12475 (Value history references, in contrast, are @emph{numbers} preceded
12476 by @samp{$}. @xref{Value History, ,Value History}.)
12478 You can save a value in a convenience variable with an assignment
12479 expression, just as you would set a variable in your program.
12483 set $foo = *object_ptr
12487 would save in @code{$foo} the value contained in the object pointed to by
12490 Using a convenience variable for the first time creates it, but its
12491 value is @code{void} until you assign a new value. You can alter the
12492 value with another assignment at any time.
12494 Convenience variables have no fixed types. You can assign a convenience
12495 variable any type of value, including structures and arrays, even if
12496 that variable already has a value of a different type. The convenience
12497 variable, when used as an expression, has the type of its current value.
12500 @kindex show convenience
12501 @cindex show all user variables and functions
12502 @item show convenience
12503 Print a list of convenience variables used so far, and their values,
12504 as well as a list of the convenience functions.
12505 Abbreviated @code{show conv}.
12507 @kindex init-if-undefined
12508 @cindex convenience variables, initializing
12509 @item init-if-undefined $@var{variable} = @var{expression}
12510 Set a convenience variable if it has not already been set. This is useful
12511 for user-defined commands that keep some state. It is similar, in concept,
12512 to using local static variables with initializers in C (except that
12513 convenience variables are global). It can also be used to allow users to
12514 override default values used in a command script.
12516 If the variable is already defined then the expression is not evaluated so
12517 any side-effects do not occur.
12520 One of the ways to use a convenience variable is as a counter to be
12521 incremented or a pointer to be advanced. For example, to print
12522 a field from successive elements of an array of structures:
12526 print bar[$i++]->contents
12530 Repeat that command by typing @key{RET}.
12532 Some convenience variables are created automatically by @value{GDBN} and given
12533 values likely to be useful.
12536 @vindex $_@r{, convenience variable}
12538 The variable @code{$_} is automatically set by the @code{x} command to
12539 the last address examined (@pxref{Memory, ,Examining Memory}). Other
12540 commands which provide a default address for @code{x} to examine also
12541 set @code{$_} to that address; these commands include @code{info line}
12542 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
12543 except when set by the @code{x} command, in which case it is a pointer
12544 to the type of @code{$__}.
12546 @vindex $__@r{, convenience variable}
12548 The variable @code{$__} is automatically set by the @code{x} command
12549 to the value found in the last address examined. Its type is chosen
12550 to match the format in which the data was printed.
12553 @vindex $_exitcode@r{, convenience variable}
12554 When the program being debugged terminates normally, @value{GDBN}
12555 automatically sets this variable to the exit code of the program, and
12556 resets @code{$_exitsignal} to @code{void}.
12559 @vindex $_exitsignal@r{, convenience variable}
12560 When the program being debugged dies due to an uncaught signal,
12561 @value{GDBN} automatically sets this variable to that signal's number,
12562 and resets @code{$_exitcode} to @code{void}.
12564 To distinguish between whether the program being debugged has exited
12565 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12566 @code{$_exitsignal} is not @code{void}), the convenience function
12567 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12568 Functions}). For example, considering the following source code:
12571 #include <signal.h>
12574 main (int argc, char *argv[])
12581 A valid way of telling whether the program being debugged has exited
12582 or signalled would be:
12585 (@value{GDBP}) define has_exited_or_signalled
12586 Type commands for definition of ``has_exited_or_signalled''.
12587 End with a line saying just ``end''.
12588 >if $_isvoid ($_exitsignal)
12589 >echo The program has exited\n
12591 >echo The program has signalled\n
12597 Program terminated with signal SIGALRM, Alarm clock.
12598 The program no longer exists.
12599 (@value{GDBP}) has_exited_or_signalled
12600 The program has signalled
12603 As can be seen, @value{GDBN} correctly informs that the program being
12604 debugged has signalled, since it calls @code{raise} and raises a
12605 @code{SIGALRM} signal. If the program being debugged had not called
12606 @code{raise}, then @value{GDBN} would report a normal exit:
12609 (@value{GDBP}) has_exited_or_signalled
12610 The program has exited
12614 The variable @code{$_exception} is set to the exception object being
12615 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12617 @item $_ada_exception
12618 The variable @code{$_ada_exception} is set to the address of the
12619 exception being caught or thrown at an Ada exception-related
12620 catchpoint. @xref{Set Catchpoints}.
12623 @itemx $_probe_arg0@dots{}$_probe_arg11
12624 Arguments to a static probe. @xref{Static Probe Points}.
12627 @vindex $_sdata@r{, inspect, convenience variable}
12628 The variable @code{$_sdata} contains extra collected static tracepoint
12629 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12630 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12631 if extra static tracepoint data has not been collected.
12634 @vindex $_siginfo@r{, convenience variable}
12635 The variable @code{$_siginfo} contains extra signal information
12636 (@pxref{extra signal information}). Note that @code{$_siginfo}
12637 could be empty, if the application has not yet received any signals.
12638 For example, it will be empty before you execute the @code{run} command.
12641 @vindex $_tlb@r{, convenience variable}
12642 The variable @code{$_tlb} is automatically set when debugging
12643 applications running on MS-Windows in native mode or connected to
12644 gdbserver that supports the @code{qGetTIBAddr} request.
12645 @xref{General Query Packets}.
12646 This variable contains the address of the thread information block.
12649 The number of the current inferior. @xref{Inferiors Connections and
12650 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12653 The thread number of the current thread. @xref{thread numbers}.
12656 The global number of the current thread. @xref{global thread numbers}.
12660 @vindex $_gdb_major@r{, convenience variable}
12661 @vindex $_gdb_minor@r{, convenience variable}
12662 The major and minor version numbers of the running @value{GDBN}.
12663 Development snapshots and pretest versions have their minor version
12664 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12665 the value 12 for @code{$_gdb_minor}. These variables allow you to
12666 write scripts that work with different versions of @value{GDBN}
12667 without errors caused by features unavailable in some of those
12670 @item $_shell_exitcode
12671 @itemx $_shell_exitsignal
12672 @vindex $_shell_exitcode@r{, convenience variable}
12673 @vindex $_shell_exitsignal@r{, convenience variable}
12674 @cindex shell command, exit code
12675 @cindex shell command, exit signal
12676 @cindex exit status of shell commands
12677 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12678 shell commands. When a launched command terminates, @value{GDBN}
12679 automatically maintains the variables @code{$_shell_exitcode}
12680 and @code{$_shell_exitsignal} according to the exit status of the last
12681 launched command. These variables are set and used similarly to
12682 the variables @code{$_exitcode} and @code{$_exitsignal}.
12686 @node Convenience Funs
12687 @section Convenience Functions
12689 @cindex convenience functions
12690 @value{GDBN} also supplies some @dfn{convenience functions}. These
12691 have a syntax similar to convenience variables. A convenience
12692 function can be used in an expression just like an ordinary function;
12693 however, a convenience function is implemented internally to
12696 These functions do not require @value{GDBN} to be configured with
12697 @code{Python} support, which means that they are always available.
12701 @item $_isvoid (@var{expr})
12702 @findex $_isvoid@r{, convenience function}
12703 Return one if the expression @var{expr} is @code{void}. Otherwise it
12706 A @code{void} expression is an expression where the type of the result
12707 is @code{void}. For example, you can examine a convenience variable
12708 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12712 (@value{GDBP}) print $_exitcode
12714 (@value{GDBP}) print $_isvoid ($_exitcode)
12717 Starting program: ./a.out
12718 [Inferior 1 (process 29572) exited normally]
12719 (@value{GDBP}) print $_exitcode
12721 (@value{GDBP}) print $_isvoid ($_exitcode)
12725 In the example above, we used @code{$_isvoid} to check whether
12726 @code{$_exitcode} is @code{void} before and after the execution of the
12727 program being debugged. Before the execution there is no exit code to
12728 be examined, therefore @code{$_exitcode} is @code{void}. After the
12729 execution the program being debugged returned zero, therefore
12730 @code{$_exitcode} is zero, which means that it is not @code{void}
12733 The @code{void} expression can also be a call of a function from the
12734 program being debugged. For example, given the following function:
12743 The result of calling it inside @value{GDBN} is @code{void}:
12746 (@value{GDBP}) print foo ()
12748 (@value{GDBP}) print $_isvoid (foo ())
12750 (@value{GDBP}) set $v = foo ()
12751 (@value{GDBP}) print $v
12753 (@value{GDBP}) print $_isvoid ($v)
12757 @item $_gdb_setting_str (@var{setting})
12758 @findex $_gdb_setting_str@r{, convenience function}
12759 Return the value of the @value{GDBN} @var{setting} as a string.
12760 @var{setting} is any setting that can be used in a @code{set} or
12761 @code{show} command (@pxref{Controlling GDB}).
12764 (@value{GDBP}) show print frame-arguments
12765 Printing of non-scalar frame arguments is "scalars".
12766 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12768 (@value{GDBP}) p $_gdb_setting_str("height")
12773 @item $_gdb_setting (@var{setting})
12774 @findex $_gdb_setting@r{, convenience function}
12775 Return the value of the @value{GDBN} @var{setting}.
12776 The type of the returned value depends on the setting.
12778 The value type for boolean and auto boolean settings is @code{int}.
12779 The boolean values @code{off} and @code{on} are converted to
12780 the integer values @code{0} and @code{1}. The value @code{auto} is
12781 converted to the value @code{-1}.
12783 The value type for integer settings is either @code{unsigned int}
12784 or @code{int}, depending on the setting.
12786 Some integer settings accept an @code{unlimited} value.
12787 Depending on the setting, the @code{set} command also accepts
12788 the value @code{0} or the value @code{@minus{}1} as a synonym for
12790 For example, @code{set height unlimited} is equivalent to
12791 @code{set height 0}.
12793 Some other settings that accept the @code{unlimited} value
12794 use the value @code{0} to literally mean zero.
12795 For example, @code{set history size 0} indicates to not
12796 record any @value{GDBN} commands in the command history.
12797 For such settings, @code{@minus{}1} is the synonym
12798 for @code{unlimited}.
12800 See the documentation of the corresponding @code{set} command for
12801 the numerical value equivalent to @code{unlimited}.
12803 The @code{$_gdb_setting} function converts the unlimited value
12804 to a @code{0} or a @code{@minus{}1} value according to what the
12805 @code{set} command uses.
12809 (@value{GDBP}) p $_gdb_setting_str("height")
12811 (@value{GDBP}) p $_gdb_setting("height")
12813 (@value{GDBP}) set height unlimited
12814 (@value{GDBP}) p $_gdb_setting_str("height")
12816 (@value{GDBP}) p $_gdb_setting("height")
12820 (@value{GDBP}) p $_gdb_setting_str("history size")
12822 (@value{GDBP}) p $_gdb_setting("history size")
12824 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12826 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12832 Other setting types (enum, filename, optional filename, string, string noescape)
12833 are returned as string values.
12836 @item $_gdb_maint_setting_str (@var{setting})
12837 @findex $_gdb_maint_setting_str@r{, convenience function}
12838 Like the @code{$_gdb_setting_str} function, but works with
12839 @code{maintenance set} variables.
12841 @item $_gdb_maint_setting (@var{setting})
12842 @findex $_gdb_maint_setting@r{, convenience function}
12843 Like the @code{$_gdb_setting} function, but works with
12844 @code{maintenance set} variables.
12848 The following functions require @value{GDBN} to be configured with
12849 @code{Python} support.
12853 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12854 @findex $_memeq@r{, convenience function}
12855 Returns one if the @var{length} bytes at the addresses given by
12856 @var{buf1} and @var{buf2} are equal.
12857 Otherwise it returns zero.
12859 @item $_regex(@var{str}, @var{regex})
12860 @findex $_regex@r{, convenience function}
12861 Returns one if the string @var{str} matches the regular expression
12862 @var{regex}. Otherwise it returns zero.
12863 The syntax of the regular expression is that specified by @code{Python}'s
12864 regular expression support.
12866 @item $_streq(@var{str1}, @var{str2})
12867 @findex $_streq@r{, convenience function}
12868 Returns one if the strings @var{str1} and @var{str2} are equal.
12869 Otherwise it returns zero.
12871 @item $_strlen(@var{str})
12872 @findex $_strlen@r{, convenience function}
12873 Returns the length of string @var{str}.
12875 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12876 @findex $_caller_is@r{, convenience function}
12877 Returns one if the calling function's name is equal to @var{name}.
12878 Otherwise it returns zero.
12880 If the optional argument @var{number_of_frames} is provided,
12881 it is the number of frames up in the stack to look.
12889 at testsuite/gdb.python/py-caller-is.c:21
12890 #1 0x00000000004005a0 in middle_func ()
12891 at testsuite/gdb.python/py-caller-is.c:27
12892 #2 0x00000000004005ab in top_func ()
12893 at testsuite/gdb.python/py-caller-is.c:33
12894 #3 0x00000000004005b6 in main ()
12895 at testsuite/gdb.python/py-caller-is.c:39
12896 (gdb) print $_caller_is ("middle_func")
12898 (gdb) print $_caller_is ("top_func", 2)
12902 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12903 @findex $_caller_matches@r{, convenience function}
12904 Returns one if the calling function's name matches the regular expression
12905 @var{regexp}. Otherwise it returns zero.
12907 If the optional argument @var{number_of_frames} is provided,
12908 it is the number of frames up in the stack to look.
12911 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12912 @findex $_any_caller_is@r{, convenience function}
12913 Returns one if any calling function's name is equal to @var{name}.
12914 Otherwise it returns zero.
12916 If the optional argument @var{number_of_frames} is provided,
12917 it is the number of frames up in the stack to look.
12920 This function differs from @code{$_caller_is} in that this function
12921 checks all stack frames from the immediate caller to the frame specified
12922 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12923 frame specified by @var{number_of_frames}.
12925 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12926 @findex $_any_caller_matches@r{, convenience function}
12927 Returns one if any calling function's name matches the regular expression
12928 @var{regexp}. Otherwise it returns zero.
12930 If the optional argument @var{number_of_frames} is provided,
12931 it is the number of frames up in the stack to look.
12934 This function differs from @code{$_caller_matches} in that this function
12935 checks all stack frames from the immediate caller to the frame specified
12936 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12937 frame specified by @var{number_of_frames}.
12939 @item $_as_string(@var{value})
12940 @findex $_as_string@r{, convenience function}
12941 Return the string representation of @var{value}.
12943 This function is useful to obtain the textual label (enumerator) of an
12944 enumeration value. For example, assuming the variable @var{node} is of
12945 an enumerated type:
12948 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12949 Visiting node of type NODE_INTEGER
12952 @item $_cimag(@var{value})
12953 @itemx $_creal(@var{value})
12954 @findex $_cimag@r{, convenience function}
12955 @findex $_creal@r{, convenience function}
12956 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12957 the complex number @var{value}.
12959 The type of the imaginary or real part depends on the type of the
12960 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12961 will return an imaginary part of type @code{float}.
12965 @value{GDBN} provides the ability to list and get help on
12966 convenience functions.
12969 @item help function
12970 @kindex help function
12971 @cindex show all convenience functions
12972 Print a list of all convenience functions.
12979 You can refer to machine register contents, in expressions, as variables
12980 with names starting with @samp{$}. The names of registers are different
12981 for each machine; use @code{info registers} to see the names used on
12985 @kindex info registers
12986 @item info registers
12987 Print the names and values of all registers except floating-point
12988 and vector registers (in the selected stack frame).
12990 @kindex info all-registers
12991 @cindex floating point registers
12992 @item info all-registers
12993 Print the names and values of all registers, including floating-point
12994 and vector registers (in the selected stack frame).
12996 @anchor{info_registers_reggroup}
12997 @item info registers @var{reggroup} @dots{}
12998 Print the name and value of the registers in each of the specified
12999 @var{reggroup}s. The @var{reggroup} can be any of those returned by
13000 @code{maint print reggroups} (@pxref{Maintenance Commands}).
13002 @item info registers @var{regname} @dots{}
13003 Print the @dfn{relativized} value of each specified register @var{regname}.
13004 As discussed in detail below, register values are normally relative to
13005 the selected stack frame. The @var{regname} may be any register name valid on
13006 the machine you are using, with or without the initial @samp{$}.
13009 @anchor{standard registers}
13010 @cindex stack pointer register
13011 @cindex program counter register
13012 @cindex process status register
13013 @cindex frame pointer register
13014 @cindex standard registers
13015 @value{GDBN} has four ``standard'' register names that are available (in
13016 expressions) on most machines---whenever they do not conflict with an
13017 architecture's canonical mnemonics for registers. The register names
13018 @code{$pc} and @code{$sp} are used for the program counter register and
13019 the stack pointer. @code{$fp} is used for a register that contains a
13020 pointer to the current stack frame, and @code{$ps} is used for a
13021 register that contains the processor status. For example,
13022 you could print the program counter in hex with
13029 or print the instruction to be executed next with
13036 or add four to the stack pointer@footnote{This is a way of removing
13037 one word from the stack, on machines where stacks grow downward in
13038 memory (most machines, nowadays). This assumes that the innermost
13039 stack frame is selected; setting @code{$sp} is not allowed when other
13040 stack frames are selected. To pop entire frames off the stack,
13041 regardless of machine architecture, use @code{return};
13042 see @ref{Returning, ,Returning from a Function}.} with
13048 Whenever possible, these four standard register names are available on
13049 your machine even though the machine has different canonical mnemonics,
13050 so long as there is no conflict. The @code{info registers} command
13051 shows the canonical names. For example, on the SPARC, @code{info
13052 registers} displays the processor status register as @code{$psr} but you
13053 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
13054 is an alias for the @sc{eflags} register.
13056 @value{GDBN} always considers the contents of an ordinary register as an
13057 integer when the register is examined in this way. Some machines have
13058 special registers which can hold nothing but floating point; these
13059 registers are considered to have floating point values. There is no way
13060 to refer to the contents of an ordinary register as floating point value
13061 (although you can @emph{print} it as a floating point value with
13062 @samp{print/f $@var{regname}}).
13064 Some registers have distinct ``raw'' and ``virtual'' data formats. This
13065 means that the data format in which the register contents are saved by
13066 the operating system is not the same one that your program normally
13067 sees. For example, the registers of the 68881 floating point
13068 coprocessor are always saved in ``extended'' (raw) format, but all C
13069 programs expect to work with ``double'' (virtual) format. In such
13070 cases, @value{GDBN} normally works with the virtual format only (the format
13071 that makes sense for your program), but the @code{info registers} command
13072 prints the data in both formats.
13074 @cindex SSE registers (x86)
13075 @cindex MMX registers (x86)
13076 Some machines have special registers whose contents can be interpreted
13077 in several different ways. For example, modern x86-based machines
13078 have SSE and MMX registers that can hold several values packed
13079 together in several different formats. @value{GDBN} refers to such
13080 registers in @code{struct} notation:
13083 (@value{GDBP}) print $xmm1
13085 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
13086 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
13087 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
13088 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
13089 v4_int32 = @{0, 20657912, 11, 13@},
13090 v2_int64 = @{88725056443645952, 55834574859@},
13091 uint128 = 0x0000000d0000000b013b36f800000000
13096 To set values of such registers, you need to tell @value{GDBN} which
13097 view of the register you wish to change, as if you were assigning
13098 value to a @code{struct} member:
13101 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
13104 Normally, register values are relative to the selected stack frame
13105 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
13106 value that the register would contain if all stack frames farther in
13107 were exited and their saved registers restored. In order to see the
13108 true contents of hardware registers, you must select the innermost
13109 frame (with @samp{frame 0}).
13111 @cindex caller-saved registers
13112 @cindex call-clobbered registers
13113 @cindex volatile registers
13114 @cindex <not saved> values
13115 Usually ABIs reserve some registers as not needed to be saved by the
13116 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
13117 registers). It may therefore not be possible for @value{GDBN} to know
13118 the value a register had before the call (in other words, in the outer
13119 frame), if the register value has since been changed by the callee.
13120 @value{GDBN} tries to deduce where the inner frame saved
13121 (``callee-saved'') registers, from the debug info, unwind info, or the
13122 machine code generated by your compiler. If some register is not
13123 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
13124 its own knowledge of the ABI, or because the debug/unwind info
13125 explicitly says the register's value is undefined), @value{GDBN}
13126 displays @w{@samp{<not saved>}} as the register's value. With targets
13127 that @value{GDBN} has no knowledge of the register saving convention,
13128 if a register was not saved by the callee, then its value and location
13129 in the outer frame are assumed to be the same of the inner frame.
13130 This is usually harmless, because if the register is call-clobbered,
13131 the caller either does not care what is in the register after the
13132 call, or has code to restore the value that it does care about. Note,
13133 however, that if you change such a register in the outer frame, you
13134 may also be affecting the inner frame. Also, the more ``outer'' the
13135 frame is you're looking at, the more likely a call-clobbered
13136 register's value is to be wrong, in the sense that it doesn't actually
13137 represent the value the register had just before the call.
13139 @node Floating Point Hardware
13140 @section Floating Point Hardware
13141 @cindex floating point
13143 Depending on the configuration, @value{GDBN} may be able to give
13144 you more information about the status of the floating point hardware.
13149 Display hardware-dependent information about the floating
13150 point unit. The exact contents and layout vary depending on the
13151 floating point chip. Currently, @samp{info float} is supported on
13152 the ARM and x86 machines.
13156 @section Vector Unit
13157 @cindex vector unit
13159 Depending on the configuration, @value{GDBN} may be able to give you
13160 more information about the status of the vector unit.
13163 @kindex info vector
13165 Display information about the vector unit. The exact contents and
13166 layout vary depending on the hardware.
13169 @node OS Information
13170 @section Operating System Auxiliary Information
13171 @cindex OS information
13173 @value{GDBN} provides interfaces to useful OS facilities that can help
13174 you debug your program.
13176 @cindex auxiliary vector
13177 @cindex vector, auxiliary
13178 Some operating systems supply an @dfn{auxiliary vector} to programs at
13179 startup. This is akin to the arguments and environment that you
13180 specify for a program, but contains a system-dependent variety of
13181 binary values that tell system libraries important details about the
13182 hardware, operating system, and process. Each value's purpose is
13183 identified by an integer tag; the meanings are well-known but system-specific.
13184 Depending on the configuration and operating system facilities,
13185 @value{GDBN} may be able to show you this information. For remote
13186 targets, this functionality may further depend on the remote stub's
13187 support of the @samp{qXfer:auxv:read} packet, see
13188 @ref{qXfer auxiliary vector read}.
13193 Display the auxiliary vector of the inferior, which can be either a
13194 live process or a core dump file. @value{GDBN} prints each tag value
13195 numerically, and also shows names and text descriptions for recognized
13196 tags. Some values in the vector are numbers, some bit masks, and some
13197 pointers to strings or other data. @value{GDBN} displays each value in the
13198 most appropriate form for a recognized tag, and in hexadecimal for
13199 an unrecognized tag.
13202 On some targets, @value{GDBN} can access operating system-specific
13203 information and show it to you. The types of information available
13204 will differ depending on the type of operating system running on the
13205 target. The mechanism used to fetch the data is described in
13206 @ref{Operating System Information}. For remote targets, this
13207 functionality depends on the remote stub's support of the
13208 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
13212 @item info os @var{infotype}
13214 Display OS information of the requested type.
13216 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
13218 @anchor{linux info os infotypes}
13220 @kindex info os cpus
13222 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
13223 the available fields from /proc/cpuinfo. For each supported architecture
13224 different fields are available. Two common entries are processor which gives
13225 CPU number and bogomips; a system constant that is calculated during
13226 kernel initialization.
13228 @kindex info os files
13230 Display the list of open file descriptors on the target. For each
13231 file descriptor, @value{GDBN} prints the identifier of the process
13232 owning the descriptor, the command of the owning process, the value
13233 of the descriptor, and the target of the descriptor.
13235 @kindex info os modules
13237 Display the list of all loaded kernel modules on the target. For each
13238 module, @value{GDBN} prints the module name, the size of the module in
13239 bytes, the number of times the module is used, the dependencies of the
13240 module, the status of the module, and the address of the loaded module
13243 @kindex info os msg
13245 Display the list of all System V message queues on the target. For each
13246 message queue, @value{GDBN} prints the message queue key, the message
13247 queue identifier, the access permissions, the current number of bytes
13248 on the queue, the current number of messages on the queue, the processes
13249 that last sent and received a message on the queue, the user and group
13250 of the owner and creator of the message queue, the times at which a
13251 message was last sent and received on the queue, and the time at which
13252 the message queue was last changed.
13254 @kindex info os processes
13256 Display the list of processes on the target. For each process,
13257 @value{GDBN} prints the process identifier, the name of the user, the
13258 command corresponding to the process, and the list of processor cores
13259 that the process is currently running on. (To understand what these
13260 properties mean, for this and the following info types, please consult
13261 the general @sc{gnu}/Linux documentation.)
13263 @kindex info os procgroups
13265 Display the list of process groups on the target. For each process,
13266 @value{GDBN} prints the identifier of the process group that it belongs
13267 to, the command corresponding to the process group leader, the process
13268 identifier, and the command line of the process. The list is sorted
13269 first by the process group identifier, then by the process identifier,
13270 so that processes belonging to the same process group are grouped together
13271 and the process group leader is listed first.
13273 @kindex info os semaphores
13275 Display the list of all System V semaphore sets on the target. For each
13276 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
13277 set identifier, the access permissions, the number of semaphores in the
13278 set, the user and group of the owner and creator of the semaphore set,
13279 and the times at which the semaphore set was operated upon and changed.
13281 @kindex info os shm
13283 Display the list of all System V shared-memory regions on the target.
13284 For each shared-memory region, @value{GDBN} prints the region key,
13285 the shared-memory identifier, the access permissions, the size of the
13286 region, the process that created the region, the process that last
13287 attached to or detached from the region, the current number of live
13288 attaches to the region, and the times at which the region was last
13289 attached to, detach from, and changed.
13291 @kindex info os sockets
13293 Display the list of Internet-domain sockets on the target. For each
13294 socket, @value{GDBN} prints the address and port of the local and
13295 remote endpoints, the current state of the connection, the creator of
13296 the socket, the IP address family of the socket, and the type of the
13299 @kindex info os threads
13301 Display the list of threads running on the target. For each thread,
13302 @value{GDBN} prints the identifier of the process that the thread
13303 belongs to, the command of the process, the thread identifier, and the
13304 processor core that it is currently running on. The main thread of a
13305 process is not listed.
13309 If @var{infotype} is omitted, then list the possible values for
13310 @var{infotype} and the kind of OS information available for each
13311 @var{infotype}. If the target does not return a list of possible
13312 types, this command will report an error.
13315 @node Memory Region Attributes
13316 @section Memory Region Attributes
13317 @cindex memory region attributes
13319 @dfn{Memory region attributes} allow you to describe special handling
13320 required by regions of your target's memory. @value{GDBN} uses
13321 attributes to determine whether to allow certain types of memory
13322 accesses; whether to use specific width accesses; and whether to cache
13323 target memory. By default the description of memory regions is
13324 fetched from the target (if the current target supports this), but the
13325 user can override the fetched regions.
13327 Defined memory regions can be individually enabled and disabled. When a
13328 memory region is disabled, @value{GDBN} uses the default attributes when
13329 accessing memory in that region. Similarly, if no memory regions have
13330 been defined, @value{GDBN} uses the default attributes when accessing
13333 When a memory region is defined, it is given a number to identify it;
13334 to enable, disable, or remove a memory region, you specify that number.
13338 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
13339 Define a memory region bounded by @var{lower} and @var{upper} with
13340 attributes @var{attributes}@dots{}, and add it to the list of regions
13341 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
13342 case: it is treated as the target's maximum memory address.
13343 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
13346 Discard any user changes to the memory regions and use target-supplied
13347 regions, if available, or no regions if the target does not support.
13350 @item delete mem @var{nums}@dots{}
13351 Remove memory regions @var{nums}@dots{} from the list of regions
13352 monitored by @value{GDBN}.
13354 @kindex disable mem
13355 @item disable mem @var{nums}@dots{}
13356 Disable monitoring of memory regions @var{nums}@dots{}.
13357 A disabled memory region is not forgotten.
13358 It may be enabled again later.
13361 @item enable mem @var{nums}@dots{}
13362 Enable monitoring of memory regions @var{nums}@dots{}.
13366 Print a table of all defined memory regions, with the following columns
13370 @item Memory Region Number
13371 @item Enabled or Disabled.
13372 Enabled memory regions are marked with @samp{y}.
13373 Disabled memory regions are marked with @samp{n}.
13376 The address defining the inclusive lower bound of the memory region.
13379 The address defining the exclusive upper bound of the memory region.
13382 The list of attributes set for this memory region.
13387 @subsection Attributes
13389 @subsubsection Memory Access Mode
13390 The access mode attributes set whether @value{GDBN} may make read or
13391 write accesses to a memory region.
13393 While these attributes prevent @value{GDBN} from performing invalid
13394 memory accesses, they do nothing to prevent the target system, I/O DMA,
13395 etc.@: from accessing memory.
13399 Memory is read only.
13401 Memory is write only.
13403 Memory is read/write. This is the default.
13406 @subsubsection Memory Access Size
13407 The access size attribute tells @value{GDBN} to use specific sized
13408 accesses in the memory region. Often memory mapped device registers
13409 require specific sized accesses. If no access size attribute is
13410 specified, @value{GDBN} may use accesses of any size.
13414 Use 8 bit memory accesses.
13416 Use 16 bit memory accesses.
13418 Use 32 bit memory accesses.
13420 Use 64 bit memory accesses.
13423 @c @subsubsection Hardware/Software Breakpoints
13424 @c The hardware/software breakpoint attributes set whether @value{GDBN}
13425 @c will use hardware or software breakpoints for the internal breakpoints
13426 @c used by the step, next, finish, until, etc. commands.
13430 @c Always use hardware breakpoints
13431 @c @item swbreak (default)
13434 @subsubsection Data Cache
13435 The data cache attributes set whether @value{GDBN} will cache target
13436 memory. While this generally improves performance by reducing debug
13437 protocol overhead, it can lead to incorrect results because @value{GDBN}
13438 does not know about volatile variables or memory mapped device
13443 Enable @value{GDBN} to cache target memory.
13445 Disable @value{GDBN} from caching target memory. This is the default.
13448 @subsection Memory Access Checking
13449 @value{GDBN} can be instructed to refuse accesses to memory that is
13450 not explicitly described. This can be useful if accessing such
13451 regions has undesired effects for a specific target, or to provide
13452 better error checking. The following commands control this behaviour.
13455 @kindex set mem inaccessible-by-default
13456 @item set mem inaccessible-by-default [on|off]
13457 If @code{on} is specified, make @value{GDBN} treat memory not
13458 explicitly described by the memory ranges as non-existent and refuse accesses
13459 to such memory. The checks are only performed if there's at least one
13460 memory range defined. If @code{off} is specified, make @value{GDBN}
13461 treat the memory not explicitly described by the memory ranges as RAM.
13462 The default value is @code{on}.
13463 @kindex show mem inaccessible-by-default
13464 @item show mem inaccessible-by-default
13465 Show the current handling of accesses to unknown memory.
13469 @c @subsubsection Memory Write Verification
13470 @c The memory write verification attributes set whether @value{GDBN}
13471 @c will re-reads data after each write to verify the write was successful.
13475 @c @item noverify (default)
13478 @node Dump/Restore Files
13479 @section Copy Between Memory and a File
13480 @cindex dump/restore files
13481 @cindex append data to a file
13482 @cindex dump data to a file
13483 @cindex restore data from a file
13485 You can use the commands @code{dump}, @code{append}, and
13486 @code{restore} to copy data between target memory and a file. The
13487 @code{dump} and @code{append} commands write data to a file, and the
13488 @code{restore} command reads data from a file back into the inferior's
13489 memory. Files may be in binary, Motorola S-record, Intel hex,
13490 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
13491 append to binary files, and cannot read from Verilog Hex files.
13496 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13497 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
13498 Dump the contents of memory from @var{start_addr} to @var{end_addr},
13499 or the value of @var{expr}, to @var{filename} in the given format.
13501 The @var{format} parameter may be any one of:
13508 Motorola S-record format.
13510 Tektronix Hex format.
13512 Verilog Hex format.
13515 @value{GDBN} uses the same definitions of these formats as the
13516 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
13517 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
13521 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13522 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
13523 Append the contents of memory from @var{start_addr} to @var{end_addr},
13524 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
13525 (@value{GDBN} can only append data to files in raw binary form.)
13528 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
13529 Restore the contents of file @var{filename} into memory. The
13530 @code{restore} command can automatically recognize any known @sc{bfd}
13531 file format, except for raw binary. To restore a raw binary file you
13532 must specify the optional keyword @code{binary} after the filename.
13534 If @var{bias} is non-zero, its value will be added to the addresses
13535 contained in the file. Binary files always start at address zero, so
13536 they will be restored at address @var{bias}. Other bfd files have
13537 a built-in location; they will be restored at offset @var{bias}
13538 from that location.
13540 If @var{start} and/or @var{end} are non-zero, then only data between
13541 file offset @var{start} and file offset @var{end} will be restored.
13542 These offsets are relative to the addresses in the file, before
13543 the @var{bias} argument is applied.
13547 @node Core File Generation
13548 @section How to Produce a Core File from Your Program
13549 @cindex dump core from inferior
13551 A @dfn{core file} or @dfn{core dump} is a file that records the memory
13552 image of a running process and its process status (register values
13553 etc.). Its primary use is post-mortem debugging of a program that
13554 crashed while it ran outside a debugger. A program that crashes
13555 automatically produces a core file, unless this feature is disabled by
13556 the user. @xref{Files}, for information on invoking @value{GDBN} in
13557 the post-mortem debugging mode.
13559 Occasionally, you may wish to produce a core file of the program you
13560 are debugging in order to preserve a snapshot of its state.
13561 @value{GDBN} has a special command for that.
13565 @kindex generate-core-file
13566 @item generate-core-file [@var{file}]
13567 @itemx gcore [@var{file}]
13568 Produce a core dump of the inferior process. The optional argument
13569 @var{file} specifies the file name where to put the core dump. If not
13570 specified, the file name defaults to @file{core.@var{pid}}, where
13571 @var{pid} is the inferior process ID.
13573 Note that this command is implemented only for some systems (as of
13574 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13576 On @sc{gnu}/Linux, this command can take into account the value of the
13577 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13578 dump (@pxref{set use-coredump-filter}), and by default honors the
13579 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13580 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13582 @kindex set use-coredump-filter
13583 @anchor{set use-coredump-filter}
13584 @item set use-coredump-filter on
13585 @itemx set use-coredump-filter off
13586 Enable or disable the use of the file
13587 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13588 files. This file is used by the Linux kernel to decide what types of
13589 memory mappings will be dumped or ignored when generating a core dump
13590 file. @var{pid} is the process ID of a currently running process.
13592 To make use of this feature, you have to write in the
13593 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13594 which is a bit mask representing the memory mapping types. If a bit
13595 is set in the bit mask, then the memory mappings of the corresponding
13596 types will be dumped; otherwise, they will be ignored. This
13597 configuration is inherited by child processes. For more information
13598 about the bits that can be set in the
13599 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13600 manpage of @code{core(5)}.
13602 By default, this option is @code{on}. If this option is turned
13603 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13604 and instead uses the same default value as the Linux kernel in order
13605 to decide which pages will be dumped in the core dump file. This
13606 value is currently @code{0x33}, which means that bits @code{0}
13607 (anonymous private mappings), @code{1} (anonymous shared mappings),
13608 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13609 This will cause these memory mappings to be dumped automatically.
13611 @kindex set dump-excluded-mappings
13612 @anchor{set dump-excluded-mappings}
13613 @item set dump-excluded-mappings on
13614 @itemx set dump-excluded-mappings off
13615 If @code{on} is specified, @value{GDBN} will dump memory mappings
13616 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13617 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13619 The default value is @code{off}.
13622 @node Character Sets
13623 @section Character Sets
13624 @cindex character sets
13626 @cindex translating between character sets
13627 @cindex host character set
13628 @cindex target character set
13630 If the program you are debugging uses a different character set to
13631 represent characters and strings than the one @value{GDBN} uses itself,
13632 @value{GDBN} can automatically translate between the character sets for
13633 you. The character set @value{GDBN} uses we call the @dfn{host
13634 character set}; the one the inferior program uses we call the
13635 @dfn{target character set}.
13637 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13638 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13639 remote protocol (@pxref{Remote Debugging}) to debug a program
13640 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13641 then the host character set is Latin-1, and the target character set is
13642 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13643 target-charset EBCDIC-US}, then @value{GDBN} translates between
13644 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13645 character and string literals in expressions.
13647 @value{GDBN} has no way to automatically recognize which character set
13648 the inferior program uses; you must tell it, using the @code{set
13649 target-charset} command, described below.
13651 Here are the commands for controlling @value{GDBN}'s character set
13655 @item set target-charset @var{charset}
13656 @kindex set target-charset
13657 Set the current target character set to @var{charset}. To display the
13658 list of supported target character sets, type
13659 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13661 @item set host-charset @var{charset}
13662 @kindex set host-charset
13663 Set the current host character set to @var{charset}.
13665 By default, @value{GDBN} uses a host character set appropriate to the
13666 system it is running on; you can override that default using the
13667 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13668 automatically determine the appropriate host character set. In this
13669 case, @value{GDBN} uses @samp{UTF-8}.
13671 @value{GDBN} can only use certain character sets as its host character
13672 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13673 @value{GDBN} will list the host character sets it supports.
13675 @item set charset @var{charset}
13676 @kindex set charset
13677 Set the current host and target character sets to @var{charset}. As
13678 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13679 @value{GDBN} will list the names of the character sets that can be used
13680 for both host and target.
13683 @kindex show charset
13684 Show the names of the current host and target character sets.
13686 @item show host-charset
13687 @kindex show host-charset
13688 Show the name of the current host character set.
13690 @item show target-charset
13691 @kindex show target-charset
13692 Show the name of the current target character set.
13694 @item set target-wide-charset @var{charset}
13695 @kindex set target-wide-charset
13696 Set the current target's wide character set to @var{charset}. This is
13697 the character set used by the target's @code{wchar_t} type. To
13698 display the list of supported wide character sets, type
13699 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13701 @item show target-wide-charset
13702 @kindex show target-wide-charset
13703 Show the name of the current target's wide character set.
13706 Here is an example of @value{GDBN}'s character set support in action.
13707 Assume that the following source code has been placed in the file
13708 @file{charset-test.c}:
13714 = @{72, 101, 108, 108, 111, 44, 32, 119,
13715 111, 114, 108, 100, 33, 10, 0@};
13716 char ibm1047_hello[]
13717 = @{200, 133, 147, 147, 150, 107, 64, 166,
13718 150, 153, 147, 132, 90, 37, 0@};
13722 printf ("Hello, world!\n");
13726 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13727 containing the string @samp{Hello, world!} followed by a newline,
13728 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13730 We compile the program, and invoke the debugger on it:
13733 $ gcc -g charset-test.c -o charset-test
13734 $ gdb -nw charset-test
13735 GNU gdb 2001-12-19-cvs
13736 Copyright 2001 Free Software Foundation, Inc.
13741 We can use the @code{show charset} command to see what character sets
13742 @value{GDBN} is currently using to interpret and display characters and
13746 (@value{GDBP}) show charset
13747 The current host and target character set is `ISO-8859-1'.
13751 For the sake of printing this manual, let's use @sc{ascii} as our
13752 initial character set:
13754 (@value{GDBP}) set charset ASCII
13755 (@value{GDBP}) show charset
13756 The current host and target character set is `ASCII'.
13760 Let's assume that @sc{ascii} is indeed the correct character set for our
13761 host system --- in other words, let's assume that if @value{GDBN} prints
13762 characters using the @sc{ascii} character set, our terminal will display
13763 them properly. Since our current target character set is also
13764 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13767 (@value{GDBP}) print ascii_hello
13768 $1 = 0x401698 "Hello, world!\n"
13769 (@value{GDBP}) print ascii_hello[0]
13774 @value{GDBN} uses the target character set for character and string
13775 literals you use in expressions:
13778 (@value{GDBP}) print '+'
13783 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13786 @value{GDBN} relies on the user to tell it which character set the
13787 target program uses. If we print @code{ibm1047_hello} while our target
13788 character set is still @sc{ascii}, we get jibberish:
13791 (@value{GDBP}) print ibm1047_hello
13792 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13793 (@value{GDBP}) print ibm1047_hello[0]
13798 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13799 @value{GDBN} tells us the character sets it supports:
13802 (@value{GDBP}) set target-charset
13803 ASCII EBCDIC-US IBM1047 ISO-8859-1
13804 (@value{GDBP}) set target-charset
13807 We can select @sc{ibm1047} as our target character set, and examine the
13808 program's strings again. Now the @sc{ascii} string is wrong, but
13809 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13810 target character set, @sc{ibm1047}, to the host character set,
13811 @sc{ascii}, and they display correctly:
13814 (@value{GDBP}) set target-charset IBM1047
13815 (@value{GDBP}) show charset
13816 The current host character set is `ASCII'.
13817 The current target character set is `IBM1047'.
13818 (@value{GDBP}) print ascii_hello
13819 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13820 (@value{GDBP}) print ascii_hello[0]
13822 (@value{GDBP}) print ibm1047_hello
13823 $8 = 0x4016a8 "Hello, world!\n"
13824 (@value{GDBP}) print ibm1047_hello[0]
13829 As above, @value{GDBN} uses the target character set for character and
13830 string literals you use in expressions:
13833 (@value{GDBP}) print '+'
13838 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13841 @node Caching Target Data
13842 @section Caching Data of Targets
13843 @cindex caching data of targets
13845 @value{GDBN} caches data exchanged between the debugger and a target.
13846 Each cache is associated with the address space of the inferior.
13847 @xref{Inferiors Connections and Programs}, about inferior and address space.
13848 Such caching generally improves performance in remote debugging
13849 (@pxref{Remote Debugging}), because it reduces the overhead of the
13850 remote protocol by bundling memory reads and writes into large chunks.
13851 Unfortunately, simply caching everything would lead to incorrect results,
13852 since @value{GDBN} does not necessarily know anything about volatile
13853 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13854 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13856 Therefore, by default, @value{GDBN} only caches data
13857 known to be on the stack@footnote{In non-stop mode, it is moderately
13858 rare for a running thread to modify the stack of a stopped thread
13859 in a way that would interfere with a backtrace, and caching of
13860 stack reads provides a significant speed up of remote backtraces.} or
13861 in the code segment.
13862 Other regions of memory can be explicitly marked as
13863 cacheable; @pxref{Memory Region Attributes}.
13866 @kindex set remotecache
13867 @item set remotecache on
13868 @itemx set remotecache off
13869 This option no longer does anything; it exists for compatibility
13872 @kindex show remotecache
13873 @item show remotecache
13874 Show the current state of the obsolete remotecache flag.
13876 @kindex set stack-cache
13877 @item set stack-cache on
13878 @itemx set stack-cache off
13879 Enable or disable caching of stack accesses. When @code{on}, use
13880 caching. By default, this option is @code{on}.
13882 @kindex show stack-cache
13883 @item show stack-cache
13884 Show the current state of data caching for memory accesses.
13886 @kindex set code-cache
13887 @item set code-cache on
13888 @itemx set code-cache off
13889 Enable or disable caching of code segment accesses. When @code{on},
13890 use caching. By default, this option is @code{on}. This improves
13891 performance of disassembly in remote debugging.
13893 @kindex show code-cache
13894 @item show code-cache
13895 Show the current state of target memory cache for code segment
13898 @kindex info dcache
13899 @item info dcache @r{[}line@r{]}
13900 Print the information about the performance of data cache of the
13901 current inferior's address space. The information displayed
13902 includes the dcache width and depth, and for each cache line, its
13903 number, address, and how many times it was referenced. This
13904 command is useful for debugging the data cache operation.
13906 If a line number is specified, the contents of that line will be
13909 @item set dcache size @var{size}
13910 @cindex dcache size
13911 @kindex set dcache size
13912 Set maximum number of entries in dcache (dcache depth above).
13914 @item set dcache line-size @var{line-size}
13915 @cindex dcache line-size
13916 @kindex set dcache line-size
13917 Set number of bytes each dcache entry caches (dcache width above).
13918 Must be a power of 2.
13920 @item show dcache size
13921 @kindex show dcache size
13922 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13924 @item show dcache line-size
13925 @kindex show dcache line-size
13926 Show default size of dcache lines.
13928 @item maint flush dcache
13929 @cindex dcache, flushing
13930 @kindex maint flush dcache
13931 Flush the contents (if any) of the dcache. This maintainer command is
13932 useful when debugging the dcache implementation.
13936 @node Searching Memory
13937 @section Search Memory
13938 @cindex searching memory
13940 Memory can be searched for a particular sequence of bytes with the
13941 @code{find} command.
13945 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13946 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13947 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13948 etc. The search begins at address @var{start_addr} and continues for either
13949 @var{len} bytes or through to @var{end_addr} inclusive.
13952 @var{s} and @var{n} are optional parameters.
13953 They may be specified in either order, apart or together.
13956 @item @var{s}, search query size
13957 The size of each search query value.
13963 halfwords (two bytes)
13967 giant words (eight bytes)
13970 All values are interpreted in the current language.
13971 This means, for example, that if the current source language is C/C@t{++}
13972 then searching for the string ``hello'' includes the trailing '\0'.
13973 The null terminator can be removed from searching by using casts,
13974 e.g.: @samp{@{char[5]@}"hello"}.
13976 If the value size is not specified, it is taken from the
13977 value's type in the current language.
13978 This is useful when one wants to specify the search
13979 pattern as a mixture of types.
13980 Note that this means, for example, that in the case of C-like languages
13981 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13982 which is typically four bytes.
13984 @item @var{n}, maximum number of finds
13985 The maximum number of matches to print. The default is to print all finds.
13988 You can use strings as search values. Quote them with double-quotes
13990 The string value is copied into the search pattern byte by byte,
13991 regardless of the endianness of the target and the size specification.
13993 The address of each match found is printed as well as a count of the
13994 number of matches found.
13996 The address of the last value found is stored in convenience variable
13998 A count of the number of matches is stored in @samp{$numfound}.
14000 For example, if stopped at the @code{printf} in this function:
14006 static char hello[] = "hello-hello";
14007 static struct @{ char c; short s; int i; @}
14008 __attribute__ ((packed)) mixed
14009 = @{ 'c', 0x1234, 0x87654321 @};
14010 printf ("%s\n", hello);
14015 you get during debugging:
14018 (gdb) find &hello[0], +sizeof(hello), "hello"
14019 0x804956d <hello.1620+6>
14021 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
14022 0x8049567 <hello.1620>
14023 0x804956d <hello.1620+6>
14025 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
14026 0x8049567 <hello.1620>
14027 0x804956d <hello.1620+6>
14029 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
14030 0x8049567 <hello.1620>
14032 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
14033 0x8049560 <mixed.1625>
14035 (gdb) print $numfound
14038 $2 = (void *) 0x8049560
14042 @section Value Sizes
14044 Whenever @value{GDBN} prints a value memory will be allocated within
14045 @value{GDBN} to hold the contents of the value. It is possible in
14046 some languages with dynamic typing systems, that an invalid program
14047 may indicate a value that is incorrectly large, this in turn may cause
14048 @value{GDBN} to try and allocate an overly large amount of memory.
14051 @kindex set max-value-size
14052 @item set max-value-size @var{bytes}
14053 @itemx set max-value-size unlimited
14054 Set the maximum size of memory that @value{GDBN} will allocate for the
14055 contents of a value to @var{bytes}, trying to display a value that
14056 requires more memory than that will result in an error.
14058 Setting this variable does not effect values that have already been
14059 allocated within @value{GDBN}, only future allocations.
14061 There's a minimum size that @code{max-value-size} can be set to in
14062 order that @value{GDBN} can still operate correctly, this minimum is
14063 currently 16 bytes.
14065 The limit applies to the results of some subexpressions as well as to
14066 complete expressions. For example, an expression denoting a simple
14067 integer component, such as @code{x.y.z}, may fail if the size of
14068 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
14069 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
14070 @var{A} is an array variable with non-constant size, will generally
14071 succeed regardless of the bounds on @var{A}, as long as the component
14072 size is less than @var{bytes}.
14074 The default value of @code{max-value-size} is currently 64k.
14076 @kindex show max-value-size
14077 @item show max-value-size
14078 Show the maximum size of memory, in bytes, that @value{GDBN} will
14079 allocate for the contents of a value.
14082 @node Optimized Code
14083 @chapter Debugging Optimized Code
14084 @cindex optimized code, debugging
14085 @cindex debugging optimized code
14087 Almost all compilers support optimization. With optimization
14088 disabled, the compiler generates assembly code that corresponds
14089 directly to your source code, in a simplistic way. As the compiler
14090 applies more powerful optimizations, the generated assembly code
14091 diverges from your original source code. With help from debugging
14092 information generated by the compiler, @value{GDBN} can map from
14093 the running program back to constructs from your original source.
14095 @value{GDBN} is more accurate with optimization disabled. If you
14096 can recompile without optimization, it is easier to follow the
14097 progress of your program during debugging. But, there are many cases
14098 where you may need to debug an optimized version.
14100 When you debug a program compiled with @samp{-g -O}, remember that the
14101 optimizer has rearranged your code; the debugger shows you what is
14102 really there. Do not be too surprised when the execution path does not
14103 exactly match your source file! An extreme example: if you define a
14104 variable, but never use it, @value{GDBN} never sees that
14105 variable---because the compiler optimizes it out of existence.
14107 Some things do not work as well with @samp{-g -O} as with just
14108 @samp{-g}, particularly on machines with instruction scheduling. If in
14109 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
14110 please report it to us as a bug (including a test case!).
14111 @xref{Variables}, for more information about debugging optimized code.
14114 * Inline Functions:: How @value{GDBN} presents inlining
14115 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
14118 @node Inline Functions
14119 @section Inline Functions
14120 @cindex inline functions, debugging
14122 @dfn{Inlining} is an optimization that inserts a copy of the function
14123 body directly at each call site, instead of jumping to a shared
14124 routine. @value{GDBN} displays inlined functions just like
14125 non-inlined functions. They appear in backtraces. You can view their
14126 arguments and local variables, step into them with @code{step}, skip
14127 them with @code{next}, and escape from them with @code{finish}.
14128 You can check whether a function was inlined by using the
14129 @code{info frame} command.
14131 For @value{GDBN} to support inlined functions, the compiler must
14132 record information about inlining in the debug information ---
14133 @value{NGCC} using the @sc{dwarf 2} format does this, and several
14134 other compilers do also. @value{GDBN} only supports inlined functions
14135 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
14136 do not emit two required attributes (@samp{DW_AT_call_file} and
14137 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
14138 function calls with earlier versions of @value{NGCC}. It instead
14139 displays the arguments and local variables of inlined functions as
14140 local variables in the caller.
14142 The body of an inlined function is directly included at its call site;
14143 unlike a non-inlined function, there are no instructions devoted to
14144 the call. @value{GDBN} still pretends that the call site and the
14145 start of the inlined function are different instructions. Stepping to
14146 the call site shows the call site, and then stepping again shows
14147 the first line of the inlined function, even though no additional
14148 instructions are executed.
14150 This makes source-level debugging much clearer; you can see both the
14151 context of the call and then the effect of the call. Only stepping by
14152 a single instruction using @code{stepi} or @code{nexti} does not do
14153 this; single instruction steps always show the inlined body.
14155 There are some ways that @value{GDBN} does not pretend that inlined
14156 function calls are the same as normal calls:
14160 Setting breakpoints at the call site of an inlined function may not
14161 work, because the call site does not contain any code. @value{GDBN}
14162 may incorrectly move the breakpoint to the next line of the enclosing
14163 function, after the call. This limitation will be removed in a future
14164 version of @value{GDBN}; until then, set a breakpoint on an earlier line
14165 or inside the inlined function instead.
14168 @value{GDBN} cannot locate the return value of inlined calls after
14169 using the @code{finish} command. This is a limitation of compiler-generated
14170 debugging information; after @code{finish}, you can step to the next line
14171 and print a variable where your program stored the return value.
14175 @node Tail Call Frames
14176 @section Tail Call Frames
14177 @cindex tail call frames, debugging
14179 Function @code{B} can call function @code{C} in its very last statement. In
14180 unoptimized compilation the call of @code{C} is immediately followed by return
14181 instruction at the end of @code{B} code. Optimizing compiler may replace the
14182 call and return in function @code{B} into one jump to function @code{C}
14183 instead. Such use of a jump instruction is called @dfn{tail call}.
14185 During execution of function @code{C}, there will be no indication in the
14186 function call stack frames that it was tail-called from @code{B}. If function
14187 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
14188 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
14189 some cases @value{GDBN} can determine that @code{C} was tail-called from
14190 @code{B}, and it will then create fictitious call frame for that, with the
14191 return address set up as if @code{B} called @code{C} normally.
14193 This functionality is currently supported only by DWARF 2 debugging format and
14194 the compiler has to produce @samp{DW_TAG_call_site} tags. With
14195 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
14198 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
14199 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
14203 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
14205 Stack level 1, frame at 0x7fffffffda30:
14206 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
14207 tail call frame, caller of frame at 0x7fffffffda30
14208 source language c++.
14209 Arglist at unknown address.
14210 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
14213 The detection of all the possible code path executions can find them ambiguous.
14214 There is no execution history stored (possible @ref{Reverse Execution} is never
14215 used for this purpose) and the last known caller could have reached the known
14216 callee by multiple different jump sequences. In such case @value{GDBN} still
14217 tries to show at least all the unambiguous top tail callers and all the
14218 unambiguous bottom tail calees, if any.
14221 @anchor{set debug entry-values}
14222 @item set debug entry-values
14223 @kindex set debug entry-values
14224 When set to on, enables printing of analysis messages for both frame argument
14225 values at function entry and tail calls. It will show all the possible valid
14226 tail calls code paths it has considered. It will also print the intersection
14227 of them with the final unambiguous (possibly partial or even empty) code path
14230 @item show debug entry-values
14231 @kindex show debug entry-values
14232 Show the current state of analysis messages printing for both frame argument
14233 values at function entry and tail calls.
14236 The analysis messages for tail calls can for example show why the virtual tail
14237 call frame for function @code{c} has not been recognized (due to the indirect
14238 reference by variable @code{x}):
14241 static void __attribute__((noinline, noclone)) c (void);
14242 void (*x) (void) = c;
14243 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14244 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
14245 int main (void) @{ x (); return 0; @}
14247 Breakpoint 1, DW_OP_entry_value resolving cannot find
14248 DW_TAG_call_site 0x40039a in main
14250 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14253 #1 0x000000000040039a in main () at t.c:5
14256 Another possibility is an ambiguous virtual tail call frames resolution:
14260 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
14261 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
14262 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
14263 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
14264 static void __attribute__((noinline, noclone)) b (void)
14265 @{ if (i) c (); else e (); @}
14266 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
14267 int main (void) @{ a (); return 0; @}
14269 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
14270 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
14271 tailcall: reduced: 0x4004d2(a) |
14274 #1 0x00000000004004d2 in a () at t.c:8
14275 #2 0x0000000000400395 in main () at t.c:9
14278 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
14279 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
14281 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
14282 @ifset HAVE_MAKEINFO_CLICK
14283 @set ARROW @click{}
14284 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
14285 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
14287 @ifclear HAVE_MAKEINFO_CLICK
14289 @set CALLSEQ1B @value{CALLSEQ1A}
14290 @set CALLSEQ2B @value{CALLSEQ2A}
14293 Frames #0 and #2 are real, #1 is a virtual tail call frame.
14294 The code can have possible execution paths @value{CALLSEQ1B} or
14295 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
14297 @code{initial:} state shows some random possible calling sequence @value{GDBN}
14298 has found. It then finds another possible calling sequence - that one is
14299 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
14300 printed as the @code{reduced:} calling sequence. That one could have many
14301 further @code{compare:} and @code{reduced:} statements as long as there remain
14302 any non-ambiguous sequence entries.
14304 For the frame of function @code{b} in both cases there are different possible
14305 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
14306 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
14307 therefore this one is displayed to the user while the ambiguous frames are
14310 There can be also reasons why printing of frame argument values at function
14315 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
14316 static void __attribute__((noinline, noclone)) a (int i);
14317 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
14318 static void __attribute__((noinline, noclone)) a (int i)
14319 @{ if (i) b (i - 1); else c (0); @}
14320 int main (void) @{ a (5); return 0; @}
14323 #0 c (i=i@@entry=0) at t.c:2
14324 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
14325 function "a" at 0x400420 can call itself via tail calls
14326 i=<optimized out>) at t.c:6
14327 #2 0x000000000040036e in main () at t.c:7
14330 @value{GDBN} cannot find out from the inferior state if and how many times did
14331 function @code{a} call itself (via function @code{b}) as these calls would be
14332 tail calls. Such tail calls would modify the @code{i} variable, therefore
14333 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
14334 prints @code{<optimized out>} instead.
14337 @chapter C Preprocessor Macros
14339 Some languages, such as C and C@t{++}, provide a way to define and invoke
14340 ``preprocessor macros'' which expand into strings of tokens.
14341 @value{GDBN} can evaluate expressions containing macro invocations, show
14342 the result of macro expansion, and show a macro's definition, including
14343 where it was defined.
14345 You may need to compile your program specially to provide @value{GDBN}
14346 with information about preprocessor macros. Most compilers do not
14347 include macros in their debugging information, even when you compile
14348 with the @option{-g} flag. @xref{Compilation}.
14350 A program may define a macro at one point, remove that definition later,
14351 and then provide a different definition after that. Thus, at different
14352 points in the program, a macro may have different definitions, or have
14353 no definition at all. If there is a current stack frame, @value{GDBN}
14354 uses the macros in scope at that frame's source code line. Otherwise,
14355 @value{GDBN} uses the macros in scope at the current listing location;
14358 Whenever @value{GDBN} evaluates an expression, it always expands any
14359 macro invocations present in the expression. @value{GDBN} also provides
14360 the following commands for working with macros explicitly.
14364 @kindex macro expand
14365 @cindex macro expansion, showing the results of preprocessor
14366 @cindex preprocessor macro expansion, showing the results of
14367 @cindex expanding preprocessor macros
14368 @item macro expand @var{expression}
14369 @itemx macro exp @var{expression}
14370 Show the results of expanding all preprocessor macro invocations in
14371 @var{expression}. Since @value{GDBN} simply expands macros, but does
14372 not parse the result, @var{expression} need not be a valid expression;
14373 it can be any string of tokens.
14376 @item macro expand-once @var{expression}
14377 @itemx macro exp1 @var{expression}
14378 @cindex expand macro once
14379 @i{(This command is not yet implemented.)} Show the results of
14380 expanding those preprocessor macro invocations that appear explicitly in
14381 @var{expression}. Macro invocations appearing in that expansion are
14382 left unchanged. This command allows you to see the effect of a
14383 particular macro more clearly, without being confused by further
14384 expansions. Since @value{GDBN} simply expands macros, but does not
14385 parse the result, @var{expression} need not be a valid expression; it
14386 can be any string of tokens.
14389 @cindex macro definition, showing
14390 @cindex definition of a macro, showing
14391 @cindex macros, from debug info
14392 @item info macro [-a|-all] [--] @var{macro}
14393 Show the current definition or all definitions of the named @var{macro},
14394 and describe the source location or compiler command-line where that
14395 definition was established. The optional double dash is to signify the end of
14396 argument processing and the beginning of @var{macro} for non C-like macros where
14397 the macro may begin with a hyphen.
14399 @kindex info macros
14400 @item info macros @var{locspec}
14401 Show all macro definitions that are in effect at the source line of
14402 the code location that results from resolving @var{locspec}, and
14403 describe the source location or compiler command-line where those
14404 definitions were established.
14406 @kindex macro define
14407 @cindex user-defined macros
14408 @cindex defining macros interactively
14409 @cindex macros, user-defined
14410 @item macro define @var{macro} @var{replacement-list}
14411 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
14412 Introduce a definition for a preprocessor macro named @var{macro},
14413 invocations of which are replaced by the tokens given in
14414 @var{replacement-list}. The first form of this command defines an
14415 ``object-like'' macro, which takes no arguments; the second form
14416 defines a ``function-like'' macro, which takes the arguments given in
14419 A definition introduced by this command is in scope in every
14420 expression evaluated in @value{GDBN}, until it is removed with the
14421 @code{macro undef} command, described below. The definition overrides
14422 all definitions for @var{macro} present in the program being debugged,
14423 as well as any previous user-supplied definition.
14425 @kindex macro undef
14426 @item macro undef @var{macro}
14427 Remove any user-supplied definition for the macro named @var{macro}.
14428 This command only affects definitions provided with the @code{macro
14429 define} command, described above; it cannot remove definitions present
14430 in the program being debugged.
14434 List all the macros defined using the @code{macro define} command.
14437 @cindex macros, example of debugging with
14438 Here is a transcript showing the above commands in action. First, we
14439 show our source files:
14444 #include "sample.h"
14447 #define ADD(x) (M + x)
14452 printf ("Hello, world!\n");
14454 printf ("We're so creative.\n");
14456 printf ("Goodbye, world!\n");
14463 Now, we compile the program using the @sc{gnu} C compiler,
14464 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
14465 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
14466 and @option{-gdwarf-4}; we recommend always choosing the most recent
14467 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
14468 includes information about preprocessor macros in the debugging
14472 $ gcc -gdwarf-2 -g3 sample.c -o sample
14476 Now, we start @value{GDBN} on our sample program:
14480 GNU gdb 2002-05-06-cvs
14481 Copyright 2002 Free Software Foundation, Inc.
14482 GDB is free software, @dots{}
14486 We can expand macros and examine their definitions, even when the
14487 program is not running. @value{GDBN} uses the current listing position
14488 to decide which macro definitions are in scope:
14491 (@value{GDBP}) list main
14494 5 #define ADD(x) (M + x)
14499 10 printf ("Hello, world!\n");
14501 12 printf ("We're so creative.\n");
14502 (@value{GDBP}) info macro ADD
14503 Defined at /home/jimb/gdb/macros/play/sample.c:5
14504 #define ADD(x) (M + x)
14505 (@value{GDBP}) info macro Q
14506 Defined at /home/jimb/gdb/macros/play/sample.h:1
14507 included at /home/jimb/gdb/macros/play/sample.c:2
14509 (@value{GDBP}) macro expand ADD(1)
14510 expands to: (42 + 1)
14511 (@value{GDBP}) macro expand-once ADD(1)
14512 expands to: once (M + 1)
14516 In the example above, note that @code{macro expand-once} expands only
14517 the macro invocation explicit in the original text --- the invocation of
14518 @code{ADD} --- but does not expand the invocation of the macro @code{M},
14519 which was introduced by @code{ADD}.
14521 Once the program is running, @value{GDBN} uses the macro definitions in
14522 force at the source line of the current stack frame:
14525 (@value{GDBP}) break main
14526 Breakpoint 1 at 0x8048370: file sample.c, line 10.
14528 Starting program: /home/jimb/gdb/macros/play/sample
14530 Breakpoint 1, main () at sample.c:10
14531 10 printf ("Hello, world!\n");
14535 At line 10, the definition of the macro @code{N} at line 9 is in force:
14538 (@value{GDBP}) info macro N
14539 Defined at /home/jimb/gdb/macros/play/sample.c:9
14541 (@value{GDBP}) macro expand N Q M
14542 expands to: 28 < 42
14543 (@value{GDBP}) print N Q M
14548 As we step over directives that remove @code{N}'s definition, and then
14549 give it a new definition, @value{GDBN} finds the definition (or lack
14550 thereof) in force at each point:
14553 (@value{GDBP}) next
14555 12 printf ("We're so creative.\n");
14556 (@value{GDBP}) info macro N
14557 The symbol `N' has no definition as a C/C++ preprocessor macro
14558 at /home/jimb/gdb/macros/play/sample.c:12
14559 (@value{GDBP}) next
14561 14 printf ("Goodbye, world!\n");
14562 (@value{GDBP}) info macro N
14563 Defined at /home/jimb/gdb/macros/play/sample.c:13
14565 (@value{GDBP}) macro expand N Q M
14566 expands to: 1729 < 42
14567 (@value{GDBP}) print N Q M
14572 In addition to source files, macros can be defined on the compilation command
14573 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14574 such a way, @value{GDBN} displays the location of their definition as line zero
14575 of the source file submitted to the compiler.
14578 (@value{GDBP}) info macro __STDC__
14579 Defined at /home/jimb/gdb/macros/play/sample.c:0
14586 @chapter Tracepoints
14587 @c This chapter is based on the documentation written by Michael
14588 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14590 @cindex tracepoints
14591 In some applications, it is not feasible for the debugger to interrupt
14592 the program's execution long enough for the developer to learn
14593 anything helpful about its behavior. If the program's correctness
14594 depends on its real-time behavior, delays introduced by a debugger
14595 might cause the program to change its behavior drastically, or perhaps
14596 fail, even when the code itself is correct. It is useful to be able
14597 to observe the program's behavior without interrupting it.
14599 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14600 specify locations in the program, called @dfn{tracepoints}, and
14601 arbitrary expressions to evaluate when those tracepoints are reached.
14602 Later, using the @code{tfind} command, you can examine the values
14603 those expressions had when the program hit the tracepoints. The
14604 expressions may also denote objects in memory---structures or arrays,
14605 for example---whose values @value{GDBN} should record; while visiting
14606 a particular tracepoint, you may inspect those objects as if they were
14607 in memory at that moment. However, because @value{GDBN} records these
14608 values without interacting with you, it can do so quickly and
14609 unobtrusively, hopefully not disturbing the program's behavior.
14611 The tracepoint facility is currently available only for remote
14612 targets. @xref{Targets}. In addition, your remote target must know
14613 how to collect trace data. This functionality is implemented in the
14614 remote stub; however, none of the stubs distributed with @value{GDBN}
14615 support tracepoints as of this writing. The format of the remote
14616 packets used to implement tracepoints are described in @ref{Tracepoint
14619 It is also possible to get trace data from a file, in a manner reminiscent
14620 of corefiles; you specify the filename, and use @code{tfind} to search
14621 through the file. @xref{Trace Files}, for more details.
14623 This chapter describes the tracepoint commands and features.
14626 * Set Tracepoints::
14627 * Analyze Collected Data::
14628 * Tracepoint Variables::
14632 @node Set Tracepoints
14633 @section Commands to Set Tracepoints
14635 Before running such a @dfn{trace experiment}, an arbitrary number of
14636 tracepoints can be set. A tracepoint is actually a special type of
14637 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14638 standard breakpoint commands. For instance, as with breakpoints,
14639 tracepoint numbers are successive integers starting from one, and many
14640 of the commands associated with tracepoints take the tracepoint number
14641 as their argument, to identify which tracepoint to work on.
14643 For each tracepoint, you can specify, in advance, some arbitrary set
14644 of data that you want the target to collect in the trace buffer when
14645 it hits that tracepoint. The collected data can include registers,
14646 local variables, or global data. Later, you can use @value{GDBN}
14647 commands to examine the values these data had at the time the
14648 tracepoint was hit.
14650 Tracepoints do not support every breakpoint feature. Ignore counts on
14651 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14652 commands when they are hit. Tracepoints may not be thread-specific
14655 @cindex fast tracepoints
14656 Some targets may support @dfn{fast tracepoints}, which are inserted in
14657 a different way (such as with a jump instead of a trap), that is
14658 faster but possibly restricted in where they may be installed.
14660 @cindex static tracepoints
14661 @cindex markers, static tracepoints
14662 @cindex probing markers, static tracepoints
14663 Regular and fast tracepoints are dynamic tracing facilities, meaning
14664 that they can be used to insert tracepoints at (almost) any location
14665 in the target. Some targets may also support controlling @dfn{static
14666 tracepoints} from @value{GDBN}. With static tracing, a set of
14667 instrumentation points, also known as @dfn{markers}, are embedded in
14668 the target program, and can be activated or deactivated by name or
14669 address. These are usually placed at locations which facilitate
14670 investigating what the target is actually doing. @value{GDBN}'s
14671 support for static tracing includes being able to list instrumentation
14672 points, and attach them with @value{GDBN} defined high level
14673 tracepoints that expose the whole range of convenience of
14674 @value{GDBN}'s tracepoints support. Namely, support for collecting
14675 registers values and values of global or local (to the instrumentation
14676 point) variables; tracepoint conditions and trace state variables.
14677 The act of installing a @value{GDBN} static tracepoint on an
14678 instrumentation point, or marker, is referred to as @dfn{probing} a
14679 static tracepoint marker.
14681 @code{gdbserver} supports tracepoints on some target systems.
14682 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14684 This section describes commands to set tracepoints and associated
14685 conditions and actions.
14688 * Create and Delete Tracepoints::
14689 * Enable and Disable Tracepoints::
14690 * Tracepoint Passcounts::
14691 * Tracepoint Conditions::
14692 * Trace State Variables::
14693 * Tracepoint Actions::
14694 * Listing Tracepoints::
14695 * Listing Static Tracepoint Markers::
14696 * Starting and Stopping Trace Experiments::
14697 * Tracepoint Restrictions::
14700 @node Create and Delete Tracepoints
14701 @subsection Create and Delete Tracepoints
14704 @cindex set tracepoint
14706 @item trace @var{locspec}
14707 The @code{trace} command is very similar to the @code{break} command.
14708 Its argument @var{locspec} can be any valid location specification.
14709 @xref{Location Specifications}. The @code{trace} command defines a tracepoint,
14710 which is a point in the target program where the debugger will briefly stop,
14711 collect some data, and then allow the program to continue. Setting a tracepoint
14712 or changing its actions takes effect immediately if the remote stub
14713 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14715 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14716 these changes don't take effect until the next @code{tstart}
14717 command, and once a trace experiment is running, further changes will
14718 not have any effect until the next trace experiment starts. In addition,
14719 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14720 address is not yet resolved. (This is similar to pending breakpoints.)
14721 Pending tracepoints are not downloaded to the target and not installed
14722 until they are resolved. The resolution of pending tracepoints requires
14723 @value{GDBN} support---when debugging with the remote target, and
14724 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14725 tracing}), pending tracepoints can not be resolved (and downloaded to
14726 the remote stub) while @value{GDBN} is disconnected.
14728 Here are some examples of using the @code{trace} command:
14731 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14733 (@value{GDBP}) @b{trace +2} // 2 lines forward
14735 (@value{GDBP}) @b{trace my_function} // first source line of function
14737 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14739 (@value{GDBP}) @b{trace *0x2117c4} // an address
14743 You can abbreviate @code{trace} as @code{tr}.
14745 @item trace @var{locspec} if @var{cond}
14746 Set a tracepoint with condition @var{cond}; evaluate the expression
14747 @var{cond} each time the tracepoint is reached, and collect data only
14748 if the value is nonzero---that is, if @var{cond} evaluates as true.
14749 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14750 information on tracepoint conditions.
14752 @item ftrace @var{locspec} [ if @var{cond} ]
14753 @cindex set fast tracepoint
14754 @cindex fast tracepoints, setting
14756 The @code{ftrace} command sets a fast tracepoint. For targets that
14757 support them, fast tracepoints will use a more efficient but possibly
14758 less general technique to trigger data collection, such as a jump
14759 instruction instead of a trap, or some sort of hardware support. It
14760 may not be possible to create a fast tracepoint at the desired
14761 location, in which case the command will exit with an explanatory
14764 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14767 On 32-bit x86-architecture systems, fast tracepoints normally need to
14768 be placed at an instruction that is 5 bytes or longer, but can be
14769 placed at 4-byte instructions if the low 64K of memory of the target
14770 program is available to install trampolines. Some Unix-type systems,
14771 such as @sc{gnu}/Linux, exclude low addresses from the program's
14772 address space; but for instance with the Linux kernel it is possible
14773 to let @value{GDBN} use this area by doing a @command{sysctl} command
14774 to set the @code{mmap_min_addr} kernel parameter, as in
14777 sudo sysctl -w vm.mmap_min_addr=32768
14781 which sets the low address to 32K, which leaves plenty of room for
14782 trampolines. The minimum address should be set to a page boundary.
14784 @item strace [@var{locspec} | -m @var{marker}] [ if @var{cond} ]
14785 @cindex set static tracepoint
14786 @cindex static tracepoints, setting
14787 @cindex probe static tracepoint marker
14789 The @code{strace} command sets a static tracepoint. For targets that
14790 support it, setting a static tracepoint probes a static
14791 instrumentation point, or marker, found at the code locations that
14792 result from resolving @var{locspec}. It may not be possible to set a
14793 static tracepoint at the desired code location, in which case the
14794 command will exit with an explanatory message.
14796 @value{GDBN} handles arguments to @code{strace} exactly as for
14797 @code{trace}, with the addition that the user can also specify
14798 @code{-m @var{marker}} instead of a location spec. This probes the marker
14799 identified by the @var{marker} string identifier. This identifier
14800 depends on the static tracepoint backend library your program is
14801 using. You can find all the marker identifiers in the @samp{ID} field
14802 of the @code{info static-tracepoint-markers} command output.
14803 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14804 Markers}. For example, in the following small program using the UST
14810 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14815 the marker id is composed of joining the first two arguments to the
14816 @code{trace_mark} call with a slash, which translates to:
14819 (@value{GDBP}) info static-tracepoint-markers
14820 Cnt Enb ID Address What
14821 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14827 so you may probe the marker above with:
14830 (@value{GDBP}) strace -m ust/bar33
14833 Static tracepoints accept an extra collect action --- @code{collect
14834 $_sdata}. This collects arbitrary user data passed in the probe point
14835 call to the tracing library. In the UST example above, you'll see
14836 that the third argument to @code{trace_mark} is a printf-like format
14837 string. The user data is then the result of running that formatting
14838 string against the following arguments. Note that @code{info
14839 static-tracepoint-markers} command output lists that format string in
14840 the @samp{Data:} field.
14842 You can inspect this data when analyzing the trace buffer, by printing
14843 the $_sdata variable like any other variable available to
14844 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14847 @cindex last tracepoint number
14848 @cindex recent tracepoint number
14849 @cindex tracepoint number
14850 The convenience variable @code{$tpnum} records the tracepoint number
14851 of the most recently set tracepoint.
14853 @kindex delete tracepoint
14854 @cindex tracepoint deletion
14855 @item delete tracepoint @r{[}@var{num}@r{]}
14856 Permanently delete one or more tracepoints. With no argument, the
14857 default is to delete all tracepoints. Note that the regular
14858 @code{delete} command can remove tracepoints also.
14863 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14865 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14869 You can abbreviate this command as @code{del tr}.
14872 @node Enable and Disable Tracepoints
14873 @subsection Enable and Disable Tracepoints
14875 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14878 @kindex disable tracepoint
14879 @item disable tracepoint @r{[}@var{num}@r{]}
14880 Disable tracepoint @var{num}, or all tracepoints if no argument
14881 @var{num} is given. A disabled tracepoint will have no effect during
14882 a trace experiment, but it is not forgotten. You can re-enable
14883 a disabled tracepoint using the @code{enable tracepoint} command.
14884 If the command is issued during a trace experiment and the debug target
14885 has support for disabling tracepoints during a trace experiment, then the
14886 change will be effective immediately. Otherwise, it will be applied to the
14887 next trace experiment.
14889 @kindex enable tracepoint
14890 @item enable tracepoint @r{[}@var{num}@r{]}
14891 Enable tracepoint @var{num}, or all tracepoints. If this command is
14892 issued during a trace experiment and the debug target supports enabling
14893 tracepoints during a trace experiment, then the enabled tracepoints will
14894 become effective immediately. Otherwise, they will become effective the
14895 next time a trace experiment is run.
14898 @node Tracepoint Passcounts
14899 @subsection Tracepoint Passcounts
14903 @cindex tracepoint pass count
14904 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14905 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14906 automatically stop a trace experiment. If a tracepoint's passcount is
14907 @var{n}, then the trace experiment will be automatically stopped on
14908 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14909 @var{num} is not specified, the @code{passcount} command sets the
14910 passcount of the most recently defined tracepoint. If no passcount is
14911 given, the trace experiment will run until stopped explicitly by the
14917 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14918 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14920 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14921 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14922 (@value{GDBP}) @b{trace foo}
14923 (@value{GDBP}) @b{pass 3}
14924 (@value{GDBP}) @b{trace bar}
14925 (@value{GDBP}) @b{pass 2}
14926 (@value{GDBP}) @b{trace baz}
14927 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14928 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14929 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14930 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14934 @node Tracepoint Conditions
14935 @subsection Tracepoint Conditions
14936 @cindex conditional tracepoints
14937 @cindex tracepoint conditions
14939 The simplest sort of tracepoint collects data every time your program
14940 reaches a specified place. You can also specify a @dfn{condition} for
14941 a tracepoint. A condition is just a Boolean expression in your
14942 programming language (@pxref{Expressions, ,Expressions}). A
14943 tracepoint with a condition evaluates the expression each time your
14944 program reaches it, and data collection happens only if the condition
14947 Tracepoint conditions can be specified when a tracepoint is set, by
14948 using @samp{if} in the arguments to the @code{trace} command.
14949 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14950 also be set or changed at any time with the @code{condition} command,
14951 just as with breakpoints.
14953 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14954 the conditional expression itself. Instead, @value{GDBN} encodes the
14955 expression into an agent expression (@pxref{Agent Expressions})
14956 suitable for execution on the target, independently of @value{GDBN}.
14957 Global variables become raw memory locations, locals become stack
14958 accesses, and so forth.
14960 For instance, suppose you have a function that is usually called
14961 frequently, but should not be called after an error has occurred. You
14962 could use the following tracepoint command to collect data about calls
14963 of that function that happen while the error code is propagating
14964 through the program; an unconditional tracepoint could end up
14965 collecting thousands of useless trace frames that you would have to
14969 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14972 @node Trace State Variables
14973 @subsection Trace State Variables
14974 @cindex trace state variables
14976 A @dfn{trace state variable} is a special type of variable that is
14977 created and managed by target-side code. The syntax is the same as
14978 that for GDB's convenience variables (a string prefixed with ``$''),
14979 but they are stored on the target. They must be created explicitly,
14980 using a @code{tvariable} command. They are always 64-bit signed
14983 Trace state variables are remembered by @value{GDBN}, and downloaded
14984 to the target along with tracepoint information when the trace
14985 experiment starts. There are no intrinsic limits on the number of
14986 trace state variables, beyond memory limitations of the target.
14988 @cindex convenience variables, and trace state variables
14989 Although trace state variables are managed by the target, you can use
14990 them in print commands and expressions as if they were convenience
14991 variables; @value{GDBN} will get the current value from the target
14992 while the trace experiment is running. Trace state variables share
14993 the same namespace as other ``$'' variables, which means that you
14994 cannot have trace state variables with names like @code{$23} or
14995 @code{$pc}, nor can you have a trace state variable and a convenience
14996 variable with the same name.
15000 @item tvariable $@var{name} [ = @var{expression} ]
15002 The @code{tvariable} command creates a new trace state variable named
15003 @code{$@var{name}}, and optionally gives it an initial value of
15004 @var{expression}. The @var{expression} is evaluated when this command is
15005 entered; the result will be converted to an integer if possible,
15006 otherwise @value{GDBN} will report an error. A subsequent
15007 @code{tvariable} command specifying the same name does not create a
15008 variable, but instead assigns the supplied initial value to the
15009 existing variable of that name, overwriting any previous initial
15010 value. The default initial value is 0.
15012 @item info tvariables
15013 @kindex info tvariables
15014 List all the trace state variables along with their initial values.
15015 Their current values may also be displayed, if the trace experiment is
15018 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
15019 @kindex delete tvariable
15020 Delete the given trace state variables, or all of them if no arguments
15025 @node Tracepoint Actions
15026 @subsection Tracepoint Action Lists
15030 @cindex tracepoint actions
15031 @item actions @r{[}@var{num}@r{]}
15032 This command will prompt for a list of actions to be taken when the
15033 tracepoint is hit. If the tracepoint number @var{num} is not
15034 specified, this command sets the actions for the one that was most
15035 recently defined (so that you can define a tracepoint and then say
15036 @code{actions} without bothering about its number). You specify the
15037 actions themselves on the following lines, one action at a time, and
15038 terminate the actions list with a line containing just @code{end}. So
15039 far, the only defined actions are @code{collect}, @code{teval}, and
15040 @code{while-stepping}.
15042 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
15043 Commands, ,Breakpoint Command Lists}), except that only the defined
15044 actions are allowed; any other @value{GDBN} command is rejected.
15046 @cindex remove actions from a tracepoint
15047 To remove all actions from a tracepoint, type @samp{actions @var{num}}
15048 and follow it immediately with @samp{end}.
15051 (@value{GDBP}) @b{collect @var{data}} // collect some data
15053 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
15055 (@value{GDBP}) @b{end} // signals the end of actions.
15058 In the following example, the action list begins with @code{collect}
15059 commands indicating the things to be collected when the tracepoint is
15060 hit. Then, in order to single-step and collect additional data
15061 following the tracepoint, a @code{while-stepping} command is used,
15062 followed by the list of things to be collected after each step in a
15063 sequence of single steps. The @code{while-stepping} command is
15064 terminated by its own separate @code{end} command. Lastly, the action
15065 list is terminated by an @code{end} command.
15068 (@value{GDBP}) @b{trace foo}
15069 (@value{GDBP}) @b{actions}
15070 Enter actions for tracepoint 1, one per line:
15073 > while-stepping 12
15074 > collect $pc, arr[i]
15079 @kindex collect @r{(tracepoints)}
15080 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
15081 Collect values of the given expressions when the tracepoint is hit.
15082 This command accepts a comma-separated list of any valid expressions.
15083 In addition to global, static, or local variables, the following
15084 special arguments are supported:
15088 Collect all registers.
15091 Collect all function arguments.
15094 Collect all local variables.
15097 Collect the return address. This is helpful if you want to see more
15100 @emph{Note:} The return address location can not always be reliably
15101 determined up front, and the wrong address / registers may end up
15102 collected instead. On some architectures the reliability is higher
15103 for tracepoints at function entry, while on others it's the opposite.
15104 When this happens, backtracing will stop because the return address is
15105 found unavailable (unless another collect rule happened to match it).
15108 Collects the number of arguments from the static probe at which the
15109 tracepoint is located.
15110 @xref{Static Probe Points}.
15112 @item $_probe_arg@var{n}
15113 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
15114 from the static probe at which the tracepoint is located.
15115 @xref{Static Probe Points}.
15118 @vindex $_sdata@r{, collect}
15119 Collect static tracepoint marker specific data. Only available for
15120 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
15121 Lists}. On the UST static tracepoints library backend, an
15122 instrumentation point resembles a @code{printf} function call. The
15123 tracing library is able to collect user specified data formatted to a
15124 character string using the format provided by the programmer that
15125 instrumented the program. Other backends have similar mechanisms.
15126 Here's an example of a UST marker call:
15129 const char master_name[] = "$your_name";
15130 trace_mark(channel1, marker1, "hello %s", master_name)
15133 In this case, collecting @code{$_sdata} collects the string
15134 @samp{hello $yourname}. When analyzing the trace buffer, you can
15135 inspect @samp{$_sdata} like any other variable available to
15139 You can give several consecutive @code{collect} commands, each one
15140 with a single argument, or one @code{collect} command with several
15141 arguments separated by commas; the effect is the same.
15143 The optional @var{mods} changes the usual handling of the arguments.
15144 @code{s} requests that pointers to chars be handled as strings, in
15145 particular collecting the contents of the memory being pointed at, up
15146 to the first zero. The upper bound is by default the value of the
15147 @code{print elements} variable; if @code{s} is followed by a decimal
15148 number, that is the upper bound instead. So for instance
15149 @samp{collect/s25 mystr} collects as many as 25 characters at
15152 The command @code{info scope} (@pxref{Symbols, info scope}) is
15153 particularly useful for figuring out what data to collect.
15155 @kindex teval @r{(tracepoints)}
15156 @item teval @var{expr1}, @var{expr2}, @dots{}
15157 Evaluate the given expressions when the tracepoint is hit. This
15158 command accepts a comma-separated list of expressions. The results
15159 are discarded, so this is mainly useful for assigning values to trace
15160 state variables (@pxref{Trace State Variables}) without adding those
15161 values to the trace buffer, as would be the case if the @code{collect}
15164 @kindex while-stepping @r{(tracepoints)}
15165 @item while-stepping @var{n}
15166 Perform @var{n} single-step instruction traces after the tracepoint,
15167 collecting new data after each step. The @code{while-stepping}
15168 command is followed by the list of what to collect while stepping
15169 (followed by its own @code{end} command):
15172 > while-stepping 12
15173 > collect $regs, myglobal
15179 Note that @code{$pc} is not automatically collected by
15180 @code{while-stepping}; you need to explicitly collect that register if
15181 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
15184 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
15185 @kindex set default-collect
15186 @cindex default collection action
15187 This variable is a list of expressions to collect at each tracepoint
15188 hit. It is effectively an additional @code{collect} action prepended
15189 to every tracepoint action list. The expressions are parsed
15190 individually for each tracepoint, so for instance a variable named
15191 @code{xyz} may be interpreted as a global for one tracepoint, and a
15192 local for another, as appropriate to the tracepoint's location.
15194 @item show default-collect
15195 @kindex show default-collect
15196 Show the list of expressions that are collected by default at each
15201 @node Listing Tracepoints
15202 @subsection Listing Tracepoints
15205 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
15206 @kindex info tp @r{[}@var{n}@dots{}@r{]}
15207 @cindex information about tracepoints
15208 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
15209 Display information about the tracepoint @var{num}. If you don't
15210 specify a tracepoint number, displays information about all the
15211 tracepoints defined so far. The format is similar to that used for
15212 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
15213 command, simply restricting itself to tracepoints.
15215 A tracepoint's listing may include additional information specific to
15220 its passcount as given by the @code{passcount @var{n}} command
15223 the state about installed on target of each location
15227 (@value{GDBP}) @b{info trace}
15228 Num Type Disp Enb Address What
15229 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
15231 collect globfoo, $regs
15236 2 tracepoint keep y <MULTIPLE>
15238 2.1 y 0x0804859c in func4 at change-loc.h:35
15239 installed on target
15240 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
15241 installed on target
15242 2.3 y <PENDING> set_tracepoint
15243 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
15244 not installed on target
15249 This command can be abbreviated @code{info tp}.
15252 @node Listing Static Tracepoint Markers
15253 @subsection Listing Static Tracepoint Markers
15256 @kindex info static-tracepoint-markers
15257 @cindex information about static tracepoint markers
15258 @item info static-tracepoint-markers
15259 Display information about all static tracepoint markers defined in the
15262 For each marker, the following columns are printed:
15266 An incrementing counter, output to help readability. This is not a
15269 The marker ID, as reported by the target.
15270 @item Enabled or Disabled
15271 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
15272 that are not enabled.
15274 Where the marker is in your program, as a memory address.
15276 Where the marker is in the source for your program, as a file and line
15277 number. If the debug information included in the program does not
15278 allow @value{GDBN} to locate the source of the marker, this column
15279 will be left blank.
15283 In addition, the following information may be printed for each marker:
15287 User data passed to the tracing library by the marker call. In the
15288 UST backend, this is the format string passed as argument to the
15290 @item Static tracepoints probing the marker
15291 The list of static tracepoints attached to the marker.
15295 (@value{GDBP}) info static-tracepoint-markers
15296 Cnt ID Enb Address What
15297 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
15298 Data: number1 %d number2 %d
15299 Probed by static tracepoints: #2
15300 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
15306 @node Starting and Stopping Trace Experiments
15307 @subsection Starting and Stopping Trace Experiments
15310 @kindex tstart [ @var{notes} ]
15311 @cindex start a new trace experiment
15312 @cindex collected data discarded
15314 This command starts the trace experiment, and begins collecting data.
15315 It has the side effect of discarding all the data collected in the
15316 trace buffer during the previous trace experiment. If any arguments
15317 are supplied, they are taken as a note and stored with the trace
15318 experiment's state. The notes may be arbitrary text, and are
15319 especially useful with disconnected tracing in a multi-user context;
15320 the notes can explain what the trace is doing, supply user contact
15321 information, and so forth.
15323 @kindex tstop [ @var{notes} ]
15324 @cindex stop a running trace experiment
15326 This command stops the trace experiment. If any arguments are
15327 supplied, they are recorded with the experiment as a note. This is
15328 useful if you are stopping a trace started by someone else, for
15329 instance if the trace is interfering with the system's behavior and
15330 needs to be stopped quickly.
15332 @strong{Note}: a trace experiment and data collection may stop
15333 automatically if any tracepoint's passcount is reached
15334 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
15337 @cindex status of trace data collection
15338 @cindex trace experiment, status of
15340 This command displays the status of the current trace data
15344 Here is an example of the commands we described so far:
15347 (@value{GDBP}) @b{trace gdb_c_test}
15348 (@value{GDBP}) @b{actions}
15349 Enter actions for tracepoint #1, one per line.
15350 > collect $regs,$locals,$args
15351 > while-stepping 11
15355 (@value{GDBP}) @b{tstart}
15356 [time passes @dots{}]
15357 (@value{GDBP}) @b{tstop}
15360 @anchor{disconnected tracing}
15361 @cindex disconnected tracing
15362 You can choose to continue running the trace experiment even if
15363 @value{GDBN} disconnects from the target, voluntarily or
15364 involuntarily. For commands such as @code{detach}, the debugger will
15365 ask what you want to do with the trace. But for unexpected
15366 terminations (@value{GDBN} crash, network outage), it would be
15367 unfortunate to lose hard-won trace data, so the variable
15368 @code{disconnected-tracing} lets you decide whether the trace should
15369 continue running without @value{GDBN}.
15372 @item set disconnected-tracing on
15373 @itemx set disconnected-tracing off
15374 @kindex set disconnected-tracing
15375 Choose whether a tracing run should continue to run if @value{GDBN}
15376 has disconnected from the target. Note that @code{detach} or
15377 @code{quit} will ask you directly what to do about a running trace no
15378 matter what this variable's setting, so the variable is mainly useful
15379 for handling unexpected situations, such as loss of the network.
15381 @item show disconnected-tracing
15382 @kindex show disconnected-tracing
15383 Show the current choice for disconnected tracing.
15387 When you reconnect to the target, the trace experiment may or may not
15388 still be running; it might have filled the trace buffer in the
15389 meantime, or stopped for one of the other reasons. If it is running,
15390 it will continue after reconnection.
15392 Upon reconnection, the target will upload information about the
15393 tracepoints in effect. @value{GDBN} will then compare that
15394 information to the set of tracepoints currently defined, and attempt
15395 to match them up, allowing for the possibility that the numbers may
15396 have changed due to creation and deletion in the meantime. If one of
15397 the target's tracepoints does not match any in @value{GDBN}, the
15398 debugger will create a new tracepoint, so that you have a number with
15399 which to specify that tracepoint. This matching-up process is
15400 necessarily heuristic, and it may result in useless tracepoints being
15401 created; you may simply delete them if they are of no use.
15403 @cindex circular trace buffer
15404 If your target agent supports a @dfn{circular trace buffer}, then you
15405 can run a trace experiment indefinitely without filling the trace
15406 buffer; when space runs out, the agent deletes already-collected trace
15407 frames, oldest first, until there is enough room to continue
15408 collecting. This is especially useful if your tracepoints are being
15409 hit too often, and your trace gets terminated prematurely because the
15410 buffer is full. To ask for a circular trace buffer, simply set
15411 @samp{circular-trace-buffer} to on. You can set this at any time,
15412 including during tracing; if the agent can do it, it will change
15413 buffer handling on the fly, otherwise it will not take effect until
15417 @item set circular-trace-buffer on
15418 @itemx set circular-trace-buffer off
15419 @kindex set circular-trace-buffer
15420 Choose whether a tracing run should use a linear or circular buffer
15421 for trace data. A linear buffer will not lose any trace data, but may
15422 fill up prematurely, while a circular buffer will discard old trace
15423 data, but it will have always room for the latest tracepoint hits.
15425 @item show circular-trace-buffer
15426 @kindex show circular-trace-buffer
15427 Show the current choice for the trace buffer. Note that this may not
15428 match the agent's current buffer handling, nor is it guaranteed to
15429 match the setting that might have been in effect during a past run,
15430 for instance if you are looking at frames from a trace file.
15435 @item set trace-buffer-size @var{n}
15436 @itemx set trace-buffer-size unlimited
15437 @kindex set trace-buffer-size
15438 Request that the target use a trace buffer of @var{n} bytes. Not all
15439 targets will honor the request; they may have a compiled-in size for
15440 the trace buffer, or some other limitation. Set to a value of
15441 @code{unlimited} or @code{-1} to let the target use whatever size it
15442 likes. This is also the default.
15444 @item show trace-buffer-size
15445 @kindex show trace-buffer-size
15446 Show the current requested size for the trace buffer. Note that this
15447 will only match the actual size if the target supports size-setting,
15448 and was able to handle the requested size. For instance, if the
15449 target can only change buffer size between runs, this variable will
15450 not reflect the change until the next run starts. Use @code{tstatus}
15451 to get a report of the actual buffer size.
15455 @item set trace-user @var{text}
15456 @kindex set trace-user
15458 @item show trace-user
15459 @kindex show trace-user
15461 @item set trace-notes @var{text}
15462 @kindex set trace-notes
15463 Set the trace run's notes.
15465 @item show trace-notes
15466 @kindex show trace-notes
15467 Show the trace run's notes.
15469 @item set trace-stop-notes @var{text}
15470 @kindex set trace-stop-notes
15471 Set the trace run's stop notes. The handling of the note is as for
15472 @code{tstop} arguments; the set command is convenient way to fix a
15473 stop note that is mistaken or incomplete.
15475 @item show trace-stop-notes
15476 @kindex show trace-stop-notes
15477 Show the trace run's stop notes.
15481 @node Tracepoint Restrictions
15482 @subsection Tracepoint Restrictions
15484 @cindex tracepoint restrictions
15485 There are a number of restrictions on the use of tracepoints. As
15486 described above, tracepoint data gathering occurs on the target
15487 without interaction from @value{GDBN}. Thus the full capabilities of
15488 the debugger are not available during data gathering, and then at data
15489 examination time, you will be limited by only having what was
15490 collected. The following items describe some common problems, but it
15491 is not exhaustive, and you may run into additional difficulties not
15497 Tracepoint expressions are intended to gather objects (lvalues). Thus
15498 the full flexibility of GDB's expression evaluator is not available.
15499 You cannot call functions, cast objects to aggregate types, access
15500 convenience variables or modify values (except by assignment to trace
15501 state variables). Some language features may implicitly call
15502 functions (for instance Objective-C fields with accessors), and therefore
15503 cannot be collected either.
15506 Collection of local variables, either individually or in bulk with
15507 @code{$locals} or @code{$args}, during @code{while-stepping} may
15508 behave erratically. The stepping action may enter a new scope (for
15509 instance by stepping into a function), or the location of the variable
15510 may change (for instance it is loaded into a register). The
15511 tracepoint data recorded uses the location information for the
15512 variables that is correct for the tracepoint location. When the
15513 tracepoint is created, it is not possible, in general, to determine
15514 where the steps of a @code{while-stepping} sequence will advance the
15515 program---particularly if a conditional branch is stepped.
15518 Collection of an incompletely-initialized or partially-destroyed object
15519 may result in something that @value{GDBN} cannot display, or displays
15520 in a misleading way.
15523 When @value{GDBN} displays a pointer to character it automatically
15524 dereferences the pointer to also display characters of the string
15525 being pointed to. However, collecting the pointer during tracing does
15526 not automatically collect the string. You need to explicitly
15527 dereference the pointer and provide size information if you want to
15528 collect not only the pointer, but the memory pointed to. For example,
15529 @code{*ptr@@50} can be used to collect the 50 element array pointed to
15533 It is not possible to collect a complete stack backtrace at a
15534 tracepoint. Instead, you may collect the registers and a few hundred
15535 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
15536 (adjust to use the name of the actual stack pointer register on your
15537 target architecture, and the amount of stack you wish to capture).
15538 Then the @code{backtrace} command will show a partial backtrace when
15539 using a trace frame. The number of stack frames that can be examined
15540 depends on the sizes of the frames in the collected stack. Note that
15541 if you ask for a block so large that it goes past the bottom of the
15542 stack, the target agent may report an error trying to read from an
15546 If you do not collect registers at a tracepoint, @value{GDBN} can
15547 infer that the value of @code{$pc} must be the same as the address of
15548 the tracepoint and use that when you are looking at a trace frame
15549 for that tracepoint. However, this cannot work if the tracepoint has
15550 multiple locations (for instance if it was set in a function that was
15551 inlined), or if it has a @code{while-stepping} loop. In those cases
15552 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
15557 @node Analyze Collected Data
15558 @section Using the Collected Data
15560 After the tracepoint experiment ends, you use @value{GDBN} commands
15561 for examining the trace data. The basic idea is that each tracepoint
15562 collects a trace @dfn{snapshot} every time it is hit and another
15563 snapshot every time it single-steps. All these snapshots are
15564 consecutively numbered from zero and go into a buffer, and you can
15565 examine them later. The way you examine them is to @dfn{focus} on a
15566 specific trace snapshot. When the remote stub is focused on a trace
15567 snapshot, it will respond to all @value{GDBN} requests for memory and
15568 registers by reading from the buffer which belongs to that snapshot,
15569 rather than from @emph{real} memory or registers of the program being
15570 debugged. This means that @strong{all} @value{GDBN} commands
15571 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15572 behave as if we were currently debugging the program state as it was
15573 when the tracepoint occurred. Any requests for data that are not in
15574 the buffer will fail.
15577 * tfind:: How to select a trace snapshot
15578 * tdump:: How to display all data for a snapshot
15579 * save tracepoints:: How to save tracepoints for a future run
15583 @subsection @code{tfind @var{n}}
15586 @cindex select trace snapshot
15587 @cindex find trace snapshot
15588 The basic command for selecting a trace snapshot from the buffer is
15589 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15590 counting from zero. If no argument @var{n} is given, the next
15591 snapshot is selected.
15593 Here are the various forms of using the @code{tfind} command.
15597 Find the first snapshot in the buffer. This is a synonym for
15598 @code{tfind 0} (since 0 is the number of the first snapshot).
15601 Stop debugging trace snapshots, resume @emph{live} debugging.
15604 Same as @samp{tfind none}.
15607 No argument means find the next trace snapshot or find the first
15608 one if no trace snapshot is selected.
15611 Find the previous trace snapshot before the current one. This permits
15612 retracing earlier steps.
15614 @item tfind tracepoint @var{num}
15615 Find the next snapshot associated with tracepoint @var{num}. Search
15616 proceeds forward from the last examined trace snapshot. If no
15617 argument @var{num} is given, it means find the next snapshot collected
15618 for the same tracepoint as the current snapshot.
15620 @item tfind pc @var{addr}
15621 Find the next snapshot associated with the value @var{addr} of the
15622 program counter. Search proceeds forward from the last examined trace
15623 snapshot. If no argument @var{addr} is given, it means find the next
15624 snapshot with the same value of PC as the current snapshot.
15626 @item tfind outside @var{addr1}, @var{addr2}
15627 Find the next snapshot whose PC is outside the given range of
15628 addresses (exclusive).
15630 @item tfind range @var{addr1}, @var{addr2}
15631 Find the next snapshot whose PC is between @var{addr1} and
15632 @var{addr2} (inclusive).
15634 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15635 Find the next snapshot associated with the source line @var{n}. If
15636 the optional argument @var{file} is given, refer to line @var{n} in
15637 that source file. Search proceeds forward from the last examined
15638 trace snapshot. If no argument @var{n} is given, it means find the
15639 next line other than the one currently being examined; thus saying
15640 @code{tfind line} repeatedly can appear to have the same effect as
15641 stepping from line to line in a @emph{live} debugging session.
15644 The default arguments for the @code{tfind} commands are specifically
15645 designed to make it easy to scan through the trace buffer. For
15646 instance, @code{tfind} with no argument selects the next trace
15647 snapshot, and @code{tfind -} with no argument selects the previous
15648 trace snapshot. So, by giving one @code{tfind} command, and then
15649 simply hitting @key{RET} repeatedly you can examine all the trace
15650 snapshots in order. Or, by saying @code{tfind -} and then hitting
15651 @key{RET} repeatedly you can examine the snapshots in reverse order.
15652 The @code{tfind line} command with no argument selects the snapshot
15653 for the next source line executed. The @code{tfind pc} command with
15654 no argument selects the next snapshot with the same program counter
15655 (PC) as the current frame. The @code{tfind tracepoint} command with
15656 no argument selects the next trace snapshot collected by the same
15657 tracepoint as the current one.
15659 In addition to letting you scan through the trace buffer manually,
15660 these commands make it easy to construct @value{GDBN} scripts that
15661 scan through the trace buffer and print out whatever collected data
15662 you are interested in. Thus, if we want to examine the PC, FP, and SP
15663 registers from each trace frame in the buffer, we can say this:
15666 (@value{GDBP}) @b{tfind start}
15667 (@value{GDBP}) @b{while ($trace_frame != -1)}
15668 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15669 $trace_frame, $pc, $sp, $fp
15673 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15674 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15675 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15676 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15677 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15678 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15679 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15680 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15681 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15682 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15683 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15686 Or, if we want to examine the variable @code{X} at each source line in
15690 (@value{GDBP}) @b{tfind start}
15691 (@value{GDBP}) @b{while ($trace_frame != -1)}
15692 > printf "Frame %d, X == %d\n", $trace_frame, X
15702 @subsection @code{tdump}
15704 @cindex dump all data collected at tracepoint
15705 @cindex tracepoint data, display
15707 This command takes no arguments. It prints all the data collected at
15708 the current trace snapshot.
15711 (@value{GDBP}) @b{trace 444}
15712 (@value{GDBP}) @b{actions}
15713 Enter actions for tracepoint #2, one per line:
15714 > collect $regs, $locals, $args, gdb_long_test
15717 (@value{GDBP}) @b{tstart}
15719 (@value{GDBP}) @b{tfind line 444}
15720 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15722 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15724 (@value{GDBP}) @b{tdump}
15725 Data collected at tracepoint 2, trace frame 1:
15726 d0 0xc4aa0085 -995491707
15730 d4 0x71aea3d 119204413
15733 d7 0x380035 3670069
15734 a0 0x19e24a 1696330
15735 a1 0x3000668 50333288
15737 a3 0x322000 3284992
15738 a4 0x3000698 50333336
15739 a5 0x1ad3cc 1758156
15740 fp 0x30bf3c 0x30bf3c
15741 sp 0x30bf34 0x30bf34
15743 pc 0x20b2c8 0x20b2c8
15747 p = 0x20e5b4 "gdb-test"
15754 gdb_long_test = 17 '\021'
15759 @code{tdump} works by scanning the tracepoint's current collection
15760 actions and printing the value of each expression listed. So
15761 @code{tdump} can fail, if after a run, you change the tracepoint's
15762 actions to mention variables that were not collected during the run.
15764 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15765 uses the collected value of @code{$pc} to distinguish between trace
15766 frames that were collected at the tracepoint hit, and frames that were
15767 collected while stepping. This allows it to correctly choose whether
15768 to display the basic list of collections, or the collections from the
15769 body of the while-stepping loop. However, if @code{$pc} was not collected,
15770 then @code{tdump} will always attempt to dump using the basic collection
15771 list, and may fail if a while-stepping frame does not include all the
15772 same data that is collected at the tracepoint hit.
15773 @c This is getting pretty arcane, example would be good.
15775 @node save tracepoints
15776 @subsection @code{save tracepoints @var{filename}}
15777 @kindex save tracepoints
15778 @kindex save-tracepoints
15779 @cindex save tracepoints for future sessions
15781 This command saves all current tracepoint definitions together with
15782 their actions and passcounts, into a file @file{@var{filename}}
15783 suitable for use in a later debugging session. To read the saved
15784 tracepoint definitions, use the @code{source} command (@pxref{Command
15785 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15786 alias for @w{@code{save tracepoints}}
15788 @node Tracepoint Variables
15789 @section Convenience Variables for Tracepoints
15790 @cindex tracepoint variables
15791 @cindex convenience variables for tracepoints
15794 @vindex $trace_frame
15795 @item (int) $trace_frame
15796 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15797 snapshot is selected.
15799 @vindex $tracepoint
15800 @item (int) $tracepoint
15801 The tracepoint for the current trace snapshot.
15803 @vindex $trace_line
15804 @item (int) $trace_line
15805 The line number for the current trace snapshot.
15807 @vindex $trace_file
15808 @item (char []) $trace_file
15809 The source file for the current trace snapshot.
15811 @vindex $trace_func
15812 @item (char []) $trace_func
15813 The name of the function containing @code{$tracepoint}.
15816 Note: @code{$trace_file} is not suitable for use in @code{printf},
15817 use @code{output} instead.
15819 Here's a simple example of using these convenience variables for
15820 stepping through all the trace snapshots and printing some of their
15821 data. Note that these are not the same as trace state variables,
15822 which are managed by the target.
15825 (@value{GDBP}) @b{tfind start}
15827 (@value{GDBP}) @b{while $trace_frame != -1}
15828 > output $trace_file
15829 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15835 @section Using Trace Files
15836 @cindex trace files
15838 In some situations, the target running a trace experiment may no
15839 longer be available; perhaps it crashed, or the hardware was needed
15840 for a different activity. To handle these cases, you can arrange to
15841 dump the trace data into a file, and later use that file as a source
15842 of trace data, via the @code{target tfile} command.
15847 @item tsave [ -r ] @var{filename}
15848 @itemx tsave [-ctf] @var{dirname}
15849 Save the trace data to @var{filename}. By default, this command
15850 assumes that @var{filename} refers to the host filesystem, so if
15851 necessary @value{GDBN} will copy raw trace data up from the target and
15852 then save it. If the target supports it, you can also supply the
15853 optional argument @code{-r} (``remote'') to direct the target to save
15854 the data directly into @var{filename} in its own filesystem, which may be
15855 more efficient if the trace buffer is very large. (Note, however, that
15856 @code{target tfile} can only read from files accessible to the host.)
15857 By default, this command will save trace frame in tfile format.
15858 You can supply the optional argument @code{-ctf} to save data in CTF
15859 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15860 that can be shared by multiple debugging and tracing tools. Please go to
15861 @indicateurl{http://www.efficios.com/ctf} to get more information.
15863 @kindex target tfile
15867 @item target tfile @var{filename}
15868 @itemx target ctf @var{dirname}
15869 Use the file named @var{filename} or directory named @var{dirname} as
15870 a source of trace data. Commands that examine data work as they do with
15871 a live target, but it is not possible to run any new trace experiments.
15872 @code{tstatus} will report the state of the trace run at the moment
15873 the data was saved, as well as the current trace frame you are examining.
15874 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15878 (@value{GDBP}) target ctf ctf.ctf
15879 (@value{GDBP}) tfind
15880 Found trace frame 0, tracepoint 2
15881 39 ++a; /* set tracepoint 1 here */
15882 (@value{GDBP}) tdump
15883 Data collected at tracepoint 2, trace frame 0:
15887 c = @{"123", "456", "789", "123", "456", "789"@}
15888 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15896 @chapter Debugging Programs That Use Overlays
15899 If your program is too large to fit completely in your target system's
15900 memory, you can sometimes use @dfn{overlays} to work around this
15901 problem. @value{GDBN} provides some support for debugging programs that
15905 * How Overlays Work:: A general explanation of overlays.
15906 * Overlay Commands:: Managing overlays in @value{GDBN}.
15907 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15908 mapped by asking the inferior.
15909 * Overlay Sample Program:: A sample program using overlays.
15912 @node How Overlays Work
15913 @section How Overlays Work
15914 @cindex mapped overlays
15915 @cindex unmapped overlays
15916 @cindex load address, overlay's
15917 @cindex mapped address
15918 @cindex overlay area
15920 Suppose you have a computer whose instruction address space is only 64
15921 kilobytes long, but which has much more memory which can be accessed by
15922 other means: special instructions, segment registers, or memory
15923 management hardware, for example. Suppose further that you want to
15924 adapt a program which is larger than 64 kilobytes to run on this system.
15926 One solution is to identify modules of your program which are relatively
15927 independent, and need not call each other directly; call these modules
15928 @dfn{overlays}. Separate the overlays from the main program, and place
15929 their machine code in the larger memory. Place your main program in
15930 instruction memory, but leave at least enough space there to hold the
15931 largest overlay as well.
15933 Now, to call a function located in an overlay, you must first copy that
15934 overlay's machine code from the large memory into the space set aside
15935 for it in the instruction memory, and then jump to its entry point
15938 @c NB: In the below the mapped area's size is greater or equal to the
15939 @c size of all overlays. This is intentional to remind the developer
15940 @c that overlays don't necessarily need to be the same size.
15944 Data Instruction Larger
15945 Address Space Address Space Address Space
15946 +-----------+ +-----------+ +-----------+
15948 +-----------+ +-----------+ +-----------+<-- overlay 1
15949 | program | | main | .----| overlay 1 | load address
15950 | variables | | program | | +-----------+
15951 | and heap | | | | | |
15952 +-----------+ | | | +-----------+<-- overlay 2
15953 | | +-----------+ | | | load address
15954 +-----------+ | | | .-| overlay 2 |
15956 mapped --->+-----------+ | | +-----------+
15957 address | | | | | |
15958 | overlay | <-' | | |
15959 | area | <---' +-----------+<-- overlay 3
15960 | | <---. | | load address
15961 +-----------+ `--| overlay 3 |
15968 @anchor{A code overlay}A code overlay
15972 The diagram (@pxref{A code overlay}) shows a system with separate data
15973 and instruction address spaces. To map an overlay, the program copies
15974 its code from the larger address space to the instruction address space.
15975 Since the overlays shown here all use the same mapped address, only one
15976 may be mapped at a time. For a system with a single address space for
15977 data and instructions, the diagram would be similar, except that the
15978 program variables and heap would share an address space with the main
15979 program and the overlay area.
15981 An overlay loaded into instruction memory and ready for use is called a
15982 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15983 instruction memory. An overlay not present (or only partially present)
15984 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15985 is its address in the larger memory. The mapped address is also called
15986 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15987 called the @dfn{load memory address}, or @dfn{LMA}.
15989 Unfortunately, overlays are not a completely transparent way to adapt a
15990 program to limited instruction memory. They introduce a new set of
15991 global constraints you must keep in mind as you design your program:
15996 Before calling or returning to a function in an overlay, your program
15997 must make sure that overlay is actually mapped. Otherwise, the call or
15998 return will transfer control to the right address, but in the wrong
15999 overlay, and your program will probably crash.
16002 If the process of mapping an overlay is expensive on your system, you
16003 will need to choose your overlays carefully to minimize their effect on
16004 your program's performance.
16007 The executable file you load onto your system must contain each
16008 overlay's instructions, appearing at the overlay's load address, not its
16009 mapped address. However, each overlay's instructions must be relocated
16010 and its symbols defined as if the overlay were at its mapped address.
16011 You can use GNU linker scripts to specify different load and relocation
16012 addresses for pieces of your program; see @ref{Overlay Description,,,
16013 ld.info, Using ld: the GNU linker}.
16016 The procedure for loading executable files onto your system must be able
16017 to load their contents into the larger address space as well as the
16018 instruction and data spaces.
16022 The overlay system described above is rather simple, and could be
16023 improved in many ways:
16028 If your system has suitable bank switch registers or memory management
16029 hardware, you could use those facilities to make an overlay's load area
16030 contents simply appear at their mapped address in instruction space.
16031 This would probably be faster than copying the overlay to its mapped
16032 area in the usual way.
16035 If your overlays are small enough, you could set aside more than one
16036 overlay area, and have more than one overlay mapped at a time.
16039 You can use overlays to manage data, as well as instructions. In
16040 general, data overlays are even less transparent to your design than
16041 code overlays: whereas code overlays only require care when you call or
16042 return to functions, data overlays require care every time you access
16043 the data. Also, if you change the contents of a data overlay, you
16044 must copy its contents back out to its load address before you can copy a
16045 different data overlay into the same mapped area.
16050 @node Overlay Commands
16051 @section Overlay Commands
16053 To use @value{GDBN}'s overlay support, each overlay in your program must
16054 correspond to a separate section of the executable file. The section's
16055 virtual memory address and load memory address must be the overlay's
16056 mapped and load addresses. Identifying overlays with sections allows
16057 @value{GDBN} to determine the appropriate address of a function or
16058 variable, depending on whether the overlay is mapped or not.
16060 @value{GDBN}'s overlay commands all start with the word @code{overlay};
16061 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
16066 Disable @value{GDBN}'s overlay support. When overlay support is
16067 disabled, @value{GDBN} assumes that all functions and variables are
16068 always present at their mapped addresses. By default, @value{GDBN}'s
16069 overlay support is disabled.
16071 @item overlay manual
16072 @cindex manual overlay debugging
16073 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
16074 relies on you to tell it which overlays are mapped, and which are not,
16075 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
16076 commands described below.
16078 @item overlay map-overlay @var{overlay}
16079 @itemx overlay map @var{overlay}
16080 @cindex map an overlay
16081 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
16082 be the name of the object file section containing the overlay. When an
16083 overlay is mapped, @value{GDBN} assumes it can find the overlay's
16084 functions and variables at their mapped addresses. @value{GDBN} assumes
16085 that any other overlays whose mapped ranges overlap that of
16086 @var{overlay} are now unmapped.
16088 @item overlay unmap-overlay @var{overlay}
16089 @itemx overlay unmap @var{overlay}
16090 @cindex unmap an overlay
16091 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
16092 must be the name of the object file section containing the overlay.
16093 When an overlay is unmapped, @value{GDBN} assumes it can find the
16094 overlay's functions and variables at their load addresses.
16097 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
16098 consults a data structure the overlay manager maintains in the inferior
16099 to see which overlays are mapped. For details, see @ref{Automatic
16100 Overlay Debugging}.
16102 @item overlay load-target
16103 @itemx overlay load
16104 @cindex reloading the overlay table
16105 Re-read the overlay table from the inferior. Normally, @value{GDBN}
16106 re-reads the table @value{GDBN} automatically each time the inferior
16107 stops, so this command should only be necessary if you have changed the
16108 overlay mapping yourself using @value{GDBN}. This command is only
16109 useful when using automatic overlay debugging.
16111 @item overlay list-overlays
16112 @itemx overlay list
16113 @cindex listing mapped overlays
16114 Display a list of the overlays currently mapped, along with their mapped
16115 addresses, load addresses, and sizes.
16119 Normally, when @value{GDBN} prints a code address, it includes the name
16120 of the function the address falls in:
16123 (@value{GDBP}) print main
16124 $3 = @{int ()@} 0x11a0 <main>
16127 When overlay debugging is enabled, @value{GDBN} recognizes code in
16128 unmapped overlays, and prints the names of unmapped functions with
16129 asterisks around them. For example, if @code{foo} is a function in an
16130 unmapped overlay, @value{GDBN} prints it this way:
16133 (@value{GDBP}) overlay list
16134 No sections are mapped.
16135 (@value{GDBP}) print foo
16136 $5 = @{int (int)@} 0x100000 <*foo*>
16139 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
16143 (@value{GDBP}) overlay list
16144 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
16145 mapped at 0x1016 - 0x104a
16146 (@value{GDBP}) print foo
16147 $6 = @{int (int)@} 0x1016 <foo>
16150 When overlay debugging is enabled, @value{GDBN} can find the correct
16151 address for functions and variables in an overlay, whether or not the
16152 overlay is mapped. This allows most @value{GDBN} commands, like
16153 @code{break} and @code{disassemble}, to work normally, even on unmapped
16154 code. However, @value{GDBN}'s breakpoint support has some limitations:
16158 @cindex breakpoints in overlays
16159 @cindex overlays, setting breakpoints in
16160 You can set breakpoints in functions in unmapped overlays, as long as
16161 @value{GDBN} can write to the overlay at its load address.
16163 @value{GDBN} can not set hardware or simulator-based breakpoints in
16164 unmapped overlays. However, if you set a breakpoint at the end of your
16165 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
16166 you are using manual overlay management), @value{GDBN} will re-set its
16167 breakpoints properly.
16171 @node Automatic Overlay Debugging
16172 @section Automatic Overlay Debugging
16173 @cindex automatic overlay debugging
16175 @value{GDBN} can automatically track which overlays are mapped and which
16176 are not, given some simple co-operation from the overlay manager in the
16177 inferior. If you enable automatic overlay debugging with the
16178 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
16179 looks in the inferior's memory for certain variables describing the
16180 current state of the overlays.
16182 Here are the variables your overlay manager must define to support
16183 @value{GDBN}'s automatic overlay debugging:
16187 @item @code{_ovly_table}:
16188 This variable must be an array of the following structures:
16193 /* The overlay's mapped address. */
16196 /* The size of the overlay, in bytes. */
16197 unsigned long size;
16199 /* The overlay's load address. */
16202 /* Non-zero if the overlay is currently mapped;
16204 unsigned long mapped;
16208 @item @code{_novlys}:
16209 This variable must be a four-byte signed integer, holding the total
16210 number of elements in @code{_ovly_table}.
16214 To decide whether a particular overlay is mapped or not, @value{GDBN}
16215 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
16216 @code{lma} members equal the VMA and LMA of the overlay's section in the
16217 executable file. When @value{GDBN} finds a matching entry, it consults
16218 the entry's @code{mapped} member to determine whether the overlay is
16221 In addition, your overlay manager may define a function called
16222 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
16223 will silently set a breakpoint there. If the overlay manager then
16224 calls this function whenever it has changed the overlay table, this
16225 will enable @value{GDBN} to accurately keep track of which overlays
16226 are in program memory, and update any breakpoints that may be set
16227 in overlays. This will allow breakpoints to work even if the
16228 overlays are kept in ROM or other non-writable memory while they
16229 are not being executed.
16231 @node Overlay Sample Program
16232 @section Overlay Sample Program
16233 @cindex overlay example program
16235 When linking a program which uses overlays, you must place the overlays
16236 at their load addresses, while relocating them to run at their mapped
16237 addresses. To do this, you must write a linker script (@pxref{Overlay
16238 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
16239 since linker scripts are specific to a particular host system, target
16240 architecture, and target memory layout, this manual cannot provide
16241 portable sample code demonstrating @value{GDBN}'s overlay support.
16243 However, the @value{GDBN} source distribution does contain an overlaid
16244 program, with linker scripts for a few systems, as part of its test
16245 suite. The program consists of the following files from
16246 @file{gdb/testsuite/gdb.base}:
16250 The main program file.
16252 A simple overlay manager, used by @file{overlays.c}.
16257 Overlay modules, loaded and used by @file{overlays.c}.
16260 Linker scripts for linking the test program on the @code{d10v-elf}
16261 and @code{m32r-elf} targets.
16264 You can build the test program using the @code{d10v-elf} GCC
16265 cross-compiler like this:
16268 $ d10v-elf-gcc -g -c overlays.c
16269 $ d10v-elf-gcc -g -c ovlymgr.c
16270 $ d10v-elf-gcc -g -c foo.c
16271 $ d10v-elf-gcc -g -c bar.c
16272 $ d10v-elf-gcc -g -c baz.c
16273 $ d10v-elf-gcc -g -c grbx.c
16274 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
16275 baz.o grbx.o -Wl,-Td10v.ld -o overlays
16278 The build process is identical for any other architecture, except that
16279 you must substitute the appropriate compiler and linker script for the
16280 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
16284 @chapter Using @value{GDBN} with Different Languages
16287 Although programming languages generally have common aspects, they are
16288 rarely expressed in the same manner. For instance, in ANSI C,
16289 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
16290 Modula-2, it is accomplished by @code{p^}. Values can also be
16291 represented (and displayed) differently. Hex numbers in C appear as
16292 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
16294 @cindex working language
16295 Language-specific information is built into @value{GDBN} for some languages,
16296 allowing you to express operations like the above in your program's
16297 native language, and allowing @value{GDBN} to output values in a manner
16298 consistent with the syntax of your program's native language. The
16299 language you use to build expressions is called the @dfn{working
16303 * Setting:: Switching between source languages
16304 * Show:: Displaying the language
16305 * Checks:: Type and range checks
16306 * Supported Languages:: Supported languages
16307 * Unsupported Languages:: Unsupported languages
16311 @section Switching Between Source Languages
16313 There are two ways to control the working language---either have @value{GDBN}
16314 set it automatically, or select it manually yourself. You can use the
16315 @code{set language} command for either purpose. On startup, @value{GDBN}
16316 defaults to setting the language automatically. The working language is
16317 used to determine how expressions you type are interpreted, how values
16320 In addition to the working language, every source file that
16321 @value{GDBN} knows about has its own working language. For some object
16322 file formats, the compiler might indicate which language a particular
16323 source file is in. However, most of the time @value{GDBN} infers the
16324 language from the name of the file. The language of a source file
16325 controls whether C@t{++} names are demangled---this way @code{backtrace} can
16326 show each frame appropriately for its own language. There is no way to
16327 set the language of a source file from within @value{GDBN}, but you can
16328 set the language associated with a filename extension. @xref{Show, ,
16329 Displaying the Language}.
16331 This is most commonly a problem when you use a program, such
16332 as @code{cfront} or @code{f2c}, that generates C but is written in
16333 another language. In that case, make the
16334 program use @code{#line} directives in its C output; that way
16335 @value{GDBN} will know the correct language of the source code of the original
16336 program, and will display that source code, not the generated C code.
16339 * Filenames:: Filename extensions and languages.
16340 * Manually:: Setting the working language manually
16341 * Automatically:: Having @value{GDBN} infer the source language
16345 @subsection List of Filename Extensions and Languages
16347 If a source file name ends in one of the following extensions, then
16348 @value{GDBN} infers that its language is the one indicated.
16366 C@t{++} source file
16372 Objective-C source file
16376 Fortran source file
16379 Modula-2 source file
16383 Assembler source file. This actually behaves almost like C, but
16384 @value{GDBN} does not skip over function prologues when stepping.
16387 In addition, you may set the language associated with a filename
16388 extension. @xref{Show, , Displaying the Language}.
16391 @subsection Setting the Working Language
16393 If you allow @value{GDBN} to set the language automatically,
16394 expressions are interpreted the same way in your debugging session and
16397 @kindex set language
16398 If you wish, you may set the language manually. To do this, issue the
16399 command @samp{set language @var{lang}}, where @var{lang} is the name of
16400 a language, such as
16401 @code{c} or @code{modula-2}.
16402 For a list of the supported languages, type @samp{set language}.
16404 Setting the language manually prevents @value{GDBN} from updating the working
16405 language automatically. This can lead to confusion if you try
16406 to debug a program when the working language is not the same as the
16407 source language, when an expression is acceptable to both
16408 languages---but means different things. For instance, if the current
16409 source file were written in C, and @value{GDBN} was parsing Modula-2, a
16417 might not have the effect you intended. In C, this means to add
16418 @code{b} and @code{c} and place the result in @code{a}. The result
16419 printed would be the value of @code{a}. In Modula-2, this means to compare
16420 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
16422 @node Automatically
16423 @subsection Having @value{GDBN} Infer the Source Language
16425 To have @value{GDBN} set the working language automatically, use
16426 @samp{set language local} or @samp{set language auto}. @value{GDBN}
16427 then infers the working language. That is, when your program stops in a
16428 frame (usually by encountering a breakpoint), @value{GDBN} sets the
16429 working language to the language recorded for the function in that
16430 frame. If the language for a frame is unknown (that is, if the function
16431 or block corresponding to the frame was defined in a source file that
16432 does not have a recognized extension), the current working language is
16433 not changed, and @value{GDBN} issues a warning.
16435 This may not seem necessary for most programs, which are written
16436 entirely in one source language. However, program modules and libraries
16437 written in one source language can be used by a main program written in
16438 a different source language. Using @samp{set language auto} in this
16439 case frees you from having to set the working language manually.
16442 @section Displaying the Language
16444 The following commands help you find out which language is the
16445 working language, and also what language source files were written in.
16448 @item show language
16449 @anchor{show language}
16450 @kindex show language
16451 Display the current working language. This is the
16452 language you can use with commands such as @code{print} to
16453 build and compute expressions that may involve variables in your program.
16456 @kindex info frame@r{, show the source language}
16457 Display the source language for this frame. This language becomes the
16458 working language if you use an identifier from this frame.
16459 @xref{Frame Info, ,Information about a Frame}, to identify the other
16460 information listed here.
16463 @kindex info source@r{, show the source language}
16464 Display the source language of this source file.
16465 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
16466 information listed here.
16469 In unusual circumstances, you may have source files with extensions
16470 not in the standard list. You can then set the extension associated
16471 with a language explicitly:
16474 @item set extension-language @var{ext} @var{language}
16475 @kindex set extension-language
16476 Tell @value{GDBN} that source files with extension @var{ext} are to be
16477 assumed as written in the source language @var{language}.
16479 @item info extensions
16480 @kindex info extensions
16481 List all the filename extensions and the associated languages.
16485 @section Type and Range Checking
16487 Some languages are designed to guard you against making seemingly common
16488 errors through a series of compile- and run-time checks. These include
16489 checking the type of arguments to functions and operators and making
16490 sure mathematical overflows are caught at run time. Checks such as
16491 these help to ensure a program's correctness once it has been compiled
16492 by eliminating type mismatches and providing active checks for range
16493 errors when your program is running.
16495 By default @value{GDBN} checks for these errors according to the
16496 rules of the current source language. Although @value{GDBN} does not check
16497 the statements in your program, it can check expressions entered directly
16498 into @value{GDBN} for evaluation via the @code{print} command, for example.
16501 * Type Checking:: An overview of type checking
16502 * Range Checking:: An overview of range checking
16505 @cindex type checking
16506 @cindex checks, type
16507 @node Type Checking
16508 @subsection An Overview of Type Checking
16510 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
16511 arguments to operators and functions have to be of the correct type,
16512 otherwise an error occurs. These checks prevent type mismatch
16513 errors from ever causing any run-time problems. For example,
16516 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
16518 (@value{GDBP}) print obj.my_method (0)
16521 (@value{GDBP}) print obj.my_method (0x1234)
16522 Cannot resolve method klass::my_method to any overloaded instance
16525 The second example fails because in C@t{++} the integer constant
16526 @samp{0x1234} is not type-compatible with the pointer parameter type.
16528 For the expressions you use in @value{GDBN} commands, you can tell
16529 @value{GDBN} to not enforce strict type checking or
16530 to treat any mismatches as errors and abandon the expression;
16531 When type checking is disabled, @value{GDBN} successfully evaluates
16532 expressions like the second example above.
16534 Even if type checking is off, there may be other reasons
16535 related to type that prevent @value{GDBN} from evaluating an expression.
16536 For instance, @value{GDBN} does not know how to add an @code{int} and
16537 a @code{struct foo}. These particular type errors have nothing to do
16538 with the language in use and usually arise from expressions which make
16539 little sense to evaluate anyway.
16541 @value{GDBN} provides some additional commands for controlling type checking:
16543 @kindex set check type
16544 @kindex show check type
16546 @item set check type on
16547 @itemx set check type off
16548 Set strict type checking on or off. If any type mismatches occur in
16549 evaluating an expression while type checking is on, @value{GDBN} prints a
16550 message and aborts evaluation of the expression.
16552 @item show check type
16553 Show the current setting of type checking and whether @value{GDBN}
16554 is enforcing strict type checking rules.
16557 @cindex range checking
16558 @cindex checks, range
16559 @node Range Checking
16560 @subsection An Overview of Range Checking
16562 In some languages (such as Modula-2), it is an error to exceed the
16563 bounds of a type; this is enforced with run-time checks. Such range
16564 checking is meant to ensure program correctness by making sure
16565 computations do not overflow, or indices on an array element access do
16566 not exceed the bounds of the array.
16568 For expressions you use in @value{GDBN} commands, you can tell
16569 @value{GDBN} to treat range errors in one of three ways: ignore them,
16570 always treat them as errors and abandon the expression, or issue
16571 warnings but evaluate the expression anyway.
16573 A range error can result from numerical overflow, from exceeding an
16574 array index bound, or when you type a constant that is not a member
16575 of any type. Some languages, however, do not treat overflows as an
16576 error. In many implementations of C, mathematical overflow causes the
16577 result to ``wrap around'' to lower values---for example, if @var{m} is
16578 the largest integer value, and @var{s} is the smallest, then
16581 @var{m} + 1 @result{} @var{s}
16584 This, too, is specific to individual languages, and in some cases
16585 specific to individual compilers or machines. @xref{Supported Languages, ,
16586 Supported Languages}, for further details on specific languages.
16588 @value{GDBN} provides some additional commands for controlling the range checker:
16590 @kindex set check range
16591 @kindex show check range
16593 @item set check range auto
16594 Set range checking on or off based on the current working language.
16595 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16598 @item set check range on
16599 @itemx set check range off
16600 Set range checking on or off, overriding the default setting for the
16601 current working language. A warning is issued if the setting does not
16602 match the language default. If a range error occurs and range checking is on,
16603 then a message is printed and evaluation of the expression is aborted.
16605 @item set check range warn
16606 Output messages when the @value{GDBN} range checker detects a range error,
16607 but attempt to evaluate the expression anyway. Evaluating the
16608 expression may still be impossible for other reasons, such as accessing
16609 memory that the process does not own (a typical example from many Unix
16612 @item show check range
16613 Show the current setting of the range checker, and whether or not it is
16614 being set automatically by @value{GDBN}.
16617 @node Supported Languages
16618 @section Supported Languages
16620 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16621 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16622 @c This is false ...
16623 Some @value{GDBN} features may be used in expressions regardless of the
16624 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16625 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16626 ,Expressions}) can be used with the constructs of any supported
16629 The following sections detail to what degree each source language is
16630 supported by @value{GDBN}. These sections are not meant to be language
16631 tutorials or references, but serve only as a reference guide to what the
16632 @value{GDBN} expression parser accepts, and what input and output
16633 formats should look like for different languages. There are many good
16634 books written on each of these languages; please look to these for a
16635 language reference or tutorial.
16638 * C:: C and C@t{++}
16641 * Objective-C:: Objective-C
16642 * OpenCL C:: OpenCL C
16643 * Fortran:: Fortran
16646 * Modula-2:: Modula-2
16651 @subsection C and C@t{++}
16653 @cindex C and C@t{++}
16654 @cindex expressions in C or C@t{++}
16656 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16657 to both languages. Whenever this is the case, we discuss those languages
16661 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16662 @cindex @sc{gnu} C@t{++}
16663 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16664 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16665 effectively, you must compile your C@t{++} programs with a supported
16666 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16667 compiler (@code{aCC}).
16670 * C Operators:: C and C@t{++} operators
16671 * C Constants:: C and C@t{++} constants
16672 * C Plus Plus Expressions:: C@t{++} expressions
16673 * C Defaults:: Default settings for C and C@t{++}
16674 * C Checks:: C and C@t{++} type and range checks
16675 * Debugging C:: @value{GDBN} and C
16676 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16677 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16681 @subsubsection C and C@t{++} Operators
16683 @cindex C and C@t{++} operators
16685 Operators must be defined on values of specific types. For instance,
16686 @code{+} is defined on numbers, but not on structures. Operators are
16687 often defined on groups of types.
16689 For the purposes of C and C@t{++}, the following definitions hold:
16694 @emph{Integral types} include @code{int} with any of its storage-class
16695 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16698 @emph{Floating-point types} include @code{float}, @code{double}, and
16699 @code{long double} (if supported by the target platform).
16702 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16705 @emph{Scalar types} include all of the above.
16710 The following operators are supported. They are listed here
16711 in order of increasing precedence:
16715 The comma or sequencing operator. Expressions in a comma-separated list
16716 are evaluated from left to right, with the result of the entire
16717 expression being the last expression evaluated.
16720 Assignment. The value of an assignment expression is the value
16721 assigned. Defined on scalar types.
16724 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16725 and translated to @w{@code{@var{a} = @var{a op b}}}.
16726 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16727 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16728 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16731 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16732 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16733 should be of an integral type.
16736 Logical @sc{or}. Defined on integral types.
16739 Logical @sc{and}. Defined on integral types.
16742 Bitwise @sc{or}. Defined on integral types.
16745 Bitwise exclusive-@sc{or}. Defined on integral types.
16748 Bitwise @sc{and}. Defined on integral types.
16751 Equality and inequality. Defined on scalar types. The value of these
16752 expressions is 0 for false and non-zero for true.
16754 @item <@r{, }>@r{, }<=@r{, }>=
16755 Less than, greater than, less than or equal, greater than or equal.
16756 Defined on scalar types. The value of these expressions is 0 for false
16757 and non-zero for true.
16760 left shift, and right shift. Defined on integral types.
16763 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16766 Addition and subtraction. Defined on integral types, floating-point types and
16769 @item *@r{, }/@r{, }%
16770 Multiplication, division, and modulus. Multiplication and division are
16771 defined on integral and floating-point types. Modulus is defined on
16775 Increment and decrement. When appearing before a variable, the
16776 operation is performed before the variable is used in an expression;
16777 when appearing after it, the variable's value is used before the
16778 operation takes place.
16781 Pointer dereferencing. Defined on pointer types. Same precedence as
16785 Address operator. Defined on variables. Same precedence as @code{++}.
16787 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16788 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16789 to examine the address
16790 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16794 Negative. Defined on integral and floating-point types. Same
16795 precedence as @code{++}.
16798 Logical negation. Defined on integral types. Same precedence as
16802 Bitwise complement operator. Defined on integral types. Same precedence as
16807 Structure member, and pointer-to-structure member. For convenience,
16808 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16809 pointer based on the stored type information.
16810 Defined on @code{struct} and @code{union} data.
16813 Dereferences of pointers to members.
16816 Array indexing. @code{@var{a}[@var{i}]} is defined as
16817 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16820 Function parameter list. Same precedence as @code{->}.
16823 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16824 and @code{class} types.
16827 Doubled colons also represent the @value{GDBN} scope operator
16828 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16832 If an operator is redefined in the user code, @value{GDBN} usually
16833 attempts to invoke the redefined version instead of using the operator's
16834 predefined meaning.
16837 @subsubsection C and C@t{++} Constants
16839 @cindex C and C@t{++} constants
16841 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16846 Integer constants are a sequence of digits. Octal constants are
16847 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16848 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16849 @samp{l}, specifying that the constant should be treated as a
16853 Floating point constants are a sequence of digits, followed by a decimal
16854 point, followed by a sequence of digits, and optionally followed by an
16855 exponent. An exponent is of the form:
16856 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16857 sequence of digits. The @samp{+} is optional for positive exponents.
16858 A floating-point constant may also end with a letter @samp{f} or
16859 @samp{F}, specifying that the constant should be treated as being of
16860 the @code{float} (as opposed to the default @code{double}) type; or with
16861 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16865 Enumerated constants consist of enumerated identifiers, or their
16866 integral equivalents.
16869 Character constants are a single character surrounded by single quotes
16870 (@code{'}), or a number---the ordinal value of the corresponding character
16871 (usually its @sc{ascii} value). Within quotes, the single character may
16872 be represented by a letter or by @dfn{escape sequences}, which are of
16873 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16874 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16875 @samp{@var{x}} is a predefined special character---for example,
16876 @samp{\n} for newline.
16878 Wide character constants can be written by prefixing a character
16879 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16880 form of @samp{x}. The target wide character set is used when
16881 computing the value of this constant (@pxref{Character Sets}).
16884 String constants are a sequence of character constants surrounded by
16885 double quotes (@code{"}). Any valid character constant (as described
16886 above) may appear. Double quotes within the string must be preceded by
16887 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16890 Wide string constants can be written by prefixing a string constant
16891 with @samp{L}, as in C. The target wide character set is used when
16892 computing the value of this constant (@pxref{Character Sets}).
16895 Pointer constants are an integral value. You can also write pointers
16896 to constants using the C operator @samp{&}.
16899 Array constants are comma-separated lists surrounded by braces @samp{@{}
16900 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16901 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16902 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16905 @node C Plus Plus Expressions
16906 @subsubsection C@t{++} Expressions
16908 @cindex expressions in C@t{++}
16909 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16911 @cindex debugging C@t{++} programs
16912 @cindex C@t{++} compilers
16913 @cindex debug formats and C@t{++}
16914 @cindex @value{NGCC} and C@t{++}
16916 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16917 the proper compiler and the proper debug format. Currently,
16918 @value{GDBN} works best when debugging C@t{++} code that is compiled
16919 with the most recent version of @value{NGCC} possible. The DWARF
16920 debugging format is preferred; @value{NGCC} defaults to this on most
16921 popular platforms. Other compilers and/or debug formats are likely to
16922 work badly or not at all when using @value{GDBN} to debug C@t{++}
16923 code. @xref{Compilation}.
16928 @cindex member functions
16930 Member function calls are allowed; you can use expressions like
16933 count = aml->GetOriginal(x, y)
16936 @vindex this@r{, inside C@t{++} member functions}
16937 @cindex namespace in C@t{++}
16939 While a member function is active (in the selected stack frame), your
16940 expressions have the same namespace available as the member function;
16941 that is, @value{GDBN} allows implicit references to the class instance
16942 pointer @code{this} following the same rules as C@t{++}. @code{using}
16943 declarations in the current scope are also respected by @value{GDBN}.
16945 @cindex call overloaded functions
16946 @cindex overloaded functions, calling
16947 @cindex type conversions in C@t{++}
16949 You can call overloaded functions; @value{GDBN} resolves the function
16950 call to the right definition, with some restrictions. @value{GDBN} does not
16951 perform overload resolution involving user-defined type conversions,
16952 calls to constructors, or instantiations of templates that do not exist
16953 in the program. It also cannot handle ellipsis argument lists or
16956 It does perform integral conversions and promotions, floating-point
16957 promotions, arithmetic conversions, pointer conversions, conversions of
16958 class objects to base classes, and standard conversions such as those of
16959 functions or arrays to pointers; it requires an exact match on the
16960 number of function arguments.
16962 Overload resolution is always performed, unless you have specified
16963 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16964 ,@value{GDBN} Features for C@t{++}}.
16966 You must specify @code{set overload-resolution off} in order to use an
16967 explicit function signature to call an overloaded function, as in
16969 p 'foo(char,int)'('x', 13)
16972 The @value{GDBN} command-completion facility can simplify this;
16973 see @ref{Completion, ,Command Completion}.
16975 @cindex reference declarations
16977 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16978 references; you can use them in expressions just as you do in C@t{++}
16979 source---they are automatically dereferenced.
16981 In the parameter list shown when @value{GDBN} displays a frame, the values of
16982 reference variables are not displayed (unlike other variables); this
16983 avoids clutter, since references are often used for large structures.
16984 The @emph{address} of a reference variable is always shown, unless
16985 you have specified @samp{set print address off}.
16988 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16989 expressions can use it just as expressions in your program do. Since
16990 one scope may be defined in another, you can use @code{::} repeatedly if
16991 necessary, for example in an expression like
16992 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16993 resolving name scope by reference to source files, in both C and C@t{++}
16994 debugging (@pxref{Variables, ,Program Variables}).
16997 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
17002 @subsubsection C and C@t{++} Defaults
17004 @cindex C and C@t{++} defaults
17006 If you allow @value{GDBN} to set range checking automatically, it
17007 defaults to @code{off} whenever the working language changes to
17008 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
17009 selects the working language.
17011 If you allow @value{GDBN} to set the language automatically, it
17012 recognizes source files whose names end with @file{.c}, @file{.C}, or
17013 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
17014 these files, it sets the working language to C or C@t{++}.
17015 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
17016 for further details.
17019 @subsubsection C and C@t{++} Type and Range Checks
17021 @cindex C and C@t{++} checks
17023 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
17024 checking is used. However, if you turn type checking off, @value{GDBN}
17025 will allow certain non-standard conversions, such as promoting integer
17026 constants to pointers.
17028 Range checking, if turned on, is done on mathematical operations. Array
17029 indices are not checked, since they are often used to index a pointer
17030 that is not itself an array.
17033 @subsubsection @value{GDBN} and C
17035 The @code{set print union} and @code{show print union} commands apply to
17036 the @code{union} type. When set to @samp{on}, any @code{union} that is
17037 inside a @code{struct} or @code{class} is also printed. Otherwise, it
17038 appears as @samp{@{...@}}.
17040 The @code{@@} operator aids in the debugging of dynamic arrays, formed
17041 with pointers and a memory allocation function. @xref{Expressions,
17044 @node Debugging C Plus Plus
17045 @subsubsection @value{GDBN} Features for C@t{++}
17047 @cindex commands for C@t{++}
17049 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
17050 designed specifically for use with C@t{++}. Here is a summary:
17053 @cindex break in overloaded functions
17054 @item @r{breakpoint menus}
17055 When you want a breakpoint in a function whose name is overloaded,
17056 @value{GDBN} has the capability to display a menu of possible breakpoint
17057 locations to help you specify which function definition you want.
17058 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
17060 @cindex overloading in C@t{++}
17061 @item rbreak @var{regex}
17062 Setting breakpoints using regular expressions is helpful for setting
17063 breakpoints on overloaded functions that are not members of any special
17065 @xref{Set Breaks, ,Setting Breakpoints}.
17067 @cindex C@t{++} exception handling
17069 @itemx catch rethrow
17071 Debug C@t{++} exception handling using these commands. @xref{Set
17072 Catchpoints, , Setting Catchpoints}.
17074 @cindex inheritance
17075 @item ptype @var{typename}
17076 Print inheritance relationships as well as other information for type
17078 @xref{Symbols, ,Examining the Symbol Table}.
17080 @item info vtbl @var{expression}.
17081 The @code{info vtbl} command can be used to display the virtual
17082 method tables of the object computed by @var{expression}. This shows
17083 one entry per virtual table; there may be multiple virtual tables when
17084 multiple inheritance is in use.
17086 @cindex C@t{++} demangling
17087 @item demangle @var{name}
17088 Demangle @var{name}.
17089 @xref{Symbols}, for a more complete description of the @code{demangle} command.
17091 @cindex C@t{++} symbol display
17092 @item set print demangle
17093 @itemx show print demangle
17094 @itemx set print asm-demangle
17095 @itemx show print asm-demangle
17096 Control whether C@t{++} symbols display in their source form, both when
17097 displaying code as C@t{++} source and when displaying disassemblies.
17098 @xref{Print Settings, ,Print Settings}.
17100 @item set print object
17101 @itemx show print object
17102 Choose whether to print derived (actual) or declared types of objects.
17103 @xref{Print Settings, ,Print Settings}.
17105 @item set print vtbl
17106 @itemx show print vtbl
17107 Control the format for printing virtual function tables.
17108 @xref{Print Settings, ,Print Settings}.
17109 (The @code{vtbl} commands do not work on programs compiled with the HP
17110 ANSI C@t{++} compiler (@code{aCC}).)
17112 @kindex set overload-resolution
17113 @cindex overloaded functions, overload resolution
17114 @item set overload-resolution on
17115 Enable overload resolution for C@t{++} expression evaluation. The default
17116 is on. For overloaded functions, @value{GDBN} evaluates the arguments
17117 and searches for a function whose signature matches the argument types,
17118 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
17119 Expressions, ,C@t{++} Expressions}, for details).
17120 If it cannot find a match, it emits a message.
17122 @item set overload-resolution off
17123 Disable overload resolution for C@t{++} expression evaluation. For
17124 overloaded functions that are not class member functions, @value{GDBN}
17125 chooses the first function of the specified name that it finds in the
17126 symbol table, whether or not its arguments are of the correct type. For
17127 overloaded functions that are class member functions, @value{GDBN}
17128 searches for a function whose signature @emph{exactly} matches the
17131 @kindex show overload-resolution
17132 @item show overload-resolution
17133 Show the current setting of overload resolution.
17135 @item @r{Overloaded symbol names}
17136 You can specify a particular definition of an overloaded symbol, using
17137 the same notation that is used to declare such symbols in C@t{++}: type
17138 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
17139 also use the @value{GDBN} command-line word completion facilities to list the
17140 available choices, or to finish the type list for you.
17141 @xref{Completion,, Command Completion}, for details on how to do this.
17143 @item @r{Breakpoints in template functions}
17145 Similar to how overloaded symbols are handled, @value{GDBN} will ignore
17146 template parameter lists when it encounters a symbol which includes a
17147 C@t{++} template. This permits setting breakpoints on families of template functions
17148 or functions whose parameters include template types.
17150 The @kbd{-qualified} flag may be used to override this behavior, causing
17151 @value{GDBN} to search for a specific function or type.
17153 The @value{GDBN} command-line word completion facility also understands
17154 template parameters and may be used to list available choices or finish
17155 template parameter lists for you. @xref{Completion,, Command Completion}, for
17156 details on how to do this.
17158 @item @r{Breakpoints in functions with ABI tags}
17160 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
17161 correspond to changes in the ABI of a type, function, or variable that
17162 would not otherwise be reflected in a mangled name. See
17163 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
17166 The ABI tags are visible in C@t{++} demangled names. For example, a
17167 function that returns a std::string:
17170 std::string function(int);
17174 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
17175 tag, and @value{GDBN} displays the symbol like this:
17178 function[abi:cxx11](int)
17181 You can set a breakpoint on such functions simply as if they had no
17185 (gdb) b function(int)
17186 Breakpoint 2 at 0x40060d: file main.cc, line 10.
17187 (gdb) info breakpoints
17188 Num Type Disp Enb Address What
17189 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
17193 On the rare occasion you need to disambiguate between different ABI
17194 tags, you can do so by simply including the ABI tag in the function
17198 (@value{GDBP}) b ambiguous[abi:other_tag](int)
17202 @node Decimal Floating Point
17203 @subsubsection Decimal Floating Point format
17204 @cindex decimal floating point format
17206 @value{GDBN} can examine, set and perform computations with numbers in
17207 decimal floating point format, which in the C language correspond to the
17208 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
17209 specified by the extension to support decimal floating-point arithmetic.
17211 There are two encodings in use, depending on the architecture: BID (Binary
17212 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
17213 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
17216 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
17217 to manipulate decimal floating point numbers, it is not possible to convert
17218 (using a cast, for example) integers wider than 32-bit to decimal float.
17220 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
17221 point computations, error checking in decimal float operations ignores
17222 underflow, overflow and divide by zero exceptions.
17224 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
17225 to inspect @code{_Decimal128} values stored in floating point registers.
17226 See @ref{PowerPC,,PowerPC} for more details.
17232 @value{GDBN} can be used to debug programs written in D and compiled with
17233 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
17234 specific feature --- dynamic arrays.
17239 @cindex Go (programming language)
17240 @value{GDBN} can be used to debug programs written in Go and compiled with
17241 @file{gccgo} or @file{6g} compilers.
17243 Here is a summary of the Go-specific features and restrictions:
17246 @cindex current Go package
17247 @item The current Go package
17248 The name of the current package does not need to be specified when
17249 specifying global variables and functions.
17251 For example, given the program:
17255 var myglob = "Shall we?"
17261 When stopped inside @code{main} either of these work:
17265 (gdb) p main.myglob
17268 @cindex builtin Go types
17269 @item Builtin Go types
17270 The @code{string} type is recognized by @value{GDBN} and is printed
17273 @cindex builtin Go functions
17274 @item Builtin Go functions
17275 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
17276 function and handles it internally.
17278 @cindex restrictions on Go expressions
17279 @item Restrictions on Go expressions
17280 All Go operators are supported except @code{&^}.
17281 The Go @code{_} ``blank identifier'' is not supported.
17282 Automatic dereferencing of pointers is not supported.
17286 @subsection Objective-C
17288 @cindex Objective-C
17289 This section provides information about some commands and command
17290 options that are useful for debugging Objective-C code. See also
17291 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
17292 few more commands specific to Objective-C support.
17295 * Method Names in Commands::
17296 * The Print Command with Objective-C::
17299 @node Method Names in Commands
17300 @subsubsection Method Names in Commands
17302 The following commands have been extended to accept Objective-C method
17303 names as line specifications:
17305 @kindex clear@r{, and Objective-C}
17306 @kindex break@r{, and Objective-C}
17307 @kindex info line@r{, and Objective-C}
17308 @kindex jump@r{, and Objective-C}
17309 @kindex list@r{, and Objective-C}
17313 @item @code{info line}
17318 A fully qualified Objective-C method name is specified as
17321 -[@var{Class} @var{methodName}]
17324 where the minus sign is used to indicate an instance method and a
17325 plus sign (not shown) is used to indicate a class method. The class
17326 name @var{Class} and method name @var{methodName} are enclosed in
17327 brackets, similar to the way messages are specified in Objective-C
17328 source code. For example, to set a breakpoint at the @code{create}
17329 instance method of class @code{Fruit} in the program currently being
17333 break -[Fruit create]
17336 To list ten program lines around the @code{initialize} class method,
17340 list +[NSText initialize]
17343 In the current version of @value{GDBN}, the plus or minus sign is
17344 required. In future versions of @value{GDBN}, the plus or minus
17345 sign will be optional, but you can use it to narrow the search. It
17346 is also possible to specify just a method name:
17352 You must specify the complete method name, including any colons. If
17353 your program's source files contain more than one @code{create} method,
17354 you'll be presented with a numbered list of classes that implement that
17355 method. Indicate your choice by number, or type @samp{0} to exit if
17358 As another example, to clear a breakpoint established at the
17359 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
17362 clear -[NSWindow makeKeyAndOrderFront:]
17365 @node The Print Command with Objective-C
17366 @subsubsection The Print Command With Objective-C
17367 @cindex Objective-C, print objects
17368 @kindex print-object
17369 @kindex po @r{(@code{print-object})}
17371 The print command has also been extended to accept methods. For example:
17374 print -[@var{object} hash]
17377 @cindex print an Objective-C object description
17378 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
17380 will tell @value{GDBN} to send the @code{hash} message to @var{object}
17381 and print the result. Also, an additional command has been added,
17382 @code{print-object} or @code{po} for short, which is meant to print
17383 the description of an object. However, this command may only work
17384 with certain Objective-C libraries that have a particular hook
17385 function, @code{_NSPrintForDebugger}, defined.
17388 @subsection OpenCL C
17391 This section provides information about @value{GDBN}s OpenCL C support.
17394 * OpenCL C Datatypes::
17395 * OpenCL C Expressions::
17396 * OpenCL C Operators::
17399 @node OpenCL C Datatypes
17400 @subsubsection OpenCL C Datatypes
17402 @cindex OpenCL C Datatypes
17403 @value{GDBN} supports the builtin scalar and vector datatypes specified
17404 by OpenCL 1.1. In addition the half- and double-precision floating point
17405 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
17406 extensions are also known to @value{GDBN}.
17408 @node OpenCL C Expressions
17409 @subsubsection OpenCL C Expressions
17411 @cindex OpenCL C Expressions
17412 @value{GDBN} supports accesses to vector components including the access as
17413 lvalue where possible. Since OpenCL C is based on C99 most C expressions
17414 supported by @value{GDBN} can be used as well.
17416 @node OpenCL C Operators
17417 @subsubsection OpenCL C Operators
17419 @cindex OpenCL C Operators
17420 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
17424 @subsection Fortran
17425 @cindex Fortran-specific support in @value{GDBN}
17427 @value{GDBN} can be used to debug programs written in Fortran. Note, that not
17428 all Fortran language features are available yet.
17430 @cindex trailing underscore, in Fortran symbols
17431 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
17432 among them) append an underscore to the names of variables and
17433 functions. When you debug programs compiled by those compilers, you
17434 will need to refer to variables and functions with a trailing
17437 @cindex Fortran Defaults
17438 Fortran symbols are usually case-insensitive, so @value{GDBN} by
17439 default uses case-insensitive matching for Fortran symbols. You can
17440 change that with the @samp{set case-insensitive} command, see
17441 @ref{Symbols}, for the details.
17444 * Fortran Types:: Fortran builtin types
17445 * Fortran Operators:: Fortran operators and expressions
17446 * Fortran Intrinsics:: Fortran intrinsic functions
17447 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
17450 @node Fortran Types
17451 @subsubsection Fortran Types
17453 @cindex Fortran Types
17455 In Fortran the primitive data-types have an associated @code{KIND} type
17456 parameter, written as @samp{@var{type}*@var{kindparam}},
17457 @samp{@var{type}*@var{kindparam}}, or in the @value{GDBN}-only dialect
17458 @samp{@var{type}_@var{kindparam}}. A concrete example would be
17459 @samp{@code{Real*4}}, @samp{@code{Real(kind=4)}}, and @samp{@code{Real_4}}.
17460 The kind of a type can be retrieved by using the intrinsic function
17461 @code{KIND}, see @ref{Fortran Intrinsics}.
17463 Generally, the actual implementation of the @code{KIND} type parameter is
17464 compiler specific. In @value{GDBN} the kind parameter is implemented in
17465 accordance with its use in the @sc{gnu} @command{gfortran} compiler. Here, the
17466 kind parameter for a given @var{type} specifies its size in memory --- a
17467 Fortran @code{Integer*4} or @code{Integer(kind=4)} would be an integer type
17468 occupying 4 bytes of memory. An exception to this rule is the @code{Complex}
17469 type for which the kind of the type does not specify its entire size, but
17470 the size of each of the two @code{Real}'s it is composed of. A
17471 @code{Complex*4} would thus consist of two @code{Real*4}s and occupy 8 bytes
17474 For every type there is also a default kind associated with it, e.g.@
17475 @code{Integer} in @value{GDBN} will internally be an @code{Integer*4} (see the
17476 table below for default types). The default types are the same as in @sc{gnu}
17477 compilers but note, that the @sc{gnu} default types can actually be changed by
17478 compiler flags such as @option{-fdefault-integer-8} and
17479 @option{-fdefault-real-8}.
17481 Not every kind parameter is valid for every type and in @value{GDBN} the
17482 following type kinds are available.
17486 @code{Integer*1}, @code{Integer*2}, @code{Integer*4}, @code{Integer*8}, and
17487 @code{Integer} = @code{Integer*4}.
17490 @code{Logical*1}, @code{Logical*2}, @code{Logical*4}, @code{Logical*8}, and
17491 @code{Logical} = @code{Logical*4}.
17494 @code{Real*4}, @code{Real*8}, @code{Real*16}, and @code{Real} = @code{Real*4}.
17497 @code{Complex*4}, @code{Complex*8}, @code{Complex*16}, and @code{Complex} =
17502 @node Fortran Operators
17503 @subsubsection Fortran Operators and Expressions
17505 @cindex Fortran operators and expressions
17507 Operators must be defined on values of specific types. For instance,
17508 @code{+} is defined on numbers, but not on characters or other non-
17509 arithmetic types. Operators are often defined on groups of types.
17513 The exponentiation operator. It raises the first operand to the power
17517 The range operator. Normally used in the form of array(low:high) to
17518 represent a section of array.
17521 The access component operator. Normally used to access elements in derived
17522 types. Also suitable for unions. As unions aren't part of regular Fortran,
17523 this can only happen when accessing a register that uses a gdbarch-defined
17526 The scope operator. Normally used to access variables in modules or
17527 to set breakpoints on subroutines nested in modules or in other
17528 subroutines (internal subroutines).
17531 @node Fortran Intrinsics
17532 @subsubsection Fortran Intrinsics
17534 @cindex Fortran Intrinsics
17536 Fortran provides a large set of intrinsic procedures. @value{GDBN} implements
17537 an incomplete subset of those procedures and their overloads. Some of these
17538 procedures take an optional @code{KIND} parameter, see @ref{Fortran Types}.
17542 Computes the absolute value of its argument @var{a}. Currently not supported
17543 for @code{Complex} arguments.
17545 @item ALLOCATE(@var{array})
17546 Returns whether @var{array} is allocated or not.
17548 @item ASSOCIATED(@var{pointer} [, @var{target}])
17549 Returns the association status of the pointer @var{pointer} or, if @var{target}
17550 is present, whether @var{pointer} is associated with the target @var{target}.
17552 @item CEILING(@var{a} [, @var{kind}])
17553 Computes the least integer greater than or equal to @var{a}. The optional
17554 parameter @var{kind} specifies the kind of the return type
17555 @code{Integer(@var{kind})}.
17557 @item CMPLX(@var{x} [, @var{y} [, @var{kind}]])
17558 Returns a complex number where @var{x} is converted to the real component. If
17559 @var{y} is present it is converted to the imaginary component. If @var{y} is
17560 not present then the imaginary component is set to @code{0.0} except if @var{x}
17561 itself is of @code{Complex} type. The optional parameter @var{kind} specifies
17562 the kind of the return type @code{Complex(@var{kind})}.
17564 @item FLOOR(@var{a} [, @var{kind}])
17565 Computes the greatest integer less than or equal to @var{a}. The optional
17566 parameter @var{kind} specifies the kind of the return type
17567 @code{Integer(@var{kind})}.
17569 @item KIND(@var{a})
17570 Returns the kind value of the argument @var{a}, see @ref{Fortran Types}.
17572 @item LBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17573 Returns the lower bounds of an @var{array}, or a single lower bound along the
17574 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17575 the kind of the return type @code{Integer(@var{kind})}.
17578 Returns the address of @var{x} as an @code{Integer}.
17580 @item MOD(@var{a}, @var{p})
17581 Computes the remainder of the division of @var{a} by @var{p}.
17583 @item MODULO(@var{a}, @var{p})
17584 Computes the @var{a} modulo @var{p}.
17586 @item RANK(@var{a})
17587 Returns the rank of a scalar or array (scalars have rank @code{0}).
17589 @item SHAPE(@var{a})
17590 Returns the shape of a scalar or array (scalars have shape @samp{()}).
17592 @item SIZE(@var{array}[, @var{dim} [, @var{kind}]])
17593 Returns the extent of @var{array} along a specified dimension @var{dim}, or the
17594 total number of elements in @var{array} if @var{dim} is absent. The optional
17595 parameter @var{kind} specifies the kind of the return type
17596 @code{Integer(@var{kind})}.
17598 @item UBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17599 Returns the upper bounds of an @var{array}, or a single upper bound along the
17600 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17601 the kind of the return type @code{Integer(@var{kind})}.
17605 @node Special Fortran Commands
17606 @subsubsection Special Fortran Commands
17608 @cindex Special Fortran commands
17610 @value{GDBN} has some commands to support Fortran-specific features,
17611 such as displaying common blocks.
17614 @cindex @code{COMMON} blocks, Fortran
17615 @kindex info common
17616 @item info common @r{[}@var{common-name}@r{]}
17617 This command prints the values contained in the Fortran @code{COMMON}
17618 block whose name is @var{common-name}. With no argument, the names of
17619 all @code{COMMON} blocks visible at the current program location are
17621 @cindex arrays slices (Fortran)
17622 @kindex set fortran repack-array-slices
17623 @kindex show fortran repack-array-slices
17624 @item set fortran repack-array-slices [on|off]
17625 @item show fortran repack-array-slices
17626 When taking a slice from an array, a Fortran compiler can choose to
17627 either produce an array descriptor that describes the slice in place,
17628 or it may repack the slice, copying the elements of the slice into a
17629 new region of memory.
17631 When this setting is on, then @value{GDBN} will also repack array
17632 slices in some situations. When this setting is off, then
17633 @value{GDBN} will create array descriptors for slices that reference
17634 the original data in place.
17636 @value{GDBN} will never repack an array slice if the data for the
17637 slice is contiguous within the original array.
17639 @value{GDBN} will always repack string slices if the data for the
17640 slice is non-contiguous within the original string as @value{GDBN}
17641 does not support printing non-contiguous strings.
17643 The default for this setting is @code{off}.
17649 @cindex Pascal support in @value{GDBN}, limitations
17650 Debugging Pascal programs which use sets, subranges, file variables, or
17651 nested functions does not currently work. @value{GDBN} does not support
17652 entering expressions, printing values, or similar features using Pascal
17655 The Pascal-specific command @code{set print pascal_static-members}
17656 controls whether static members of Pascal objects are displayed.
17657 @xref{Print Settings, pascal_static-members}.
17662 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
17663 Programming Language}. Type- and value-printing, and expression
17664 parsing, are reasonably complete. However, there are a few
17665 peculiarities and holes to be aware of.
17669 Linespecs (@pxref{Location Specifications}) are never relative to the
17670 current crate. Instead, they act as if there were a global namespace
17671 of crates, somewhat similar to the way @code{extern crate} behaves.
17673 That is, if @value{GDBN} is stopped at a breakpoint in a function in
17674 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
17675 to set a breakpoint in a function named @samp{f} in a crate named
17678 As a consequence of this approach, linespecs also cannot refer to
17679 items using @samp{self::} or @samp{super::}.
17682 Because @value{GDBN} implements Rust name-lookup semantics in
17683 expressions, it will sometimes prepend the current crate to a name.
17684 For example, if @value{GDBN} is stopped at a breakpoint in the crate
17685 @samp{K}, then @code{print ::x::y} will try to find the symbol
17688 However, since it is useful to be able to refer to other crates when
17689 debugging, @value{GDBN} provides the @code{extern} extension to
17690 circumvent this. To use the extension, just put @code{extern} before
17691 a path expression to refer to the otherwise unavailable ``global''
17694 In the above example, if you wanted to refer to the symbol @samp{y} in
17695 the crate @samp{x}, you would use @code{print extern x::y}.
17698 The Rust expression evaluator does not support ``statement-like''
17699 expressions such as @code{if} or @code{match}, or lambda expressions.
17702 Tuple expressions are not implemented.
17705 The Rust expression evaluator does not currently implement the
17706 @code{Drop} trait. Objects that may be created by the evaluator will
17707 never be destroyed.
17710 @value{GDBN} does not implement type inference for generics. In order
17711 to call generic functions or otherwise refer to generic items, you
17712 will have to specify the type parameters manually.
17715 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
17716 cases this does not cause any problems. However, in an expression
17717 context, completing a generic function name will give syntactically
17718 invalid results. This happens because Rust requires the @samp{::}
17719 operator between the function name and its generic arguments. For
17720 example, @value{GDBN} might provide a completion like
17721 @code{crate::f<u32>}, where the parser would require
17722 @code{crate::f::<u32>}.
17725 As of this writing, the Rust compiler (version 1.8) has a few holes in
17726 the debugging information it generates. These holes prevent certain
17727 features from being implemented by @value{GDBN}:
17731 Method calls cannot be made via traits.
17734 Operator overloading is not implemented.
17737 When debugging in a monomorphized function, you cannot use the generic
17741 The type @code{Self} is not available.
17744 @code{use} statements are not available, so some names may not be
17745 available in the crate.
17750 @subsection Modula-2
17752 @cindex Modula-2, @value{GDBN} support
17754 The extensions made to @value{GDBN} to support Modula-2 only support
17755 output from the @sc{gnu} Modula-2 compiler (which is currently being
17756 developed). Other Modula-2 compilers are not currently supported, and
17757 attempting to debug executables produced by them is most likely
17758 to give an error as @value{GDBN} reads in the executable's symbol
17761 @cindex expressions in Modula-2
17763 * M2 Operators:: Built-in operators
17764 * Built-In Func/Proc:: Built-in functions and procedures
17765 * M2 Constants:: Modula-2 constants
17766 * M2 Types:: Modula-2 types
17767 * M2 Defaults:: Default settings for Modula-2
17768 * Deviations:: Deviations from standard Modula-2
17769 * M2 Checks:: Modula-2 type and range checks
17770 * M2 Scope:: The scope operators @code{::} and @code{.}
17771 * GDB/M2:: @value{GDBN} and Modula-2
17775 @subsubsection Operators
17776 @cindex Modula-2 operators
17778 Operators must be defined on values of specific types. For instance,
17779 @code{+} is defined on numbers, but not on structures. Operators are
17780 often defined on groups of types. For the purposes of Modula-2, the
17781 following definitions hold:
17786 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17790 @emph{Character types} consist of @code{CHAR} and its subranges.
17793 @emph{Floating-point types} consist of @code{REAL}.
17796 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17800 @emph{Scalar types} consist of all of the above.
17803 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17806 @emph{Boolean types} consist of @code{BOOLEAN}.
17810 The following operators are supported, and appear in order of
17811 increasing precedence:
17815 Function argument or array index separator.
17818 Assignment. The value of @var{var} @code{:=} @var{value} is
17822 Less than, greater than on integral, floating-point, or enumerated
17826 Less than or equal to, greater than or equal to
17827 on integral, floating-point and enumerated types, or set inclusion on
17828 set types. Same precedence as @code{<}.
17830 @item =@r{, }<>@r{, }#
17831 Equality and two ways of expressing inequality, valid on scalar types.
17832 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17833 available for inequality, since @code{#} conflicts with the script
17837 Set membership. Defined on set types and the types of their members.
17838 Same precedence as @code{<}.
17841 Boolean disjunction. Defined on boolean types.
17844 Boolean conjunction. Defined on boolean types.
17847 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17850 Addition and subtraction on integral and floating-point types, or union
17851 and difference on set types.
17854 Multiplication on integral and floating-point types, or set intersection
17858 Division on floating-point types, or symmetric set difference on set
17859 types. Same precedence as @code{*}.
17862 Integer division and remainder. Defined on integral types. Same
17863 precedence as @code{*}.
17866 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17869 Pointer dereferencing. Defined on pointer types.
17872 Boolean negation. Defined on boolean types. Same precedence as
17876 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17877 precedence as @code{^}.
17880 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17883 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17887 @value{GDBN} and Modula-2 scope operators.
17891 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17892 treats the use of the operator @code{IN}, or the use of operators
17893 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17894 @code{<=}, and @code{>=} on sets as an error.
17898 @node Built-In Func/Proc
17899 @subsubsection Built-in Functions and Procedures
17900 @cindex Modula-2 built-ins
17902 Modula-2 also makes available several built-in procedures and functions.
17903 In describing these, the following metavariables are used:
17908 represents an @code{ARRAY} variable.
17911 represents a @code{CHAR} constant or variable.
17914 represents a variable or constant of integral type.
17917 represents an identifier that belongs to a set. Generally used in the
17918 same function with the metavariable @var{s}. The type of @var{s} should
17919 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
17922 represents a variable or constant of integral or floating-point type.
17925 represents a variable or constant of floating-point type.
17931 represents a variable.
17934 represents a variable or constant of one of many types. See the
17935 explanation of the function for details.
17938 All Modula-2 built-in procedures also return a result, described below.
17942 Returns the absolute value of @var{n}.
17945 If @var{c} is a lower case letter, it returns its upper case
17946 equivalent, otherwise it returns its argument.
17949 Returns the character whose ordinal value is @var{i}.
17952 Decrements the value in the variable @var{v} by one. Returns the new value.
17954 @item DEC(@var{v},@var{i})
17955 Decrements the value in the variable @var{v} by @var{i}. Returns the
17958 @item EXCL(@var{m},@var{s})
17959 Removes the element @var{m} from the set @var{s}. Returns the new
17962 @item FLOAT(@var{i})
17963 Returns the floating point equivalent of the integer @var{i}.
17965 @item HIGH(@var{a})
17966 Returns the index of the last member of @var{a}.
17969 Increments the value in the variable @var{v} by one. Returns the new value.
17971 @item INC(@var{v},@var{i})
17972 Increments the value in the variable @var{v} by @var{i}. Returns the
17975 @item INCL(@var{m},@var{s})
17976 Adds the element @var{m} to the set @var{s} if it is not already
17977 there. Returns the new set.
17980 Returns the maximum value of the type @var{t}.
17983 Returns the minimum value of the type @var{t}.
17986 Returns boolean TRUE if @var{i} is an odd number.
17989 Returns the ordinal value of its argument. For example, the ordinal
17990 value of a character is its @sc{ascii} value (on machines supporting
17991 the @sc{ascii} character set). The argument @var{x} must be of an
17992 ordered type, which include integral, character and enumerated types.
17994 @item SIZE(@var{x})
17995 Returns the size of its argument. The argument @var{x} can be a
17996 variable or a type.
17998 @item TRUNC(@var{r})
17999 Returns the integral part of @var{r}.
18001 @item TSIZE(@var{x})
18002 Returns the size of its argument. The argument @var{x} can be a
18003 variable or a type.
18005 @item VAL(@var{t},@var{i})
18006 Returns the member of the type @var{t} whose ordinal value is @var{i}.
18010 @emph{Warning:} Sets and their operations are not yet supported, so
18011 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
18015 @cindex Modula-2 constants
18017 @subsubsection Constants
18019 @value{GDBN} allows you to express the constants of Modula-2 in the following
18025 Integer constants are simply a sequence of digits. When used in an
18026 expression, a constant is interpreted to be type-compatible with the
18027 rest of the expression. Hexadecimal integers are specified by a
18028 trailing @samp{H}, and octal integers by a trailing @samp{B}.
18031 Floating point constants appear as a sequence of digits, followed by a
18032 decimal point and another sequence of digits. An optional exponent can
18033 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
18034 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
18035 digits of the floating point constant must be valid decimal (base 10)
18039 Character constants consist of a single character enclosed by a pair of
18040 like quotes, either single (@code{'}) or double (@code{"}). They may
18041 also be expressed by their ordinal value (their @sc{ascii} value, usually)
18042 followed by a @samp{C}.
18045 String constants consist of a sequence of characters enclosed by a
18046 pair of like quotes, either single (@code{'}) or double (@code{"}).
18047 Escape sequences in the style of C are also allowed. @xref{C
18048 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
18052 Enumerated constants consist of an enumerated identifier.
18055 Boolean constants consist of the identifiers @code{TRUE} and
18059 Pointer constants consist of integral values only.
18062 Set constants are not yet supported.
18066 @subsubsection Modula-2 Types
18067 @cindex Modula-2 types
18069 Currently @value{GDBN} can print the following data types in Modula-2
18070 syntax: array types, record types, set types, pointer types, procedure
18071 types, enumerated types, subrange types and base types. You can also
18072 print the contents of variables declared using these type.
18073 This section gives a number of simple source code examples together with
18074 sample @value{GDBN} sessions.
18076 The first example contains the following section of code:
18085 and you can request @value{GDBN} to interrogate the type and value of
18086 @code{r} and @code{s}.
18089 (@value{GDBP}) print s
18091 (@value{GDBP}) ptype s
18093 (@value{GDBP}) print r
18095 (@value{GDBP}) ptype r
18100 Likewise if your source code declares @code{s} as:
18104 s: SET ['A'..'Z'] ;
18108 then you may query the type of @code{s} by:
18111 (@value{GDBP}) ptype s
18112 type = SET ['A'..'Z']
18116 Note that at present you cannot interactively manipulate set
18117 expressions using the debugger.
18119 The following example shows how you might declare an array in Modula-2
18120 and how you can interact with @value{GDBN} to print its type and contents:
18124 s: ARRAY [-10..10] OF CHAR ;
18128 (@value{GDBP}) ptype s
18129 ARRAY [-10..10] OF CHAR
18132 Note that the array handling is not yet complete and although the type
18133 is printed correctly, expression handling still assumes that all
18134 arrays have a lower bound of zero and not @code{-10} as in the example
18137 Here are some more type related Modula-2 examples:
18141 colour = (blue, red, yellow, green) ;
18142 t = [blue..yellow] ;
18150 The @value{GDBN} interaction shows how you can query the data type
18151 and value of a variable.
18154 (@value{GDBP}) print s
18156 (@value{GDBP}) ptype t
18157 type = [blue..yellow]
18161 In this example a Modula-2 array is declared and its contents
18162 displayed. Observe that the contents are written in the same way as
18163 their @code{C} counterparts.
18167 s: ARRAY [1..5] OF CARDINAL ;
18173 (@value{GDBP}) print s
18174 $1 = @{1, 0, 0, 0, 0@}
18175 (@value{GDBP}) ptype s
18176 type = ARRAY [1..5] OF CARDINAL
18179 The Modula-2 language interface to @value{GDBN} also understands
18180 pointer types as shown in this example:
18184 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
18191 and you can request that @value{GDBN} describes the type of @code{s}.
18194 (@value{GDBP}) ptype s
18195 type = POINTER TO ARRAY [1..5] OF CARDINAL
18198 @value{GDBN} handles compound types as we can see in this example.
18199 Here we combine array types, record types, pointer types and subrange
18210 myarray = ARRAY myrange OF CARDINAL ;
18211 myrange = [-2..2] ;
18213 s: POINTER TO ARRAY myrange OF foo ;
18217 and you can ask @value{GDBN} to describe the type of @code{s} as shown
18221 (@value{GDBP}) ptype s
18222 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
18225 f3 : ARRAY [-2..2] OF CARDINAL;
18230 @subsubsection Modula-2 Defaults
18231 @cindex Modula-2 defaults
18233 If type and range checking are set automatically by @value{GDBN}, they
18234 both default to @code{on} whenever the working language changes to
18235 Modula-2. This happens regardless of whether you or @value{GDBN}
18236 selected the working language.
18238 If you allow @value{GDBN} to set the language automatically, then entering
18239 code compiled from a file whose name ends with @file{.mod} sets the
18240 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
18241 Infer the Source Language}, for further details.
18244 @subsubsection Deviations from Standard Modula-2
18245 @cindex Modula-2, deviations from
18247 A few changes have been made to make Modula-2 programs easier to debug.
18248 This is done primarily via loosening its type strictness:
18252 Unlike in standard Modula-2, pointer constants can be formed by
18253 integers. This allows you to modify pointer variables during
18254 debugging. (In standard Modula-2, the actual address contained in a
18255 pointer variable is hidden from you; it can only be modified
18256 through direct assignment to another pointer variable or expression that
18257 returned a pointer.)
18260 C escape sequences can be used in strings and characters to represent
18261 non-printable characters. @value{GDBN} prints out strings with these
18262 escape sequences embedded. Single non-printable characters are
18263 printed using the @samp{CHR(@var{nnn})} format.
18266 The assignment operator (@code{:=}) returns the value of its right-hand
18270 All built-in procedures both modify @emph{and} return their argument.
18274 @subsubsection Modula-2 Type and Range Checks
18275 @cindex Modula-2 checks
18278 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
18281 @c FIXME remove warning when type/range checks added
18283 @value{GDBN} considers two Modula-2 variables type equivalent if:
18287 They are of types that have been declared equivalent via a @code{TYPE
18288 @var{t1} = @var{t2}} statement
18291 They have been declared on the same line. (Note: This is true of the
18292 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
18295 As long as type checking is enabled, any attempt to combine variables
18296 whose types are not equivalent is an error.
18298 Range checking is done on all mathematical operations, assignment, array
18299 index bounds, and all built-in functions and procedures.
18302 @subsubsection The Scope Operators @code{::} and @code{.}
18304 @cindex @code{.}, Modula-2 scope operator
18305 @cindex colon, doubled as scope operator
18307 @vindex colon-colon@r{, in Modula-2}
18308 @c Info cannot handle :: but TeX can.
18311 @vindex ::@r{, in Modula-2}
18314 There are a few subtle differences between the Modula-2 scope operator
18315 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
18320 @var{module} . @var{id}
18321 @var{scope} :: @var{id}
18325 where @var{scope} is the name of a module or a procedure,
18326 @var{module} the name of a module, and @var{id} is any declared
18327 identifier within your program, except another module.
18329 Using the @code{::} operator makes @value{GDBN} search the scope
18330 specified by @var{scope} for the identifier @var{id}. If it is not
18331 found in the specified scope, then @value{GDBN} searches all scopes
18332 enclosing the one specified by @var{scope}.
18334 Using the @code{.} operator makes @value{GDBN} search the current scope for
18335 the identifier specified by @var{id} that was imported from the
18336 definition module specified by @var{module}. With this operator, it is
18337 an error if the identifier @var{id} was not imported from definition
18338 module @var{module}, or if @var{id} is not an identifier in
18342 @subsubsection @value{GDBN} and Modula-2
18344 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
18345 Five subcommands of @code{set print} and @code{show print} apply
18346 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
18347 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
18348 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
18349 analogue in Modula-2.
18351 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
18352 with any language, is not useful with Modula-2. Its
18353 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
18354 created in Modula-2 as they can in C or C@t{++}. However, because an
18355 address can be specified by an integral constant, the construct
18356 @samp{@{@var{type}@}@var{adrexp}} is still useful.
18358 @cindex @code{#} in Modula-2
18359 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
18360 interpreted as the beginning of a comment. Use @code{<>} instead.
18366 The extensions made to @value{GDBN} for Ada only support
18367 output from the @sc{gnu} Ada (GNAT) compiler.
18368 Other Ada compilers are not currently supported, and
18369 attempting to debug executables produced by them is most likely
18373 @cindex expressions in Ada
18375 * Ada Mode Intro:: General remarks on the Ada syntax
18376 and semantics supported by Ada mode
18378 * Omissions from Ada:: Restrictions on the Ada expression syntax.
18379 * Additions to Ada:: Extensions of the Ada expression syntax.
18380 * Overloading support for Ada:: Support for expressions involving overloaded
18382 * Stopping Before Main Program:: Debugging the program during elaboration.
18383 * Ada Exceptions:: Ada Exceptions
18384 * Ada Tasks:: Listing and setting breakpoints in tasks.
18385 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
18386 * Ravenscar Profile:: Tasking Support when using the Ravenscar
18388 * Ada Source Character Set:: Character set of Ada source files.
18389 * Ada Glitches:: Known peculiarities of Ada mode.
18392 @node Ada Mode Intro
18393 @subsubsection Introduction
18394 @cindex Ada mode, general
18396 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
18397 syntax, with some extensions.
18398 The philosophy behind the design of this subset is
18402 That @value{GDBN} should provide basic literals and access to operations for
18403 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18404 leaving more sophisticated computations to subprograms written into the
18405 program (which therefore may be called from @value{GDBN}).
18408 That type safety and strict adherence to Ada language restrictions
18409 are not particularly important to the @value{GDBN} user.
18412 That brevity is important to the @value{GDBN} user.
18415 Thus, for brevity, the debugger acts as if all names declared in
18416 user-written packages are directly visible, even if they are not visible
18417 according to Ada rules, thus making it unnecessary to fully qualify most
18418 names with their packages, regardless of context. Where this causes
18419 ambiguity, @value{GDBN} asks the user's intent.
18421 The debugger will start in Ada mode if it detects an Ada main program.
18422 As for other languages, it will enter Ada mode when stopped in a program that
18423 was translated from an Ada source file.
18425 While in Ada mode, you may use `@t{--}' for comments. This is useful
18426 mostly for documenting command files. The standard @value{GDBN} comment
18427 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
18428 middle (to allow based literals).
18430 @node Omissions from Ada
18431 @subsubsection Omissions from Ada
18432 @cindex Ada, omissions from
18434 Here are the notable omissions from the subset:
18438 Only a subset of the attributes are supported:
18442 @t{'First}, @t{'Last}, and @t{'Length}
18443 on array objects (not on types and subtypes).
18446 @t{'Min} and @t{'Max}.
18449 @t{'Pos} and @t{'Val}.
18455 @t{'Range} on array objects (not subtypes), but only as the right
18456 operand of the membership (@code{in}) operator.
18459 @t{'Access}, @t{'Unchecked_Access}, and
18460 @t{'Unrestricted_Access} (a GNAT extension).
18467 The names in @code{Characters.Latin_1} are not available.
18470 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
18471 equality of representations. They will generally work correctly
18472 for strings and arrays whose elements have integer or enumeration types.
18473 They may not work correctly for arrays whose element
18474 types have user-defined equality, for arrays of real values
18475 (in particular, IEEE-conformant floating point, because of negative
18476 zeroes and NaNs), and for arrays whose elements contain unused bits with
18477 indeterminate values.
18480 The other component-by-component array operations (@code{and}, @code{or},
18481 @code{xor}, @code{not}, and relational tests other than equality)
18482 are not implemented.
18485 @cindex array aggregates (Ada)
18486 @cindex record aggregates (Ada)
18487 @cindex aggregates (Ada)
18488 There is limited support for array and record aggregates. They are
18489 permitted only on the right sides of assignments, as in these examples:
18492 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
18493 (@value{GDBP}) set An_Array := (1, others => 0)
18494 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
18495 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
18496 (@value{GDBP}) set A_Record := (1, "Peter", True);
18497 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
18501 discriminant's value by assigning an aggregate has an
18502 undefined effect if that discriminant is used within the record.
18503 However, you can first modify discriminants by directly assigning to
18504 them (which normally would not be allowed in Ada), and then performing an
18505 aggregate assignment. For example, given a variable @code{A_Rec}
18506 declared to have a type such as:
18509 type Rec (Len : Small_Integer := 0) is record
18511 Vals : IntArray (1 .. Len);
18515 you can assign a value with a different size of @code{Vals} with two
18519 (@value{GDBP}) set A_Rec.Len := 4
18520 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
18523 As this example also illustrates, @value{GDBN} is very loose about the usual
18524 rules concerning aggregates. You may leave out some of the
18525 components of an array or record aggregate (such as the @code{Len}
18526 component in the assignment to @code{A_Rec} above); they will retain their
18527 original values upon assignment. You may freely use dynamic values as
18528 indices in component associations. You may even use overlapping or
18529 redundant component associations, although which component values are
18530 assigned in such cases is not defined.
18533 Calls to dispatching subprograms are not implemented.
18536 The overloading algorithm is much more limited (i.e., less selective)
18537 than that of real Ada. It makes only limited use of the context in
18538 which a subexpression appears to resolve its meaning, and it is much
18539 looser in its rules for allowing type matches. As a result, some
18540 function calls will be ambiguous, and the user will be asked to choose
18541 the proper resolution.
18544 The @code{new} operator is not implemented.
18547 Entry calls are not implemented.
18550 Aside from printing, arithmetic operations on the native VAX floating-point
18551 formats are not supported.
18554 It is not possible to slice a packed array.
18557 The names @code{True} and @code{False}, when not part of a qualified name,
18558 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
18560 Should your program
18561 redefine these names in a package or procedure (at best a dubious practice),
18562 you will have to use fully qualified names to access their new definitions.
18565 Based real literals are not implemented.
18568 @node Additions to Ada
18569 @subsubsection Additions to Ada
18570 @cindex Ada, deviations from
18572 As it does for other languages, @value{GDBN} makes certain generic
18573 extensions to Ada (@pxref{Expressions}):
18577 If the expression @var{E} is a variable residing in memory (typically
18578 a local variable or array element) and @var{N} is a positive integer,
18579 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
18580 @var{N}-1 adjacent variables following it in memory as an array. In
18581 Ada, this operator is generally not necessary, since its prime use is
18582 in displaying parts of an array, and slicing will usually do this in
18583 Ada. However, there are occasional uses when debugging programs in
18584 which certain debugging information has been optimized away.
18587 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
18588 appears in function or file @var{B}.'' When @var{B} is a file name,
18589 you must typically surround it in single quotes.
18592 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
18593 @var{type} that appears at address @var{addr}.''
18596 A name starting with @samp{$} is a convenience variable
18597 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
18600 In addition, @value{GDBN} provides a few other shortcuts and outright
18601 additions specific to Ada:
18605 The assignment statement is allowed as an expression, returning
18606 its right-hand operand as its value. Thus, you may enter
18609 (@value{GDBP}) set x := y + 3
18610 (@value{GDBP}) print A(tmp := y + 1)
18614 The semicolon is allowed as an ``operator,'' returning as its value
18615 the value of its right-hand operand.
18616 This allows, for example,
18617 complex conditional breaks:
18620 (@value{GDBP}) break f
18621 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
18625 An extension to based literals can be used to specify the exact byte
18626 contents of a floating-point literal. After the base, you can use
18627 from zero to two @samp{l} characters, followed by an @samp{f}. The
18628 number of @samp{l} characters controls the width of the resulting real
18629 constant: zero means @code{Float} is used, one means
18630 @code{Long_Float}, and two means @code{Long_Long_Float}.
18633 (@value{GDBP}) print 16f#41b80000#
18638 Rather than use catenation and symbolic character names to introduce special
18639 characters into strings, one may instead use a special bracket notation,
18640 which is also used to print strings. A sequence of characters of the form
18641 @samp{["@var{XX}"]} within a string or character literal denotes the
18642 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
18643 sequence of characters @samp{["""]} also denotes a single quotation mark
18644 in strings. For example,
18646 "One line.["0a"]Next line.["0a"]"
18649 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
18653 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
18654 @t{'Max} is optional (and is ignored in any case). For example, it is valid
18658 (@value{GDBP}) print 'max(x, y)
18662 When printing arrays, @value{GDBN} uses positional notation when the
18663 array has a lower bound of 1, and uses a modified named notation otherwise.
18664 For example, a one-dimensional array of three integers with a lower bound
18665 of 3 might print as
18672 That is, in contrast to valid Ada, only the first component has a @code{=>}
18676 You may abbreviate attributes in expressions with any unique,
18677 multi-character subsequence of
18678 their names (an exact match gets preference).
18679 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
18680 in place of @t{a'length}.
18683 @cindex quoting Ada internal identifiers
18684 Since Ada is case-insensitive, the debugger normally maps identifiers you type
18685 to lower case. The GNAT compiler uses upper-case characters for
18686 some of its internal identifiers, which are normally of no interest to users.
18687 For the rare occasions when you actually have to look at them,
18688 enclose them in angle brackets to avoid the lower-case mapping.
18691 (@value{GDBP}) print <JMPBUF_SAVE>[0]
18695 Printing an object of class-wide type or dereferencing an
18696 access-to-class-wide value will display all the components of the object's
18697 specific type (as indicated by its run-time tag). Likewise, component
18698 selection on such a value will operate on the specific type of the
18703 @node Overloading support for Ada
18704 @subsubsection Overloading support for Ada
18705 @cindex overloading, Ada
18707 The debugger supports limited overloading. Given a subprogram call in which
18708 the function symbol has multiple definitions, it will use the number of
18709 actual parameters and some information about their types to attempt to narrow
18710 the set of definitions. It also makes very limited use of context, preferring
18711 procedures to functions in the context of the @code{call} command, and
18712 functions to procedures elsewhere.
18714 If, after narrowing, the set of matching definitions still contains more than
18715 one definition, @value{GDBN} will display a menu to query which one it should
18719 (@value{GDBP}) print f(1)
18720 Multiple matches for f
18722 [1] foo.f (integer) return boolean at foo.adb:23
18723 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
18727 In this case, just select one menu entry either to cancel expression evaluation
18728 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
18729 instance (type the corresponding number and press @key{RET}).
18731 Here are a couple of commands to customize @value{GDBN}'s behavior in this
18736 @kindex set ada print-signatures
18737 @item set ada print-signatures
18738 Control whether parameter types and return types are displayed in overloads
18739 selection menus. It is @code{on} by default.
18740 @xref{Overloading support for Ada}.
18742 @kindex show ada print-signatures
18743 @item show ada print-signatures
18744 Show the current setting for displaying parameter types and return types in
18745 overloads selection menu.
18746 @xref{Overloading support for Ada}.
18750 @node Stopping Before Main Program
18751 @subsubsection Stopping at the Very Beginning
18753 @cindex breakpointing Ada elaboration code
18754 It is sometimes necessary to debug the program during elaboration, and
18755 before reaching the main procedure.
18756 As defined in the Ada Reference
18757 Manual, the elaboration code is invoked from a procedure called
18758 @code{adainit}. To run your program up to the beginning of
18759 elaboration, simply use the following two commands:
18760 @code{tbreak adainit} and @code{run}.
18762 @node Ada Exceptions
18763 @subsubsection Ada Exceptions
18765 A command is provided to list all Ada exceptions:
18768 @kindex info exceptions
18769 @item info exceptions
18770 @itemx info exceptions @var{regexp}
18771 The @code{info exceptions} command allows you to list all Ada exceptions
18772 defined within the program being debugged, as well as their addresses.
18773 With a regular expression, @var{regexp}, as argument, only those exceptions
18774 whose names match @var{regexp} are listed.
18777 Below is a small example, showing how the command can be used, first
18778 without argument, and next with a regular expression passed as an
18782 (@value{GDBP}) info exceptions
18783 All defined Ada exceptions:
18784 constraint_error: 0x613da0
18785 program_error: 0x613d20
18786 storage_error: 0x613ce0
18787 tasking_error: 0x613ca0
18788 const.aint_global_e: 0x613b00
18789 (@value{GDBP}) info exceptions const.aint
18790 All Ada exceptions matching regular expression "const.aint":
18791 constraint_error: 0x613da0
18792 const.aint_global_e: 0x613b00
18795 It is also possible to ask @value{GDBN} to stop your program's execution
18796 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18799 @subsubsection Extensions for Ada Tasks
18800 @cindex Ada, tasking
18802 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18803 @value{GDBN} provides the following task-related commands:
18808 This command shows a list of current Ada tasks, as in the following example:
18815 (@value{GDBP}) info tasks
18816 ID TID P-ID Pri State Name
18817 1 8088000 0 15 Child Activation Wait main_task
18818 2 80a4000 1 15 Accept Statement b
18819 3 809a800 1 15 Child Activation Wait a
18820 * 4 80ae800 3 15 Runnable c
18825 In this listing, the asterisk before the last task indicates it to be the
18826 task currently being inspected.
18830 Represents @value{GDBN}'s internal task number.
18836 The parent's task ID (@value{GDBN}'s internal task number).
18839 The base priority of the task.
18842 Current state of the task.
18846 The task has been created but has not been activated. It cannot be
18850 The task is not blocked for any reason known to Ada. (It may be waiting
18851 for a mutex, though.) It is conceptually "executing" in normal mode.
18854 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18855 that were waiting on terminate alternatives have been awakened and have
18856 terminated themselves.
18858 @item Child Activation Wait
18859 The task is waiting for created tasks to complete activation.
18861 @item Accept Statement
18862 The task is waiting on an accept or selective wait statement.
18864 @item Waiting on entry call
18865 The task is waiting on an entry call.
18867 @item Async Select Wait
18868 The task is waiting to start the abortable part of an asynchronous
18872 The task is waiting on a select statement with only a delay
18875 @item Child Termination Wait
18876 The task is sleeping having completed a master within itself, and is
18877 waiting for the tasks dependent on that master to become terminated or
18878 waiting on a terminate Phase.
18880 @item Wait Child in Term Alt
18881 The task is sleeping waiting for tasks on terminate alternatives to
18882 finish terminating.
18884 @item Accepting RV with @var{taskno}
18885 The task is accepting a rendez-vous with the task @var{taskno}.
18889 Name of the task in the program.
18893 @kindex info task @var{taskno}
18894 @item info task @var{taskno}
18895 This command shows detailed informations on the specified task, as in
18896 the following example:
18901 (@value{GDBP}) info tasks
18902 ID TID P-ID Pri State Name
18903 1 8077880 0 15 Child Activation Wait main_task
18904 * 2 807c468 1 15 Runnable task_1
18905 (@value{GDBP}) info task 2
18906 Ada Task: 0x807c468
18910 Parent: 1 ("main_task")
18916 @kindex task@r{ (Ada)}
18917 @cindex current Ada task ID
18918 This command prints the ID and name of the current task.
18924 (@value{GDBP}) info tasks
18925 ID TID P-ID Pri State Name
18926 1 8077870 0 15 Child Activation Wait main_task
18927 * 2 807c458 1 15 Runnable some_task
18928 (@value{GDBP}) task
18929 [Current task is 2 "some_task"]
18932 @item task @var{taskno}
18933 @cindex Ada task switching
18934 This command is like the @code{thread @var{thread-id}}
18935 command (@pxref{Threads}). It switches the context of debugging
18936 from the current task to the given task.
18942 (@value{GDBP}) info tasks
18943 ID TID P-ID Pri State Name
18944 1 8077870 0 15 Child Activation Wait main_task
18945 * 2 807c458 1 15 Runnable some_task
18946 (@value{GDBP}) task 1
18947 [Switching to task 1 "main_task"]
18948 #0 0x8067726 in pthread_cond_wait ()
18950 #0 0x8067726 in pthread_cond_wait ()
18951 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
18952 #2 0x805cb63 in system.task_primitives.operations.sleep ()
18953 #3 0x806153e in system.tasking.stages.activate_tasks ()
18954 #4 0x804aacc in un () at un.adb:5
18957 @item task apply [@var{task-id-list} | all] [@var{flag}]@dots{} @var{command}
18958 The @code{task apply} command is the Ada tasking analogue of
18959 @code{thread apply} (@pxref{Threads}). It allows you to apply the
18960 named @var{command} to one or more tasks. Specify the tasks that you
18961 want affected using a list of task IDs, or specify @code{all} to apply
18964 The @var{flag} arguments control what output to produce and how to
18965 handle errors raised when applying @var{command} to a task.
18966 @var{flag} must start with a @code{-} directly followed by one letter
18967 in @code{qcs}. If several flags are provided, they must be given
18968 individually, such as @code{-c -q}.
18970 By default, @value{GDBN} displays some task information before the
18971 output produced by @var{command}, and an error raised during the
18972 execution of a @var{command} will abort @code{task apply}. The
18973 following flags can be used to fine-tune this behavior:
18977 The flag @code{-c}, which stands for @samp{continue}, causes any
18978 errors in @var{command} to be displayed, and the execution of
18979 @code{task apply} then continues.
18981 The flag @code{-s}, which stands for @samp{silent}, causes any errors
18982 or empty output produced by a @var{command} to be silently ignored.
18983 That is, the execution continues, but the task information and errors
18986 The flag @code{-q} (@samp{quiet}) disables printing the task
18990 Flags @code{-c} and @code{-s} cannot be used together.
18992 @item break @var{locspec} task @var{taskno}
18993 @itemx break @var{locspec} task @var{taskno} if @dots{}
18994 @cindex breakpoints and tasks, in Ada
18995 @cindex task breakpoints, in Ada
18996 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
18997 These commands are like the @code{break @dots{} thread @dots{}}
18998 command (@pxref{Thread Stops}). @xref{Location Specifications}, for
18999 the various forms of @var{locspec}.
19001 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
19002 to specify that you only want @value{GDBN} to stop the program when a
19003 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
19004 numeric task identifiers assigned by @value{GDBN}, shown in the first
19005 column of the @samp{info tasks} display.
19007 If you do not specify @samp{task @var{taskno}} when you set a
19008 breakpoint, the breakpoint applies to @emph{all} tasks of your
19011 You can use the @code{task} qualifier on conditional breakpoints as
19012 well; in this case, place @samp{task @var{taskno}} before the
19013 breakpoint condition (before the @code{if}).
19021 (@value{GDBP}) info tasks
19022 ID TID P-ID Pri State Name
19023 1 140022020 0 15 Child Activation Wait main_task
19024 2 140045060 1 15 Accept/Select Wait t2
19025 3 140044840 1 15 Runnable t1
19026 * 4 140056040 1 15 Runnable t3
19027 (@value{GDBP}) b 15 task 2
19028 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
19029 (@value{GDBP}) cont
19034 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
19036 (@value{GDBP}) info tasks
19037 ID TID P-ID Pri State Name
19038 1 140022020 0 15 Child Activation Wait main_task
19039 * 2 140045060 1 15 Runnable t2
19040 3 140044840 1 15 Runnable t1
19041 4 140056040 1 15 Delay Sleep t3
19045 @node Ada Tasks and Core Files
19046 @subsubsection Tasking Support when Debugging Core Files
19047 @cindex Ada tasking and core file debugging
19049 When inspecting a core file, as opposed to debugging a live program,
19050 tasking support may be limited or even unavailable, depending on
19051 the platform being used.
19052 For instance, on x86-linux, the list of tasks is available, but task
19053 switching is not supported.
19055 On certain platforms, the debugger needs to perform some
19056 memory writes in order to provide Ada tasking support. When inspecting
19057 a core file, this means that the core file must be opened with read-write
19058 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
19059 Under these circumstances, you should make a backup copy of the core
19060 file before inspecting it with @value{GDBN}.
19062 @node Ravenscar Profile
19063 @subsubsection Tasking Support when using the Ravenscar Profile
19064 @cindex Ravenscar Profile
19066 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
19067 specifically designed for systems with safety-critical real-time
19071 @kindex set ravenscar task-switching on
19072 @cindex task switching with program using Ravenscar Profile
19073 @item set ravenscar task-switching on
19074 Allows task switching when debugging a program that uses the Ravenscar
19075 Profile. This is the default.
19077 @kindex set ravenscar task-switching off
19078 @item set ravenscar task-switching off
19079 Turn off task switching when debugging a program that uses the Ravenscar
19080 Profile. This is mostly intended to disable the code that adds support
19081 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
19082 the Ravenscar runtime is preventing @value{GDBN} from working properly.
19083 To be effective, this command should be run before the program is started.
19085 @kindex show ravenscar task-switching
19086 @item show ravenscar task-switching
19087 Show whether it is possible to switch from task to task in a program
19088 using the Ravenscar Profile.
19092 @cindex Ravenscar thread
19093 When Ravenscar task-switching is enabled, Ravenscar tasks are
19094 announced by @value{GDBN} as if they were threads:
19098 [New Ravenscar Thread 0x2b8f0]
19101 Both Ravenscar tasks and the underlying CPU threads will show up in
19102 the output of @code{info threads}:
19107 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
19108 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
19109 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
19110 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
19111 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
19112 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
19115 One known limitation of the Ravenscar support in @value{GDBN} is that
19116 it isn't currently possible to single-step through the runtime
19117 initialization sequence. If you need to debug this code, you should
19118 use @code{set ravenscar task-switching off}.
19120 @node Ada Source Character Set
19121 @subsubsection Ada Source Character Set
19122 @cindex Ada, source character set
19124 The GNAT compiler supports a number of character sets for source
19125 files. @xref{Character Set Control, , Character Set Control,
19126 gnat_ugn}. @value{GDBN} includes support for this as well.
19129 @item set ada source-charset @var{charset}
19130 @kindex set ada source-charset
19131 Set the source character set for Ada. The character set must be
19132 supported by GNAT. Because this setting affects the decoding of
19133 symbols coming from the debug information in your program, the setting
19134 should be set as early as possible. The default is @code{ISO-8859-1},
19135 because that is also GNAT's default.
19137 @item show ada source-charset
19138 @kindex show ada source-charset
19139 Show the current source character set for Ada.
19143 @subsubsection Known Peculiarities of Ada Mode
19144 @cindex Ada, problems
19146 Besides the omissions listed previously (@pxref{Omissions from Ada}),
19147 we know of several problems with and limitations of Ada mode in
19149 some of which will be fixed with planned future releases of the debugger
19150 and the GNU Ada compiler.
19154 Static constants that the compiler chooses not to materialize as objects in
19155 storage are invisible to the debugger.
19158 Named parameter associations in function argument lists are ignored (the
19159 argument lists are treated as positional).
19162 Many useful library packages are currently invisible to the debugger.
19165 Fixed-point arithmetic, conversions, input, and output is carried out using
19166 floating-point arithmetic, and may give results that only approximate those on
19170 The GNAT compiler never generates the prefix @code{Standard} for any of
19171 the standard symbols defined by the Ada language. @value{GDBN} knows about
19172 this: it will strip the prefix from names when you use it, and will never
19173 look for a name you have so qualified among local symbols, nor match against
19174 symbols in other packages or subprograms. If you have
19175 defined entities anywhere in your program other than parameters and
19176 local variables whose simple names match names in @code{Standard},
19177 GNAT's lack of qualification here can cause confusion. When this happens,
19178 you can usually resolve the confusion
19179 by qualifying the problematic names with package
19180 @code{Standard} explicitly.
19183 Older versions of the compiler sometimes generate erroneous debugging
19184 information, resulting in the debugger incorrectly printing the value
19185 of affected entities. In some cases, the debugger is able to work
19186 around an issue automatically. In other cases, the debugger is able
19187 to work around the issue, but the work-around has to be specifically
19190 @kindex set ada trust-PAD-over-XVS
19191 @kindex show ada trust-PAD-over-XVS
19194 @item set ada trust-PAD-over-XVS on
19195 Configure GDB to strictly follow the GNAT encoding when computing the
19196 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
19197 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
19198 a complete description of the encoding used by the GNAT compiler).
19199 This is the default.
19201 @item set ada trust-PAD-over-XVS off
19202 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
19203 sometimes prints the wrong value for certain entities, changing @code{ada
19204 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
19205 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
19206 @code{off}, but this incurs a slight performance penalty, so it is
19207 recommended to leave this setting to @code{on} unless necessary.
19211 @cindex GNAT descriptive types
19212 @cindex GNAT encoding
19213 Internally, the debugger also relies on the compiler following a number
19214 of conventions known as the @samp{GNAT Encoding}, all documented in
19215 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
19216 how the debugging information should be generated for certain types.
19217 In particular, this convention makes use of @dfn{descriptive types},
19218 which are artificial types generated purely to help the debugger.
19220 These encodings were defined at a time when the debugging information
19221 format used was not powerful enough to describe some of the more complex
19222 types available in Ada. Since DWARF allows us to express nearly all
19223 Ada features, the long-term goal is to slowly replace these descriptive
19224 types by their pure DWARF equivalent. To facilitate that transition,
19225 a new maintenance option is available to force the debugger to ignore
19226 those descriptive types. It allows the user to quickly evaluate how
19227 well @value{GDBN} works without them.
19231 @kindex maint ada set ignore-descriptive-types
19232 @item maintenance ada set ignore-descriptive-types [on|off]
19233 Control whether the debugger should ignore descriptive types.
19234 The default is not to ignore descriptives types (@code{off}).
19236 @kindex maint ada show ignore-descriptive-types
19237 @item maintenance ada show ignore-descriptive-types
19238 Show if descriptive types are ignored by @value{GDBN}.
19242 @node Unsupported Languages
19243 @section Unsupported Languages
19245 @cindex unsupported languages
19246 @cindex minimal language
19247 In addition to the other fully-supported programming languages,
19248 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
19249 It does not represent a real programming language, but provides a set
19250 of capabilities close to what the C or assembly languages provide.
19251 This should allow most simple operations to be performed while debugging
19252 an application that uses a language currently not supported by @value{GDBN}.
19254 If the language is set to @code{auto}, @value{GDBN} will automatically
19255 select this language if the current frame corresponds to an unsupported
19259 @chapter Examining the Symbol Table
19261 The commands described in this chapter allow you to inquire about the
19262 symbols (names of variables, functions and types) defined in your
19263 program. This information is inherent in the text of your program and
19264 does not change as your program executes. @value{GDBN} finds it in your
19265 program's symbol table, in the file indicated when you started @value{GDBN}
19266 (@pxref{File Options, ,Choosing Files}), or by one of the
19267 file-management commands (@pxref{Files, ,Commands to Specify Files}).
19269 @cindex symbol names
19270 @cindex names of symbols
19271 @cindex quoting names
19272 @anchor{quoting names}
19273 Occasionally, you may need to refer to symbols that contain unusual
19274 characters, which @value{GDBN} ordinarily treats as word delimiters. The
19275 most frequent case is in referring to static variables in other
19276 source files (@pxref{Variables,,Program Variables}). File names
19277 are recorded in object files as debugging symbols, but @value{GDBN} would
19278 ordinarily parse a typical file name, like @file{foo.c}, as the three words
19279 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
19280 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
19287 looks up the value of @code{x} in the scope of the file @file{foo.c}.
19290 @cindex case-insensitive symbol names
19291 @cindex case sensitivity in symbol names
19292 @kindex set case-sensitive
19293 @item set case-sensitive on
19294 @itemx set case-sensitive off
19295 @itemx set case-sensitive auto
19296 Normally, when @value{GDBN} looks up symbols, it matches their names
19297 with case sensitivity determined by the current source language.
19298 Occasionally, you may wish to control that. The command @code{set
19299 case-sensitive} lets you do that by specifying @code{on} for
19300 case-sensitive matches or @code{off} for case-insensitive ones. If
19301 you specify @code{auto}, case sensitivity is reset to the default
19302 suitable for the source language. The default is case-sensitive
19303 matches for all languages except for Fortran, for which the default is
19304 case-insensitive matches.
19306 @kindex show case-sensitive
19307 @item show case-sensitive
19308 This command shows the current setting of case sensitivity for symbols
19311 @kindex set print type methods
19312 @item set print type methods
19313 @itemx set print type methods on
19314 @itemx set print type methods off
19315 Normally, when @value{GDBN} prints a class, it displays any methods
19316 declared in that class. You can control this behavior either by
19317 passing the appropriate flag to @code{ptype}, or using @command{set
19318 print type methods}. Specifying @code{on} will cause @value{GDBN} to
19319 display the methods; this is the default. Specifying @code{off} will
19320 cause @value{GDBN} to omit the methods.
19322 @kindex show print type methods
19323 @item show print type methods
19324 This command shows the current setting of method display when printing
19327 @kindex set print type nested-type-limit
19328 @item set print type nested-type-limit @var{limit}
19329 @itemx set print type nested-type-limit unlimited
19330 Set the limit of displayed nested types that the type printer will
19331 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
19332 nested definitions. By default, the type printer will not show any nested
19333 types defined in classes.
19335 @kindex show print type nested-type-limit
19336 @item show print type nested-type-limit
19337 This command shows the current display limit of nested types when
19340 @kindex set print type typedefs
19341 @item set print type typedefs
19342 @itemx set print type typedefs on
19343 @itemx set print type typedefs off
19345 Normally, when @value{GDBN} prints a class, it displays any typedefs
19346 defined in that class. You can control this behavior either by
19347 passing the appropriate flag to @code{ptype}, or using @command{set
19348 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
19349 display the typedef definitions; this is the default. Specifying
19350 @code{off} will cause @value{GDBN} to omit the typedef definitions.
19351 Note that this controls whether the typedef definition itself is
19352 printed, not whether typedef names are substituted when printing other
19355 @kindex show print type typedefs
19356 @item show print type typedefs
19357 This command shows the current setting of typedef display when
19360 @kindex set print type hex
19361 @item set print type hex
19362 @itemx set print type hex on
19363 @itemx set print type hex off
19365 When @value{GDBN} prints sizes and offsets of struct members, it can use
19366 either the decimal or hexadecimal notation. You can select one or the
19367 other either by passing the appropriate flag to @code{ptype}, or by using
19368 the @command{set print type hex} command.
19370 @kindex show print type hex
19371 @item show print type hex
19372 This command shows whether the sizes and offsets of struct members are
19373 printed in decimal or hexadecimal notation.
19375 @kindex info address
19376 @cindex address of a symbol
19377 @item info address @var{symbol}
19378 Describe where the data for @var{symbol} is stored. For a register
19379 variable, this says which register it is kept in. For a non-register
19380 local variable, this prints the stack-frame offset at which the variable
19383 Note the contrast with @samp{print &@var{symbol}}, which does not work
19384 at all for a register variable, and for a stack local variable prints
19385 the exact address of the current instantiation of the variable.
19387 @kindex info symbol
19388 @cindex symbol from address
19389 @cindex closest symbol and offset for an address
19390 @item info symbol @var{addr}
19391 Print the name of a symbol which is stored at the address @var{addr}.
19392 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
19393 nearest symbol and an offset from it:
19396 (@value{GDBP}) info symbol 0x54320
19397 _initialize_vx + 396 in section .text
19401 This is the opposite of the @code{info address} command. You can use
19402 it to find out the name of a variable or a function given its address.
19404 For dynamically linked executables, the name of executable or shared
19405 library containing the symbol is also printed:
19408 (@value{GDBP}) info symbol 0x400225
19409 _start + 5 in section .text of /tmp/a.out
19410 (@value{GDBP}) info symbol 0x2aaaac2811cf
19411 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
19416 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
19417 Demangle @var{name}.
19418 If @var{language} is provided it is the name of the language to demangle
19419 @var{name} in. Otherwise @var{name} is demangled in the current language.
19421 The @samp{--} option specifies the end of options,
19422 and is useful when @var{name} begins with a dash.
19424 The parameter @code{demangle-style} specifies how to interpret the kind
19425 of mangling used. @xref{Print Settings}.
19428 @item whatis[/@var{flags}] [@var{arg}]
19429 Print the data type of @var{arg}, which can be either an expression
19430 or a name of a data type. With no argument, print the data type of
19431 @code{$}, the last value in the value history.
19433 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
19434 is not actually evaluated, and any side-effecting operations (such as
19435 assignments or function calls) inside it do not take place.
19437 If @var{arg} is a variable or an expression, @code{whatis} prints its
19438 literal type as it is used in the source code. If the type was
19439 defined using a @code{typedef}, @code{whatis} will @emph{not} print
19440 the data type underlying the @code{typedef}. If the type of the
19441 variable or the expression is a compound data type, such as
19442 @code{struct} or @code{class}, @code{whatis} never prints their
19443 fields or methods. It just prints the @code{struct}/@code{class}
19444 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
19445 such a compound data type, use @code{ptype}.
19447 If @var{arg} is a type name that was defined using @code{typedef},
19448 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
19449 Unrolling means that @code{whatis} will show the underlying type used
19450 in the @code{typedef} declaration of @var{arg}. However, if that
19451 underlying type is also a @code{typedef}, @code{whatis} will not
19454 For C code, the type names may also have the form @samp{class
19455 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
19456 @var{union-tag}} or @samp{enum @var{enum-tag}}.
19458 @var{flags} can be used to modify how the type is displayed.
19459 Available flags are:
19463 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
19464 parameters and typedefs defined in a class when printing the class'
19465 members. The @code{/r} flag disables this.
19468 Do not print methods defined in the class.
19471 Print methods defined in the class. This is the default, but the flag
19472 exists in case you change the default with @command{set print type methods}.
19475 Do not print typedefs defined in the class. Note that this controls
19476 whether the typedef definition itself is printed, not whether typedef
19477 names are substituted when printing other types.
19480 Print typedefs defined in the class. This is the default, but the flag
19481 exists in case you change the default with @command{set print type typedefs}.
19484 Print the offsets and sizes of fields in a struct, similar to what the
19485 @command{pahole} tool does. This option implies the @code{/tm} flags.
19488 Use hexadecimal notation when printing offsets and sizes of fields in a
19492 Use decimal notation when printing offsets and sizes of fields in a
19495 For example, given the following declarations:
19531 Issuing a @kbd{ptype /o struct tuv} command would print:
19534 (@value{GDBP}) ptype /o struct tuv
19535 /* offset | size */ type = struct tuv @{
19536 /* 0 | 4 */ int a1;
19537 /* XXX 4-byte hole */
19538 /* 8 | 8 */ char *a2;
19539 /* 16 | 4 */ int a3;
19541 /* total size (bytes): 24 */
19545 Notice the format of the first column of comments. There, you can
19546 find two parts separated by the @samp{|} character: the @emph{offset},
19547 which indicates where the field is located inside the struct, in
19548 bytes, and the @emph{size} of the field. Another interesting line is
19549 the marker of a @emph{hole} in the struct, indicating that it may be
19550 possible to pack the struct and make it use less space by reorganizing
19553 It is also possible to print offsets inside an union:
19556 (@value{GDBP}) ptype /o union qwe
19557 /* offset | size */ type = union qwe @{
19558 /* 24 */ struct tuv @{
19559 /* 0 | 4 */ int a1;
19560 /* XXX 4-byte hole */
19561 /* 8 | 8 */ char *a2;
19562 /* 16 | 4 */ int a3;
19564 /* total size (bytes): 24 */
19566 /* 40 */ struct xyz @{
19567 /* 0 | 4 */ int f1;
19568 /* 4 | 1 */ char f2;
19569 /* XXX 3-byte hole */
19570 /* 8 | 8 */ void *f3;
19571 /* 16 | 24 */ struct tuv @{
19572 /* 16 | 4 */ int a1;
19573 /* XXX 4-byte hole */
19574 /* 24 | 8 */ char *a2;
19575 /* 32 | 4 */ int a3;
19577 /* total size (bytes): 24 */
19580 /* total size (bytes): 40 */
19583 /* total size (bytes): 40 */
19587 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
19588 same space (because we are dealing with an union), the offset is not
19589 printed for them. However, you can still examine the offset of each
19590 of these structures' fields.
19592 Another useful scenario is printing the offsets of a struct containing
19596 (@value{GDBP}) ptype /o struct tyu
19597 /* offset | size */ type = struct tyu @{
19598 /* 0:31 | 4 */ int a1 : 1;
19599 /* 0:28 | 4 */ int a2 : 3;
19600 /* 0: 5 | 4 */ int a3 : 23;
19601 /* 3: 3 | 1 */ signed char a4 : 2;
19602 /* XXX 3-bit hole */
19603 /* XXX 4-byte hole */
19604 /* 8 | 8 */ int64_t a5;
19605 /* 16: 0 | 4 */ int a6 : 5;
19606 /* 16: 5 | 8 */ int64_t a7 : 3;
19607 /* XXX 7-byte padding */
19609 /* total size (bytes): 24 */
19613 Note how the offset information is now extended to also include the
19614 first bit of the bitfield.
19618 @item ptype[/@var{flags}] [@var{arg}]
19619 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
19620 detailed description of the type, instead of just the name of the type.
19621 @xref{Expressions, ,Expressions}.
19623 Contrary to @code{whatis}, @code{ptype} always unrolls any
19624 @code{typedef}s in its argument declaration, whether the argument is
19625 a variable, expression, or a data type. This means that @code{ptype}
19626 of a variable or an expression will not print literally its type as
19627 present in the source code---use @code{whatis} for that. @code{typedef}s at
19628 the pointer or reference targets are also unrolled. Only @code{typedef}s of
19629 fields, methods and inner @code{class typedef}s of @code{struct}s,
19630 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
19632 For example, for this variable declaration:
19635 typedef double real_t;
19636 struct complex @{ real_t real; double imag; @};
19637 typedef struct complex complex_t;
19639 real_t *real_pointer_var;
19643 the two commands give this output:
19647 (@value{GDBP}) whatis var
19649 (@value{GDBP}) ptype var
19650 type = struct complex @{
19654 (@value{GDBP}) whatis complex_t
19655 type = struct complex
19656 (@value{GDBP}) whatis struct complex
19657 type = struct complex
19658 (@value{GDBP}) ptype struct complex
19659 type = struct complex @{
19663 (@value{GDBP}) whatis real_pointer_var
19665 (@value{GDBP}) ptype real_pointer_var
19671 As with @code{whatis}, using @code{ptype} without an argument refers to
19672 the type of @code{$}, the last value in the value history.
19674 @cindex incomplete type
19675 Sometimes, programs use opaque data types or incomplete specifications
19676 of complex data structure. If the debug information included in the
19677 program does not allow @value{GDBN} to display a full declaration of
19678 the data type, it will say @samp{<incomplete type>}. For example,
19679 given these declarations:
19683 struct foo *fooptr;
19687 but no definition for @code{struct foo} itself, @value{GDBN} will say:
19690 (@value{GDBP}) ptype foo
19691 $1 = <incomplete type>
19695 ``Incomplete type'' is C terminology for data types that are not
19696 completely specified.
19698 @cindex unknown type
19699 Othertimes, information about a variable's type is completely absent
19700 from the debug information included in the program. This most often
19701 happens when the program or library where the variable is defined
19702 includes no debug information at all. @value{GDBN} knows the variable
19703 exists from inspecting the linker/loader symbol table (e.g., the ELF
19704 dynamic symbol table), but such symbols do not contain type
19705 information. Inspecting the type of a (global) variable for which
19706 @value{GDBN} has no type information shows:
19709 (@value{GDBP}) ptype var
19710 type = <data variable, no debug info>
19713 @xref{Variables, no debug info variables}, for how to print the values
19717 @item info types [-q] [@var{regexp}]
19718 Print a brief description of all types whose names match the regular
19719 expression @var{regexp} (or all types in your program, if you supply
19720 no argument). Each complete typename is matched as though it were a
19721 complete line; thus, @samp{i type value} gives information on all
19722 types in your program whose names include the string @code{value}, but
19723 @samp{i type ^value$} gives information only on types whose complete
19724 name is @code{value}.
19726 In programs using different languages, @value{GDBN} chooses the syntax
19727 to print the type description according to the
19728 @samp{set language} value: using @samp{set language auto}
19729 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19730 language of the type, other values mean to use
19731 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19733 This command differs from @code{ptype} in two ways: first, like
19734 @code{whatis}, it does not print a detailed description; second, it
19735 lists all source files and line numbers where a type is defined.
19737 The output from @samp{into types} is proceeded with a header line
19738 describing what types are being listed. The optional flag @samp{-q},
19739 which stands for @samp{quiet}, disables printing this header
19742 @kindex info type-printers
19743 @item info type-printers
19744 Versions of @value{GDBN} that ship with Python scripting enabled may
19745 have ``type printers'' available. When using @command{ptype} or
19746 @command{whatis}, these printers are consulted when the name of a type
19747 is needed. @xref{Type Printing API}, for more information on writing
19750 @code{info type-printers} displays all the available type printers.
19752 @kindex enable type-printer
19753 @kindex disable type-printer
19754 @item enable type-printer @var{name}@dots{}
19755 @item disable type-printer @var{name}@dots{}
19756 These commands can be used to enable or disable type printers.
19759 @cindex local variables
19760 @item info scope @var{locspec}
19761 List all the variables local to the lexical scope of the code location
19762 that results from resolving @var{locspec}. @xref{Location
19763 Specifications}, for details about supported forms of @var{locspec}.
19767 (@value{GDBP}) @b{info scope command_line_handler}
19768 Scope for command_line_handler:
19769 Symbol rl is an argument at stack/frame offset 8, length 4.
19770 Symbol linebuffer is in static storage at address 0x150a18, length 4.
19771 Symbol linelength is in static storage at address 0x150a1c, length 4.
19772 Symbol p is a local variable in register $esi, length 4.
19773 Symbol p1 is a local variable in register $ebx, length 4.
19774 Symbol nline is a local variable in register $edx, length 4.
19775 Symbol repeat is a local variable at frame offset -8, length 4.
19779 This command is especially useful for determining what data to collect
19780 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
19783 @kindex info source
19785 Show information about the current source file---that is, the source file for
19786 the function containing the current point of execution:
19789 the name of the source file, and the directory containing it,
19791 the directory it was compiled in,
19793 its length, in lines,
19795 which programming language it is written in,
19797 if the debug information provides it, the program that compiled the file
19798 (which may include, e.g., the compiler version and command line arguments),
19800 whether the executable includes debugging information for that file, and
19801 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
19803 whether the debugging information includes information about
19804 preprocessor macros.
19808 @kindex info sources
19809 @item info sources @r{[}-dirname | -basename@r{]} @r{[}--@r{]} @r{[}@var{regexp}@r{]}
19812 With no options @samp{info sources} prints the names of all source
19813 files in your program for which there is debugging information. The
19814 source files are presented based on a list of object files
19815 (executables and libraries) currently loaded into @value{GDBN}. For
19816 each object file all of the associated source files are listed.
19818 Each source file will only be printed once for each object file, but a
19819 single source file can be repeated in the output if it is part of
19820 multiple object files.
19822 If the optional @var{regexp} is provided, then only source files that
19823 match the regular expression will be printed. The matching is
19824 case-sensitive, except on operating systems that have case-insensitive
19825 filesystem (e.g., MS-Windows). @samp{--} can be used before
19826 @var{regexp} to prevent @value{GDBN} interpreting @var{regexp} as a
19827 command option (e.g. if @var{regexp} starts with @samp{-}).
19829 By default, the @var{regexp} is used to match anywhere in the
19830 filename. If @code{-dirname}, only files having a dirname matching
19831 @var{regexp} are shown. If @code{-basename}, only files having a
19832 basename matching @var{regexp} are shown.
19834 It is possible that an object file may be printed in the list with no
19835 associated source files. This can happen when either no source files
19836 match @var{regexp}, or, the object file was compiled without debug
19837 information and so @value{GDBN} is unable to find any source file
19840 @kindex info functions
19841 @item info functions [-q] [-n]
19842 Print the names and data types of all defined functions.
19843 Similarly to @samp{info types}, this command groups its output by source
19844 files and annotates each function definition with its source line
19847 In programs using different languages, @value{GDBN} chooses the syntax
19848 to print the function name and type according to the
19849 @samp{set language} value: using @samp{set language auto}
19850 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19851 language of the function, other values mean to use
19852 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19854 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19855 results. A non-debugging symbol is a symbol that comes from the
19856 executable's symbol table, not from the debug information (for
19857 example, DWARF) associated with the executable.
19859 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19860 printing header information and messages explaining why no functions
19863 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19864 Like @samp{info functions}, but only print the names and data types
19865 of the functions selected with the provided regexp(s).
19867 If @var{regexp} is provided, print only the functions whose names
19868 match the regular expression @var{regexp}.
19869 Thus, @samp{info fun step} finds all functions whose
19870 names include @code{step}; @samp{info fun ^step} finds those whose names
19871 start with @code{step}. If a function name contains characters that
19872 conflict with the regular expression language (e.g.@:
19873 @samp{operator*()}), they may be quoted with a backslash.
19875 If @var{type_regexp} is provided, print only the functions whose
19876 types, as printed by the @code{whatis} command, match
19877 the regular expression @var{type_regexp}.
19878 If @var{type_regexp} contains space(s), it should be enclosed in
19879 quote characters. If needed, use backslash to escape the meaning
19880 of special characters or quotes.
19881 Thus, @samp{info fun -t '^int ('} finds the functions that return
19882 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
19883 have an argument type containing int; @samp{info fun -t '^int (' ^step}
19884 finds the functions whose names start with @code{step} and that return
19887 If both @var{regexp} and @var{type_regexp} are provided, a function
19888 is printed only if its name matches @var{regexp} and its type matches
19892 @kindex info variables
19893 @item info variables [-q] [-n]
19894 Print the names and data types of all variables that are defined
19895 outside of functions (i.e.@: excluding local variables).
19896 The printed variables are grouped by source files and annotated with
19897 their respective source line numbers.
19899 In programs using different languages, @value{GDBN} chooses the syntax
19900 to print the variable name and type according to the
19901 @samp{set language} value: using @samp{set language auto}
19902 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19903 language of the variable, other values mean to use
19904 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19906 The @samp{-n} flag excludes non-debugging symbols from the results.
19908 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19909 printing header information and messages explaining why no variables
19912 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19913 Like @kbd{info variables}, but only print the variables selected
19914 with the provided regexp(s).
19916 If @var{regexp} is provided, print only the variables whose names
19917 match the regular expression @var{regexp}.
19919 If @var{type_regexp} is provided, print only the variables whose
19920 types, as printed by the @code{whatis} command, match
19921 the regular expression @var{type_regexp}.
19922 If @var{type_regexp} contains space(s), it should be enclosed in
19923 quote characters. If needed, use backslash to escape the meaning
19924 of special characters or quotes.
19926 If both @var{regexp} and @var{type_regexp} are provided, an argument
19927 is printed only if its name matches @var{regexp} and its type matches
19930 @kindex info modules
19932 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
19933 List all Fortran modules in the program, or all modules matching the
19934 optional regular expression @var{regexp}.
19936 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19937 printing header information and messages explaining why no modules
19940 @kindex info module
19941 @cindex Fortran modules, information about
19942 @cindex functions and variables by Fortran module
19943 @cindex module functions and variables
19944 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19945 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19946 List all functions or variables within all Fortran modules. The set
19947 of functions or variables listed can be limited by providing some or
19948 all of the optional regular expressions. If @var{module-regexp} is
19949 provided, then only Fortran modules matching @var{module-regexp} will
19950 be searched. Only functions or variables whose type matches the
19951 optional regular expression @var{type-regexp} will be listed. And
19952 only functions or variables whose name matches the optional regular
19953 expression @var{regexp} will be listed.
19955 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19956 printing header information and messages explaining why no functions
19957 or variables have been printed.
19959 @kindex info classes
19960 @cindex Objective-C, classes and selectors
19962 @itemx info classes @var{regexp}
19963 Display all Objective-C classes in your program, or
19964 (with the @var{regexp} argument) all those matching a particular regular
19967 @kindex info selectors
19968 @item info selectors
19969 @itemx info selectors @var{regexp}
19970 Display all Objective-C selectors in your program, or
19971 (with the @var{regexp} argument) all those matching a particular regular
19975 This was never implemented.
19976 @kindex info methods
19978 @itemx info methods @var{regexp}
19979 The @code{info methods} command permits the user to examine all defined
19980 methods within C@t{++} program, or (with the @var{regexp} argument) a
19981 specific set of methods found in the various C@t{++} classes. Many
19982 C@t{++} classes provide a large number of methods. Thus, the output
19983 from the @code{ptype} command can be overwhelming and hard to use. The
19984 @code{info-methods} command filters the methods, printing only those
19985 which match the regular-expression @var{regexp}.
19988 @cindex opaque data types
19989 @kindex set opaque-type-resolution
19990 @item set opaque-type-resolution on
19991 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
19992 declared as a pointer to a @code{struct}, @code{class}, or
19993 @code{union}---for example, @code{struct MyType *}---that is used in one
19994 source file although the full declaration of @code{struct MyType} is in
19995 another source file. The default is on.
19997 A change in the setting of this subcommand will not take effect until
19998 the next time symbols for a file are loaded.
20000 @item set opaque-type-resolution off
20001 Tell @value{GDBN} not to resolve opaque types. In this case, the type
20002 is printed as follows:
20004 @{<no data fields>@}
20007 @kindex show opaque-type-resolution
20008 @item show opaque-type-resolution
20009 Show whether opaque types are resolved or not.
20011 @kindex set print symbol-loading
20012 @cindex print messages when symbols are loaded
20013 @item set print symbol-loading
20014 @itemx set print symbol-loading full
20015 @itemx set print symbol-loading brief
20016 @itemx set print symbol-loading off
20017 The @code{set print symbol-loading} command allows you to control the
20018 printing of messages when @value{GDBN} loads symbol information.
20019 By default a message is printed for the executable and one for each
20020 shared library, and normally this is what you want. However, when
20021 debugging apps with large numbers of shared libraries these messages
20023 When set to @code{brief} a message is printed for each executable,
20024 and when @value{GDBN} loads a collection of shared libraries at once
20025 it will only print one message regardless of the number of shared
20026 libraries. When set to @code{off} no messages are printed.
20028 @kindex show print symbol-loading
20029 @item show print symbol-loading
20030 Show whether messages will be printed when a @value{GDBN} command
20031 entered from the keyboard causes symbol information to be loaded.
20033 @kindex maint print symbols
20034 @cindex symbol dump
20035 @kindex maint print psymbols
20036 @cindex partial symbol dump
20037 @kindex maint print msymbols
20038 @cindex minimal symbol dump
20039 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
20040 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20041 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20042 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20043 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20044 Write a dump of debugging symbol data into the file @var{filename} or
20045 the terminal if @var{filename} is unspecified.
20046 If @code{-objfile @var{objfile}} is specified, only dump symbols for
20048 If @code{-pc @var{address}} is specified, only dump symbols for the file
20049 with code at that address. Note that @var{address} may be a symbol like
20051 If @code{-source @var{source}} is specified, only dump symbols for that
20054 These commands are used to debug the @value{GDBN} symbol-reading code.
20055 These commands do not modify internal @value{GDBN} state, therefore
20056 @samp{maint print symbols} will only print symbols for already expanded symbol
20058 You can use the command @code{info sources} to find out which files these are.
20059 If you use @samp{maint print psymbols} instead, the dump shows information
20060 about symbols that @value{GDBN} only knows partially---that is, symbols
20061 defined in files that @value{GDBN} has skimmed, but not yet read completely.
20062 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
20065 @xref{Files, ,Commands to Specify Files}, for a discussion of how
20066 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
20068 @kindex maint info symtabs
20069 @kindex maint info psymtabs
20070 @cindex listing @value{GDBN}'s internal symbol tables
20071 @cindex symbol tables, listing @value{GDBN}'s internal
20072 @cindex full symbol tables, listing @value{GDBN}'s internal
20073 @cindex partial symbol tables, listing @value{GDBN}'s internal
20074 @item maint info symtabs @r{[} @var{regexp} @r{]}
20075 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
20077 List the @code{struct symtab} or @code{struct partial_symtab}
20078 structures whose names match @var{regexp}. If @var{regexp} is not
20079 given, list them all. The output includes expressions which you can
20080 copy into a @value{GDBN} debugging this one to examine a particular
20081 structure in more detail. For example:
20084 (@value{GDBP}) maint info psymtabs dwarf2read
20085 @{ objfile /home/gnu/build/gdb/gdb
20086 ((struct objfile *) 0x82e69d0)
20087 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
20088 ((struct partial_symtab *) 0x8474b10)
20091 text addresses 0x814d3c8 -- 0x8158074
20092 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
20093 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
20094 dependencies (none)
20097 (@value{GDBP}) maint info symtabs
20101 We see that there is one partial symbol table whose filename contains
20102 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
20103 and we see that @value{GDBN} has not read in any symtabs yet at all.
20104 If we set a breakpoint on a function, that will cause @value{GDBN} to
20105 read the symtab for the compilation unit containing that function:
20108 (@value{GDBP}) break dwarf2_psymtab_to_symtab
20109 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
20111 (@value{GDBP}) maint info symtabs
20112 @{ objfile /home/gnu/build/gdb/gdb
20113 ((struct objfile *) 0x82e69d0)
20114 @{ symtab /home/gnu/src/gdb/dwarf2read.c
20115 ((struct symtab *) 0x86c1f38)
20118 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
20119 linetable ((struct linetable *) 0x8370fa0)
20120 debugformat DWARF 2
20126 @kindex maint info line-table
20127 @cindex listing @value{GDBN}'s internal line tables
20128 @cindex line tables, listing @value{GDBN}'s internal
20129 @item maint info line-table @r{[} @var{regexp} @r{]}
20131 List the @code{struct linetable} from all @code{struct symtab}
20132 instances whose name matches @var{regexp}. If @var{regexp} is not
20133 given, list the @code{struct linetable} from all @code{struct symtab}.
20137 (@value{GDBP}) maint info line-table
20138 objfile: /home/gnu/build/a.out ((struct objfile *) 0x6120000e0d40)
20139 compunit_symtab: simple.cpp ((struct compunit_symtab *) 0x6210000ff450)
20140 symtab: /home/gnu/src/simple.cpp ((struct symtab *) 0x6210000ff4d0)
20141 linetable: ((struct linetable *) 0x62100012b760):
20142 INDEX LINE ADDRESS IS-STMT PROLOGUE-END
20143 0 3 0x0000000000401110 Y
20144 1 4 0x0000000000401114 Y Y
20145 2 9 0x0000000000401120 Y
20146 3 10 0x0000000000401124 Y Y
20147 4 10 0x0000000000401129
20148 5 15 0x0000000000401130 Y
20149 6 16 0x0000000000401134 Y Y
20150 7 16 0x0000000000401139
20151 8 21 0x0000000000401140 Y
20152 9 22 0x000000000040114f Y Y
20153 10 22 0x0000000000401154
20154 11 END 0x000000000040115a Y
20157 The @samp{IS-STMT} column indicates if the address is a recommended breakpoint
20158 location to represent a line or a statement. The @samp{PROLOGUE-END} column
20159 indicates that a given address is an adequate place to set a breakpoint at the
20160 first instruction following a function prologue.
20162 @kindex maint set symbol-cache-size
20163 @cindex symbol cache size
20164 @item maint set symbol-cache-size @var{size}
20165 Set the size of the symbol cache to @var{size}.
20166 The default size is intended to be good enough for debugging
20167 most applications. This option exists to allow for experimenting
20168 with different sizes.
20170 @kindex maint show symbol-cache-size
20171 @item maint show symbol-cache-size
20172 Show the size of the symbol cache.
20174 @kindex maint print symbol-cache
20175 @cindex symbol cache, printing its contents
20176 @item maint print symbol-cache
20177 Print the contents of the symbol cache.
20178 This is useful when debugging symbol cache issues.
20180 @kindex maint print symbol-cache-statistics
20181 @cindex symbol cache, printing usage statistics
20182 @item maint print symbol-cache-statistics
20183 Print symbol cache usage statistics.
20184 This helps determine how well the cache is being utilized.
20186 @kindex maint flush symbol-cache
20187 @kindex maint flush-symbol-cache
20188 @cindex symbol cache, flushing
20189 @item maint flush symbol-cache
20190 @itemx maint flush-symbol-cache
20191 Flush the contents of the symbol cache, all entries are removed. This
20192 command is useful when debugging the symbol cache. It is also useful
20193 when collecting performance data. The command @code{maint
20194 flush-symbol-cache} is deprecated in favor of @code{maint flush
20197 @kindex maint set ignore-prologue-end-flag
20198 @cindex prologue-end
20199 @item maint set ignore-prologue-end-flag [on|off]
20200 Enable or disable the use of the @samp{PROLOGUE-END} flag from the line-table.
20201 When @samp{off} (the default), @value{GDBN} uses the @samp{PROLOGUE-END} flag
20202 to place breakpoints past the end of a function prologue. When @samp{on},
20203 @value{GDBN} ignores the flag and relies on prologue analyzers to skip function
20206 @kindex maint show ignore-prologue-end-flag
20207 @item maint show ignore-prologue-end-flag
20208 Show whether @value{GDBN} will ignore the @samp{PROLOGUE-END} flag.
20213 @chapter Altering Execution
20215 Once you think you have found an error in your program, you might want to
20216 find out for certain whether correcting the apparent error would lead to
20217 correct results in the rest of the run. You can find the answer by
20218 experiment, using the @value{GDBN} features for altering execution of the
20221 For example, you can store new values into variables or memory
20222 locations, give your program a signal, restart it at a different
20223 address, or even return prematurely from a function.
20226 * Assignment:: Assignment to variables
20227 * Jumping:: Continuing at a different address
20228 * Signaling:: Giving your program a signal
20229 * Returning:: Returning from a function
20230 * Calling:: Calling your program's functions
20231 * Patching:: Patching your program
20232 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
20236 @section Assignment to Variables
20239 @cindex setting variables
20240 To alter the value of a variable, evaluate an assignment expression.
20241 @xref{Expressions, ,Expressions}. For example,
20248 stores the value 4 into the variable @code{x}, and then prints the
20249 value of the assignment expression (which is 4).
20250 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
20251 information on operators in supported languages.
20253 @kindex set variable
20254 @cindex variables, setting
20255 If you are not interested in seeing the value of the assignment, use the
20256 @code{set} command instead of the @code{print} command. @code{set} is
20257 really the same as @code{print} except that the expression's value is
20258 not printed and is not put in the value history (@pxref{Value History,
20259 ,Value History}). The expression is evaluated only for its effects.
20261 If the beginning of the argument string of the @code{set} command
20262 appears identical to a @code{set} subcommand, use the @code{set
20263 variable} command instead of just @code{set}. This command is identical
20264 to @code{set} except for its lack of subcommands. For example, if your
20265 program has a variable @code{width}, you get an error if you try to set
20266 a new value with just @samp{set width=13}, because @value{GDBN} has the
20267 command @code{set width}:
20270 (@value{GDBP}) whatis width
20272 (@value{GDBP}) p width
20274 (@value{GDBP}) set width=47
20275 Invalid syntax in expression.
20279 The invalid expression, of course, is @samp{=47}. In
20280 order to actually set the program's variable @code{width}, use
20283 (@value{GDBP}) set var width=47
20286 Because the @code{set} command has many subcommands that can conflict
20287 with the names of program variables, it is a good idea to use the
20288 @code{set variable} command instead of just @code{set}. For example, if
20289 your program has a variable @code{g}, you run into problems if you try
20290 to set a new value with just @samp{set g=4}, because @value{GDBN} has
20291 the command @code{set gnutarget}, abbreviated @code{set g}:
20295 (@value{GDBP}) whatis g
20299 (@value{GDBP}) set g=4
20303 The program being debugged has been started already.
20304 Start it from the beginning? (y or n) y
20305 Starting program: /home/smith/cc_progs/a.out
20306 "/home/smith/cc_progs/a.out": can't open to read symbols:
20307 Invalid bfd target.
20308 (@value{GDBP}) show g
20309 The current BFD target is "=4".
20314 The program variable @code{g} did not change, and you silently set the
20315 @code{gnutarget} to an invalid value. In order to set the variable
20319 (@value{GDBP}) set var g=4
20322 @value{GDBN} allows more implicit conversions in assignments than C; you can
20323 freely store an integer value into a pointer variable or vice versa,
20324 and you can convert any structure to any other structure that is the
20325 same length or shorter.
20326 @comment FIXME: how do structs align/pad in these conversions?
20327 @comment /doc@cygnus.com 18dec1990
20329 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
20330 construct to generate a value of specified type at a specified address
20331 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
20332 to memory location @code{0x83040} as an integer (which implies a certain size
20333 and representation in memory), and
20336 set @{int@}0x83040 = 4
20340 stores the value 4 into that memory location.
20343 @section Continuing at a Different Address
20345 Ordinarily, when you continue your program, you do so at the place where
20346 it stopped, with the @code{continue} command. You can instead continue at
20347 an address of your own choosing, with the following commands:
20351 @kindex j @r{(@code{jump})}
20352 @item jump @var{locspec}
20353 @itemx j @var{locspec}
20354 Resume execution at the address of the code location that results from
20355 resolving @var{locspec}.
20356 @xref{Location Specifications}, for a description of the different
20357 forms of @var{locspec}. If @var{locspec} resolves to more than one
20358 address, the command aborts before jumping.
20359 Execution stops again immediately if there is a breakpoint there. It
20360 is common practice to use the @code{tbreak} command in conjunction
20361 with @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
20363 The @code{jump} command does not change the current stack frame, or
20364 the stack pointer, or the contents of any memory location or any
20365 register other than the program counter. If @var{locspec} resolves to
20366 an address in a different function from the one currently executing, the
20367 results may be bizarre if the two functions expect different patterns
20368 of arguments or of local variables. For this reason, the @code{jump}
20369 command requests confirmation if the jump address is not in the
20370 function currently executing. However, even bizarre results are
20371 predictable if you are well acquainted with the machine-language code
20375 On many systems, you can get much the same effect as the @code{jump}
20376 command by storing a new value into the register @code{$pc}. The
20377 difference is that this does not start your program running; it only
20378 changes the address of where it @emph{will} run when you continue. For
20386 makes the next @code{continue} command or stepping command execute at
20387 address @code{0x485}, rather than at the address where your program stopped.
20388 @xref{Continuing and Stepping, ,Continuing and Stepping}.
20390 The most common occasion to use the @code{jump} command is to back
20391 up---perhaps with more breakpoints set---over a portion of a program
20392 that has already executed, in order to examine its execution in more
20397 @section Giving your Program a Signal
20398 @cindex deliver a signal to a program
20402 @item signal @var{signal}
20403 Resume execution where your program is stopped, but immediately give it the
20404 signal @var{signal}. The @var{signal} can be the name or the number of a
20405 signal. For example, on many systems @code{signal 2} and @code{signal
20406 SIGINT} are both ways of sending an interrupt signal.
20408 Alternatively, if @var{signal} is zero, continue execution without
20409 giving a signal. This is useful when your program stopped on account of
20410 a signal and would ordinarily see the signal when resumed with the
20411 @code{continue} command; @samp{signal 0} causes it to resume without a
20414 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
20415 delivered to the currently selected thread, not the thread that last
20416 reported a stop. This includes the situation where a thread was
20417 stopped due to a signal. So if you want to continue execution
20418 suppressing the signal that stopped a thread, you should select that
20419 same thread before issuing the @samp{signal 0} command. If you issue
20420 the @samp{signal 0} command with another thread as the selected one,
20421 @value{GDBN} detects that and asks for confirmation.
20423 Invoking the @code{signal} command is not the same as invoking the
20424 @code{kill} utility from the shell. Sending a signal with @code{kill}
20425 causes @value{GDBN} to decide what to do with the signal depending on
20426 the signal handling tables (@pxref{Signals}). The @code{signal} command
20427 passes the signal directly to your program.
20429 @code{signal} does not repeat when you press @key{RET} a second time
20430 after executing the command.
20432 @kindex queue-signal
20433 @item queue-signal @var{signal}
20434 Queue @var{signal} to be delivered immediately to the current thread
20435 when execution of the thread resumes. The @var{signal} can be the name or
20436 the number of a signal. For example, on many systems @code{signal 2} and
20437 @code{signal SIGINT} are both ways of sending an interrupt signal.
20438 The handling of the signal must be set to pass the signal to the program,
20439 otherwise @value{GDBN} will report an error.
20440 You can control the handling of signals from @value{GDBN} with the
20441 @code{handle} command (@pxref{Signals}).
20443 Alternatively, if @var{signal} is zero, any currently queued signal
20444 for the current thread is discarded and when execution resumes no signal
20445 will be delivered. This is useful when your program stopped on account
20446 of a signal and would ordinarily see the signal when resumed with the
20447 @code{continue} command.
20449 This command differs from the @code{signal} command in that the signal
20450 is just queued, execution is not resumed. And @code{queue-signal} cannot
20451 be used to pass a signal whose handling state has been set to @code{nopass}
20456 @xref{stepping into signal handlers}, for information on how stepping
20457 commands behave when the thread has a signal queued.
20460 @section Returning from a Function
20463 @cindex returning from a function
20466 @itemx return @var{expression}
20467 You can cancel execution of a function call with the @code{return}
20468 command. If you give an
20469 @var{expression} argument, its value is used as the function's return
20473 When you use @code{return}, @value{GDBN} discards the selected stack frame
20474 (and all frames within it). You can think of this as making the
20475 discarded frame return prematurely. If you wish to specify a value to
20476 be returned, give that value as the argument to @code{return}.
20478 This pops the selected stack frame (@pxref{Selection, ,Selecting a
20479 Frame}), and any other frames inside of it, leaving its caller as the
20480 innermost remaining frame. That frame becomes selected. The
20481 specified value is stored in the registers used for returning values
20484 The @code{return} command does not resume execution; it leaves the
20485 program stopped in the state that would exist if the function had just
20486 returned. In contrast, the @code{finish} command (@pxref{Continuing
20487 and Stepping, ,Continuing and Stepping}) resumes execution until the
20488 selected stack frame returns naturally.
20490 @value{GDBN} needs to know how the @var{expression} argument should be set for
20491 the inferior. The concrete registers assignment depends on the OS ABI and the
20492 type being returned by the selected stack frame. For example it is common for
20493 OS ABI to return floating point values in FPU registers while integer values in
20494 CPU registers. Still some ABIs return even floating point values in CPU
20495 registers. Larger integer widths (such as @code{long long int}) also have
20496 specific placement rules. @value{GDBN} already knows the OS ABI from its
20497 current target so it needs to find out also the type being returned to make the
20498 assignment into the right register(s).
20500 Normally, the selected stack frame has debug info. @value{GDBN} will always
20501 use the debug info instead of the implicit type of @var{expression} when the
20502 debug info is available. For example, if you type @kbd{return -1}, and the
20503 function in the current stack frame is declared to return a @code{long long
20504 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
20505 into a @code{long long int}:
20508 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
20510 (@value{GDBP}) return -1
20511 Make func return now? (y or n) y
20512 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
20513 43 printf ("result=%lld\n", func ());
20517 However, if the selected stack frame does not have a debug info, e.g., if the
20518 function was compiled without debug info, @value{GDBN} has to find out the type
20519 to return from user. Specifying a different type by mistake may set the value
20520 in different inferior registers than the caller code expects. For example,
20521 typing @kbd{return -1} with its implicit type @code{int} would set only a part
20522 of a @code{long long int} result for a debug info less function (on 32-bit
20523 architectures). Therefore the user is required to specify the return type by
20524 an appropriate cast explicitly:
20527 Breakpoint 2, 0x0040050b in func ()
20528 (@value{GDBP}) return -1
20529 Return value type not available for selected stack frame.
20530 Please use an explicit cast of the value to return.
20531 (@value{GDBP}) return (long long int) -1
20532 Make selected stack frame return now? (y or n) y
20533 #0 0x00400526 in main ()
20538 @section Calling Program Functions
20541 @cindex calling functions
20542 @cindex inferior functions, calling
20543 @item print @var{expr}
20544 Evaluate the expression @var{expr} and display the resulting value.
20545 The expression may include calls to functions in the program being
20549 @item call @var{expr}
20550 Evaluate the expression @var{expr} without displaying @code{void}
20553 You can use this variant of the @code{print} command if you want to
20554 execute a function from your program that does not return anything
20555 (a.k.a.@: @dfn{a void function}), but without cluttering the output
20556 with @code{void} returned values that @value{GDBN} will otherwise
20557 print. If the result is not void, it is printed and saved in the
20561 It is possible for the function you call via the @code{print} or
20562 @code{call} command to generate a signal (e.g., if there's a bug in
20563 the function, or if you passed it incorrect arguments). What happens
20564 in that case is controlled by the @code{set unwindonsignal} command.
20566 Similarly, with a C@t{++} program it is possible for the function you
20567 call via the @code{print} or @code{call} command to generate an
20568 exception that is not handled due to the constraints of the dummy
20569 frame. In this case, any exception that is raised in the frame, but has
20570 an out-of-frame exception handler will not be found. GDB builds a
20571 dummy-frame for the inferior function call, and the unwinder cannot
20572 seek for exception handlers outside of this dummy-frame. What happens
20573 in that case is controlled by the
20574 @code{set unwind-on-terminating-exception} command.
20577 @item set unwindonsignal
20578 @kindex set unwindonsignal
20579 @cindex unwind stack in called functions
20580 @cindex call dummy stack unwinding
20581 Set unwinding of the stack if a signal is received while in a function
20582 that @value{GDBN} called in the program being debugged. If set to on,
20583 @value{GDBN} unwinds the stack it created for the call and restores
20584 the context to what it was before the call. If set to off (the
20585 default), @value{GDBN} stops in the frame where the signal was
20588 @item show unwindonsignal
20589 @kindex show unwindonsignal
20590 Show the current setting of stack unwinding in the functions called by
20593 @item set unwind-on-terminating-exception
20594 @kindex set unwind-on-terminating-exception
20595 @cindex unwind stack in called functions with unhandled exceptions
20596 @cindex call dummy stack unwinding on unhandled exception.
20597 Set unwinding of the stack if a C@t{++} exception is raised, but left
20598 unhandled while in a function that @value{GDBN} called in the program being
20599 debugged. If set to on (the default), @value{GDBN} unwinds the stack
20600 it created for the call and restores the context to what it was before
20601 the call. If set to off, @value{GDBN} the exception is delivered to
20602 the default C@t{++} exception handler and the inferior terminated.
20604 @item show unwind-on-terminating-exception
20605 @kindex show unwind-on-terminating-exception
20606 Show the current setting of stack unwinding in the functions called by
20609 @item set may-call-functions
20610 @kindex set may-call-functions
20611 @cindex disabling calling functions in the program
20612 @cindex calling functions in the program, disabling
20613 Set permission to call functions in the program.
20614 This controls whether @value{GDBN} will attempt to call functions in
20615 the program, such as with expressions in the @code{print} command. It
20616 defaults to @code{on}.
20618 To call a function in the program, @value{GDBN} has to temporarily
20619 modify the state of the inferior. This has potentially undesired side
20620 effects. Also, having @value{GDBN} call nested functions is likely to
20621 be erroneous and may even crash the program being debugged. You can
20622 avoid such hazards by forbidding @value{GDBN} from calling functions
20623 in the program being debugged. If calling functions in the program
20624 is forbidden, GDB will throw an error when a command (such as printing
20625 an expression) starts a function call in the program.
20627 @item show may-call-functions
20628 @kindex show may-call-functions
20629 Show permission to call functions in the program.
20633 @subsection Calling functions with no debug info
20635 @cindex no debug info functions
20636 Sometimes, a function you wish to call is missing debug information.
20637 In such case, @value{GDBN} does not know the type of the function,
20638 including the types of the function's parameters. To avoid calling
20639 the inferior function incorrectly, which could result in the called
20640 function functioning erroneously and even crash, @value{GDBN} refuses
20641 to call the function unless you tell it the type of the function.
20643 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
20644 to do that. The simplest is to cast the call to the function's
20645 declared return type. For example:
20648 (@value{GDBP}) p getenv ("PATH")
20649 'getenv' has unknown return type; cast the call to its declared return type
20650 (@value{GDBP}) p (char *) getenv ("PATH")
20651 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
20654 Casting the return type of a no-debug function is equivalent to
20655 casting the function to a pointer to a prototyped function that has a
20656 prototype that matches the types of the passed-in arguments, and
20657 calling that. I.e., the call above is equivalent to:
20660 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
20664 and given this prototyped C or C++ function with float parameters:
20667 float multiply (float v1, float v2) @{ return v1 * v2; @}
20671 these calls are equivalent:
20674 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
20675 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
20678 If the function you wish to call is declared as unprototyped (i.e.@:
20679 old K&R style), you must use the cast-to-function-pointer syntax, so
20680 that @value{GDBN} knows that it needs to apply default argument
20681 promotions (promote float arguments to double). @xref{ABI, float
20682 promotion}. For example, given this unprototyped C function with
20683 float parameters, and no debug info:
20687 multiply_noproto (v1, v2)
20695 you call it like this:
20698 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
20702 @section Patching Programs
20704 @cindex patching binaries
20705 @cindex writing into executables
20706 @cindex writing into corefiles
20708 By default, @value{GDBN} opens the file containing your program's
20709 executable code (or the corefile) read-only. This prevents accidental
20710 alterations to machine code; but it also prevents you from intentionally
20711 patching your program's binary.
20713 If you'd like to be able to patch the binary, you can specify that
20714 explicitly with the @code{set write} command. For example, you might
20715 want to turn on internal debugging flags, or even to make emergency
20721 @itemx set write off
20722 If you specify @samp{set write on}, @value{GDBN} opens executable and
20723 core files for both reading and writing; if you specify @kbd{set write
20724 off} (the default), @value{GDBN} opens them read-only.
20726 If you have already loaded a file, you must load it again (using the
20727 @code{exec-file} or @code{core-file} command) after changing @code{set
20728 write}, for your new setting to take effect.
20732 Display whether executable files and core files are opened for writing
20733 as well as reading.
20736 @node Compiling and Injecting Code
20737 @section Compiling and injecting code in @value{GDBN}
20738 @cindex injecting code
20739 @cindex writing into executables
20740 @cindex compiling code
20742 @value{GDBN} supports on-demand compilation and code injection into
20743 programs running under @value{GDBN}. GCC 5.0 or higher built with
20744 @file{libcc1.so} must be installed for this functionality to be enabled.
20745 This functionality is implemented with the following commands.
20748 @kindex compile code
20749 @item compile code @var{source-code}
20750 @itemx compile code -raw @var{--} @var{source-code}
20751 Compile @var{source-code} with the compiler language found as the current
20752 language in @value{GDBN} (@pxref{Languages}). If compilation and
20753 injection is not supported with the current language specified in
20754 @value{GDBN}, or the compiler does not support this feature, an error
20755 message will be printed. If @var{source-code} compiles and links
20756 successfully, @value{GDBN} will load the object-code emitted,
20757 and execute it within the context of the currently selected inferior.
20758 It is important to note that the compiled code is executed immediately.
20759 After execution, the compiled code is removed from @value{GDBN} and any
20760 new types or variables you have defined will be deleted.
20762 The command allows you to specify @var{source-code} in two ways.
20763 The simplest method is to provide a single line of code to the command.
20767 compile code printf ("hello world\n");
20770 If you specify options on the command line as well as source code, they
20771 may conflict. The @samp{--} delimiter can be used to separate options
20772 from actual source code. E.g.:
20775 compile code -r -- printf ("hello world\n");
20778 Alternatively you can enter source code as multiple lines of text. To
20779 enter this mode, invoke the @samp{compile code} command without any text
20780 following the command. This will start the multiple-line editor and
20781 allow you to type as many lines of source code as required. When you
20782 have completed typing, enter @samp{end} on its own line to exit the
20787 >printf ("hello\n");
20788 >printf ("world\n");
20792 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
20793 provided @var{source-code} in a callable scope. In this case, you must
20794 specify the entry point of the code by defining a function named
20795 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
20796 inferior. Using @samp{-raw} option may be needed for example when
20797 @var{source-code} requires @samp{#include} lines which may conflict with
20798 inferior symbols otherwise.
20800 @kindex compile file
20801 @item compile file @var{filename}
20802 @itemx compile file -raw @var{filename}
20803 Like @code{compile code}, but take the source code from @var{filename}.
20806 compile file /home/user/example.c
20811 @item compile print [[@var{options}] --] @var{expr}
20812 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
20813 Compile and execute @var{expr} with the compiler language found as the
20814 current language in @value{GDBN} (@pxref{Languages}). By default the
20815 value of @var{expr} is printed in a format appropriate to its data type;
20816 you can choose a different format by specifying @samp{/@var{f}}, where
20817 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
20818 Formats}. The @code{compile print} command accepts the same options
20819 as the @code{print} command; see @ref{print options}.
20821 @item compile print [[@var{options}] --]
20822 @itemx compile print [[@var{options}] --] /@var{f}
20823 @cindex reprint the last value
20824 Alternatively you can enter the expression (source code producing it) as
20825 multiple lines of text. To enter this mode, invoke the @samp{compile print}
20826 command without any text following the command. This will start the
20827 multiple-line editor.
20831 The process of compiling and injecting the code can be inspected using:
20834 @anchor{set debug compile}
20835 @item set debug compile
20836 @cindex compile command debugging info
20837 Turns on or off display of @value{GDBN} process of compiling and
20838 injecting the code. The default is off.
20840 @item show debug compile
20841 Displays the current state of displaying @value{GDBN} process of
20842 compiling and injecting the code.
20844 @anchor{set debug compile-cplus-types}
20845 @item set debug compile-cplus-types
20846 @cindex compile C@t{++} type conversion
20847 Turns on or off the display of C@t{++} type conversion debugging information.
20848 The default is off.
20850 @item show debug compile-cplus-types
20851 Displays the current state of displaying debugging information for
20852 C@t{++} type conversion.
20855 @subsection Compilation options for the @code{compile} command
20857 @value{GDBN} needs to specify the right compilation options for the code
20858 to be injected, in part to make its ABI compatible with the inferior
20859 and in part to make the injected code compatible with @value{GDBN}'s
20863 The options used, in increasing precedence:
20866 @item target architecture and OS options (@code{gdbarch})
20867 These options depend on target processor type and target operating
20868 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
20869 (@code{-m64}) compilation option.
20871 @item compilation options recorded in the target
20872 @value{NGCC} (since version 4.7) stores the options used for compilation
20873 into @code{DW_AT_producer} part of DWARF debugging information according
20874 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
20875 explicitly specify @code{-g} during inferior compilation otherwise
20876 @value{NGCC} produces no DWARF. This feature is only relevant for
20877 platforms where @code{-g} produces DWARF by default, otherwise one may
20878 try to enforce DWARF by using @code{-gdwarf-4}.
20880 @item compilation options set by @code{set compile-args}
20884 You can override compilation options using the following command:
20887 @item set compile-args
20888 @cindex compile command options override
20889 Set compilation options used for compiling and injecting code with the
20890 @code{compile} commands. These options override any conflicting ones
20891 from the target architecture and/or options stored during inferior
20894 @item show compile-args
20895 Displays the current state of compilation options override.
20896 This does not show all the options actually used during compilation,
20897 use @ref{set debug compile} for that.
20900 @subsection Caveats when using the @code{compile} command
20902 There are a few caveats to keep in mind when using the @code{compile}
20903 command. As the caveats are different per language, the table below
20904 highlights specific issues on a per language basis.
20907 @item C code examples and caveats
20908 When the language in @value{GDBN} is set to @samp{C}, the compiler will
20909 attempt to compile the source code with a @samp{C} compiler. The source
20910 code provided to the @code{compile} command will have much the same
20911 access to variables and types as it normally would if it were part of
20912 the program currently being debugged in @value{GDBN}.
20914 Below is a sample program that forms the basis of the examples that
20915 follow. This program has been compiled and loaded into @value{GDBN},
20916 much like any other normal debugging session.
20919 void function1 (void)
20922 printf ("function 1\n");
20925 void function2 (void)
20940 For the purposes of the examples in this section, the program above has
20941 been compiled, loaded into @value{GDBN}, stopped at the function
20942 @code{main}, and @value{GDBN} is awaiting input from the user.
20944 To access variables and types for any program in @value{GDBN}, the
20945 program must be compiled and packaged with debug information. The
20946 @code{compile} command is not an exception to this rule. Without debug
20947 information, you can still use the @code{compile} command, but you will
20948 be very limited in what variables and types you can access.
20950 So with that in mind, the example above has been compiled with debug
20951 information enabled. The @code{compile} command will have access to
20952 all variables and types (except those that may have been optimized
20953 out). Currently, as @value{GDBN} has stopped the program in the
20954 @code{main} function, the @code{compile} command would have access to
20955 the variable @code{k}. You could invoke the @code{compile} command
20956 and type some source code to set the value of @code{k}. You can also
20957 read it, or do anything with that variable you would normally do in
20958 @code{C}. Be aware that changes to inferior variables in the
20959 @code{compile} command are persistent. In the following example:
20962 compile code k = 3;
20966 the variable @code{k} is now 3. It will retain that value until
20967 something else in the example program changes it, or another
20968 @code{compile} command changes it.
20970 Normal scope and access rules apply to source code compiled and
20971 injected by the @code{compile} command. In the example, the variables
20972 @code{j} and @code{k} are not accessible yet, because the program is
20973 currently stopped in the @code{main} function, where these variables
20974 are not in scope. Therefore, the following command
20977 compile code j = 3;
20981 will result in a compilation error message.
20983 Once the program is continued, execution will bring these variables in
20984 scope, and they will become accessible; then the code you specify via
20985 the @code{compile} command will be able to access them.
20987 You can create variables and types with the @code{compile} command as
20988 part of your source code. Variables and types that are created as part
20989 of the @code{compile} command are not visible to the rest of the program for
20990 the duration of its run. This example is valid:
20993 compile code int ff = 5; printf ("ff is %d\n", ff);
20996 However, if you were to type the following into @value{GDBN} after that
20997 command has completed:
21000 compile code printf ("ff is %d\n'', ff);
21004 a compiler error would be raised as the variable @code{ff} no longer
21005 exists. Object code generated and injected by the @code{compile}
21006 command is removed when its execution ends. Caution is advised
21007 when assigning to program variables values of variables created by the
21008 code submitted to the @code{compile} command. This example is valid:
21011 compile code int ff = 5; k = ff;
21014 The value of the variable @code{ff} is assigned to @code{k}. The variable
21015 @code{k} does not require the existence of @code{ff} to maintain the value
21016 it has been assigned. However, pointers require particular care in
21017 assignment. If the source code compiled with the @code{compile} command
21018 changed the address of a pointer in the example program, perhaps to a
21019 variable created in the @code{compile} command, that pointer would point
21020 to an invalid location when the command exits. The following example
21021 would likely cause issues with your debugged program:
21024 compile code int ff = 5; p = &ff;
21027 In this example, @code{p} would point to @code{ff} when the
21028 @code{compile} command is executing the source code provided to it.
21029 However, as variables in the (example) program persist with their
21030 assigned values, the variable @code{p} would point to an invalid
21031 location when the command exists. A general rule should be followed
21032 in that you should either assign @code{NULL} to any assigned pointers,
21033 or restore a valid location to the pointer before the command exits.
21035 Similar caution must be exercised with any structs, unions, and typedefs
21036 defined in @code{compile} command. Types defined in the @code{compile}
21037 command will no longer be available in the next @code{compile} command.
21038 Therefore, if you cast a variable to a type defined in the
21039 @code{compile} command, care must be taken to ensure that any future
21040 need to resolve the type can be achieved.
21043 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
21044 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
21045 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
21046 Compilation failed.
21047 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
21051 Variables that have been optimized away by the compiler are not
21052 accessible to the code submitted to the @code{compile} command.
21053 Access to those variables will generate a compiler error which @value{GDBN}
21054 will print to the console.
21057 @subsection Compiler search for the @code{compile} command
21059 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
21060 which may not be obvious for remote targets of different architecture
21061 than where @value{GDBN} is running. Environment variable @env{PATH} on
21062 @value{GDBN} host is searched for @value{NGCC} binary matching the
21063 target architecture and operating system. This search can be overriden
21064 by @code{set compile-gcc} @value{GDBN} command below. @env{PATH} is
21065 taken from shell that executed @value{GDBN}, it is not the value set by
21066 @value{GDBN} command @code{set environment}). @xref{Environment}.
21069 Specifically @env{PATH} is searched for binaries matching regular expression
21070 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
21071 debugged. @var{arch} is processor name --- multiarch is supported, so for
21072 example both @code{i386} and @code{x86_64} targets look for pattern
21073 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
21074 for pattern @code{s390x?}. @var{os} is currently supported only for
21075 pattern @code{linux(-gnu)?}.
21077 On Posix hosts the compiler driver @value{GDBN} needs to find also
21078 shared library @file{libcc1.so} from the compiler. It is searched in
21079 default shared library search path (overridable with usual environment
21080 variable @env{LD_LIBRARY_PATH}), unrelated to @env{PATH} or @code{set
21081 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
21082 according to the installation of the found compiler --- as possibly
21083 specified by the @code{set compile-gcc} command.
21086 @item set compile-gcc
21087 @cindex compile command driver filename override
21088 Set compilation command used for compiling and injecting code with the
21089 @code{compile} commands. If this option is not set (it is set to
21090 an empty string), the search described above will occur --- that is the
21093 @item show compile-gcc
21094 Displays the current compile command @value{NGCC} driver filename.
21095 If set, it is the main command @command{gcc}, found usually for example
21096 under name @file{x86_64-linux-gnu-gcc}.
21100 @chapter @value{GDBN} Files
21102 @value{GDBN} needs to know the file name of the program to be debugged,
21103 both in order to read its symbol table and in order to start your
21104 program. To debug a core dump of a previous run, you must also tell
21105 @value{GDBN} the name of the core dump file.
21108 * Files:: Commands to specify files
21109 * File Caching:: Information about @value{GDBN}'s file caching
21110 * Separate Debug Files:: Debugging information in separate files
21111 * MiniDebugInfo:: Debugging information in a special section
21112 * Index Files:: Index files speed up GDB
21113 * Symbol Errors:: Errors reading symbol files
21114 * Data Files:: GDB data files
21118 @section Commands to Specify Files
21120 @cindex symbol table
21121 @cindex core dump file
21123 You may want to specify executable and core dump file names. The usual
21124 way to do this is at start-up time, using the arguments to
21125 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
21126 Out of @value{GDBN}}).
21128 Occasionally it is necessary to change to a different file during a
21129 @value{GDBN} session. Or you may run @value{GDBN} and forget to
21130 specify a file you want to use. Or you are debugging a remote target
21131 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
21132 Program}). In these situations the @value{GDBN} commands to specify
21133 new files are useful.
21136 @cindex executable file
21138 @item file @var{filename}
21139 Use @var{filename} as the program to be debugged. It is read for its
21140 symbols and for the contents of pure memory. It is also the program
21141 executed when you use the @code{run} command. If you do not specify a
21142 directory and the file is not found in the @value{GDBN} working directory,
21143 @value{GDBN} uses the environment variable @env{PATH} as a list of
21144 directories to search, just as the shell does when looking for a program
21145 to run. You can change the value of this variable, for both @value{GDBN}
21146 and your program, using the @code{path} command.
21148 @cindex unlinked object files
21149 @cindex patching object files
21150 You can load unlinked object @file{.o} files into @value{GDBN} using
21151 the @code{file} command. You will not be able to ``run'' an object
21152 file, but you can disassemble functions and inspect variables. Also,
21153 if the underlying BFD functionality supports it, you could use
21154 @kbd{gdb -write} to patch object files using this technique. Note
21155 that @value{GDBN} can neither interpret nor modify relocations in this
21156 case, so branches and some initialized variables will appear to go to
21157 the wrong place. But this feature is still handy from time to time.
21160 @code{file} with no argument makes @value{GDBN} discard any information it
21161 has on both executable file and the symbol table.
21164 @item exec-file @r{[} @var{filename} @r{]}
21165 Specify that the program to be run (but not the symbol table) is found
21166 in @var{filename}. @value{GDBN} searches the environment variable @env{PATH}
21167 if necessary to locate your program. Omitting @var{filename} means to
21168 discard information on the executable file.
21170 @kindex symbol-file
21171 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
21172 Read symbol table information from file @var{filename}. @env{PATH} is
21173 searched when necessary. Use the @code{file} command to get both symbol
21174 table and program to run from the same file.
21176 If an optional @var{offset} is specified, it is added to the start
21177 address of each section in the symbol file. This is useful if the
21178 program is relocated at runtime, such as the Linux kernel with kASLR
21181 @code{symbol-file} with no argument clears out @value{GDBN} information on your
21182 program's symbol table.
21184 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
21185 some breakpoints and auto-display expressions. This is because they may
21186 contain pointers to the internal data recording symbols and data types,
21187 which are part of the old symbol table data being discarded inside
21190 @code{symbol-file} does not repeat if you press @key{RET} again after
21193 When @value{GDBN} is configured for a particular environment, it
21194 understands debugging information in whatever format is the standard
21195 generated for that environment; you may use either a @sc{gnu} compiler, or
21196 other compilers that adhere to the local conventions.
21197 Best results are usually obtained from @sc{gnu} compilers; for example,
21198 using @code{@value{NGCC}} you can generate debugging information for
21201 For most kinds of object files, with the exception of old SVR3 systems
21202 using COFF, the @code{symbol-file} command does not normally read the
21203 symbol table in full right away. Instead, it scans the symbol table
21204 quickly to find which source files and which symbols are present. The
21205 details are read later, one source file at a time, as they are needed.
21207 The purpose of this two-stage reading strategy is to make @value{GDBN}
21208 start up faster. For the most part, it is invisible except for
21209 occasional pauses while the symbol table details for a particular source
21210 file are being read. (The @code{set verbose} command can turn these
21211 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
21212 Warnings and Messages}.)
21214 We have not implemented the two-stage strategy for COFF yet. When the
21215 symbol table is stored in COFF format, @code{symbol-file} reads the
21216 symbol table data in full right away. Note that ``stabs-in-COFF''
21217 still does the two-stage strategy, since the debug info is actually
21221 @cindex reading symbols immediately
21222 @cindex symbols, reading immediately
21223 @item symbol-file @r{[} -readnow @r{]} @var{filename}
21224 @itemx file @r{[} -readnow @r{]} @var{filename}
21225 You can override the @value{GDBN} two-stage strategy for reading symbol
21226 tables by using the @samp{-readnow} option with any of the commands that
21227 load symbol table information, if you want to be sure @value{GDBN} has the
21228 entire symbol table available.
21230 @cindex @code{-readnever}, option for symbol-file command
21231 @cindex never read symbols
21232 @cindex symbols, never read
21233 @item symbol-file @r{[} -readnever @r{]} @var{filename}
21234 @itemx file @r{[} -readnever @r{]} @var{filename}
21235 You can instruct @value{GDBN} to never read the symbolic information
21236 contained in @var{filename} by using the @samp{-readnever} option.
21237 @xref{--readnever}.
21239 @c FIXME: for now no mention of directories, since this seems to be in
21240 @c flux. 13mar1992 status is that in theory GDB would look either in
21241 @c current dir or in same dir as myprog; but issues like competing
21242 @c GDB's, or clutter in system dirs, mean that in practice right now
21243 @c only current dir is used. FFish says maybe a special GDB hierarchy
21244 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
21248 @item core-file @r{[}@var{filename}@r{]}
21250 Specify the whereabouts of a core dump file to be used as the ``contents
21251 of memory''. Traditionally, core files contain only some parts of the
21252 address space of the process that generated them; @value{GDBN} can access the
21253 executable file itself for other parts.
21255 @code{core-file} with no argument specifies that no core file is
21258 Note that the core file is ignored when your program is actually running
21259 under @value{GDBN}. So, if you have been running your program and you
21260 wish to debug a core file instead, you must kill the subprocess in which
21261 the program is running. To do this, use the @code{kill} command
21262 (@pxref{Kill Process, ,Killing the Child Process}).
21264 @kindex add-symbol-file
21265 @cindex dynamic linking
21266 @item add-symbol-file @var{filename} @r{[} -readnow @r{|} -readnever @r{]} @r{[} -o @var{offset} @r{]} @r{[} @var{textaddress} @r{]} @r{[} -s @var{section} @var{address} @dots{} @r{]}
21267 The @code{add-symbol-file} command reads additional symbol table
21268 information from the file @var{filename}. You would use this command
21269 when @var{filename} has been dynamically loaded (by some other means)
21270 into the program that is running. The @var{textaddress} parameter gives
21271 the memory address at which the file's text section has been loaded.
21272 You can additionally specify the base address of other sections using
21273 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
21274 If a section is omitted, @value{GDBN} will use its default addresses
21275 as found in @var{filename}. Any @var{address} or @var{textaddress}
21276 can be given as an expression.
21278 If an optional @var{offset} is specified, it is added to the start
21279 address of each section, except those for which the address was
21280 specified explicitly.
21282 The symbol table of the file @var{filename} is added to the symbol table
21283 originally read with the @code{symbol-file} command. You can use the
21284 @code{add-symbol-file} command any number of times; the new symbol data
21285 thus read is kept in addition to the old.
21287 Changes can be reverted using the command @code{remove-symbol-file}.
21289 @cindex relocatable object files, reading symbols from
21290 @cindex object files, relocatable, reading symbols from
21291 @cindex reading symbols from relocatable object files
21292 @cindex symbols, reading from relocatable object files
21293 @cindex @file{.o} files, reading symbols from
21294 Although @var{filename} is typically a shared library file, an
21295 executable file, or some other object file which has been fully
21296 relocated for loading into a process, you can also load symbolic
21297 information from relocatable @file{.o} files, as long as:
21301 the file's symbolic information refers only to linker symbols defined in
21302 that file, not to symbols defined by other object files,
21304 every section the file's symbolic information refers to has actually
21305 been loaded into the inferior, as it appears in the file, and
21307 you can determine the address at which every section was loaded, and
21308 provide these to the @code{add-symbol-file} command.
21312 Some embedded operating systems, like Sun Chorus and VxWorks, can load
21313 relocatable files into an already running program; such systems
21314 typically make the requirements above easy to meet. However, it's
21315 important to recognize that many native systems use complex link
21316 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
21317 assembly, for example) that make the requirements difficult to meet. In
21318 general, one cannot assume that using @code{add-symbol-file} to read a
21319 relocatable object file's symbolic information will have the same effect
21320 as linking the relocatable object file into the program in the normal
21323 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
21325 @kindex remove-symbol-file
21326 @item remove-symbol-file @var{filename}
21327 @item remove-symbol-file -a @var{address}
21328 Remove a symbol file added via the @code{add-symbol-file} command. The
21329 file to remove can be identified by its @var{filename} or by an @var{address}
21330 that lies within the boundaries of this symbol file in memory. Example:
21333 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
21334 add symbol table from file "/home/user/gdb/mylib.so" at
21335 .text_addr = 0x7ffff7ff9480
21337 Reading symbols from /home/user/gdb/mylib.so...
21338 (gdb) remove-symbol-file -a 0x7ffff7ff9480
21339 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
21344 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
21346 @kindex add-symbol-file-from-memory
21347 @cindex @code{syscall DSO}
21348 @cindex load symbols from memory
21349 @item add-symbol-file-from-memory @var{address}
21350 Load symbols from the given @var{address} in a dynamically loaded
21351 object file whose image is mapped directly into the inferior's memory.
21352 For example, the Linux kernel maps a @code{syscall DSO} into each
21353 process's address space; this DSO provides kernel-specific code for
21354 some system calls. The argument can be any expression whose
21355 evaluation yields the address of the file's shared object file header.
21356 For this command to work, you must have used @code{symbol-file} or
21357 @code{exec-file} commands in advance.
21360 @item section @var{section} @var{addr}
21361 The @code{section} command changes the base address of the named
21362 @var{section} of the exec file to @var{addr}. This can be used if the
21363 exec file does not contain section addresses, (such as in the
21364 @code{a.out} format), or when the addresses specified in the file
21365 itself are wrong. Each section must be changed separately. The
21366 @code{info files} command, described below, lists all the sections and
21370 @kindex info target
21373 @code{info files} and @code{info target} are synonymous; both print the
21374 current target (@pxref{Targets, ,Specifying a Debugging Target}),
21375 including the names of the executable and core dump files currently in
21376 use by @value{GDBN}, and the files from which symbols were loaded. The
21377 command @code{help target} lists all possible targets rather than
21380 @kindex maint info sections
21381 @item maint info sections @r{[}-all-objects@r{]} @r{[}@var{filter-list}@r{]}
21382 Another command that can give you extra information about program sections
21383 is @code{maint info sections}. In addition to the section information
21384 displayed by @code{info files}, this command displays the flags and file
21385 offset of each section in the executable and core dump files.
21387 When @samp{-all-objects} is passed then sections from all loaded object
21388 files, including shared libraries, are printed.
21390 The optional @var{filter-list} is a space separated list of filter
21391 keywords. Sections that match any one of the filter criteria will be
21392 printed. There are two types of filter:
21395 @item @var{section-name}
21396 Display information about any section named @var{section-name}.
21397 @item @var{section-flag}
21398 Display information for any section with @var{section-flag}. The
21399 section flags that @value{GDBN} currently knows about are:
21402 Section will have space allocated in the process when loaded.
21403 Set for all sections except those containing debug information.
21405 Section will be loaded from the file into the child process memory.
21406 Set for pre-initialized code and data, clear for @code{.bss} sections.
21408 Section needs to be relocated before loading.
21410 Section cannot be modified by the child process.
21412 Section contains executable code only.
21414 Section contains data only (no executable code).
21416 Section will reside in ROM.
21418 Section contains data for constructor/destructor lists.
21420 Section is not empty.
21422 An instruction to the linker to not output the section.
21423 @item COFF_SHARED_LIBRARY
21424 A notification to the linker that the section contains
21425 COFF shared library information.
21427 Section contains common symbols.
21431 @kindex maint info target-sections
21432 @item maint info target-sections
21433 This command prints @value{GDBN}'s internal section table. For each
21434 target @value{GDBN} maintains a table containing the allocatable
21435 sections from all currently mapped objects, along with information
21436 about where the section is mapped.
21438 @kindex set trust-readonly-sections
21439 @cindex read-only sections
21440 @item set trust-readonly-sections on
21441 Tell @value{GDBN} that readonly sections in your object file
21442 really are read-only (i.e.@: that their contents will not change).
21443 In that case, @value{GDBN} can fetch values from these sections
21444 out of the object file, rather than from the target program.
21445 For some targets (notably embedded ones), this can be a significant
21446 enhancement to debugging performance.
21448 The default is off.
21450 @item set trust-readonly-sections off
21451 Tell @value{GDBN} not to trust readonly sections. This means that
21452 the contents of the section might change while the program is running,
21453 and must therefore be fetched from the target when needed.
21455 @item show trust-readonly-sections
21456 Show the current setting of trusting readonly sections.
21459 All file-specifying commands allow both absolute and relative file names
21460 as arguments. @value{GDBN} always converts the file name to an absolute file
21461 name and remembers it that way.
21463 @cindex shared libraries
21464 @anchor{Shared Libraries}
21465 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
21466 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
21467 DSBT (TIC6X) shared libraries.
21469 On MS-Windows @value{GDBN} must be linked with the Expat library to support
21470 shared libraries. @xref{Expat}.
21472 @value{GDBN} automatically loads symbol definitions from shared libraries
21473 when you use the @code{run} command, or when you examine a core file.
21474 (Before you issue the @code{run} command, @value{GDBN} does not understand
21475 references to a function in a shared library, however---unless you are
21476 debugging a core file).
21478 @c FIXME: some @value{GDBN} release may permit some refs to undef
21479 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
21480 @c FIXME...lib; check this from time to time when updating manual
21482 There are times, however, when you may wish to not automatically load
21483 symbol definitions from shared libraries, such as when they are
21484 particularly large or there are many of them.
21486 To control the automatic loading of shared library symbols, use the
21490 @kindex set auto-solib-add
21491 @item set auto-solib-add @var{mode}
21492 If @var{mode} is @code{on}, symbols from all shared object libraries
21493 will be loaded automatically when the inferior begins execution, you
21494 attach to an independently started inferior, or when the dynamic linker
21495 informs @value{GDBN} that a new library has been loaded. If @var{mode}
21496 is @code{off}, symbols must be loaded manually, using the
21497 @code{sharedlibrary} command. The default value is @code{on}.
21499 @cindex memory used for symbol tables
21500 If your program uses lots of shared libraries with debug info that
21501 takes large amounts of memory, you can decrease the @value{GDBN}
21502 memory footprint by preventing it from automatically loading the
21503 symbols from shared libraries. To that end, type @kbd{set
21504 auto-solib-add off} before running the inferior, then load each
21505 library whose debug symbols you do need with @kbd{sharedlibrary
21506 @var{regexp}}, where @var{regexp} is a regular expression that matches
21507 the libraries whose symbols you want to be loaded.
21509 @kindex show auto-solib-add
21510 @item show auto-solib-add
21511 Display the current autoloading mode.
21514 @cindex load shared library
21515 To explicitly load shared library symbols, use the @code{sharedlibrary}
21519 @kindex info sharedlibrary
21521 @item info share @var{regex}
21522 @itemx info sharedlibrary @var{regex}
21523 Print the names of the shared libraries which are currently loaded
21524 that match @var{regex}. If @var{regex} is omitted then print
21525 all shared libraries that are loaded.
21528 @item info dll @var{regex}
21529 This is an alias of @code{info sharedlibrary}.
21531 @kindex sharedlibrary
21533 @item sharedlibrary @var{regex}
21534 @itemx share @var{regex}
21535 Load shared object library symbols for files matching a
21536 Unix regular expression.
21537 As with files loaded automatically, it only loads shared libraries
21538 required by your program for a core file or after typing @code{run}. If
21539 @var{regex} is omitted all shared libraries required by your program are
21542 @item nosharedlibrary
21543 @kindex nosharedlibrary
21544 @cindex unload symbols from shared libraries
21545 Unload all shared object library symbols. This discards all symbols
21546 that have been loaded from all shared libraries. Symbols from shared
21547 libraries that were loaded by explicit user requests are not
21551 Sometimes you may wish that @value{GDBN} stops and gives you control
21552 when any of shared library events happen. The best way to do this is
21553 to use @code{catch load} and @code{catch unload} (@pxref{Set
21556 @value{GDBN} also supports the @code{set stop-on-solib-events}
21557 command for this. This command exists for historical reasons. It is
21558 less useful than setting a catchpoint, because it does not allow for
21559 conditions or commands as a catchpoint does.
21562 @item set stop-on-solib-events
21563 @kindex set stop-on-solib-events
21564 This command controls whether @value{GDBN} should give you control
21565 when the dynamic linker notifies it about some shared library event.
21566 The most common event of interest is loading or unloading of a new
21569 @item show stop-on-solib-events
21570 @kindex show stop-on-solib-events
21571 Show whether @value{GDBN} stops and gives you control when shared
21572 library events happen.
21575 Shared libraries are also supported in many cross or remote debugging
21576 configurations. @value{GDBN} needs to have access to the target's libraries;
21577 this can be accomplished either by providing copies of the libraries
21578 on the host system, or by asking @value{GDBN} to automatically retrieve the
21579 libraries from the target. If copies of the target libraries are
21580 provided, they need to be the same as the target libraries, although the
21581 copies on the target can be stripped as long as the copies on the host are
21584 @cindex where to look for shared libraries
21585 For remote debugging, you need to tell @value{GDBN} where the target
21586 libraries are, so that it can load the correct copies---otherwise, it
21587 may try to load the host's libraries. @value{GDBN} has two variables
21588 to specify the search directories for target libraries.
21591 @cindex prefix for executable and shared library file names
21592 @cindex system root, alternate
21593 @kindex set solib-absolute-prefix
21594 @kindex set sysroot
21595 @item set sysroot @var{path}
21596 Use @var{path} as the system root for the program being debugged. Any
21597 absolute shared library paths will be prefixed with @var{path}; many
21598 runtime loaders store the absolute paths to the shared library in the
21599 target program's memory. When starting processes remotely, and when
21600 attaching to already-running processes (local or remote), their
21601 executable filenames will be prefixed with @var{path} if reported to
21602 @value{GDBN} as absolute by the operating system. If you use
21603 @code{set sysroot} to find executables and shared libraries, they need
21604 to be laid out in the same way that they are on the target, with
21605 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
21608 If @var{path} starts with the sequence @file{target:} and the target
21609 system is remote then @value{GDBN} will retrieve the target binaries
21610 from the remote system. This is only supported when using a remote
21611 target that supports the @code{remote get} command (@pxref{File
21612 Transfer,,Sending files to a remote system}). The part of @var{path}
21613 following the initial @file{target:} (if present) is used as system
21614 root prefix on the remote file system. If @var{path} starts with the
21615 sequence @file{remote:} this is converted to the sequence
21616 @file{target:} by @code{set sysroot}@footnote{Historically the
21617 functionality to retrieve binaries from the remote system was
21618 provided by prefixing @var{path} with @file{remote:}}. If you want
21619 to specify a local system root using a directory that happens to be
21620 named @file{target:} or @file{remote:}, you need to use some
21621 equivalent variant of the name like @file{./target:}.
21623 For targets with an MS-DOS based filesystem, such as MS-Windows,
21624 @value{GDBN} tries prefixing a few variants of the target
21625 absolute file name with @var{path}. But first, on Unix hosts,
21626 @value{GDBN} converts all backslash directory separators into forward
21627 slashes, because the backslash is not a directory separator on Unix:
21630 c:\foo\bar.dll @result{} c:/foo/bar.dll
21633 Then, @value{GDBN} attempts prefixing the target file name with
21634 @var{path}, and looks for the resulting file name in the host file
21638 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
21641 If that does not find the binary, @value{GDBN} tries removing
21642 the @samp{:} character from the drive spec, both for convenience, and,
21643 for the case of the host file system not supporting file names with
21647 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
21650 This makes it possible to have a system root that mirrors a target
21651 with more than one drive. E.g., you may want to setup your local
21652 copies of the target system shared libraries like so (note @samp{c} vs
21656 @file{/path/to/sysroot/c/sys/bin/foo.dll}
21657 @file{/path/to/sysroot/c/sys/bin/bar.dll}
21658 @file{/path/to/sysroot/z/sys/bin/bar.dll}
21662 and point the system root at @file{/path/to/sysroot}, so that
21663 @value{GDBN} can find the correct copies of both
21664 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
21666 If that still does not find the binary, @value{GDBN} tries
21667 removing the whole drive spec from the target file name:
21670 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
21673 This last lookup makes it possible to not care about the drive name,
21674 if you don't want or need to.
21676 The @code{set solib-absolute-prefix} command is an alias for @code{set
21679 @cindex default system root
21680 @cindex @samp{--with-sysroot}
21681 You can set the default system root by using the configure-time
21682 @samp{--with-sysroot} option. If the system root is inside
21683 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21684 @samp{--exec-prefix}), then the default system root will be updated
21685 automatically if the installed @value{GDBN} is moved to a new
21688 @kindex show sysroot
21690 Display the current executable and shared library prefix.
21692 @kindex set solib-search-path
21693 @item set solib-search-path @var{path}
21694 If this variable is set, @var{path} is a colon-separated list of
21695 directories to search for shared libraries. @samp{solib-search-path}
21696 is used after @samp{sysroot} fails to locate the library, or if the
21697 path to the library is relative instead of absolute. If you want to
21698 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
21699 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
21700 finding your host's libraries. @samp{sysroot} is preferred; setting
21701 it to a nonexistent directory may interfere with automatic loading
21702 of shared library symbols.
21704 @kindex show solib-search-path
21705 @item show solib-search-path
21706 Display the current shared library search path.
21708 @cindex DOS file-name semantics of file names.
21709 @kindex set target-file-system-kind (unix|dos-based|auto)
21710 @kindex show target-file-system-kind
21711 @item set target-file-system-kind @var{kind}
21712 Set assumed file system kind for target reported file names.
21714 Shared library file names as reported by the target system may not
21715 make sense as is on the system @value{GDBN} is running on. For
21716 example, when remote debugging a target that has MS-DOS based file
21717 system semantics, from a Unix host, the target may be reporting to
21718 @value{GDBN} a list of loaded shared libraries with file names such as
21719 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
21720 drive letters, so the @samp{c:\} prefix is not normally understood as
21721 indicating an absolute file name, and neither is the backslash
21722 normally considered a directory separator character. In that case,
21723 the native file system would interpret this whole absolute file name
21724 as a relative file name with no directory components. This would make
21725 it impossible to point @value{GDBN} at a copy of the remote target's
21726 shared libraries on the host using @code{set sysroot}, and impractical
21727 with @code{set solib-search-path}. Setting
21728 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
21729 to interpret such file names similarly to how the target would, and to
21730 map them to file names valid on @value{GDBN}'s native file system
21731 semantics. The value of @var{kind} can be @code{"auto"}, in addition
21732 to one of the supported file system kinds. In that case, @value{GDBN}
21733 tries to determine the appropriate file system variant based on the
21734 current target's operating system (@pxref{ABI, ,Configuring the
21735 Current ABI}). The supported file system settings are:
21739 Instruct @value{GDBN} to assume the target file system is of Unix
21740 kind. Only file names starting the forward slash (@samp{/}) character
21741 are considered absolute, and the directory separator character is also
21745 Instruct @value{GDBN} to assume the target file system is DOS based.
21746 File names starting with either a forward slash, or a drive letter
21747 followed by a colon (e.g., @samp{c:}), are considered absolute, and
21748 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
21749 considered directory separators.
21752 Instruct @value{GDBN} to use the file system kind associated with the
21753 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
21754 This is the default.
21758 @cindex file name canonicalization
21759 @cindex base name differences
21760 When processing file names provided by the user, @value{GDBN}
21761 frequently needs to compare them to the file names recorded in the
21762 program's debug info. Normally, @value{GDBN} compares just the
21763 @dfn{base names} of the files as strings, which is reasonably fast
21764 even for very large programs. (The base name of a file is the last
21765 portion of its name, after stripping all the leading directories.)
21766 This shortcut in comparison is based upon the assumption that files
21767 cannot have more than one base name. This is usually true, but
21768 references to files that use symlinks or similar filesystem
21769 facilities violate that assumption. If your program records files
21770 using such facilities, or if you provide file names to @value{GDBN}
21771 using symlinks etc., you can set @code{basenames-may-differ} to
21772 @code{true} to instruct @value{GDBN} to completely canonicalize each
21773 pair of file names it needs to compare. This will make file-name
21774 comparisons accurate, but at a price of a significant slowdown.
21777 @item set basenames-may-differ
21778 @kindex set basenames-may-differ
21779 Set whether a source file may have multiple base names.
21781 @item show basenames-may-differ
21782 @kindex show basenames-may-differ
21783 Show whether a source file may have multiple base names.
21787 @section File Caching
21788 @cindex caching of opened files
21789 @cindex caching of bfd objects
21791 To speed up file loading, and reduce memory usage, @value{GDBN} will
21792 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
21793 BFD, bfd, The Binary File Descriptor Library}. The following commands
21794 allow visibility and control of the caching behavior.
21797 @kindex maint info bfds
21798 @item maint info bfds
21799 This prints information about each @code{bfd} object that is known to
21802 @kindex maint set bfd-sharing
21803 @kindex maint show bfd-sharing
21804 @kindex bfd caching
21805 @item maint set bfd-sharing
21806 @item maint show bfd-sharing
21807 Control whether @code{bfd} objects can be shared. When sharing is
21808 enabled @value{GDBN} reuses already open @code{bfd} objects rather
21809 than reopening the same file. Turning sharing off does not cause
21810 already shared @code{bfd} objects to be unshared, but all future files
21811 that are opened will create a new @code{bfd} object. Similarly,
21812 re-enabling sharing does not cause multiple existing @code{bfd}
21813 objects to be collapsed into a single shared @code{bfd} object.
21815 @kindex set debug bfd-cache @var{level}
21816 @kindex bfd caching
21817 @item set debug bfd-cache @var{level}
21818 Turns on debugging of the bfd cache, setting the level to @var{level}.
21820 @kindex show debug bfd-cache
21821 @kindex bfd caching
21822 @item show debug bfd-cache
21823 Show the current debugging level of the bfd cache.
21826 @node Separate Debug Files
21827 @section Debugging Information in Separate Files
21828 @cindex separate debugging information files
21829 @cindex debugging information in separate files
21830 @cindex @file{.debug} subdirectories
21831 @cindex debugging information directory, global
21832 @cindex global debugging information directories
21833 @cindex build ID, and separate debugging files
21834 @cindex @file{.build-id} directory
21836 @value{GDBN} allows you to put a program's debugging information in a
21837 file separate from the executable itself, in a way that allows
21838 @value{GDBN} to find and load the debugging information automatically.
21839 Since debugging information can be very large---sometimes larger
21840 than the executable code itself---some systems distribute debugging
21841 information for their executables in separate files, which users can
21842 install only when they need to debug a problem.
21844 @value{GDBN} supports two ways of specifying the separate debug info
21849 The executable contains a @dfn{debug link} that specifies the name of
21850 the separate debug info file. The separate debug file's name is
21851 usually @file{@var{executable}.debug}, where @var{executable} is the
21852 name of the corresponding executable file without leading directories
21853 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
21854 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
21855 checksum for the debug file, which @value{GDBN} uses to validate that
21856 the executable and the debug file came from the same build.
21860 The executable contains a @dfn{build ID}, a unique bit string that is
21861 also present in the corresponding debug info file. (This is supported
21862 only on some operating systems, when using the ELF or PE file formats
21863 for binary files and the @sc{gnu} Binutils.) For more details about
21864 this feature, see the description of the @option{--build-id}
21865 command-line option in @ref{Options, , Command Line Options, ld,
21866 The GNU Linker}. The debug info file's name is not specified
21867 explicitly by the build ID, but can be computed from the build ID, see
21871 Depending on the way the debug info file is specified, @value{GDBN}
21872 uses two different methods of looking for the debug file:
21876 For the ``debug link'' method, @value{GDBN} looks up the named file in
21877 the directory of the executable file, then in a subdirectory of that
21878 directory named @file{.debug}, and finally under each one of the
21879 global debug directories, in a subdirectory whose name is identical to
21880 the leading directories of the executable's absolute file name. (On
21881 MS-Windows/MS-DOS, the drive letter of the executable's leading
21882 directories is converted to a one-letter subdirectory, i.e.@:
21883 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
21884 filesystems disallow colons in file names.)
21887 For the ``build ID'' method, @value{GDBN} looks in the
21888 @file{.build-id} subdirectory of each one of the global debug directories for
21889 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
21890 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
21891 are the rest of the bit string. (Real build ID strings are 32 or more
21892 hex characters, not 10.) @value{GDBN} can automatically query
21893 @code{debuginfod} servers using build IDs in order to download separate debug
21894 files that cannot be found locally. For more information see @ref{Debuginfod}.
21897 So, for example, suppose you ask @value{GDBN} to debug
21898 @file{/usr/bin/ls}, which has a debug link that specifies the
21899 file @file{ls.debug}, and a build ID whose value in hex is
21900 @code{abcdef1234}. If the list of the global debug directories includes
21901 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
21902 debug information files, in the indicated order:
21906 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
21908 @file{/usr/bin/ls.debug}
21910 @file{/usr/bin/.debug/ls.debug}
21912 @file{/usr/lib/debug/usr/bin/ls.debug}.
21915 If the debug file still has not been found and @code{debuginfod}
21916 (@pxref{Debuginfod}) is enabled, @value{GDBN} will attempt to download the
21917 file from @code{debuginfod} servers.
21919 @anchor{debug-file-directory}
21920 Global debugging info directories default to what is set by @value{GDBN}
21921 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
21922 you can also set the global debugging info directories, and view the list
21923 @value{GDBN} is currently using.
21927 @kindex set debug-file-directory
21928 @item set debug-file-directory @var{directories}
21929 Set the directories which @value{GDBN} searches for separate debugging
21930 information files to @var{directory}. Multiple path components can be set
21931 concatenating them by a path separator.
21933 @kindex show debug-file-directory
21934 @item show debug-file-directory
21935 Show the directories @value{GDBN} searches for separate debugging
21940 @cindex @code{.gnu_debuglink} sections
21941 @cindex debug link sections
21942 A debug link is a special section of the executable file named
21943 @code{.gnu_debuglink}. The section must contain:
21947 A filename, with any leading directory components removed, followed by
21950 zero to three bytes of padding, as needed to reach the next four-byte
21951 boundary within the section, and
21953 a four-byte CRC checksum, stored in the same endianness used for the
21954 executable file itself. The checksum is computed on the debugging
21955 information file's full contents by the function given below, passing
21956 zero as the @var{crc} argument.
21959 Any executable file format can carry a debug link, as long as it can
21960 contain a section named @code{.gnu_debuglink} with the contents
21963 @cindex @code{.note.gnu.build-id} sections
21964 @cindex build ID sections
21965 The build ID is a special section in the executable file (and in other
21966 ELF binary files that @value{GDBN} may consider). This section is
21967 often named @code{.note.gnu.build-id}, but that name is not mandatory.
21968 It contains unique identification for the built files---the ID remains
21969 the same across multiple builds of the same build tree. The default
21970 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
21971 content for the build ID string. The same section with an identical
21972 value is present in the original built binary with symbols, in its
21973 stripped variant, and in the separate debugging information file.
21975 The debugging information file itself should be an ordinary
21976 executable, containing a full set of linker symbols, sections, and
21977 debugging information. The sections of the debugging information file
21978 should have the same names, addresses, and sizes as the original file,
21979 but they need not contain any data---much like a @code{.bss} section
21980 in an ordinary executable.
21982 The @sc{gnu} binary utilities (Binutils) package includes the
21983 @samp{objcopy} utility that can produce
21984 the separated executable / debugging information file pairs using the
21985 following commands:
21988 @kbd{objcopy --only-keep-debug foo foo.debug}
21993 These commands remove the debugging
21994 information from the executable file @file{foo} and place it in the file
21995 @file{foo.debug}. You can use the first, second or both methods to link the
22000 The debug link method needs the following additional command to also leave
22001 behind a debug link in @file{foo}:
22004 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
22007 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
22008 a version of the @code{strip} command such that the command @kbd{strip foo -f
22009 foo.debug} has the same functionality as the two @code{objcopy} commands and
22010 the @code{ln -s} command above, together.
22013 Build ID gets embedded into the main executable using @code{ld --build-id} or
22014 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
22015 compatibility fixes for debug files separation are present in @sc{gnu} binary
22016 utilities (Binutils) package since version 2.18.
22021 @cindex CRC algorithm definition
22022 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
22023 IEEE 802.3 using the polynomial:
22025 @c TexInfo requires naked braces for multi-digit exponents for Tex
22026 @c output, but this causes HTML output to barf. HTML has to be set using
22027 @c raw commands. So we end up having to specify this equation in 2
22032 <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
22033 + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
22039 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
22040 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
22044 The function is computed byte at a time, taking the least
22045 significant bit of each byte first. The initial pattern
22046 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
22047 the final result is inverted to ensure trailing zeros also affect the
22050 @emph{Note:} This is the same CRC polynomial as used in handling the
22051 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
22052 However in the case of the Remote Serial Protocol, the CRC is computed
22053 @emph{most} significant bit first, and the result is not inverted, so
22054 trailing zeros have no effect on the CRC value.
22056 To complete the description, we show below the code of the function
22057 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
22058 initially supplied @code{crc} argument means that an initial call to
22059 this function passing in zero will start computing the CRC using
22062 @kindex gnu_debuglink_crc32
22065 gnu_debuglink_crc32 (unsigned long crc,
22066 unsigned char *buf, size_t len)
22068 static const unsigned long crc32_table[256] =
22070 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
22071 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
22072 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
22073 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
22074 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
22075 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
22076 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
22077 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
22078 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
22079 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
22080 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
22081 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
22082 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
22083 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
22084 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
22085 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
22086 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
22087 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
22088 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
22089 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
22090 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
22091 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
22092 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
22093 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
22094 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
22095 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
22096 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
22097 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
22098 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
22099 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
22100 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
22101 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
22102 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
22103 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
22104 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
22105 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
22106 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
22107 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
22108 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
22109 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
22110 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
22111 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
22112 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
22113 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
22114 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
22115 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
22116 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
22117 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
22118 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
22119 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
22120 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
22123 unsigned char *end;
22125 crc = ~crc & 0xffffffff;
22126 for (end = buf + len; buf < end; ++buf)
22127 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
22128 return ~crc & 0xffffffff;
22133 This computation does not apply to the ``build ID'' method.
22135 @node MiniDebugInfo
22136 @section Debugging information in a special section
22137 @cindex separate debug sections
22138 @cindex @samp{.gnu_debugdata} section
22140 Some systems ship pre-built executables and libraries that have a
22141 special @samp{.gnu_debugdata} section. This feature is called
22142 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
22143 is used to supply extra symbols for backtraces.
22145 The intent of this section is to provide extra minimal debugging
22146 information for use in simple backtraces. It is not intended to be a
22147 replacement for full separate debugging information (@pxref{Separate
22148 Debug Files}). The example below shows the intended use; however,
22149 @value{GDBN} does not currently put restrictions on what sort of
22150 debugging information might be included in the section.
22152 @value{GDBN} has support for this extension. If the section exists,
22153 then it is used provided that no other source of debugging information
22154 can be found, and that @value{GDBN} was configured with LZMA support.
22156 This section can be easily created using @command{objcopy} and other
22157 standard utilities:
22160 # Extract the dynamic symbols from the main binary, there is no need
22161 # to also have these in the normal symbol table.
22162 nm -D @var{binary} --format=posix --defined-only \
22163 | awk '@{ print $1 @}' | sort > dynsyms
22165 # Extract all the text (i.e. function) symbols from the debuginfo.
22166 # (Note that we actually also accept "D" symbols, for the benefit
22167 # of platforms like PowerPC64 that use function descriptors.)
22168 nm @var{binary} --format=posix --defined-only \
22169 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
22172 # Keep all the function symbols not already in the dynamic symbol
22174 comm -13 dynsyms funcsyms > keep_symbols
22176 # Separate full debug info into debug binary.
22177 objcopy --only-keep-debug @var{binary} debug
22179 # Copy the full debuginfo, keeping only a minimal set of symbols and
22180 # removing some unnecessary sections.
22181 objcopy -S --remove-section .gdb_index --remove-section .comment \
22182 --keep-symbols=keep_symbols debug mini_debuginfo
22184 # Drop the full debug info from the original binary.
22185 strip --strip-all -R .comment @var{binary}
22187 # Inject the compressed data into the .gnu_debugdata section of the
22190 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
22194 @section Index Files Speed Up @value{GDBN}
22195 @cindex index files
22196 @cindex @samp{.gdb_index} section
22198 When @value{GDBN} finds a symbol file, it scans the symbols in the
22199 file in order to construct an internal symbol table. This lets most
22200 @value{GDBN} operations work quickly---at the cost of a delay early
22201 on. For large programs, this delay can be quite lengthy, so
22202 @value{GDBN} provides a way to build an index, which speeds up
22205 For convenience, @value{GDBN} comes with a program,
22206 @command{gdb-add-index}, which can be used to add the index to a
22207 symbol file. It takes the symbol file as its only argument:
22210 $ gdb-add-index symfile
22213 @xref{gdb-add-index}.
22215 It is also possible to do the work manually. Here is what
22216 @command{gdb-add-index} does behind the curtains.
22218 The index is stored as a section in the symbol file. @value{GDBN} can
22219 write the index to a file, then you can put it into the symbol file
22220 using @command{objcopy}.
22222 To create an index file, use the @code{save gdb-index} command:
22225 @item save gdb-index [-dwarf-5] @var{directory}
22226 @kindex save gdb-index
22227 Create index files for all symbol files currently known by
22228 @value{GDBN}. For each known @var{symbol-file}, this command by
22229 default creates it produces a single file
22230 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
22231 the @option{-dwarf-5} option, it produces 2 files:
22232 @file{@var{symbol-file}.debug_names} and
22233 @file{@var{symbol-file}.debug_str}. The files are created in the
22234 given @var{directory}.
22237 Once you have created an index file you can merge it into your symbol
22238 file, here named @file{symfile}, using @command{objcopy}:
22241 $ objcopy --add-section .gdb_index=symfile.gdb-index \
22242 --set-section-flags .gdb_index=readonly symfile symfile
22245 Or for @code{-dwarf-5}:
22248 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
22249 $ cat symfile.debug_str >>symfile.debug_str.new
22250 $ objcopy --add-section .debug_names=symfile.gdb-index \
22251 --set-section-flags .debug_names=readonly \
22252 --update-section .debug_str=symfile.debug_str.new symfile symfile
22255 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
22256 sections that have been deprecated. Usually they are deprecated because
22257 they are missing a new feature or have performance issues.
22258 To tell @value{GDBN} to use a deprecated index section anyway
22259 specify @code{set use-deprecated-index-sections on}.
22260 The default is @code{off}.
22261 This can speed up startup, but may result in some functionality being lost.
22262 @xref{Index Section Format}.
22264 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
22265 must be done before gdb reads the file. The following will not work:
22268 $ gdb -ex "set use-deprecated-index-sections on" <program>
22271 Instead you must do, for example,
22274 $ gdb -iex "set use-deprecated-index-sections on" <program>
22277 Indices only work when using DWARF debugging information, not stabs.
22279 @subsection Automatic symbol index cache
22281 @cindex automatic symbol index cache
22282 It is possible for @value{GDBN} to automatically save a copy of this index in a
22283 cache on disk and retrieve it from there when loading the same binary in the
22284 future. This feature can be turned on with @kbd{set index-cache enabled on}.
22285 The following commands can be used to tweak the behavior of the index cache.
22289 @kindex set index-cache
22290 @item set index-cache enabled on
22291 @itemx set index-cache enabled off
22292 Enable or disable the use of the symbol index cache.
22294 @item set index-cache directory @var{directory}
22295 @kindex show index-cache
22296 @itemx show index-cache directory
22297 Set/show the directory where index files will be saved.
22299 The default value for this directory depends on the host platform. On
22300 most systems, the index is cached in the @file{gdb} subdirectory of
22301 the directory pointed to by the @env{XDG_CACHE_HOME} environment
22302 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
22303 of your home directory. However, on some systems, the default may
22304 differ according to local convention.
22306 There is no limit on the disk space used by index cache. It is perfectly safe
22307 to delete the content of that directory to free up disk space.
22309 @item show index-cache stats
22310 Print the number of cache hits and misses since the launch of @value{GDBN}.
22314 @node Symbol Errors
22315 @section Errors Reading Symbol Files
22317 While reading a symbol file, @value{GDBN} occasionally encounters problems,
22318 such as symbol types it does not recognize, or known bugs in compiler
22319 output. By default, @value{GDBN} does not notify you of such problems, since
22320 they are relatively common and primarily of interest to people
22321 debugging compilers. If you are interested in seeing information
22322 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
22323 only one message about each such type of problem, no matter how many
22324 times the problem occurs; or you can ask @value{GDBN} to print more messages,
22325 to see how many times the problems occur, with the @code{set
22326 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
22329 The messages currently printed, and their meanings, include:
22332 @item inner block not inside outer block in @var{symbol}
22334 The symbol information shows where symbol scopes begin and end
22335 (such as at the start of a function or a block of statements). This
22336 error indicates that an inner scope block is not fully contained
22337 in its outer scope blocks.
22339 @value{GDBN} circumvents the problem by treating the inner block as if it had
22340 the same scope as the outer block. In the error message, @var{symbol}
22341 may be shown as ``@code{(don't know)}'' if the outer block is not a
22344 @item block at @var{address} out of order
22346 The symbol information for symbol scope blocks should occur in
22347 order of increasing addresses. This error indicates that it does not
22350 @value{GDBN} does not circumvent this problem, and has trouble
22351 locating symbols in the source file whose symbols it is reading. (You
22352 can often determine what source file is affected by specifying
22353 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
22356 @item bad block start address patched
22358 The symbol information for a symbol scope block has a start address
22359 smaller than the address of the preceding source line. This is known
22360 to occur in the SunOS 4.1.1 (and earlier) C compiler.
22362 @value{GDBN} circumvents the problem by treating the symbol scope block as
22363 starting on the previous source line.
22365 @item bad string table offset in symbol @var{n}
22368 Symbol number @var{n} contains a pointer into the string table which is
22369 larger than the size of the string table.
22371 @value{GDBN} circumvents the problem by considering the symbol to have the
22372 name @code{foo}, which may cause other problems if many symbols end up
22375 @item unknown symbol type @code{0x@var{nn}}
22377 The symbol information contains new data types that @value{GDBN} does
22378 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
22379 uncomprehended information, in hexadecimal.
22381 @value{GDBN} circumvents the error by ignoring this symbol information.
22382 This usually allows you to debug your program, though certain symbols
22383 are not accessible. If you encounter such a problem and feel like
22384 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
22385 on @code{complain}, then go up to the function @code{read_dbx_symtab}
22386 and examine @code{*bufp} to see the symbol.
22388 @item stub type has NULL name
22390 @value{GDBN} could not find the full definition for a struct or class.
22392 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
22393 The symbol information for a C@t{++} member function is missing some
22394 information that recent versions of the compiler should have output for
22397 @item info mismatch between compiler and debugger
22399 @value{GDBN} could not parse a type specification output by the compiler.
22404 @section GDB Data Files
22406 @cindex prefix for data files
22407 @value{GDBN} will sometimes read an auxiliary data file. These files
22408 are kept in a directory known as the @dfn{data directory}.
22410 You can set the data directory's name, and view the name @value{GDBN}
22411 is currently using.
22414 @kindex set data-directory
22415 @item set data-directory @var{directory}
22416 Set the directory which @value{GDBN} searches for auxiliary data files
22417 to @var{directory}.
22419 @kindex show data-directory
22420 @item show data-directory
22421 Show the directory @value{GDBN} searches for auxiliary data files.
22424 @cindex default data directory
22425 @cindex @samp{--with-gdb-datadir}
22426 You can set the default data directory by using the configure-time
22427 @samp{--with-gdb-datadir} option. If the data directory is inside
22428 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
22429 @samp{--exec-prefix}), then the default data directory will be updated
22430 automatically if the installed @value{GDBN} is moved to a new
22433 The data directory may also be specified with the
22434 @code{--data-directory} command line option.
22435 @xref{Mode Options}.
22438 @chapter Specifying a Debugging Target
22440 @cindex debugging target
22441 A @dfn{target} is the execution environment occupied by your program.
22443 Often, @value{GDBN} runs in the same host environment as your program;
22444 in that case, the debugging target is specified as a side effect when
22445 you use the @code{file} or @code{core} commands. When you need more
22446 flexibility---for example, running @value{GDBN} on a physically separate
22447 host, or controlling a standalone system over a serial port or a
22448 realtime system over a TCP/IP connection---you can use the @code{target}
22449 command to specify one of the target types configured for @value{GDBN}
22450 (@pxref{Target Commands, ,Commands for Managing Targets}).
22452 @cindex target architecture
22453 It is possible to build @value{GDBN} for several different @dfn{target
22454 architectures}. When @value{GDBN} is built like that, you can choose
22455 one of the available architectures with the @kbd{set architecture}
22459 @kindex set architecture
22460 @kindex show architecture
22461 @item set architecture @var{arch}
22462 This command sets the current target architecture to @var{arch}. The
22463 value of @var{arch} can be @code{"auto"}, in addition to one of the
22464 supported architectures.
22466 @item show architecture
22467 Show the current target architecture.
22469 @item set processor
22471 @kindex set processor
22472 @kindex show processor
22473 These are alias commands for, respectively, @code{set architecture}
22474 and @code{show architecture}.
22478 * Active Targets:: Active targets
22479 * Target Commands:: Commands for managing targets
22480 * Byte Order:: Choosing target byte order
22483 @node Active Targets
22484 @section Active Targets
22486 @cindex stacking targets
22487 @cindex active targets
22488 @cindex multiple targets
22490 There are multiple classes of targets such as: processes, executable files or
22491 recording sessions. Core files belong to the process class, making core file
22492 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
22493 on multiple active targets, one in each class. This allows you to (for
22494 example) start a process and inspect its activity, while still having access to
22495 the executable file after the process finishes. Or if you start process
22496 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
22497 presented a virtual layer of the recording target, while the process target
22498 remains stopped at the chronologically last point of the process execution.
22500 Use the @code{core-file} and @code{exec-file} commands to select a new core
22501 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
22502 specify as a target a process that is already running, use the @code{attach}
22503 command (@pxref{Attach, ,Debugging an Already-running Process}).
22505 @node Target Commands
22506 @section Commands for Managing Targets
22509 @item target @var{type} @var{parameters}
22510 Connects the @value{GDBN} host environment to a target machine or
22511 process. A target is typically a protocol for talking to debugging
22512 facilities. You use the argument @var{type} to specify the type or
22513 protocol of the target machine.
22515 Further @var{parameters} are interpreted by the target protocol, but
22516 typically include things like device names or host names to connect
22517 with, process numbers, and baud rates.
22519 The @code{target} command does not repeat if you press @key{RET} again
22520 after executing the command.
22522 @kindex help target
22524 Displays the names of all targets available. To display targets
22525 currently selected, use either @code{info target} or @code{info files}
22526 (@pxref{Files, ,Commands to Specify Files}).
22528 @item help target @var{name}
22529 Describe a particular target, including any parameters necessary to
22532 @kindex set gnutarget
22533 @item set gnutarget @var{args}
22534 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
22535 knows whether it is reading an @dfn{executable},
22536 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
22537 with the @code{set gnutarget} command. Unlike most @code{target} commands,
22538 with @code{gnutarget} the @code{target} refers to a program, not a machine.
22541 @emph{Warning:} To specify a file format with @code{set gnutarget},
22542 you must know the actual BFD name.
22546 @xref{Files, , Commands to Specify Files}.
22548 @kindex show gnutarget
22549 @item show gnutarget
22550 Use the @code{show gnutarget} command to display what file format
22551 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
22552 @value{GDBN} will determine the file format for each file automatically,
22553 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
22556 @cindex common targets
22557 Here are some common targets (available, or not, depending on the GDB
22562 @item target exec @var{program}
22563 @cindex executable file target
22564 An executable file. @samp{target exec @var{program}} is the same as
22565 @samp{exec-file @var{program}}.
22567 @item target core @var{filename}
22568 @cindex core dump file target
22569 A core dump file. @samp{target core @var{filename}} is the same as
22570 @samp{core-file @var{filename}}.
22572 @item target remote @var{medium}
22573 @cindex remote target
22574 A remote system connected to @value{GDBN} via a serial line or network
22575 connection. This command tells @value{GDBN} to use its own remote
22576 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
22578 For example, if you have a board connected to @file{/dev/ttya} on the
22579 machine running @value{GDBN}, you could say:
22582 target remote /dev/ttya
22585 @code{target remote} supports the @code{load} command. This is only
22586 useful if you have some other way of getting the stub to the target
22587 system, and you can put it somewhere in memory where it won't get
22588 clobbered by the download.
22590 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22591 @cindex built-in simulator target
22592 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
22600 works; however, you cannot assume that a specific memory map, device
22601 drivers, or even basic I/O is available, although some simulators do
22602 provide these. For info about any processor-specific simulator details,
22603 see the appropriate section in @ref{Embedded Processors, ,Embedded
22606 @item target native
22607 @cindex native target
22608 Setup for local/native process debugging. Useful to make the
22609 @code{run} command spawn native processes (likewise @code{attach},
22610 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
22611 (@pxref{set auto-connect-native-target}).
22615 Different targets are available on different configurations of @value{GDBN};
22616 your configuration may have more or fewer targets.
22618 Many remote targets require you to download the executable's code once
22619 you've successfully established a connection. You may wish to control
22620 various aspects of this process.
22625 @kindex set hash@r{, for remote monitors}
22626 @cindex hash mark while downloading
22627 This command controls whether a hash mark @samp{#} is displayed while
22628 downloading a file to the remote monitor. If on, a hash mark is
22629 displayed after each S-record is successfully downloaded to the
22633 @kindex show hash@r{, for remote monitors}
22634 Show the current status of displaying the hash mark.
22636 @item set debug monitor
22637 @kindex set debug monitor
22638 @cindex display remote monitor communications
22639 Enable or disable display of communications messages between
22640 @value{GDBN} and the remote monitor.
22642 @item show debug monitor
22643 @kindex show debug monitor
22644 Show the current status of displaying communications between
22645 @value{GDBN} and the remote monitor.
22650 @kindex load @var{filename} @var{offset}
22651 @item load @var{filename} @var{offset}
22653 Depending on what remote debugging facilities are configured into
22654 @value{GDBN}, the @code{load} command may be available. Where it exists, it
22655 is meant to make @var{filename} (an executable) available for debugging
22656 on the remote system---by downloading, or dynamic linking, for example.
22657 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
22658 the @code{add-symbol-file} command.
22660 If your @value{GDBN} does not have a @code{load} command, attempting to
22661 execute it gets the error message ``@code{You can't do that when your
22662 target is @dots{}}''
22664 The file is loaded at whatever address is specified in the executable.
22665 For some object file formats, you can specify the load address when you
22666 link the program; for other formats, like a.out, the object file format
22667 specifies a fixed address.
22668 @c FIXME! This would be a good place for an xref to the GNU linker doc.
22670 It is also possible to tell @value{GDBN} to load the executable file at a
22671 specific offset described by the optional argument @var{offset}. When
22672 @var{offset} is provided, @var{filename} must also be provided.
22674 Depending on the remote side capabilities, @value{GDBN} may be able to
22675 load programs into flash memory.
22677 @code{load} does not repeat if you press @key{RET} again after using it.
22682 @kindex flash-erase
22684 @anchor{flash-erase}
22686 Erases all known flash memory regions on the target.
22691 @section Choosing Target Byte Order
22693 @cindex choosing target byte order
22694 @cindex target byte order
22696 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
22697 offer the ability to run either big-endian or little-endian byte
22698 orders. Usually the executable or symbol will include a bit to
22699 designate the endian-ness, and you will not need to worry about
22700 which to use. However, you may still find it useful to adjust
22701 @value{GDBN}'s idea of processor endian-ness manually.
22705 @item set endian big
22706 Instruct @value{GDBN} to assume the target is big-endian.
22708 @item set endian little
22709 Instruct @value{GDBN} to assume the target is little-endian.
22711 @item set endian auto
22712 Instruct @value{GDBN} to use the byte order associated with the
22716 Display @value{GDBN}'s current idea of the target byte order.
22720 If the @code{set endian auto} mode is in effect and no executable has
22721 been selected, then the endianness used is the last one chosen either
22722 by one of the @code{set endian big} and @code{set endian little}
22723 commands or by inferring from the last executable used. If no
22724 endianness has been previously chosen, then the default for this mode
22725 is inferred from the target @value{GDBN} has been built for, and is
22726 @code{little} if the name of the target CPU has an @code{el} suffix
22727 and @code{big} otherwise.
22729 Note that these commands merely adjust interpretation of symbolic
22730 data on the host, and that they have absolutely no effect on the
22734 @node Remote Debugging
22735 @chapter Debugging Remote Programs
22736 @cindex remote debugging
22738 If you are trying to debug a program running on a machine that cannot run
22739 @value{GDBN} in the usual way, it is often useful to use remote debugging.
22740 For example, you might use remote debugging on an operating system kernel,
22741 or on a small system which does not have a general purpose operating system
22742 powerful enough to run a full-featured debugger.
22744 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
22745 to make this work with particular debugging targets. In addition,
22746 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
22747 but not specific to any particular target system) which you can use if you
22748 write the remote stubs---the code that runs on the remote system to
22749 communicate with @value{GDBN}.
22751 Other remote targets may be available in your
22752 configuration of @value{GDBN}; use @code{help target} to list them.
22755 * Connecting:: Connecting to a remote target
22756 * File Transfer:: Sending files to a remote system
22757 * Server:: Using the gdbserver program
22758 * Remote Configuration:: Remote configuration
22759 * Remote Stub:: Implementing a remote stub
22763 @section Connecting to a Remote Target
22764 @cindex remote debugging, connecting
22765 @cindex @code{gdbserver}, connecting
22766 @cindex remote debugging, types of connections
22767 @cindex @code{gdbserver}, types of connections
22768 @cindex @code{gdbserver}, @code{target remote} mode
22769 @cindex @code{gdbserver}, @code{target extended-remote} mode
22771 This section describes how to connect to a remote target, including the
22772 types of connections and their differences, how to set up executable and
22773 symbol files on the host and target, and the commands used for
22774 connecting to and disconnecting from the remote target.
22776 @subsection Types of Remote Connections
22778 @value{GDBN} supports two types of remote connections, @code{target remote}
22779 mode and @code{target extended-remote} mode. Note that many remote targets
22780 support only @code{target remote} mode. There are several major
22781 differences between the two types of connections, enumerated here:
22785 @cindex remote debugging, detach and program exit
22786 @item Result of detach or program exit
22787 @strong{With target remote mode:} When the debugged program exits or you
22788 detach from it, @value{GDBN} disconnects from the target. When using
22789 @code{gdbserver}, @code{gdbserver} will exit.
22791 @strong{With target extended-remote mode:} When the debugged program exits or
22792 you detach from it, @value{GDBN} remains connected to the target, even
22793 though no program is running. You can rerun the program, attach to a
22794 running program, or use @code{monitor} commands specific to the target.
22796 When using @code{gdbserver} in this case, it does not exit unless it was
22797 invoked using the @option{--once} option. If the @option{--once} option
22798 was not used, you can ask @code{gdbserver} to exit using the
22799 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
22801 @item Specifying the program to debug
22802 For both connection types you use the @code{file} command to specify the
22803 program on the host system. If you are using @code{gdbserver} there are
22804 some differences in how to specify the location of the program on the
22807 @strong{With target remote mode:} You must either specify the program to debug
22808 on the @code{gdbserver} command line or use the @option{--attach} option
22809 (@pxref{Attaching to a program,,Attaching to a Running Program}).
22811 @cindex @option{--multi}, @code{gdbserver} option
22812 @strong{With target extended-remote mode:} You may specify the program to debug
22813 on the @code{gdbserver} command line, or you can load the program or attach
22814 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
22816 @anchor{--multi Option in Types of Remote Connnections}
22817 You can start @code{gdbserver} without supplying an initial command to run
22818 or process ID to attach. To do this, use the @option{--multi} command line
22819 option. Then you can connect using @code{target extended-remote} and start
22820 the program you want to debug (see below for details on using the
22821 @code{run} command in this scenario). Note that the conditions under which
22822 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
22823 (@code{target remote} or @code{target extended-remote}). The
22824 @option{--multi} option to @code{gdbserver} has no influence on that.
22826 @item The @code{run} command
22827 @strong{With target remote mode:} The @code{run} command is not
22828 supported. Once a connection has been established, you can use all
22829 the usual @value{GDBN} commands to examine and change data. The
22830 remote program is already running, so you can use commands like
22831 @kbd{step} and @kbd{continue}.
22833 @strong{With target extended-remote mode:} The @code{run} command is
22834 supported. The @code{run} command uses the value set by
22835 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
22836 the program to run. Command line arguments are supported, except for
22837 wildcard expansion and I/O redirection (@pxref{Arguments}).
22839 If you specify the program to debug on the command line, then the
22840 @code{run} command is not required to start execution, and you can
22841 resume using commands like @kbd{step} and @kbd{continue} as with
22842 @code{target remote} mode.
22844 @anchor{Attaching in Types of Remote Connections}
22846 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
22847 not supported. To attach to a running program using @code{gdbserver}, you
22848 must use the @option{--attach} option (@pxref{Running gdbserver}).
22850 @strong{With target extended-remote mode:} To attach to a running program,
22851 you may use the @code{attach} command after the connection has been
22852 established. If you are using @code{gdbserver}, you may also invoke
22853 @code{gdbserver} using the @option{--attach} option
22854 (@pxref{Running gdbserver}).
22856 Some remote targets allow @value{GDBN} to determine the executable file running
22857 in the process the debugger is attaching to. In such a case, @value{GDBN}
22858 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
22859 between the executable file name running in the process and the name of the
22860 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
22864 @anchor{Host and target files}
22865 @subsection Host and Target Files
22866 @cindex remote debugging, symbol files
22867 @cindex symbol files, remote debugging
22869 @value{GDBN}, running on the host, needs access to symbol and debugging
22870 information for your program running on the target. This requires
22871 access to an unstripped copy of your program, and possibly any associated
22872 symbol files. Note that this section applies equally to both @code{target
22873 remote} mode and @code{target extended-remote} mode.
22875 Some remote targets (@pxref{qXfer executable filename read}, and
22876 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
22877 the same connection used to communicate with @value{GDBN}. With such a
22878 target, if the remote program is unstripped, the only command you need is
22879 @code{target remote} (or @code{target extended-remote}).
22881 If the remote program is stripped, or the target does not support remote
22882 program file access, start up @value{GDBN} using the name of the local
22883 unstripped copy of your program as the first argument, or use the
22884 @code{file} command. Use @code{set sysroot} to specify the location (on
22885 the host) of target libraries (unless your @value{GDBN} was compiled with
22886 the correct sysroot using @code{--with-sysroot}). Alternatively, you
22887 may use @code{set solib-search-path} to specify how @value{GDBN} locates
22890 The symbol file and target libraries must exactly match the executable
22891 and libraries on the target, with one exception: the files on the host
22892 system should not be stripped, even if the files on the target system
22893 are. Mismatched or missing files will lead to confusing results
22894 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
22895 files may also prevent @code{gdbserver} from debugging multi-threaded
22898 @subsection Remote Connection Commands
22899 @cindex remote connection commands
22900 @value{GDBN} can communicate with the target over a serial line, a
22901 local Unix domain socket, or
22902 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
22903 each case, @value{GDBN} uses the same protocol for debugging your
22904 program; only the medium carrying the debugging packets varies. The
22905 @code{target remote} and @code{target extended-remote} commands
22906 establish a connection to the target. Both commands accept the same
22907 arguments, which indicate the medium to use:
22911 @item target remote @var{serial-device}
22912 @itemx target extended-remote @var{serial-device}
22913 @cindex serial line, @code{target remote}
22914 Use @var{serial-device} to communicate with the target. For example,
22915 to use a serial line connected to the device named @file{/dev/ttyb}:
22918 target remote /dev/ttyb
22921 If you're using a serial line, you may want to give @value{GDBN} the
22922 @samp{--baud} option, or use the @code{set serial baud} command
22923 (@pxref{Remote Configuration, set serial baud}) before the
22924 @code{target} command.
22926 @item target remote @var{local-socket}
22927 @itemx target extended-remote @var{local-socket}
22928 @cindex local socket, @code{target remote}
22929 @cindex Unix domain socket
22930 Use @var{local-socket} to communicate with the target. For example,
22931 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
22934 target remote /tmp/gdb-socket0
22937 Note that this command has the same form as the command to connect
22938 to a serial line. @value{GDBN} will automatically determine which
22939 kind of file you have specified and will make the appropriate kind
22941 This feature is not available if the host system does not support
22942 Unix domain sockets.
22944 @item target remote @code{@var{host}:@var{port}}
22945 @itemx target remote @code{[@var{host}]:@var{port}}
22946 @itemx target remote @code{tcp:@var{host}:@var{port}}
22947 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
22948 @itemx target remote @code{tcp4:@var{host}:@var{port}}
22949 @itemx target remote @code{tcp6:@var{host}:@var{port}}
22950 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
22951 @itemx target extended-remote @code{@var{host}:@var{port}}
22952 @itemx target extended-remote @code{[@var{host}]:@var{port}}
22953 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
22954 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
22955 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
22956 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
22957 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
22958 @cindex @acronym{TCP} port, @code{target remote}
22959 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
22960 The @var{host} may be either a host name, a numeric @acronym{IPv4}
22961 address, or a numeric @acronym{IPv6} address (with or without the
22962 square brackets to separate the address from the port); @var{port}
22963 must be a decimal number. The @var{host} could be the target machine
22964 itself, if it is directly connected to the net, or it might be a
22965 terminal server which in turn has a serial line to the target.
22967 For example, to connect to port 2828 on a terminal server named
22971 target remote manyfarms:2828
22974 To connect to port 2828 on a terminal server whose address is
22975 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
22976 square bracket syntax:
22979 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
22983 or explicitly specify the @acronym{IPv6} protocol:
22986 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
22989 This last example may be confusing to the reader, because there is no
22990 visible separation between the hostname and the port number.
22991 Therefore, we recommend the user to provide @acronym{IPv6} addresses
22992 using square brackets for clarity. However, it is important to
22993 mention that for @value{GDBN} there is no ambiguity: the number after
22994 the last colon is considered to be the port number.
22996 If your remote target is actually running on the same machine as your
22997 debugger session (e.g.@: a simulator for your target running on the
22998 same host), you can omit the hostname. For example, to connect to
22999 port 1234 on your local machine:
23002 target remote :1234
23006 Note that the colon is still required here.
23008 @item target remote @code{udp:@var{host}:@var{port}}
23009 @itemx target remote @code{udp:[@var{host}]:@var{port}}
23010 @itemx target remote @code{udp4:@var{host}:@var{port}}
23011 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
23012 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
23013 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
23014 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
23015 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
23016 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
23017 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
23018 @cindex @acronym{UDP} port, @code{target remote}
23019 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
23020 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
23023 target remote udp:manyfarms:2828
23026 When using a @acronym{UDP} connection for remote debugging, you should
23027 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
23028 can silently drop packets on busy or unreliable networks, which will
23029 cause havoc with your debugging session.
23031 @item target remote | @var{command}
23032 @itemx target extended-remote | @var{command}
23033 @cindex pipe, @code{target remote} to
23034 Run @var{command} in the background and communicate with it using a
23035 pipe. The @var{command} is a shell command, to be parsed and expanded
23036 by the system's command shell, @code{/bin/sh}; it should expect remote
23037 protocol packets on its standard input, and send replies on its
23038 standard output. You could use this to run a stand-alone simulator
23039 that speaks the remote debugging protocol, to make net connections
23040 using programs like @code{ssh}, or for other similar tricks.
23042 If @var{command} closes its standard output (perhaps by exiting),
23043 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
23044 program has already exited, this will have no effect.)
23048 @cindex interrupting remote programs
23049 @cindex remote programs, interrupting
23050 Whenever @value{GDBN} is waiting for the remote program, if you type the
23051 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
23052 program. This may or may not succeed, depending in part on the hardware
23053 and the serial drivers the remote system uses. If you type the
23054 interrupt character once again, @value{GDBN} displays this prompt:
23057 Interrupted while waiting for the program.
23058 Give up (and stop debugging it)? (y or n)
23061 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
23062 the remote debugging session. (If you decide you want to try again later,
23063 you can use @kbd{target remote} again to connect once more.) If you type
23064 @kbd{n}, @value{GDBN} goes back to waiting.
23066 In @code{target extended-remote} mode, typing @kbd{n} will leave
23067 @value{GDBN} connected to the target.
23070 @kindex detach (remote)
23072 When you have finished debugging the remote program, you can use the
23073 @code{detach} command to release it from @value{GDBN} control.
23074 Detaching from the target normally resumes its execution, but the results
23075 will depend on your particular remote stub. After the @code{detach}
23076 command in @code{target remote} mode, @value{GDBN} is free to connect to
23077 another target. In @code{target extended-remote} mode, @value{GDBN} is
23078 still connected to the target.
23082 The @code{disconnect} command closes the connection to the target, and
23083 the target is generally not resumed. It will wait for @value{GDBN}
23084 (this instance or another one) to connect and continue debugging. After
23085 the @code{disconnect} command, @value{GDBN} is again free to connect to
23088 @cindex send command to remote monitor
23089 @cindex extend @value{GDBN} for remote targets
23090 @cindex add new commands for external monitor
23092 @item monitor @var{cmd}
23093 This command allows you to send arbitrary commands directly to the
23094 remote monitor. Since @value{GDBN} doesn't care about the commands it
23095 sends like this, this command is the way to extend @value{GDBN}---you
23096 can add new commands that only the external monitor will understand
23100 @node File Transfer
23101 @section Sending files to a remote system
23102 @cindex remote target, file transfer
23103 @cindex file transfer
23104 @cindex sending files to remote systems
23106 Some remote targets offer the ability to transfer files over the same
23107 connection used to communicate with @value{GDBN}. This is convenient
23108 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
23109 running @code{gdbserver} over a network interface. For other targets,
23110 e.g.@: embedded devices with only a single serial port, this may be
23111 the only way to upload or download files.
23113 Not all remote targets support these commands.
23117 @item remote put @var{hostfile} @var{targetfile}
23118 Copy file @var{hostfile} from the host system (the machine running
23119 @value{GDBN}) to @var{targetfile} on the target system.
23122 @item remote get @var{targetfile} @var{hostfile}
23123 Copy file @var{targetfile} from the target system to @var{hostfile}
23124 on the host system.
23126 @kindex remote delete
23127 @item remote delete @var{targetfile}
23128 Delete @var{targetfile} from the target system.
23133 @section Using the @code{gdbserver} Program
23136 @cindex remote connection without stubs
23137 @code{gdbserver} is a control program for Unix-like systems, which
23138 allows you to connect your program with a remote @value{GDBN} via
23139 @code{target remote} or @code{target extended-remote}---but without
23140 linking in the usual debugging stub.
23142 @code{gdbserver} is not a complete replacement for the debugging stubs,
23143 because it requires essentially the same operating-system facilities
23144 that @value{GDBN} itself does. In fact, a system that can run
23145 @code{gdbserver} to connect to a remote @value{GDBN} could also run
23146 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
23147 because it is a much smaller program than @value{GDBN} itself. It is
23148 also easier to port than all of @value{GDBN}, so you may be able to get
23149 started more quickly on a new system by using @code{gdbserver}.
23150 Finally, if you develop code for real-time systems, you may find that
23151 the tradeoffs involved in real-time operation make it more convenient to
23152 do as much development work as possible on another system, for example
23153 by cross-compiling. You can use @code{gdbserver} to make a similar
23154 choice for debugging.
23156 @value{GDBN} and @code{gdbserver} communicate via either a serial line
23157 or a TCP connection, using the standard @value{GDBN} remote serial
23161 @emph{Warning:} @code{gdbserver} does not have any built-in security.
23162 Do not run @code{gdbserver} connected to any public network; a
23163 @value{GDBN} connection to @code{gdbserver} provides access to the
23164 target system with the same privileges as the user running
23168 @anchor{Running gdbserver}
23169 @subsection Running @code{gdbserver}
23170 @cindex arguments, to @code{gdbserver}
23171 @cindex @code{gdbserver}, command-line arguments
23173 Run @code{gdbserver} on the target system. You need a copy of the
23174 program you want to debug, including any libraries it requires.
23175 @code{gdbserver} does not need your program's symbol table, so you can
23176 strip the program if necessary to save space. @value{GDBN} on the host
23177 system does all the symbol handling.
23179 To use the server, you must tell it how to communicate with @value{GDBN};
23180 the name of your program; and the arguments for your program. The usual
23184 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
23187 @var{comm} is either a device name (to use a serial line), or a TCP
23188 hostname and portnumber, or @code{-} or @code{stdio} to use
23189 stdin/stdout of @code{gdbserver}.
23190 For example, to debug Emacs with the argument
23191 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
23195 target> gdbserver /dev/com1 emacs foo.txt
23198 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
23201 To use a TCP connection instead of a serial line:
23204 target> gdbserver host:2345 emacs foo.txt
23207 The only difference from the previous example is the first argument,
23208 specifying that you are communicating with the host @value{GDBN} via
23209 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
23210 expect a TCP connection from machine @samp{host} to local TCP port 2345.
23211 (Currently, the @samp{host} part is ignored.) You can choose any number
23212 you want for the port number as long as it does not conflict with any
23213 TCP ports already in use on the target system (for example, @code{23} is
23214 reserved for @code{telnet}).@footnote{If you choose a port number that
23215 conflicts with another service, @code{gdbserver} prints an error message
23216 and exits.} You must use the same port number with the host @value{GDBN}
23217 @code{target remote} command.
23219 The @code{stdio} connection is useful when starting @code{gdbserver}
23223 (gdb) target remote | ssh -T hostname gdbserver - hello
23226 The @samp{-T} option to ssh is provided because we don't need a remote pty,
23227 and we don't want escape-character handling. Ssh does this by default when
23228 a command is provided, the flag is provided to make it explicit.
23229 You could elide it if you want to.
23231 Programs started with stdio-connected gdbserver have @file{/dev/null} for
23232 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
23233 display through a pipe connected to gdbserver.
23234 Both @code{stdout} and @code{stderr} use the same pipe.
23236 @anchor{Attaching to a program}
23237 @subsubsection Attaching to a Running Program
23238 @cindex attach to a program, @code{gdbserver}
23239 @cindex @option{--attach}, @code{gdbserver} option
23241 On some targets, @code{gdbserver} can also attach to running programs.
23242 This is accomplished via the @code{--attach} argument. The syntax is:
23245 target> gdbserver --attach @var{comm} @var{pid}
23248 @var{pid} is the process ID of a currently running process. It isn't
23249 necessary to point @code{gdbserver} at a binary for the running process.
23251 In @code{target extended-remote} mode, you can also attach using the
23252 @value{GDBN} attach command
23253 (@pxref{Attaching in Types of Remote Connections}).
23256 You can debug processes by name instead of process ID if your target has the
23257 @code{pidof} utility:
23260 target> gdbserver --attach @var{comm} `pidof @var{program}`
23263 In case more than one copy of @var{program} is running, or @var{program}
23264 has multiple threads, most versions of @code{pidof} support the
23265 @code{-s} option to only return the first process ID.
23267 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
23269 This section applies only when @code{gdbserver} is run to listen on a TCP
23272 @code{gdbserver} normally terminates after all of its debugged processes have
23273 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
23274 extended-remote}, @code{gdbserver} stays running even with no processes left.
23275 @value{GDBN} normally terminates the spawned debugged process on its exit,
23276 which normally also terminates @code{gdbserver} in the @kbd{target remote}
23277 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
23278 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
23279 stays running even in the @kbd{target remote} mode.
23281 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
23282 Such reconnecting is useful for features like @ref{disconnected tracing}. For
23283 completeness, at most one @value{GDBN} can be connected at a time.
23285 @cindex @option{--once}, @code{gdbserver} option
23286 By default, @code{gdbserver} keeps the listening TCP port open, so that
23287 subsequent connections are possible. However, if you start @code{gdbserver}
23288 with the @option{--once} option, it will stop listening for any further
23289 connection attempts after connecting to the first @value{GDBN} session. This
23290 means no further connections to @code{gdbserver} will be possible after the
23291 first one. It also means @code{gdbserver} will terminate after the first
23292 connection with remote @value{GDBN} has closed, even for unexpectedly closed
23293 connections and even in the @kbd{target extended-remote} mode. The
23294 @option{--once} option allows reusing the same port number for connecting to
23295 multiple instances of @code{gdbserver} running on the same host, since each
23296 instance closes its port after the first connection.
23298 @anchor{Other Command-Line Arguments for gdbserver}
23299 @subsubsection Other Command-Line Arguments for @code{gdbserver}
23301 You can use the @option{--multi} option to start @code{gdbserver} without
23302 specifying a program to debug or a process to attach to. Then you can
23303 attach in @code{target extended-remote} mode and run or attach to a
23304 program. For more information,
23305 @pxref{--multi Option in Types of Remote Connnections}.
23307 @cindex @option{--debug}, @code{gdbserver} option
23308 The @option{--debug} option tells @code{gdbserver} to display extra
23309 status information about the debugging process.
23310 @cindex @option{--remote-debug}, @code{gdbserver} option
23311 The @option{--remote-debug} option tells @code{gdbserver} to display
23312 remote protocol debug output.
23313 @cindex @option{--debug-file}, @code{gdbserver} option
23314 @cindex @code{gdbserver}, send all debug output to a single file
23315 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
23316 write any debug output to the given @var{filename}. These options are intended
23317 for @code{gdbserver} development and for bug reports to the developers.
23319 @cindex @option{--debug-format}, @code{gdbserver} option
23320 The @option{--debug-format=option1[,option2,...]} option tells
23321 @code{gdbserver} to include additional information in each output.
23322 Possible options are:
23326 Turn off all extra information in debugging output.
23328 Turn on all extra information in debugging output.
23330 Include a timestamp in each line of debugging output.
23333 Options are processed in order. Thus, for example, if @option{none}
23334 appears last then no additional information is added to debugging output.
23336 @cindex @option{--wrapper}, @code{gdbserver} option
23337 The @option{--wrapper} option specifies a wrapper to launch programs
23338 for debugging. The option should be followed by the name of the
23339 wrapper, then any command-line arguments to pass to the wrapper, then
23340 @kbd{--} indicating the end of the wrapper arguments.
23342 @code{gdbserver} runs the specified wrapper program with a combined
23343 command line including the wrapper arguments, then the name of the
23344 program to debug, then any arguments to the program. The wrapper
23345 runs until it executes your program, and then @value{GDBN} gains control.
23347 You can use any program that eventually calls @code{execve} with
23348 its arguments as a wrapper. Several standard Unix utilities do
23349 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
23350 with @code{exec "$@@"} will also work.
23352 For example, you can use @code{env} to pass an environment variable to
23353 the debugged program, without setting the variable in @code{gdbserver}'s
23357 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
23360 @cindex @option{--selftest}
23361 The @option{--selftest} option runs the self tests in @code{gdbserver}:
23364 $ gdbserver --selftest
23365 Ran 2 unit tests, 0 failed
23368 These tests are disabled in release.
23369 @subsection Connecting to @code{gdbserver}
23371 The basic procedure for connecting to the remote target is:
23375 Run @value{GDBN} on the host system.
23378 Make sure you have the necessary symbol files
23379 (@pxref{Host and target files}).
23380 Load symbols for your application using the @code{file} command before you
23381 connect. Use @code{set sysroot} to locate target libraries (unless your
23382 @value{GDBN} was compiled with the correct sysroot using
23383 @code{--with-sysroot}).
23386 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
23387 For TCP connections, you must start up @code{gdbserver} prior to using
23388 the @code{target} command. Otherwise you may get an error whose
23389 text depends on the host system, but which usually looks something like
23390 @samp{Connection refused}. Don't use the @code{load}
23391 command in @value{GDBN} when using @code{target remote} mode, since the
23392 program is already on the target.
23396 @anchor{Monitor Commands for gdbserver}
23397 @subsection Monitor Commands for @code{gdbserver}
23398 @cindex monitor commands, for @code{gdbserver}
23400 During a @value{GDBN} session using @code{gdbserver}, you can use the
23401 @code{monitor} command to send special requests to @code{gdbserver}.
23402 Here are the available commands.
23406 List the available monitor commands.
23408 @item monitor set debug 0
23409 @itemx monitor set debug 1
23410 Disable or enable general debugging messages.
23412 @item monitor set remote-debug 0
23413 @itemx monitor set remote-debug 1
23414 Disable or enable specific debugging messages associated with the remote
23415 protocol (@pxref{Remote Protocol}).
23417 @item monitor set debug-file filename
23418 @itemx monitor set debug-file
23419 Send any debug output to the given file, or to stderr.
23421 @item monitor set debug-format option1@r{[},option2,...@r{]}
23422 Specify additional text to add to debugging messages.
23423 Possible options are:
23427 Turn off all extra information in debugging output.
23429 Turn on all extra information in debugging output.
23431 Include a timestamp in each line of debugging output.
23434 Options are processed in order. Thus, for example, if @option{none}
23435 appears last then no additional information is added to debugging output.
23437 @item monitor set libthread-db-search-path [PATH]
23438 @cindex gdbserver, search path for @code{libthread_db}
23439 When this command is issued, @var{path} is a colon-separated list of
23440 directories to search for @code{libthread_db} (@pxref{Threads,,set
23441 libthread-db-search-path}). If you omit @var{path},
23442 @samp{libthread-db-search-path} will be reset to its default value.
23444 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
23445 not supported in @code{gdbserver}.
23448 Tell gdbserver to exit immediately. This command should be followed by
23449 @code{disconnect} to close the debugging session. @code{gdbserver} will
23450 detach from any attached processes and kill any processes it created.
23451 Use @code{monitor exit} to terminate @code{gdbserver} at the end
23452 of a multi-process mode debug session.
23456 @subsection Tracepoints support in @code{gdbserver}
23457 @cindex tracepoints support in @code{gdbserver}
23459 On some targets, @code{gdbserver} supports tracepoints, fast
23460 tracepoints and static tracepoints.
23462 For fast or static tracepoints to work, a special library called the
23463 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
23464 This library is built and distributed as an integral part of
23465 @code{gdbserver}. In addition, support for static tracepoints
23466 requires building the in-process agent library with static tracepoints
23467 support. At present, the UST (LTTng Userspace Tracer,
23468 @url{http://lttng.org/ust}) tracing engine is supported. This support
23469 is automatically available if UST development headers are found in the
23470 standard include path when @code{gdbserver} is built, or if
23471 @code{gdbserver} was explicitly configured using @option{--with-ust}
23472 to point at such headers. You can explicitly disable the support
23473 using @option{--with-ust=no}.
23475 There are several ways to load the in-process agent in your program:
23478 @item Specifying it as dependency at link time
23480 You can link your program dynamically with the in-process agent
23481 library. On most systems, this is accomplished by adding
23482 @code{-linproctrace} to the link command.
23484 @item Using the system's preloading mechanisms
23486 You can force loading the in-process agent at startup time by using
23487 your system's support for preloading shared libraries. Many Unixes
23488 support the concept of preloading user defined libraries. In most
23489 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
23490 in the environment. See also the description of @code{gdbserver}'s
23491 @option{--wrapper} command line option.
23493 @item Using @value{GDBN} to force loading the agent at run time
23495 On some systems, you can force the inferior to load a shared library,
23496 by calling a dynamic loader function in the inferior that takes care
23497 of dynamically looking up and loading a shared library. On most Unix
23498 systems, the function is @code{dlopen}. You'll use the @code{call}
23499 command for that. For example:
23502 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
23505 Note that on most Unix systems, for the @code{dlopen} function to be
23506 available, the program needs to be linked with @code{-ldl}.
23509 On systems that have a userspace dynamic loader, like most Unix
23510 systems, when you connect to @code{gdbserver} using @code{target
23511 remote}, you'll find that the program is stopped at the dynamic
23512 loader's entry point, and no shared library has been loaded in the
23513 program's address space yet, including the in-process agent. In that
23514 case, before being able to use any of the fast or static tracepoints
23515 features, you need to let the loader run and load the shared
23516 libraries. The simplest way to do that is to run the program to the
23517 main procedure. E.g., if debugging a C or C@t{++} program, start
23518 @code{gdbserver} like so:
23521 $ gdbserver :9999 myprogram
23524 Start GDB and connect to @code{gdbserver} like so, and run to main:
23528 (@value{GDBP}) target remote myhost:9999
23529 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
23530 (@value{GDBP}) b main
23531 (@value{GDBP}) continue
23534 The in-process tracing agent library should now be loaded into the
23535 process; you can confirm it with the @code{info sharedlibrary}
23536 command, which will list @file{libinproctrace.so} as loaded in the
23537 process. You are now ready to install fast tracepoints, list static
23538 tracepoint markers, probe static tracepoints markers, and start
23541 @node Remote Configuration
23542 @section Remote Configuration
23545 @kindex show remote
23546 This section documents the configuration options available when
23547 debugging remote programs. For the options related to the File I/O
23548 extensions of the remote protocol, see @ref{system,
23549 system-call-allowed}.
23552 @item set remoteaddresssize @var{bits}
23553 @cindex address size for remote targets
23554 @cindex bits in remote address
23555 Set the maximum size of address in a memory packet to the specified
23556 number of bits. @value{GDBN} will mask off the address bits above
23557 that number, when it passes addresses to the remote target. The
23558 default value is the number of bits in the target's address.
23560 @item show remoteaddresssize
23561 Show the current value of remote address size in bits.
23563 @item set serial baud @var{n}
23564 @cindex baud rate for remote targets
23565 Set the baud rate for the remote serial I/O to @var{n} baud. The
23566 value is used to set the speed of the serial port used for debugging
23569 @item show serial baud
23570 Show the current speed of the remote connection.
23572 @item set serial parity @var{parity}
23573 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
23574 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
23576 @item show serial parity
23577 Show the current parity of the serial port.
23579 @item set remotebreak
23580 @cindex interrupt remote programs
23581 @cindex BREAK signal instead of Ctrl-C
23582 @anchor{set remotebreak}
23583 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
23584 when you type @kbd{Ctrl-c} to interrupt the program running
23585 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
23586 character instead. The default is off, since most remote systems
23587 expect to see @samp{Ctrl-C} as the interrupt signal.
23589 @item show remotebreak
23590 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
23591 interrupt the remote program.
23593 @item set remoteflow on
23594 @itemx set remoteflow off
23595 @kindex set remoteflow
23596 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
23597 on the serial port used to communicate to the remote target.
23599 @item show remoteflow
23600 @kindex show remoteflow
23601 Show the current setting of hardware flow control.
23603 @item set remotelogbase @var{base}
23604 Set the base (a.k.a.@: radix) of logging serial protocol
23605 communications to @var{base}. Supported values of @var{base} are:
23606 @code{ascii}, @code{octal}, and @code{hex}. The default is
23609 @item show remotelogbase
23610 Show the current setting of the radix for logging remote serial
23613 @item set remotelogfile @var{file}
23614 @cindex record serial communications on file
23615 Record remote serial communications on the named @var{file}. The
23616 default is not to record at all.
23618 @item show remotelogfile
23619 Show the current setting of the file name on which to record the
23620 serial communications.
23622 @item set remotetimeout @var{num}
23623 @cindex timeout for serial communications
23624 @cindex remote timeout
23625 Set the timeout limit to wait for the remote target to respond to
23626 @var{num} seconds. The default is 2 seconds.
23628 @item show remotetimeout
23629 Show the current number of seconds to wait for the remote target
23632 @cindex limit hardware breakpoints and watchpoints
23633 @cindex remote target, limit break- and watchpoints
23634 @anchor{set remote hardware-watchpoint-limit}
23635 @anchor{set remote hardware-breakpoint-limit}
23636 @item set remote hardware-watchpoint-limit @var{limit}
23637 @itemx set remote hardware-breakpoint-limit @var{limit}
23638 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
23639 or breakpoints. The @var{limit} can be set to 0 to disable hardware
23640 watchpoints or breakpoints, and @code{unlimited} for unlimited
23641 watchpoints or breakpoints.
23643 @item show remote hardware-watchpoint-limit
23644 @itemx show remote hardware-breakpoint-limit
23645 Show the current limit for the number of hardware watchpoints or
23646 breakpoints that @value{GDBN} can use.
23648 @cindex limit hardware watchpoints length
23649 @cindex remote target, limit watchpoints length
23650 @anchor{set remote hardware-watchpoint-length-limit}
23651 @item set remote hardware-watchpoint-length-limit @var{limit}
23652 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
23653 length of a remote hardware watchpoint. A @var{limit} of 0 disables
23654 hardware watchpoints and @code{unlimited} allows watchpoints of any
23657 @item show remote hardware-watchpoint-length-limit
23658 Show the current limit (in bytes) of the maximum length of
23659 a remote hardware watchpoint.
23661 @item set remote exec-file @var{filename}
23662 @itemx show remote exec-file
23663 @anchor{set remote exec-file}
23664 @cindex executable file, for remote target
23665 Select the file used for @code{run} with @code{target
23666 extended-remote}. This should be set to a filename valid on the
23667 target system. If it is not set, the target will use a default
23668 filename (e.g.@: the last program run).
23670 @item set remote interrupt-sequence
23671 @cindex interrupt remote programs
23672 @cindex select Ctrl-C, BREAK or BREAK-g
23673 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
23674 @samp{BREAK-g} as the
23675 sequence to the remote target in order to interrupt the execution.
23676 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
23677 is high level of serial line for some certain time.
23678 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
23679 It is @code{BREAK} signal followed by character @code{g}.
23681 @item show remote interrupt-sequence
23682 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
23683 is sent by @value{GDBN} to interrupt the remote program.
23684 @code{BREAK-g} is BREAK signal followed by @code{g} and
23685 also known as Magic SysRq g.
23687 @item set remote interrupt-on-connect
23688 @cindex send interrupt-sequence on start
23689 Specify whether interrupt-sequence is sent to remote target when
23690 @value{GDBN} connects to it. This is mostly needed when you debug
23691 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
23692 which is known as Magic SysRq g in order to connect @value{GDBN}.
23694 @item show remote interrupt-on-connect
23695 Show whether interrupt-sequence is sent
23696 to remote target when @value{GDBN} connects to it.
23700 @item set tcp auto-retry on
23701 @cindex auto-retry, for remote TCP target
23702 Enable auto-retry for remote TCP connections. This is useful if the remote
23703 debugging agent is launched in parallel with @value{GDBN}; there is a race
23704 condition because the agent may not become ready to accept the connection
23705 before @value{GDBN} attempts to connect. When auto-retry is
23706 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
23707 to establish the connection using the timeout specified by
23708 @code{set tcp connect-timeout}.
23710 @item set tcp auto-retry off
23711 Do not auto-retry failed TCP connections.
23713 @item show tcp auto-retry
23714 Show the current auto-retry setting.
23716 @item set tcp connect-timeout @var{seconds}
23717 @itemx set tcp connect-timeout unlimited
23718 @cindex connection timeout, for remote TCP target
23719 @cindex timeout, for remote target connection
23720 Set the timeout for establishing a TCP connection to the remote target to
23721 @var{seconds}. The timeout affects both polling to retry failed connections
23722 (enabled by @code{set tcp auto-retry on}) and waiting for connections
23723 that are merely slow to complete, and represents an approximate cumulative
23724 value. If @var{seconds} is @code{unlimited}, there is no timeout and
23725 @value{GDBN} will keep attempting to establish a connection forever,
23726 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
23728 @item show tcp connect-timeout
23729 Show the current connection timeout setting.
23732 @cindex remote packets, enabling and disabling
23733 The @value{GDBN} remote protocol autodetects the packets supported by
23734 your debugging stub. If you need to override the autodetection, you
23735 can use these commands to enable or disable individual packets. Each
23736 packet can be set to @samp{on} (the remote target supports this
23737 packet), @samp{off} (the remote target does not support this packet),
23738 or @samp{auto} (detect remote target support for this packet). They
23739 all default to @samp{auto}. For more information about each packet,
23740 see @ref{Remote Protocol}.
23742 During normal use, you should not have to use any of these commands.
23743 If you do, that may be a bug in your remote debugging stub, or a bug
23744 in @value{GDBN}. You may want to report the problem to the
23745 @value{GDBN} developers.
23747 For each packet @var{name}, the command to enable or disable the
23748 packet is @code{set remote @var{name}-packet}. The available settings
23751 @multitable @columnfractions 0.28 0.32 0.25
23754 @tab Related Features
23756 @item @code{fetch-register}
23758 @tab @code{info registers}
23760 @item @code{set-register}
23764 @item @code{binary-download}
23766 @tab @code{load}, @code{set}
23768 @item @code{read-aux-vector}
23769 @tab @code{qXfer:auxv:read}
23770 @tab @code{info auxv}
23772 @item @code{symbol-lookup}
23773 @tab @code{qSymbol}
23774 @tab Detecting multiple threads
23776 @item @code{attach}
23777 @tab @code{vAttach}
23780 @item @code{verbose-resume}
23782 @tab Stepping or resuming multiple threads
23788 @item @code{software-breakpoint}
23792 @item @code{hardware-breakpoint}
23796 @item @code{write-watchpoint}
23800 @item @code{read-watchpoint}
23804 @item @code{access-watchpoint}
23808 @item @code{pid-to-exec-file}
23809 @tab @code{qXfer:exec-file:read}
23810 @tab @code{attach}, @code{run}
23812 @item @code{target-features}
23813 @tab @code{qXfer:features:read}
23814 @tab @code{set architecture}
23816 @item @code{library-info}
23817 @tab @code{qXfer:libraries:read}
23818 @tab @code{info sharedlibrary}
23820 @item @code{memory-map}
23821 @tab @code{qXfer:memory-map:read}
23822 @tab @code{info mem}
23824 @item @code{read-sdata-object}
23825 @tab @code{qXfer:sdata:read}
23826 @tab @code{print $_sdata}
23828 @item @code{read-siginfo-object}
23829 @tab @code{qXfer:siginfo:read}
23830 @tab @code{print $_siginfo}
23832 @item @code{write-siginfo-object}
23833 @tab @code{qXfer:siginfo:write}
23834 @tab @code{set $_siginfo}
23836 @item @code{threads}
23837 @tab @code{qXfer:threads:read}
23838 @tab @code{info threads}
23840 @item @code{get-thread-local-@*storage-address}
23841 @tab @code{qGetTLSAddr}
23842 @tab Displaying @code{__thread} variables
23844 @item @code{get-thread-information-block-address}
23845 @tab @code{qGetTIBAddr}
23846 @tab Display MS-Windows Thread Information Block.
23848 @item @code{search-memory}
23849 @tab @code{qSearch:memory}
23852 @item @code{supported-packets}
23853 @tab @code{qSupported}
23854 @tab Remote communications parameters
23856 @item @code{catch-syscalls}
23857 @tab @code{QCatchSyscalls}
23858 @tab @code{catch syscall}
23860 @item @code{pass-signals}
23861 @tab @code{QPassSignals}
23862 @tab @code{handle @var{signal}}
23864 @item @code{program-signals}
23865 @tab @code{QProgramSignals}
23866 @tab @code{handle @var{signal}}
23868 @item @code{hostio-close-packet}
23869 @tab @code{vFile:close}
23870 @tab @code{remote get}, @code{remote put}
23872 @item @code{hostio-open-packet}
23873 @tab @code{vFile:open}
23874 @tab @code{remote get}, @code{remote put}
23876 @item @code{hostio-pread-packet}
23877 @tab @code{vFile:pread}
23878 @tab @code{remote get}, @code{remote put}
23880 @item @code{hostio-pwrite-packet}
23881 @tab @code{vFile:pwrite}
23882 @tab @code{remote get}, @code{remote put}
23884 @item @code{hostio-unlink-packet}
23885 @tab @code{vFile:unlink}
23886 @tab @code{remote delete}
23888 @item @code{hostio-readlink-packet}
23889 @tab @code{vFile:readlink}
23892 @item @code{hostio-fstat-packet}
23893 @tab @code{vFile:fstat}
23896 @item @code{hostio-setfs-packet}
23897 @tab @code{vFile:setfs}
23900 @item @code{noack-packet}
23901 @tab @code{QStartNoAckMode}
23902 @tab Packet acknowledgment
23904 @item @code{osdata}
23905 @tab @code{qXfer:osdata:read}
23906 @tab @code{info os}
23908 @item @code{query-attached}
23909 @tab @code{qAttached}
23910 @tab Querying remote process attach state.
23912 @item @code{trace-buffer-size}
23913 @tab @code{QTBuffer:size}
23914 @tab @code{set trace-buffer-size}
23916 @item @code{trace-status}
23917 @tab @code{qTStatus}
23918 @tab @code{tstatus}
23920 @item @code{traceframe-info}
23921 @tab @code{qXfer:traceframe-info:read}
23922 @tab Traceframe info
23924 @item @code{install-in-trace}
23925 @tab @code{InstallInTrace}
23926 @tab Install tracepoint in tracing
23928 @item @code{disable-randomization}
23929 @tab @code{QDisableRandomization}
23930 @tab @code{set disable-randomization}
23932 @item @code{startup-with-shell}
23933 @tab @code{QStartupWithShell}
23934 @tab @code{set startup-with-shell}
23936 @item @code{environment-hex-encoded}
23937 @tab @code{QEnvironmentHexEncoded}
23938 @tab @code{set environment}
23940 @item @code{environment-unset}
23941 @tab @code{QEnvironmentUnset}
23942 @tab @code{unset environment}
23944 @item @code{environment-reset}
23945 @tab @code{QEnvironmentReset}
23946 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
23948 @item @code{set-working-dir}
23949 @tab @code{QSetWorkingDir}
23950 @tab @code{set cwd}
23952 @item @code{conditional-breakpoints-packet}
23953 @tab @code{Z0 and Z1}
23954 @tab @code{Support for target-side breakpoint condition evaluation}
23956 @item @code{multiprocess-extensions}
23957 @tab @code{multiprocess extensions}
23958 @tab Debug multiple processes and remote process PID awareness
23960 @item @code{swbreak-feature}
23961 @tab @code{swbreak stop reason}
23964 @item @code{hwbreak-feature}
23965 @tab @code{hwbreak stop reason}
23968 @item @code{fork-event-feature}
23969 @tab @code{fork stop reason}
23972 @item @code{vfork-event-feature}
23973 @tab @code{vfork stop reason}
23976 @item @code{exec-event-feature}
23977 @tab @code{exec stop reason}
23980 @item @code{thread-events}
23981 @tab @code{QThreadEvents}
23982 @tab Tracking thread lifetime.
23984 @item @code{no-resumed-stop-reply}
23985 @tab @code{no resumed thread left stop reply}
23986 @tab Tracking thread lifetime.
23991 @section Implementing a Remote Stub
23993 @cindex debugging stub, example
23994 @cindex remote stub, example
23995 @cindex stub example, remote debugging
23996 The stub files provided with @value{GDBN} implement the target side of the
23997 communication protocol, and the @value{GDBN} side is implemented in the
23998 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
23999 these subroutines to communicate, and ignore the details. (If you're
24000 implementing your own stub file, you can still ignore the details: start
24001 with one of the existing stub files. @file{sparc-stub.c} is the best
24002 organized, and therefore the easiest to read.)
24004 @cindex remote serial debugging, overview
24005 To debug a program running on another machine (the debugging
24006 @dfn{target} machine), you must first arrange for all the usual
24007 prerequisites for the program to run by itself. For example, for a C
24012 A startup routine to set up the C runtime environment; these usually
24013 have a name like @file{crt0}. The startup routine may be supplied by
24014 your hardware supplier, or you may have to write your own.
24017 A C subroutine library to support your program's
24018 subroutine calls, notably managing input and output.
24021 A way of getting your program to the other machine---for example, a
24022 download program. These are often supplied by the hardware
24023 manufacturer, but you may have to write your own from hardware
24027 The next step is to arrange for your program to use a serial port to
24028 communicate with the machine where @value{GDBN} is running (the @dfn{host}
24029 machine). In general terms, the scheme looks like this:
24033 @value{GDBN} already understands how to use this protocol; when everything
24034 else is set up, you can simply use the @samp{target remote} command
24035 (@pxref{Targets,,Specifying a Debugging Target}).
24037 @item On the target,
24038 you must link with your program a few special-purpose subroutines that
24039 implement the @value{GDBN} remote serial protocol. The file containing these
24040 subroutines is called a @dfn{debugging stub}.
24042 On certain remote targets, you can use an auxiliary program
24043 @code{gdbserver} instead of linking a stub into your program.
24044 @xref{Server,,Using the @code{gdbserver} Program}, for details.
24047 The debugging stub is specific to the architecture of the remote
24048 machine; for example, use @file{sparc-stub.c} to debug programs on
24051 @cindex remote serial stub list
24052 These working remote stubs are distributed with @value{GDBN}:
24057 @cindex @file{i386-stub.c}
24060 For Intel 386 and compatible architectures.
24063 @cindex @file{m68k-stub.c}
24064 @cindex Motorola 680x0
24066 For Motorola 680x0 architectures.
24069 @cindex @file{sh-stub.c}
24072 For Renesas SH architectures.
24075 @cindex @file{sparc-stub.c}
24077 For @sc{sparc} architectures.
24079 @item sparcl-stub.c
24080 @cindex @file{sparcl-stub.c}
24083 For Fujitsu @sc{sparclite} architectures.
24087 The @file{README} file in the @value{GDBN} distribution may list other
24088 recently added stubs.
24091 * Stub Contents:: What the stub can do for you
24092 * Bootstrapping:: What you must do for the stub
24093 * Debug Session:: Putting it all together
24096 @node Stub Contents
24097 @subsection What the Stub Can Do for You
24099 @cindex remote serial stub
24100 The debugging stub for your architecture supplies these three
24104 @item set_debug_traps
24105 @findex set_debug_traps
24106 @cindex remote serial stub, initialization
24107 This routine arranges for @code{handle_exception} to run when your
24108 program stops. You must call this subroutine explicitly in your
24109 program's startup code.
24111 @item handle_exception
24112 @findex handle_exception
24113 @cindex remote serial stub, main routine
24114 This is the central workhorse, but your program never calls it
24115 explicitly---the setup code arranges for @code{handle_exception} to
24116 run when a trap is triggered.
24118 @code{handle_exception} takes control when your program stops during
24119 execution (for example, on a breakpoint), and mediates communications
24120 with @value{GDBN} on the host machine. This is where the communications
24121 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
24122 representative on the target machine. It begins by sending summary
24123 information on the state of your program, then continues to execute,
24124 retrieving and transmitting any information @value{GDBN} needs, until you
24125 execute a @value{GDBN} command that makes your program resume; at that point,
24126 @code{handle_exception} returns control to your own code on the target
24130 @cindex @code{breakpoint} subroutine, remote
24131 Use this auxiliary subroutine to make your program contain a
24132 breakpoint. Depending on the particular situation, this may be the only
24133 way for @value{GDBN} to get control. For instance, if your target
24134 machine has some sort of interrupt button, you won't need to call this;
24135 pressing the interrupt button transfers control to
24136 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
24137 simply receiving characters on the serial port may also trigger a trap;
24138 again, in that situation, you don't need to call @code{breakpoint} from
24139 your own program---simply running @samp{target remote} from the host
24140 @value{GDBN} session gets control.
24142 Call @code{breakpoint} if none of these is true, or if you simply want
24143 to make certain your program stops at a predetermined point for the
24144 start of your debugging session.
24147 @node Bootstrapping
24148 @subsection What You Must Do for the Stub
24150 @cindex remote stub, support routines
24151 The debugging stubs that come with @value{GDBN} are set up for a particular
24152 chip architecture, but they have no information about the rest of your
24153 debugging target machine.
24155 First of all you need to tell the stub how to communicate with the
24159 @item int getDebugChar()
24160 @findex getDebugChar
24161 Write this subroutine to read a single character from the serial port.
24162 It may be identical to @code{getchar} for your target system; a
24163 different name is used to allow you to distinguish the two if you wish.
24165 @item void putDebugChar(int)
24166 @findex putDebugChar
24167 Write this subroutine to write a single character to the serial port.
24168 It may be identical to @code{putchar} for your target system; a
24169 different name is used to allow you to distinguish the two if you wish.
24172 @cindex control C, and remote debugging
24173 @cindex interrupting remote targets
24174 If you want @value{GDBN} to be able to stop your program while it is
24175 running, you need to use an interrupt-driven serial driver, and arrange
24176 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
24177 character). That is the character which @value{GDBN} uses to tell the
24178 remote system to stop.
24180 Getting the debugging target to return the proper status to @value{GDBN}
24181 probably requires changes to the standard stub; one quick and dirty way
24182 is to just execute a breakpoint instruction (the ``dirty'' part is that
24183 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
24185 Other routines you need to supply are:
24188 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
24189 @findex exceptionHandler
24190 Write this function to install @var{exception_address} in the exception
24191 handling tables. You need to do this because the stub does not have any
24192 way of knowing what the exception handling tables on your target system
24193 are like (for example, the processor's table might be in @sc{rom},
24194 containing entries which point to a table in @sc{ram}).
24195 The @var{exception_number} specifies the exception which should be changed;
24196 its meaning is architecture-dependent (for example, different numbers
24197 might represent divide by zero, misaligned access, etc). When this
24198 exception occurs, control should be transferred directly to
24199 @var{exception_address}, and the processor state (stack, registers,
24200 and so on) should be just as it is when a processor exception occurs. So if
24201 you want to use a jump instruction to reach @var{exception_address}, it
24202 should be a simple jump, not a jump to subroutine.
24204 For the 386, @var{exception_address} should be installed as an interrupt
24205 gate so that interrupts are masked while the handler runs. The gate
24206 should be at privilege level 0 (the most privileged level). The
24207 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
24208 help from @code{exceptionHandler}.
24210 @item void flush_i_cache()
24211 @findex flush_i_cache
24212 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
24213 instruction cache, if any, on your target machine. If there is no
24214 instruction cache, this subroutine may be a no-op.
24216 On target machines that have instruction caches, @value{GDBN} requires this
24217 function to make certain that the state of your program is stable.
24221 You must also make sure this library routine is available:
24224 @item void *memset(void *, int, int)
24226 This is the standard library function @code{memset} that sets an area of
24227 memory to a known value. If you have one of the free versions of
24228 @code{libc.a}, @code{memset} can be found there; otherwise, you must
24229 either obtain it from your hardware manufacturer, or write your own.
24232 If you do not use the GNU C compiler, you may need other standard
24233 library subroutines as well; this varies from one stub to another,
24234 but in general the stubs are likely to use any of the common library
24235 subroutines which @code{@value{NGCC}} generates as inline code.
24238 @node Debug Session
24239 @subsection Putting it All Together
24241 @cindex remote serial debugging summary
24242 In summary, when your program is ready to debug, you must follow these
24247 Make sure you have defined the supporting low-level routines
24248 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
24250 @code{getDebugChar}, @code{putDebugChar},
24251 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
24255 Insert these lines in your program's startup code, before the main
24256 procedure is called:
24263 On some machines, when a breakpoint trap is raised, the hardware
24264 automatically makes the PC point to the instruction after the
24265 breakpoint. If your machine doesn't do that, you may need to adjust
24266 @code{handle_exception} to arrange for it to return to the instruction
24267 after the breakpoint on this first invocation, so that your program
24268 doesn't keep hitting the initial breakpoint instead of making
24272 For the 680x0 stub only, you need to provide a variable called
24273 @code{exceptionHook}. Normally you just use:
24276 void (*exceptionHook)() = 0;
24280 but if before calling @code{set_debug_traps}, you set it to point to a
24281 function in your program, that function is called when
24282 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
24283 error). The function indicated by @code{exceptionHook} is called with
24284 one parameter: an @code{int} which is the exception number.
24287 Compile and link together: your program, the @value{GDBN} debugging stub for
24288 your target architecture, and the supporting subroutines.
24291 Make sure you have a serial connection between your target machine and
24292 the @value{GDBN} host, and identify the serial port on the host.
24295 @c The "remote" target now provides a `load' command, so we should
24296 @c document that. FIXME.
24297 Download your program to your target machine (or get it there by
24298 whatever means the manufacturer provides), and start it.
24301 Start @value{GDBN} on the host, and connect to the target
24302 (@pxref{Connecting,,Connecting to a Remote Target}).
24306 @node Configurations
24307 @chapter Configuration-Specific Information
24309 While nearly all @value{GDBN} commands are available for all native and
24310 cross versions of the debugger, there are some exceptions. This chapter
24311 describes things that are only available in certain configurations.
24313 There are three major categories of configurations: native
24314 configurations, where the host and target are the same, embedded
24315 operating system configurations, which are usually the same for several
24316 different processor architectures, and bare embedded processors, which
24317 are quite different from each other.
24322 * Embedded Processors::
24329 This section describes details specific to particular native
24333 * BSD libkvm Interface:: Debugging BSD kernel memory images
24334 * Process Information:: Process information
24335 * DJGPP Native:: Features specific to the DJGPP port
24336 * Cygwin Native:: Features specific to the Cygwin port
24337 * Hurd Native:: Features specific to @sc{gnu} Hurd
24338 * Darwin:: Features specific to Darwin
24339 * FreeBSD:: Features specific to FreeBSD
24342 @node BSD libkvm Interface
24343 @subsection BSD libkvm Interface
24346 @cindex kernel memory image
24347 @cindex kernel crash dump
24349 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
24350 interface that provides a uniform interface for accessing kernel virtual
24351 memory images, including live systems and crash dumps. @value{GDBN}
24352 uses this interface to allow you to debug live kernels and kernel crash
24353 dumps on many native BSD configurations. This is implemented as a
24354 special @code{kvm} debugging target. For debugging a live system, load
24355 the currently running kernel into @value{GDBN} and connect to the
24359 (@value{GDBP}) @b{target kvm}
24362 For debugging crash dumps, provide the file name of the crash dump as an
24366 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
24369 Once connected to the @code{kvm} target, the following commands are
24375 Set current context from the @dfn{Process Control Block} (PCB) address.
24378 Set current context from proc address. This command isn't available on
24379 modern FreeBSD systems.
24382 @node Process Information
24383 @subsection Process Information
24385 @cindex examine process image
24386 @cindex process info via @file{/proc}
24388 Some operating systems provide interfaces to fetch additional
24389 information about running processes beyond memory and per-thread
24390 register state. If @value{GDBN} is configured for an operating system
24391 with a supported interface, the command @code{info proc} is available
24392 to report information about the process running your program, or about
24393 any process running on your system.
24395 One supported interface is a facility called @samp{/proc} that can be
24396 used to examine the image of a running process using file-system
24397 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
24400 On FreeBSD and NetBSD systems, system control nodes are used to query
24401 process information.
24403 In addition, some systems may provide additional process information
24404 in core files. Note that a core file may include a subset of the
24405 information available from a live process. Process information is
24406 currently available from cores created on @sc{gnu}/Linux and FreeBSD
24413 @itemx info proc @var{process-id}
24414 Summarize available information about a process. If a
24415 process ID is specified by @var{process-id}, display information about
24416 that process; otherwise display information about the program being
24417 debugged. The summary includes the debugged process ID, the command
24418 line used to invoke it, its current working directory, and its
24419 executable file's absolute file name.
24421 On some systems, @var{process-id} can be of the form
24422 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
24423 within a process. If the optional @var{pid} part is missing, it means
24424 a thread from the process being debugged (the leading @samp{/} still
24425 needs to be present, or else @value{GDBN} will interpret the number as
24426 a process ID rather than a thread ID).
24428 @item info proc cmdline
24429 @cindex info proc cmdline
24430 Show the original command line of the process. This command is
24431 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24433 @item info proc cwd
24434 @cindex info proc cwd
24435 Show the current working directory of the process. This command is
24436 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24438 @item info proc exe
24439 @cindex info proc exe
24440 Show the name of executable of the process. This command is supported
24441 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24443 @item info proc files
24444 @cindex info proc files
24445 Show the file descriptors open by the process. For each open file
24446 descriptor, @value{GDBN} shows its number, type (file, directory,
24447 character device, socket), file pointer offset, and the name of the
24448 resource open on the descriptor. The resource name can be a file name
24449 (for files, directories, and devices) or a protocol followed by socket
24450 address (for network connections). This command is supported on
24453 This example shows the open file descriptors for a process using a
24454 tty for standard input and output as well as two network sockets:
24457 (gdb) info proc files 22136
24461 FD Type Offset Flags Name
24462 text file - r-------- /usr/bin/ssh
24463 ctty chr - rw------- /dev/pts/20
24464 cwd dir - r-------- /usr/home/john
24465 root dir - r-------- /
24466 0 chr 0x32933a4 rw------- /dev/pts/20
24467 1 chr 0x32933a4 rw------- /dev/pts/20
24468 2 chr 0x32933a4 rw------- /dev/pts/20
24469 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
24470 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
24473 @item info proc mappings
24474 @cindex memory address space mappings
24475 Report the memory address space ranges accessible in a process. On
24476 Solaris, FreeBSD and NetBSD systems, each memory range includes information
24477 on whether the process has read, write, or execute access rights to each
24478 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
24479 includes the object file which is mapped to that range.
24481 @item info proc stat
24482 @itemx info proc status
24483 @cindex process detailed status information
24484 Show additional process-related information, including the user ID and
24485 group ID; virtual memory usage; the signals that are pending, blocked,
24486 and ignored; its TTY; its consumption of system and user time; its
24487 stack size; its @samp{nice} value; etc. These commands are supported
24488 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24490 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
24491 information (type @kbd{man 5 proc} from your shell prompt).
24493 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
24494 @code{info proc status}.
24496 @item info proc all
24497 Show all the information about the process described under all of the
24498 above @code{info proc} subcommands.
24501 @comment These sub-options of 'info proc' were not included when
24502 @comment procfs.c was re-written. Keep their descriptions around
24503 @comment against the day when someone finds the time to put them back in.
24504 @kindex info proc times
24505 @item info proc times
24506 Starting time, user CPU time, and system CPU time for your program and
24509 @kindex info proc id
24511 Report on the process IDs related to your program: its own process ID,
24512 the ID of its parent, the process group ID, and the session ID.
24515 @item set procfs-trace
24516 @kindex set procfs-trace
24517 @cindex @code{procfs} API calls
24518 This command enables and disables tracing of @code{procfs} API calls.
24520 @item show procfs-trace
24521 @kindex show procfs-trace
24522 Show the current state of @code{procfs} API call tracing.
24524 @item set procfs-file @var{file}
24525 @kindex set procfs-file
24526 Tell @value{GDBN} to write @code{procfs} API trace to the named
24527 @var{file}. @value{GDBN} appends the trace info to the previous
24528 contents of the file. The default is to display the trace on the
24531 @item show procfs-file
24532 @kindex show procfs-file
24533 Show the file to which @code{procfs} API trace is written.
24535 @item proc-trace-entry
24536 @itemx proc-trace-exit
24537 @itemx proc-untrace-entry
24538 @itemx proc-untrace-exit
24539 @kindex proc-trace-entry
24540 @kindex proc-trace-exit
24541 @kindex proc-untrace-entry
24542 @kindex proc-untrace-exit
24543 These commands enable and disable tracing of entries into and exits
24544 from the @code{syscall} interface.
24547 @kindex info pidlist
24548 @cindex process list, QNX Neutrino
24549 For QNX Neutrino only, this command displays the list of all the
24550 processes and all the threads within each process.
24553 @kindex info meminfo
24554 @cindex mapinfo list, QNX Neutrino
24555 For QNX Neutrino only, this command displays the list of all mapinfos.
24559 @subsection Features for Debugging @sc{djgpp} Programs
24560 @cindex @sc{djgpp} debugging
24561 @cindex native @sc{djgpp} debugging
24562 @cindex MS-DOS-specific commands
24565 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
24566 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
24567 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
24568 top of real-mode DOS systems and their emulations.
24570 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
24571 defines a few commands specific to the @sc{djgpp} port. This
24572 subsection describes those commands.
24577 This is a prefix of @sc{djgpp}-specific commands which print
24578 information about the target system and important OS structures.
24581 @cindex MS-DOS system info
24582 @cindex free memory information (MS-DOS)
24583 @item info dos sysinfo
24584 This command displays assorted information about the underlying
24585 platform: the CPU type and features, the OS version and flavor, the
24586 DPMI version, and the available conventional and DPMI memory.
24591 @cindex segment descriptor tables
24592 @cindex descriptor tables display
24594 @itemx info dos ldt
24595 @itemx info dos idt
24596 These 3 commands display entries from, respectively, Global, Local,
24597 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
24598 tables are data structures which store a descriptor for each segment
24599 that is currently in use. The segment's selector is an index into a
24600 descriptor table; the table entry for that index holds the
24601 descriptor's base address and limit, and its attributes and access
24604 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
24605 segment (used for both data and the stack), and a DOS segment (which
24606 allows access to DOS/BIOS data structures and absolute addresses in
24607 conventional memory). However, the DPMI host will usually define
24608 additional segments in order to support the DPMI environment.
24610 @cindex garbled pointers
24611 These commands allow to display entries from the descriptor tables.
24612 Without an argument, all entries from the specified table are
24613 displayed. An argument, which should be an integer expression, means
24614 display a single entry whose index is given by the argument. For
24615 example, here's a convenient way to display information about the
24616 debugged program's data segment:
24619 @exdent @code{(@value{GDBP}) info dos ldt $ds}
24620 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
24624 This comes in handy when you want to see whether a pointer is outside
24625 the data segment's limit (i.e.@: @dfn{garbled}).
24627 @cindex page tables display (MS-DOS)
24629 @itemx info dos pte
24630 These two commands display entries from, respectively, the Page
24631 Directory and the Page Tables. Page Directories and Page Tables are
24632 data structures which control how virtual memory addresses are mapped
24633 into physical addresses. A Page Table includes an entry for every
24634 page of memory that is mapped into the program's address space; there
24635 may be several Page Tables, each one holding up to 4096 entries. A
24636 Page Directory has up to 4096 entries, one each for every Page Table
24637 that is currently in use.
24639 Without an argument, @kbd{info dos pde} displays the entire Page
24640 Directory, and @kbd{info dos pte} displays all the entries in all of
24641 the Page Tables. An argument, an integer expression, given to the
24642 @kbd{info dos pde} command means display only that entry from the Page
24643 Directory table. An argument given to the @kbd{info dos pte} command
24644 means display entries from a single Page Table, the one pointed to by
24645 the specified entry in the Page Directory.
24647 @cindex direct memory access (DMA) on MS-DOS
24648 These commands are useful when your program uses @dfn{DMA} (Direct
24649 Memory Access), which needs physical addresses to program the DMA
24652 These commands are supported only with some DPMI servers.
24654 @cindex physical address from linear address
24655 @item info dos address-pte @var{addr}
24656 This command displays the Page Table entry for a specified linear
24657 address. The argument @var{addr} is a linear address which should
24658 already have the appropriate segment's base address added to it,
24659 because this command accepts addresses which may belong to @emph{any}
24660 segment. For example, here's how to display the Page Table entry for
24661 the page where a variable @code{i} is stored:
24664 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
24665 @exdent @code{Page Table entry for address 0x11a00d30:}
24666 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
24670 This says that @code{i} is stored at offset @code{0xd30} from the page
24671 whose physical base address is @code{0x02698000}, and shows all the
24672 attributes of that page.
24674 Note that you must cast the addresses of variables to a @code{char *},
24675 since otherwise the value of @code{__djgpp_base_address}, the base
24676 address of all variables and functions in a @sc{djgpp} program, will
24677 be added using the rules of C pointer arithmetics: if @code{i} is
24678 declared an @code{int}, @value{GDBN} will add 4 times the value of
24679 @code{__djgpp_base_address} to the address of @code{i}.
24681 Here's another example, it displays the Page Table entry for the
24685 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
24686 @exdent @code{Page Table entry for address 0x29110:}
24687 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
24691 (The @code{+ 3} offset is because the transfer buffer's address is the
24692 3rd member of the @code{_go32_info_block} structure.) The output
24693 clearly shows that this DPMI server maps the addresses in conventional
24694 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
24695 linear (@code{0x29110}) addresses are identical.
24697 This command is supported only with some DPMI servers.
24700 @cindex DOS serial data link, remote debugging
24701 In addition to native debugging, the DJGPP port supports remote
24702 debugging via a serial data link. The following commands are specific
24703 to remote serial debugging in the DJGPP port of @value{GDBN}.
24706 @kindex set com1base
24707 @kindex set com1irq
24708 @kindex set com2base
24709 @kindex set com2irq
24710 @kindex set com3base
24711 @kindex set com3irq
24712 @kindex set com4base
24713 @kindex set com4irq
24714 @item set com1base @var{addr}
24715 This command sets the base I/O port address of the @file{COM1} serial
24718 @item set com1irq @var{irq}
24719 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
24720 for the @file{COM1} serial port.
24722 There are similar commands @samp{set com2base}, @samp{set com3irq},
24723 etc.@: for setting the port address and the @code{IRQ} lines for the
24726 @kindex show com1base
24727 @kindex show com1irq
24728 @kindex show com2base
24729 @kindex show com2irq
24730 @kindex show com3base
24731 @kindex show com3irq
24732 @kindex show com4base
24733 @kindex show com4irq
24734 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
24735 display the current settings of the base address and the @code{IRQ}
24736 lines used by the COM ports.
24739 @kindex info serial
24740 @cindex DOS serial port status
24741 This command prints the status of the 4 DOS serial ports. For each
24742 port, it prints whether it's active or not, its I/O base address and
24743 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
24744 counts of various errors encountered so far.
24748 @node Cygwin Native
24749 @subsection Features for Debugging MS Windows PE Executables
24750 @cindex MS Windows debugging
24751 @cindex native Cygwin debugging
24752 @cindex Cygwin-specific commands
24754 @value{GDBN} supports native debugging of MS Windows programs, including
24755 DLLs with and without symbolic debugging information.
24757 @cindex Ctrl-BREAK, MS-Windows
24758 @cindex interrupt debuggee on MS-Windows
24759 MS-Windows programs that call @code{SetConsoleMode} to switch off the
24760 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
24761 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
24762 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
24763 sequence, which can be used to interrupt the debuggee even if it
24766 There are various additional Cygwin-specific commands, described in
24767 this section. Working with DLLs that have no debugging symbols is
24768 described in @ref{Non-debug DLL Symbols}.
24773 This is a prefix of MS Windows-specific commands which print
24774 information about the target system and important OS structures.
24776 @item info w32 selector
24777 This command displays information returned by
24778 the Win32 API @code{GetThreadSelectorEntry} function.
24779 It takes an optional argument that is evaluated to
24780 a long value to give the information about this given selector.
24781 Without argument, this command displays information
24782 about the six segment registers.
24784 @item info w32 thread-information-block
24785 This command displays thread specific information stored in the
24786 Thread Information Block (readable on the X86 CPU family using @code{$fs}
24787 selector for 32-bit programs and @code{$gs} for 64-bit programs).
24789 @kindex signal-event
24790 @item signal-event @var{id}
24791 This command signals an event with user-provided @var{id}. Used to resume
24792 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
24794 To use it, create or edit the following keys in
24795 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
24796 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
24797 (for x86_64 versions):
24801 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
24802 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
24803 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
24805 The first @code{%ld} will be replaced by the process ID of the
24806 crashing process, the second @code{%ld} will be replaced by the ID of
24807 the event that blocks the crashing process, waiting for @value{GDBN}
24811 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
24812 make the system run debugger specified by the Debugger key
24813 automatically, @code{0} will cause a dialog box with ``OK'' and
24814 ``Cancel'' buttons to appear, which allows the user to either
24815 terminate the crashing process (OK) or debug it (Cancel).
24818 @kindex set cygwin-exceptions
24819 @cindex debugging the Cygwin DLL
24820 @cindex Cygwin DLL, debugging
24821 @item set cygwin-exceptions @var{mode}
24822 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
24823 happen inside the Cygwin DLL. If @var{mode} is @code{off},
24824 @value{GDBN} will delay recognition of exceptions, and may ignore some
24825 exceptions which seem to be caused by internal Cygwin DLL
24826 ``bookkeeping''. This option is meant primarily for debugging the
24827 Cygwin DLL itself; the default value is @code{off} to avoid annoying
24828 @value{GDBN} users with false @code{SIGSEGV} signals.
24830 @kindex show cygwin-exceptions
24831 @item show cygwin-exceptions
24832 Displays whether @value{GDBN} will break on exceptions that happen
24833 inside the Cygwin DLL itself.
24835 @kindex set new-console
24836 @item set new-console @var{mode}
24837 If @var{mode} is @code{on} the debuggee will
24838 be started in a new console on next start.
24839 If @var{mode} is @code{off}, the debuggee will
24840 be started in the same console as the debugger.
24842 @kindex show new-console
24843 @item show new-console
24844 Displays whether a new console is used
24845 when the debuggee is started.
24847 @kindex set new-group
24848 @item set new-group @var{mode}
24849 This boolean value controls whether the debuggee should
24850 start a new group or stay in the same group as the debugger.
24851 This affects the way the Windows OS handles
24854 @kindex show new-group
24855 @item show new-group
24856 Displays current value of new-group boolean.
24858 @kindex set debugevents
24859 @item set debugevents
24860 This boolean value adds debug output concerning kernel events related
24861 to the debuggee seen by the debugger. This includes events that
24862 signal thread and process creation and exit, DLL loading and
24863 unloading, console interrupts, and debugging messages produced by the
24864 Windows @code{OutputDebugString} API call.
24866 @kindex set debugexec
24867 @item set debugexec
24868 This boolean value adds debug output concerning execute events
24869 (such as resume thread) seen by the debugger.
24871 @kindex set debugexceptions
24872 @item set debugexceptions
24873 This boolean value adds debug output concerning exceptions in the
24874 debuggee seen by the debugger.
24876 @kindex set debugmemory
24877 @item set debugmemory
24878 This boolean value adds debug output concerning debuggee memory reads
24879 and writes by the debugger.
24883 This boolean values specifies whether the debuggee is called
24884 via a shell or directly (default value is on).
24888 Displays if the debuggee will be started with a shell.
24893 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
24896 @node Non-debug DLL Symbols
24897 @subsubsection Support for DLLs without Debugging Symbols
24898 @cindex DLLs with no debugging symbols
24899 @cindex Minimal symbols and DLLs
24901 Very often on windows, some of the DLLs that your program relies on do
24902 not include symbolic debugging information (for example,
24903 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
24904 symbols in a DLL, it relies on the minimal amount of symbolic
24905 information contained in the DLL's export table. This section
24906 describes working with such symbols, known internally to @value{GDBN} as
24907 ``minimal symbols''.
24909 Note that before the debugged program has started execution, no DLLs
24910 will have been loaded. The easiest way around this problem is simply to
24911 start the program --- either by setting a breakpoint or letting the
24912 program run once to completion.
24914 @subsubsection DLL Name Prefixes
24916 In keeping with the naming conventions used by the Microsoft debugging
24917 tools, DLL export symbols are made available with a prefix based on the
24918 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
24919 also entered into the symbol table, so @code{CreateFileA} is often
24920 sufficient. In some cases there will be name clashes within a program
24921 (particularly if the executable itself includes full debugging symbols)
24922 necessitating the use of the fully qualified name when referring to the
24923 contents of the DLL. Use single-quotes around the name to avoid the
24924 exclamation mark (``!'') being interpreted as a language operator.
24926 Note that the internal name of the DLL may be all upper-case, even
24927 though the file name of the DLL is lower-case, or vice-versa. Since
24928 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
24929 some confusion. If in doubt, try the @code{info functions} and
24930 @code{info variables} commands or even @code{maint print msymbols}
24931 (@pxref{Symbols}). Here's an example:
24934 (@value{GDBP}) info function CreateFileA
24935 All functions matching regular expression "CreateFileA":
24937 Non-debugging symbols:
24938 0x77e885f4 CreateFileA
24939 0x77e885f4 KERNEL32!CreateFileA
24943 (@value{GDBP}) info function !
24944 All functions matching regular expression "!":
24946 Non-debugging symbols:
24947 0x6100114c cygwin1!__assert
24948 0x61004034 cygwin1!_dll_crt0@@0
24949 0x61004240 cygwin1!dll_crt0(per_process *)
24953 @subsubsection Working with Minimal Symbols
24955 Symbols extracted from a DLL's export table do not contain very much
24956 type information. All that @value{GDBN} can do is guess whether a symbol
24957 refers to a function or variable depending on the linker section that
24958 contains the symbol. Also note that the actual contents of the memory
24959 contained in a DLL are not available unless the program is running. This
24960 means that you cannot examine the contents of a variable or disassemble
24961 a function within a DLL without a running program.
24963 Variables are generally treated as pointers and dereferenced
24964 automatically. For this reason, it is often necessary to prefix a
24965 variable name with the address-of operator (``&'') and provide explicit
24966 type information in the command. Here's an example of the type of
24970 (@value{GDBP}) print 'cygwin1!__argv'
24971 'cygwin1!__argv' has unknown type; cast it to its declared type
24975 (@value{GDBP}) x 'cygwin1!__argv'
24976 'cygwin1!__argv' has unknown type; cast it to its declared type
24979 And two possible solutions:
24982 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
24983 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
24987 (@value{GDBP}) x/2x &'cygwin1!__argv'
24988 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
24989 (@value{GDBP}) x/x 0x10021608
24990 0x10021608: 0x0022fd98
24991 (@value{GDBP}) x/s 0x0022fd98
24992 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
24995 Setting a break point within a DLL is possible even before the program
24996 starts execution. However, under these circumstances, @value{GDBN} can't
24997 examine the initial instructions of the function in order to skip the
24998 function's frame set-up code. You can work around this by using ``*&''
24999 to set the breakpoint at a raw memory address:
25002 (@value{GDBP}) break *&'python22!PyOS_Readline'
25003 Breakpoint 1 at 0x1e04eff0
25006 The author of these extensions is not entirely convinced that setting a
25007 break point within a shared DLL like @file{kernel32.dll} is completely
25011 @subsection Commands Specific to @sc{gnu} Hurd Systems
25012 @cindex @sc{gnu} Hurd debugging
25014 This subsection describes @value{GDBN} commands specific to the
25015 @sc{gnu} Hurd native debugging.
25020 @kindex set signals@r{, Hurd command}
25021 @kindex set sigs@r{, Hurd command}
25022 This command toggles the state of inferior signal interception by
25023 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
25024 affected by this command. @code{sigs} is a shorthand alias for
25029 @kindex show signals@r{, Hurd command}
25030 @kindex show sigs@r{, Hurd command}
25031 Show the current state of intercepting inferior's signals.
25033 @item set signal-thread
25034 @itemx set sigthread
25035 @kindex set signal-thread
25036 @kindex set sigthread
25037 This command tells @value{GDBN} which thread is the @code{libc} signal
25038 thread. That thread is run when a signal is delivered to a running
25039 process. @code{set sigthread} is the shorthand alias of @code{set
25042 @item show signal-thread
25043 @itemx show sigthread
25044 @kindex show signal-thread
25045 @kindex show sigthread
25046 These two commands show which thread will run when the inferior is
25047 delivered a signal.
25050 @kindex set stopped@r{, Hurd command}
25051 This commands tells @value{GDBN} that the inferior process is stopped,
25052 as with the @code{SIGSTOP} signal. The stopped process can be
25053 continued by delivering a signal to it.
25056 @kindex show stopped@r{, Hurd command}
25057 This command shows whether @value{GDBN} thinks the debuggee is
25060 @item set exceptions
25061 @kindex set exceptions@r{, Hurd command}
25062 Use this command to turn off trapping of exceptions in the inferior.
25063 When exception trapping is off, neither breakpoints nor
25064 single-stepping will work. To restore the default, set exception
25067 @item show exceptions
25068 @kindex show exceptions@r{, Hurd command}
25069 Show the current state of trapping exceptions in the inferior.
25071 @item set task pause
25072 @kindex set task@r{, Hurd commands}
25073 @cindex task attributes (@sc{gnu} Hurd)
25074 @cindex pause current task (@sc{gnu} Hurd)
25075 This command toggles task suspension when @value{GDBN} has control.
25076 Setting it to on takes effect immediately, and the task is suspended
25077 whenever @value{GDBN} gets control. Setting it to off will take
25078 effect the next time the inferior is continued. If this option is set
25079 to off, you can use @code{set thread default pause on} or @code{set
25080 thread pause on} (see below) to pause individual threads.
25082 @item show task pause
25083 @kindex show task@r{, Hurd commands}
25084 Show the current state of task suspension.
25086 @item set task detach-suspend-count
25087 @cindex task suspend count
25088 @cindex detach from task, @sc{gnu} Hurd
25089 This command sets the suspend count the task will be left with when
25090 @value{GDBN} detaches from it.
25092 @item show task detach-suspend-count
25093 Show the suspend count the task will be left with when detaching.
25095 @item set task exception-port
25096 @itemx set task excp
25097 @cindex task exception port, @sc{gnu} Hurd
25098 This command sets the task exception port to which @value{GDBN} will
25099 forward exceptions. The argument should be the value of the @dfn{send
25100 rights} of the task. @code{set task excp} is a shorthand alias.
25102 @item set noninvasive
25103 @cindex noninvasive task options
25104 This command switches @value{GDBN} to a mode that is the least
25105 invasive as far as interfering with the inferior is concerned. This
25106 is the same as using @code{set task pause}, @code{set exceptions}, and
25107 @code{set signals} to values opposite to the defaults.
25109 @item info send-rights
25110 @itemx info receive-rights
25111 @itemx info port-rights
25112 @itemx info port-sets
25113 @itemx info dead-names
25116 @cindex send rights, @sc{gnu} Hurd
25117 @cindex receive rights, @sc{gnu} Hurd
25118 @cindex port rights, @sc{gnu} Hurd
25119 @cindex port sets, @sc{gnu} Hurd
25120 @cindex dead names, @sc{gnu} Hurd
25121 These commands display information about, respectively, send rights,
25122 receive rights, port rights, port sets, and dead names of a task.
25123 There are also shorthand aliases: @code{info ports} for @code{info
25124 port-rights} and @code{info psets} for @code{info port-sets}.
25126 @item set thread pause
25127 @kindex set thread@r{, Hurd command}
25128 @cindex thread properties, @sc{gnu} Hurd
25129 @cindex pause current thread (@sc{gnu} Hurd)
25130 This command toggles current thread suspension when @value{GDBN} has
25131 control. Setting it to on takes effect immediately, and the current
25132 thread is suspended whenever @value{GDBN} gets control. Setting it to
25133 off will take effect the next time the inferior is continued.
25134 Normally, this command has no effect, since when @value{GDBN} has
25135 control, the whole task is suspended. However, if you used @code{set
25136 task pause off} (see above), this command comes in handy to suspend
25137 only the current thread.
25139 @item show thread pause
25140 @kindex show thread@r{, Hurd command}
25141 This command shows the state of current thread suspension.
25143 @item set thread run
25144 This command sets whether the current thread is allowed to run.
25146 @item show thread run
25147 Show whether the current thread is allowed to run.
25149 @item set thread detach-suspend-count
25150 @cindex thread suspend count, @sc{gnu} Hurd
25151 @cindex detach from thread, @sc{gnu} Hurd
25152 This command sets the suspend count @value{GDBN} will leave on a
25153 thread when detaching. This number is relative to the suspend count
25154 found by @value{GDBN} when it notices the thread; use @code{set thread
25155 takeover-suspend-count} to force it to an absolute value.
25157 @item show thread detach-suspend-count
25158 Show the suspend count @value{GDBN} will leave on the thread when
25161 @item set thread exception-port
25162 @itemx set thread excp
25163 Set the thread exception port to which to forward exceptions. This
25164 overrides the port set by @code{set task exception-port} (see above).
25165 @code{set thread excp} is the shorthand alias.
25167 @item set thread takeover-suspend-count
25168 Normally, @value{GDBN}'s thread suspend counts are relative to the
25169 value @value{GDBN} finds when it notices each thread. This command
25170 changes the suspend counts to be absolute instead.
25172 @item set thread default
25173 @itemx show thread default
25174 @cindex thread default settings, @sc{gnu} Hurd
25175 Each of the above @code{set thread} commands has a @code{set thread
25176 default} counterpart (e.g., @code{set thread default pause}, @code{set
25177 thread default exception-port}, etc.). The @code{thread default}
25178 variety of commands sets the default thread properties for all
25179 threads; you can then change the properties of individual threads with
25180 the non-default commands.
25187 @value{GDBN} provides the following commands specific to the Darwin target:
25190 @item set debug darwin @var{num}
25191 @kindex set debug darwin
25192 When set to a non zero value, enables debugging messages specific to
25193 the Darwin support. Higher values produce more verbose output.
25195 @item show debug darwin
25196 @kindex show debug darwin
25197 Show the current state of Darwin messages.
25199 @item set debug mach-o @var{num}
25200 @kindex set debug mach-o
25201 When set to a non zero value, enables debugging messages while
25202 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
25203 file format used on Darwin for object and executable files.) Higher
25204 values produce more verbose output. This is a command to diagnose
25205 problems internal to @value{GDBN} and should not be needed in normal
25208 @item show debug mach-o
25209 @kindex show debug mach-o
25210 Show the current state of Mach-O file messages.
25212 @item set mach-exceptions on
25213 @itemx set mach-exceptions off
25214 @kindex set mach-exceptions
25215 On Darwin, faults are first reported as a Mach exception and are then
25216 mapped to a Posix signal. Use this command to turn on trapping of
25217 Mach exceptions in the inferior. This might be sometimes useful to
25218 better understand the cause of a fault. The default is off.
25220 @item show mach-exceptions
25221 @kindex show mach-exceptions
25222 Show the current state of exceptions trapping.
25226 @subsection FreeBSD
25229 When the ABI of a system call is changed in the FreeBSD kernel, this
25230 is implemented by leaving a compatibility system call using the old
25231 ABI at the existing number and allocating a new system call number for
25232 the version using the new ABI. As a convenience, when a system call
25233 is caught by name (@pxref{catch syscall}), compatibility system calls
25236 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
25237 system call and catching the @code{kevent} system call by name catches
25241 (@value{GDBP}) catch syscall kevent
25242 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
25248 @section Embedded Operating Systems
25250 This section describes configurations involving the debugging of
25251 embedded operating systems that are available for several different
25254 @value{GDBN} includes the ability to debug programs running on
25255 various real-time operating systems.
25257 @node Embedded Processors
25258 @section Embedded Processors
25260 This section goes into details specific to particular embedded
25263 @cindex send command to simulator
25264 Whenever a specific embedded processor has a simulator, @value{GDBN}
25265 allows to send an arbitrary command to the simulator.
25268 @item sim @var{command}
25269 @kindex sim@r{, a command}
25270 Send an arbitrary @var{command} string to the simulator. Consult the
25271 documentation for the specific simulator in use for information about
25272 acceptable commands.
25277 * ARC:: Synopsys ARC
25280 * M68K:: Motorola M68K
25281 * MicroBlaze:: Xilinx MicroBlaze
25282 * MIPS Embedded:: MIPS Embedded
25283 * OpenRISC 1000:: OpenRISC 1000 (or1k)
25284 * PowerPC Embedded:: PowerPC Embedded
25287 * Super-H:: Renesas Super-H
25291 @subsection Synopsys ARC
25292 @cindex Synopsys ARC
25293 @cindex ARC specific commands
25299 @value{GDBN} provides the following ARC-specific commands:
25302 @item set debug arc
25303 @kindex set debug arc
25304 Control the level of ARC specific debug messages. Use 0 for no messages (the
25305 default), 1 for debug messages, and 2 for even more debug messages.
25307 @item show debug arc
25308 @kindex show debug arc
25309 Show the level of ARC specific debugging in operation.
25311 @item maint print arc arc-instruction @var{address}
25312 @kindex maint print arc arc-instruction
25313 Print internal disassembler information about instruction at a given address.
25320 @value{GDBN} provides the following ARM-specific commands:
25323 @item set arm disassembler
25325 This commands selects from a list of disassembly styles. The
25326 @code{"std"} style is the standard style.
25328 @item show arm disassembler
25330 Show the current disassembly style.
25332 @item set arm apcs32
25333 @cindex ARM 32-bit mode
25334 This command toggles ARM operation mode between 32-bit and 26-bit.
25336 @item show arm apcs32
25337 Display the current usage of the ARM 32-bit mode.
25339 @item set arm fpu @var{fputype}
25340 This command sets the ARM floating-point unit (FPU) type. The
25341 argument @var{fputype} can be one of these:
25345 Determine the FPU type by querying the OS ABI.
25347 Software FPU, with mixed-endian doubles on little-endian ARM
25350 GCC-compiled FPA co-processor.
25352 Software FPU with pure-endian doubles.
25358 Show the current type of the FPU.
25361 This command forces @value{GDBN} to use the specified ABI.
25364 Show the currently used ABI.
25366 @item set arm fallback-mode (arm|thumb|auto)
25367 @value{GDBN} uses the symbol table, when available, to determine
25368 whether instructions are ARM or Thumb. This command controls
25369 @value{GDBN}'s default behavior when the symbol table is not
25370 available. The default is @samp{auto}, which causes @value{GDBN} to
25371 use the current execution mode (from the @code{T} bit in the @code{CPSR}
25374 @item show arm fallback-mode
25375 Show the current fallback instruction mode.
25377 @item set arm force-mode (arm|thumb|auto)
25378 This command overrides use of the symbol table to determine whether
25379 instructions are ARM or Thumb. The default is @samp{auto}, which
25380 causes @value{GDBN} to use the symbol table and then the setting
25381 of @samp{set arm fallback-mode}.
25383 @item show arm force-mode
25384 Show the current forced instruction mode.
25386 @item set arm unwind-secure-frames
25387 This command enables unwinding from Non-secure to Secure mode on
25388 Cortex-M with Security extension.
25389 This can trigger security exceptions when unwinding the exception
25391 It is enabled by default.
25393 @item show arm unwind-secure-frames
25394 Show whether unwinding from Non-secure to Secure mode is enabled.
25396 @item set debug arm
25397 Toggle whether to display ARM-specific debugging messages from the ARM
25398 target support subsystem.
25400 @item show debug arm
25401 Show whether ARM-specific debugging messages are enabled.
25405 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25406 The @value{GDBN} ARM simulator accepts the following optional arguments.
25409 @item --swi-support=@var{type}
25410 Tell the simulator which SWI interfaces to support. The argument
25411 @var{type} may be a comma separated list of the following values.
25412 The default value is @code{all}.
25428 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25429 The @value{GDBN} BPF simulator accepts the following optional arguments.
25432 @item --skb-data-offset=@var{offset}
25433 Tell the simulator the offset, measured in bytes, of the
25434 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
25435 This offset is used by some BPF specific-purpose load/store
25436 instructions. Defaults to 0.
25443 The Motorola m68k configuration includes ColdFire support.
25446 @subsection MicroBlaze
25447 @cindex Xilinx MicroBlaze
25448 @cindex XMD, Xilinx Microprocessor Debugger
25450 The MicroBlaze is a soft-core processor supported on various Xilinx
25451 FPGAs, such as Spartan or Virtex series. Boards with these processors
25452 usually have JTAG ports which connect to a host system running the Xilinx
25453 Embedded Development Kit (EDK) or Software Development Kit (SDK).
25454 This host system is used to download the configuration bitstream to
25455 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
25456 communicates with the target board using the JTAG interface and
25457 presents a @code{gdbserver} interface to the board. By default
25458 @code{xmd} uses port @code{1234}. (While it is possible to change
25459 this default port, it requires the use of undocumented @code{xmd}
25460 commands. Contact Xilinx support if you need to do this.)
25462 Use these GDB commands to connect to the MicroBlaze target processor.
25465 @item target remote :1234
25466 Use this command to connect to the target if you are running @value{GDBN}
25467 on the same system as @code{xmd}.
25469 @item target remote @var{xmd-host}:1234
25470 Use this command to connect to the target if it is connected to @code{xmd}
25471 running on a different system named @var{xmd-host}.
25474 Use this command to download a program to the MicroBlaze target.
25476 @item set debug microblaze @var{n}
25477 Enable MicroBlaze-specific debugging messages if non-zero.
25479 @item show debug microblaze @var{n}
25480 Show MicroBlaze-specific debugging level.
25483 @node MIPS Embedded
25484 @subsection @acronym{MIPS} Embedded
25487 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
25490 @item set mipsfpu double
25491 @itemx set mipsfpu single
25492 @itemx set mipsfpu none
25493 @itemx set mipsfpu auto
25494 @itemx show mipsfpu
25495 @kindex set mipsfpu
25496 @kindex show mipsfpu
25497 @cindex @acronym{MIPS} remote floating point
25498 @cindex floating point, @acronym{MIPS} remote
25499 If your target board does not support the @acronym{MIPS} floating point
25500 coprocessor, you should use the command @samp{set mipsfpu none} (if you
25501 need this, you may wish to put the command in your @value{GDBN} init
25502 file). This tells @value{GDBN} how to find the return value of
25503 functions which return floating point values. It also allows
25504 @value{GDBN} to avoid saving the floating point registers when calling
25505 functions on the board. If you are using a floating point coprocessor
25506 with only single precision floating point support, as on the @sc{r4650}
25507 processor, use the command @samp{set mipsfpu single}. The default
25508 double precision floating point coprocessor may be selected using
25509 @samp{set mipsfpu double}.
25511 In previous versions the only choices were double precision or no
25512 floating point, so @samp{set mipsfpu on} will select double precision
25513 and @samp{set mipsfpu off} will select no floating point.
25515 As usual, you can inquire about the @code{mipsfpu} variable with
25516 @samp{show mipsfpu}.
25519 @node OpenRISC 1000
25520 @subsection OpenRISC 1000
25521 @cindex OpenRISC 1000
25524 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
25525 mainly provided as a soft-core which can run on Xilinx, Altera and other
25528 @value{GDBN} for OpenRISC supports the below commands when connecting to
25536 Runs the builtin CPU simulator which can run very basic
25537 programs but does not support most hardware functions like MMU.
25538 For more complex use cases the user is advised to run an external
25539 target, and connect using @samp{target remote}.
25541 Example: @code{target sim}
25543 @item set debug or1k
25544 Toggle whether to display OpenRISC-specific debugging messages from the
25545 OpenRISC target support subsystem.
25547 @item show debug or1k
25548 Show whether OpenRISC-specific debugging messages are enabled.
25551 @node PowerPC Embedded
25552 @subsection PowerPC Embedded
25554 @cindex DVC register
25555 @value{GDBN} supports using the DVC (Data Value Compare) register to
25556 implement in hardware simple hardware watchpoint conditions of the form:
25559 (@value{GDBP}) watch @var{address|variable} \
25560 if @var{address|variable} == @var{constant expression}
25563 The DVC register will be automatically used when @value{GDBN} detects
25564 such pattern in a condition expression, and the created watchpoint uses one
25565 debug register (either the @code{exact-watchpoints} option is on and the
25566 variable is scalar, or the variable has a length of one byte). This feature
25567 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
25570 When running on PowerPC embedded processors, @value{GDBN} automatically uses
25571 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
25572 in which case watchpoints using only one debug register are created when
25573 watching variables of scalar types.
25575 You can create an artificial array to watch an arbitrary memory
25576 region using one of the following commands (@pxref{Expressions}):
25579 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
25580 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
25583 PowerPC embedded processors support masked watchpoints. See the discussion
25584 about the @code{mask} argument in @ref{Set Watchpoints}.
25586 @cindex ranged breakpoint
25587 PowerPC embedded processors support hardware accelerated
25588 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
25589 the inferior whenever it executes an instruction at any address within
25590 the range it was set at. To set a ranged breakpoint in @value{GDBN},
25591 use the @code{break-range} command.
25593 @value{GDBN} provides the following PowerPC-specific commands:
25596 @kindex break-range
25597 @item break-range @var{start-locspec}, @var{end-locspec}
25598 Set a breakpoint for an address range given by @var{start-locspec} and
25599 @var{end-locspec}, which are location specs. @xref{Location
25600 Specifications}, for a list of all the possible forms of location
25601 specs. @value{GDBN} resolves both @var{start-locspec} and
25602 @var{end-locspec}, and uses the addresses of the resolved code
25603 locations as start and end addresses of the range to break at. The
25604 breakpoint will stop execution of the inferior whenever it executes an
25605 instruction at any address between the start and end addresses,
25606 inclusive. If either @var{start-locspec} or @var{end-locspec} resolve
25607 to multiple code locations in the program, then the command aborts
25608 with an error without creating a breakpoint.
25610 @kindex set powerpc
25611 @item set powerpc soft-float
25612 @itemx show powerpc soft-float
25613 Force @value{GDBN} to use (or not use) a software floating point calling
25614 convention. By default, @value{GDBN} selects the calling convention based
25615 on the selected architecture and the provided executable file.
25617 @item set powerpc vector-abi
25618 @itemx show powerpc vector-abi
25619 Force @value{GDBN} to use the specified calling convention for vector
25620 arguments and return values. The valid options are @samp{auto};
25621 @samp{generic}, to avoid vector registers even if they are present;
25622 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
25623 registers. By default, @value{GDBN} selects the calling convention
25624 based on the selected architecture and the provided executable file.
25626 @item set powerpc exact-watchpoints
25627 @itemx show powerpc exact-watchpoints
25628 Allow @value{GDBN} to use only one debug register when watching a variable
25629 of scalar type, thus assuming that the variable is accessed through the
25630 address of its first byte.
25635 @subsection Atmel AVR
25638 When configured for debugging the Atmel AVR, @value{GDBN} supports the
25639 following AVR-specific commands:
25642 @item info io_registers
25643 @kindex info io_registers@r{, AVR}
25644 @cindex I/O registers (Atmel AVR)
25645 This command displays information about the AVR I/O registers. For
25646 each register, @value{GDBN} prints its number and value.
25653 When configured for debugging CRIS, @value{GDBN} provides the
25654 following CRIS-specific commands:
25657 @item set cris-version @var{ver}
25658 @cindex CRIS version
25659 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
25660 The CRIS version affects register names and sizes. This command is useful in
25661 case autodetection of the CRIS version fails.
25663 @item show cris-version
25664 Show the current CRIS version.
25666 @item set cris-dwarf2-cfi
25667 @cindex DWARF-2 CFI and CRIS
25668 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
25669 Change to @samp{off} when using @code{gcc-cris} whose version is below
25672 @item show cris-dwarf2-cfi
25673 Show the current state of using DWARF-2 CFI.
25675 @item set cris-mode @var{mode}
25677 Set the current CRIS mode to @var{mode}. It should only be changed when
25678 debugging in guru mode, in which case it should be set to
25679 @samp{guru} (the default is @samp{normal}).
25681 @item show cris-mode
25682 Show the current CRIS mode.
25686 @subsection Renesas Super-H
25689 For the Renesas Super-H processor, @value{GDBN} provides these
25693 @item set sh calling-convention @var{convention}
25694 @kindex set sh calling-convention
25695 Set the calling-convention used when calling functions from @value{GDBN}.
25696 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
25697 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
25698 convention. If the DWARF-2 information of the called function specifies
25699 that the function follows the Renesas calling convention, the function
25700 is called using the Renesas calling convention. If the calling convention
25701 is set to @samp{renesas}, the Renesas calling convention is always used,
25702 regardless of the DWARF-2 information. This can be used to override the
25703 default of @samp{gcc} if debug information is missing, or the compiler
25704 does not emit the DWARF-2 calling convention entry for a function.
25706 @item show sh calling-convention
25707 @kindex show sh calling-convention
25708 Show the current calling convention setting.
25713 @node Architectures
25714 @section Architectures
25716 This section describes characteristics of architectures that affect
25717 all uses of @value{GDBN} with the architecture, both native and cross.
25724 * HPPA:: HP PA architecture
25732 @subsection AArch64
25733 @cindex AArch64 support
25735 When @value{GDBN} is debugging the AArch64 architecture, it provides the
25736 following special commands:
25739 @item set debug aarch64
25740 @kindex set debug aarch64
25741 This command determines whether AArch64 architecture-specific debugging
25742 messages are to be displayed.
25744 @item show debug aarch64
25745 Show whether AArch64 debugging messages are displayed.
25749 @subsubsection AArch64 SVE.
25750 @cindex AArch64 SVE.
25752 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
25753 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
25754 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
25755 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
25756 @code{$vg} will be provided. This is the vector granule for the current thread
25757 and represents the number of 64-bit chunks in an SVE @code{z} register.
25759 If the vector length changes, then the @code{$vg} register will be updated,
25760 but the lengths of the @code{z} and @code{p} registers will not change. This
25761 is a known limitation of @value{GDBN} and does not affect the execution of the
25764 @subsubsection AArch64 Pointer Authentication.
25765 @cindex AArch64 Pointer Authentication.
25766 @anchor{AArch64 PAC}
25768 When @value{GDBN} is debugging the AArch64 architecture, and the program is
25769 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
25770 register @code{$lr} is pointing to an PAC function its value will be masked.
25771 When GDB prints a backtrace, any addresses that required unmasking will be
25772 postfixed with the marker [PAC]. When using the MI, this is printed as part
25773 of the @code{addr_flags} field.
25775 @subsubsection AArch64 Memory Tagging Extension.
25776 @cindex AArch64 Memory Tagging Extension.
25778 When @value{GDBN} is debugging the AArch64 architecture, the program is
25779 using the v8.5-A feature Memory Tagging Extension (MTE) and there is support
25780 in the kernel for MTE, @value{GDBN} will make memory tagging functionality
25781 available for inspection and editing of logical and allocation tags.
25782 @xref{Memory Tagging}.
25784 To aid debugging, @value{GDBN} will output additional information when SIGSEGV
25785 signals are generated as a result of memory tag failures.
25787 If the tag violation is synchronous, the following will be shown:
25790 Program received signal SIGSEGV, Segmentation fault
25791 Memory tag violation while accessing address 0x0500fffff7ff8000
25796 If the tag violation is asynchronous, the fault address is not available.
25797 In this case @value{GDBN} will show the following:
25800 Program received signal SIGSEGV, Segmentation fault
25801 Memory tag violation
25802 Fault address unavailable.
25805 A special register, @code{tag_ctl}, is made available through the
25806 @code{org.gnu.gdb.aarch64.mte} feature. This register exposes some
25807 options that can be controlled at runtime and emulates the @code{prctl}
25808 option @code{PR_SET_TAGGED_ADDR_CTRL}. For further information, see the
25809 documentation in the Linux kernel.
25811 @value{GDBN} supports dumping memory tag data to core files through the
25812 @command{gcore} command and reading memory tag data from core files generated
25813 by the @command{gcore} command or the Linux kernel.
25815 When a process uses memory-mapped pages protected by memory tags (for
25816 example, AArch64 MTE), this additional information will be recorded in
25817 the core file in the event of a crash or if @value{GDBN} generates a core file
25818 from the current process state.
25820 The memory tag data will be used so developers can display the memory
25821 tags from a particular memory region (using the @samp{m} modifier to the
25822 @command{x} command, using the @command{print} command or using the various
25823 @command{memory-tag} subcommands.
25825 In the case of a crash, @value{GDBN} will attempt to retrieve the memory tag
25826 information automatically from the core file, and will show one of the above
25827 messages depending on whether the synchronous or asynchronous mode is selected.
25828 @xref{Memory Tagging}. @xref{Memory}.
25831 @subsection x86 Architecture-specific Issues
25834 @item set struct-convention @var{mode}
25835 @kindex set struct-convention
25836 @cindex struct return convention
25837 @cindex struct/union returned in registers
25838 Set the convention used by the inferior to return @code{struct}s and
25839 @code{union}s from functions to @var{mode}. Possible values of
25840 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
25841 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
25842 are returned on the stack, while @code{"reg"} means that a
25843 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
25844 be returned in a register.
25846 @item show struct-convention
25847 @kindex show struct-convention
25848 Show the current setting of the convention to return @code{struct}s
25853 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
25854 @cindex Intel Memory Protection Extensions (MPX).
25856 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
25857 @footnote{The register named with capital letters represent the architecture
25858 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
25859 which are the lower bound and upper bound. Bounds are effective addresses or
25860 memory locations. The upper bounds are architecturally represented in 1's
25861 complement form. A bound having lower bound = 0, and upper bound = 0
25862 (1's complement of all bits set) will allow access to the entire address space.
25864 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
25865 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
25866 display the upper bound performing the complement of one operation on the
25867 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
25868 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
25869 can also be noted that the upper bounds are inclusive.
25871 As an example, assume that the register BND0 holds bounds for a pointer having
25872 access allowed for the range between 0x32 and 0x71. The values present on
25873 bnd0raw and bnd registers are presented as follows:
25876 bnd0raw = @{0x32, 0xffffffff8e@}
25877 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
25880 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
25881 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
25882 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
25883 Python, the display includes the memory size, in bits, accessible to
25886 Bounds can also be stored in bounds tables, which are stored in
25887 application memory. These tables store bounds for pointers by specifying
25888 the bounds pointer's value along with its bounds. Evaluating and changing
25889 bounds located in bound tables is therefore interesting while investigating
25890 bugs on MPX context. @value{GDBN} provides commands for this purpose:
25893 @item show mpx bound @var{pointer}
25894 @kindex show mpx bound
25895 Display bounds of the given @var{pointer}.
25897 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
25898 @kindex set mpx bound
25899 Set the bounds of a pointer in the bound table.
25900 This command takes three parameters: @var{pointer} is the pointers
25901 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
25902 for lower and upper bounds respectively.
25905 When you call an inferior function on an Intel MPX enabled program,
25906 GDB sets the inferior's bound registers to the init (disabled) state
25907 before calling the function. As a consequence, bounds checks for the
25908 pointer arguments passed to the function will always pass.
25910 This is necessary because when you call an inferior function, the
25911 program is usually in the middle of the execution of other function.
25912 Since at that point bound registers are in an arbitrary state, not
25913 clearing them would lead to random bound violations in the called
25916 You can still examine the influence of the bound registers on the
25917 execution of the called function by stopping the execution of the
25918 called function at its prologue, setting bound registers, and
25919 continuing the execution. For example:
25923 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
25924 $ print upper (a, b, c, d, 1)
25925 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
25927 @{lbound = 0x0, ubound = ffffffff@} : size -1
25930 At this last step the value of bnd0 can be changed for investigation of bound
25931 violations caused along the execution of the call. In order to know how to
25932 set the bound registers or bound table for the call consult the ABI.
25937 See the following section.
25940 @subsection @acronym{MIPS}
25942 @cindex stack on Alpha
25943 @cindex stack on @acronym{MIPS}
25944 @cindex Alpha stack
25945 @cindex @acronym{MIPS} stack
25946 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
25947 sometimes requires @value{GDBN} to search backward in the object code to
25948 find the beginning of a function.
25950 @cindex response time, @acronym{MIPS} debugging
25951 To improve response time (especially for embedded applications, where
25952 @value{GDBN} may be restricted to a slow serial line for this search)
25953 you may want to limit the size of this search, using one of these
25957 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
25958 @item set heuristic-fence-post @var{limit}
25959 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
25960 search for the beginning of a function. A value of @var{0} (the
25961 default) means there is no limit. However, except for @var{0}, the
25962 larger the limit the more bytes @code{heuristic-fence-post} must search
25963 and therefore the longer it takes to run. You should only need to use
25964 this command when debugging a stripped executable.
25966 @item show heuristic-fence-post
25967 Display the current limit.
25971 These commands are available @emph{only} when @value{GDBN} is configured
25972 for debugging programs on Alpha or @acronym{MIPS} processors.
25974 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
25978 @item set mips abi @var{arg}
25979 @kindex set mips abi
25980 @cindex set ABI for @acronym{MIPS}
25981 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
25982 values of @var{arg} are:
25986 The default ABI associated with the current binary (this is the
25996 @item show mips abi
25997 @kindex show mips abi
25998 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
26000 @item set mips compression @var{arg}
26001 @kindex set mips compression
26002 @cindex code compression, @acronym{MIPS}
26003 Tell @value{GDBN} which @acronym{MIPS} compressed
26004 @acronym{ISA, Instruction Set Architecture} encoding is used by the
26005 inferior. @value{GDBN} uses this for code disassembly and other
26006 internal interpretation purposes. This setting is only referred to
26007 when no executable has been associated with the debugging session or
26008 the executable does not provide information about the encoding it uses.
26009 Otherwise this setting is automatically updated from information
26010 provided by the executable.
26012 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
26013 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
26014 executables containing @acronym{MIPS16} code frequently are not
26015 identified as such.
26017 This setting is ``sticky''; that is, it retains its value across
26018 debugging sessions until reset either explicitly with this command or
26019 implicitly from an executable.
26021 The compiler and/or assembler typically add symbol table annotations to
26022 identify functions compiled for the @acronym{MIPS16} or
26023 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
26024 are present, @value{GDBN} uses them in preference to the global
26025 compressed @acronym{ISA} encoding setting.
26027 @item show mips compression
26028 @kindex show mips compression
26029 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
26030 @value{GDBN} to debug the inferior.
26033 @itemx show mipsfpu
26034 @xref{MIPS Embedded, set mipsfpu}.
26036 @item set mips mask-address @var{arg}
26037 @kindex set mips mask-address
26038 @cindex @acronym{MIPS} addresses, masking
26039 This command determines whether the most-significant 32 bits of 64-bit
26040 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
26041 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
26042 setting, which lets @value{GDBN} determine the correct value.
26044 @item show mips mask-address
26045 @kindex show mips mask-address
26046 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
26049 @item set remote-mips64-transfers-32bit-regs
26050 @kindex set remote-mips64-transfers-32bit-regs
26051 This command controls compatibility with 64-bit @acronym{MIPS} targets that
26052 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
26053 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
26054 and 64 bits for other registers, set this option to @samp{on}.
26056 @item show remote-mips64-transfers-32bit-regs
26057 @kindex show remote-mips64-transfers-32bit-regs
26058 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
26060 @item set debug mips
26061 @kindex set debug mips
26062 This command turns on and off debugging messages for the @acronym{MIPS}-specific
26063 target code in @value{GDBN}.
26065 @item show debug mips
26066 @kindex show debug mips
26067 Show the current setting of @acronym{MIPS} debugging messages.
26073 @cindex HPPA support
26075 When @value{GDBN} is debugging the HP PA architecture, it provides the
26076 following special commands:
26079 @item set debug hppa
26080 @kindex set debug hppa
26081 This command determines whether HPPA architecture-specific debugging
26082 messages are to be displayed.
26084 @item show debug hppa
26085 Show whether HPPA debugging messages are displayed.
26087 @item maint print unwind @var{address}
26088 @kindex maint print unwind@r{, HPPA}
26089 This command displays the contents of the unwind table entry at the
26090 given @var{address}.
26096 @subsection PowerPC
26097 @cindex PowerPC architecture
26099 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
26100 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
26101 numbers stored in the floating point registers. These values must be stored
26102 in two consecutive registers, always starting at an even register like
26103 @code{f0} or @code{f2}.
26105 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
26106 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
26107 @code{f2} and @code{f3} for @code{$dl1} and so on.
26109 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
26110 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
26113 @subsection Nios II
26114 @cindex Nios II architecture
26116 When @value{GDBN} is debugging the Nios II architecture,
26117 it provides the following special commands:
26121 @item set debug nios2
26122 @kindex set debug nios2
26123 This command turns on and off debugging messages for the Nios II
26124 target code in @value{GDBN}.
26126 @item show debug nios2
26127 @kindex show debug nios2
26128 Show the current setting of Nios II debugging messages.
26132 @subsection Sparc64
26133 @cindex Sparc64 support
26134 @cindex Application Data Integrity
26135 @subsubsection ADI Support
26137 The M7 processor supports an Application Data Integrity (ADI) feature that
26138 detects invalid data accesses. When software allocates memory and enables
26139 ADI on the allocated memory, it chooses a 4-bit version number, sets the
26140 version in the upper 4 bits of the 64-bit pointer to that data, and stores
26141 the 4-bit version in every cacheline of that data. Hardware saves the latter
26142 in spare bits in the cache and memory hierarchy. On each load and store,
26143 the processor compares the upper 4 VA (virtual address) bits to the
26144 cacheline's version. If there is a mismatch, the processor generates a
26145 version mismatch trap which can be either precise or disrupting. The trap
26146 is an error condition which the kernel delivers to the process as a SIGSEGV
26149 Note that only 64-bit applications can use ADI and need to be built with
26152 Values of the ADI version tags, which are in granularity of a
26153 cacheline (64 bytes), can be viewed or modified.
26157 @kindex adi examine
26158 @item adi (examine | x) [ / @var{n} ] @var{addr}
26160 The @code{adi examine} command displays the value of one ADI version tag per
26163 @var{n} is a decimal integer specifying the number in bytes; the default
26164 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
26165 block size, to display.
26167 @var{addr} is the address in user address space where you want @value{GDBN}
26168 to begin displaying the ADI version tags.
26170 Below is an example of displaying ADI versions of variable "shmaddr".
26173 (@value{GDBP}) adi x/100 shmaddr
26174 0xfff800010002c000: 0 0
26178 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
26180 The @code{adi assign} command is used to assign new ADI version tag
26183 @var{n} is a decimal integer specifying the number in bytes;
26184 the default is 1. It specifies how much ADI version information, at the
26185 ratio of 1:ADI block size, to modify.
26187 @var{addr} is the address in user address space where you want @value{GDBN}
26188 to begin modifying the ADI version tags.
26190 @var{tag} is the new ADI version tag.
26192 For example, do the following to modify then verify ADI versions of
26193 variable "shmaddr":
26196 (@value{GDBP}) adi a/100 shmaddr = 7
26197 (@value{GDBP}) adi x/100 shmaddr
26198 0xfff800010002c000: 7 7
26205 @cindex S12Z support
26207 When @value{GDBN} is debugging the S12Z architecture,
26208 it provides the following special command:
26211 @item maint info bdccsr
26212 @kindex maint info bdccsr@r{, S12Z}
26213 This command displays the current value of the microprocessor's
26218 @node Controlling GDB
26219 @chapter Controlling @value{GDBN}
26221 You can alter the way @value{GDBN} interacts with you by using the
26222 @code{set} command. For commands controlling how @value{GDBN} displays
26223 data, see @ref{Print Settings, ,Print Settings}. Other settings are
26228 * Editing:: Command editing
26229 * Command History:: Command history
26230 * Screen Size:: Screen size
26231 * Output Styling:: Output styling
26232 * Numbers:: Numbers
26233 * ABI:: Configuring the current ABI
26234 * Auto-loading:: Automatically loading associated files
26235 * Messages/Warnings:: Optional warnings and messages
26236 * Debugging Output:: Optional messages about internal happenings
26237 * Other Misc Settings:: Other Miscellaneous Settings
26245 @value{GDBN} indicates its readiness to read a command by printing a string
26246 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
26247 can change the prompt string with the @code{set prompt} command. For
26248 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
26249 the prompt in one of the @value{GDBN} sessions so that you can always tell
26250 which one you are talking to.
26252 @emph{Note:} @code{set prompt} does not add a space for you after the
26253 prompt you set. This allows you to set a prompt which ends in a space
26254 or a prompt that does not.
26258 @item set prompt @var{newprompt}
26259 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
26261 @kindex show prompt
26263 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
26266 Versions of @value{GDBN} that ship with Python scripting enabled have
26267 prompt extensions. The commands for interacting with these extensions
26271 @kindex set extended-prompt
26272 @item set extended-prompt @var{prompt}
26273 Set an extended prompt that allows for substitutions.
26274 @xref{gdb.prompt}, for a list of escape sequences that can be used for
26275 substitution. Any escape sequences specified as part of the prompt
26276 string are replaced with the corresponding strings each time the prompt
26282 set extended-prompt Current working directory: \w (gdb)
26285 Note that when an extended-prompt is set, it takes control of the
26286 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
26288 @kindex show extended-prompt
26289 @item show extended-prompt
26290 Prints the extended prompt. Any escape sequences specified as part of
26291 the prompt string with @code{set extended-prompt}, are replaced with the
26292 corresponding strings each time the prompt is displayed.
26296 @section Command Editing
26298 @cindex command line editing
26300 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
26301 @sc{gnu} library provides consistent behavior for programs which provide a
26302 command line interface to the user. Advantages are @sc{gnu} Emacs-style
26303 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
26304 substitution, and a storage and recall of command history across
26305 debugging sessions.
26307 You may control the behavior of command line editing in @value{GDBN} with the
26308 command @code{set}.
26311 @kindex set editing
26314 @itemx set editing on
26315 Enable command line editing (enabled by default).
26317 @item set editing off
26318 Disable command line editing.
26320 @kindex show editing
26322 Show whether command line editing is enabled.
26325 @ifset SYSTEM_READLINE
26326 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
26328 @ifclear SYSTEM_READLINE
26329 @xref{Command Line Editing},
26331 for more details about the Readline
26332 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
26333 encouraged to read that chapter.
26335 @cindex Readline application name
26336 @value{GDBN} sets the Readline application name to @samp{gdb}. This
26337 is useful for conditions in @file{.inputrc}.
26339 @cindex operate-and-get-next
26340 @value{GDBN} defines a bindable Readline command,
26341 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
26342 This command accepts the current line for execution and fetches the
26343 next line relative to the current line from the history for editing.
26344 Any argument is ignored.
26346 @node Command History
26347 @section Command History
26348 @cindex command history
26350 @value{GDBN} can keep track of the commands you type during your
26351 debugging sessions, so that you can be certain of precisely what
26352 happened. Use these commands to manage the @value{GDBN} command
26355 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
26356 package, to provide the history facility.
26357 @ifset SYSTEM_READLINE
26358 @xref{Using History Interactively, , , history, GNU History Library},
26360 @ifclear SYSTEM_READLINE
26361 @xref{Using History Interactively},
26363 for the detailed description of the History library.
26365 To issue a command to @value{GDBN} without affecting certain aspects of
26366 the state which is seen by users, prefix it with @samp{server }
26367 (@pxref{Server Prefix}). This
26368 means that this command will not affect the command history, nor will it
26369 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
26370 pressed on a line by itself.
26372 @cindex @code{server}, command prefix
26373 The server prefix does not affect the recording of values into the value
26374 history; to print a value without recording it into the value history,
26375 use the @code{output} command instead of the @code{print} command.
26377 Here is the description of @value{GDBN} commands related to command
26381 @cindex history substitution
26382 @cindex history file
26383 @kindex set history filename
26384 @cindex @env{GDBHISTFILE}, environment variable
26385 @item set history filename @r{[}@var{fname}@r{]}
26386 Set the name of the @value{GDBN} command history file to @var{fname}.
26387 This is the file where @value{GDBN} reads an initial command history
26388 list, and where it writes the command history from this session when it
26389 exits. You can access this list through history expansion or through
26390 the history command editing characters listed below. This file defaults
26391 to the value of the environment variable @env{GDBHISTFILE}, or to
26392 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
26395 The @env{GDBHISTFILE} environment variable is read after processing
26396 any @value{GDBN} initialization files (@pxref{Startup}) and after
26397 processing any commands passed using command line options (for
26398 example, @code{-ex}).
26400 If the @var{fname} argument is not given, or if the @env{GDBHISTFILE}
26401 is the empty string then @value{GDBN} will neither try to load an
26402 existing history file, nor will it try to save the history on exit.
26404 @cindex save command history
26405 @kindex set history save
26406 @item set history save
26407 @itemx set history save on
26408 Record command history in a file, whose name may be specified with the
26409 @code{set history filename} command. By default, this option is
26410 disabled. The command history will be recorded when @value{GDBN}
26411 exits. If @code{set history filename} is set to the empty string then
26412 history saving is disabled, even when @code{set history save} is
26415 @item set history save off
26416 Don't record the command history into the file specified by @code{set
26417 history filename} when @value{GDBN} exits.
26419 @cindex history size
26420 @kindex set history size
26421 @cindex @env{GDBHISTSIZE}, environment variable
26422 @item set history size @var{size}
26423 @itemx set history size unlimited
26424 Set the number of commands which @value{GDBN} keeps in its history list.
26425 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
26426 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
26427 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
26428 either a negative number or the empty string, then the number of commands
26429 @value{GDBN} keeps in the history list is unlimited.
26431 The @env{GDBHISTSIZE} environment variable is read after processing
26432 any @value{GDBN} initialization files (@pxref{Startup}) and after
26433 processing any commands passed using command line options (for
26434 example, @code{-ex}).
26436 @cindex remove duplicate history
26437 @kindex set history remove-duplicates
26438 @item set history remove-duplicates @var{count}
26439 @itemx set history remove-duplicates unlimited
26440 Control the removal of duplicate history entries in the command history list.
26441 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
26442 history entries and remove the first entry that is a duplicate of the current
26443 entry being added to the command history list. If @var{count} is
26444 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
26445 removal of duplicate history entries is disabled.
26447 Only history entries added during the current session are considered for
26448 removal. This option is set to 0 by default.
26452 History expansion assigns special meaning to the character @kbd{!}.
26453 @ifset SYSTEM_READLINE
26454 @xref{Event Designators, , , history, GNU History Library},
26456 @ifclear SYSTEM_READLINE
26457 @xref{Event Designators},
26461 @cindex history expansion, turn on/off
26462 Since @kbd{!} is also the logical not operator in C, history expansion
26463 is off by default. If you decide to enable history expansion with the
26464 @code{set history expansion on} command, you may sometimes need to
26465 follow @kbd{!} (when it is used as logical not, in an expression) with
26466 a space or a tab to prevent it from being expanded. The readline
26467 history facilities do not attempt substitution on the strings
26468 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
26470 The commands to control history expansion are:
26473 @item set history expansion on
26474 @itemx set history expansion
26475 @kindex set history expansion
26476 Enable history expansion. History expansion is off by default.
26478 @item set history expansion off
26479 Disable history expansion.
26482 @kindex show history
26484 @itemx show history filename
26485 @itemx show history save
26486 @itemx show history size
26487 @itemx show history expansion
26488 These commands display the state of the @value{GDBN} history parameters.
26489 @code{show history} by itself displays all four states.
26494 @kindex show commands
26495 @cindex show last commands
26496 @cindex display command history
26497 @item show commands
26498 Display the last ten commands in the command history.
26500 @item show commands @var{n}
26501 Print ten commands centered on command number @var{n}.
26503 @item show commands +
26504 Print ten commands just after the commands last printed.
26508 @section Screen Size
26509 @cindex size of screen
26510 @cindex screen size
26513 @cindex pauses in output
26515 Certain commands to @value{GDBN} may produce large amounts of
26516 information output to the screen. To help you read all of it,
26517 @value{GDBN} pauses and asks you for input at the end of each page of
26518 output. Type @key{RET} when you want to see one more page of output,
26519 @kbd{q} to discard the remaining output, or @kbd{c} to continue
26520 without paging for the rest of the current command. Also, the screen
26521 width setting determines when to wrap lines of output. Depending on
26522 what is being printed, @value{GDBN} tries to break the line at a
26523 readable place, rather than simply letting it overflow onto the
26526 Normally @value{GDBN} knows the size of the screen from the terminal
26527 driver software. For example, on Unix @value{GDBN} uses the termcap data base
26528 together with the value of the @env{TERM} environment variable and the
26529 @code{stty rows} and @code{stty cols} settings. If this is not correct,
26530 you can override it with the @code{set height} and @code{set
26537 @kindex show height
26538 @item set height @var{lpp}
26539 @itemx set height unlimited
26541 @itemx set width @var{cpl}
26542 @itemx set width unlimited
26544 These @code{set} commands specify a screen height of @var{lpp} lines and
26545 a screen width of @var{cpl} characters. The associated @code{show}
26546 commands display the current settings.
26548 If you specify a height of either @code{unlimited} or zero lines,
26549 @value{GDBN} does not pause during output no matter how long the
26550 output is. This is useful if output is to a file or to an editor
26553 Likewise, you can specify @samp{set width unlimited} or @samp{set
26554 width 0} to prevent @value{GDBN} from wrapping its output.
26556 @item set pagination on
26557 @itemx set pagination off
26558 @kindex set pagination
26559 Turn the output pagination on or off; the default is on. Turning
26560 pagination off is the alternative to @code{set height unlimited}. Note that
26561 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
26562 Options, -batch}) also automatically disables pagination.
26564 @item show pagination
26565 @kindex show pagination
26566 Show the current pagination mode.
26569 @node Output Styling
26570 @section Output Styling
26576 @value{GDBN} can style its output on a capable terminal. This is
26577 enabled by default on most systems, but disabled by default when in
26578 batch mode (@pxref{Mode Options}). Various style settings are available;
26579 and styles can also be disabled entirely.
26582 @item set style enabled @samp{on|off}
26583 Enable or disable all styling. The default is host-dependent, with
26584 most hosts defaulting to @samp{on}.
26586 @item show style enabled
26587 Show the current state of styling.
26589 @item set style sources @samp{on|off}
26590 Enable or disable source code styling. This affects whether source
26591 code, such as the output of the @code{list} command, is styled. The
26592 default is @samp{on}. Note that source styling only works if styling
26593 in general is enabled, and if a source highlighting library is
26594 available to @value{GDBN}.
26596 There are two ways that highlighting can be done. First, if
26597 @value{GDBN} was linked with the GNU Source Highlight library, then it
26598 is used. Otherwise, if @value{GDBN} was configured with Python
26599 scripting support, and if the Python Pygments package is available,
26600 then it will be used.
26602 @item show style sources
26603 Show the current state of source code styling.
26605 @anchor{style_disassembler_enabled}
26606 @item set style disassembler enabled @samp{on|off}
26607 Enable or disable disassembler styling. This affects whether
26608 disassembler output, such as the output of the @code{disassemble}
26609 command, is styled. Disassembler styling only works if styling in
26610 general is enabled (with @code{set style enabled on}), and if a source
26611 highlighting library is available to @value{GDBN}.
26613 The two source highlighting libraries that @value{GDBN} could use to
26614 style disassembler output are; @value{GDBN}'s builtin disassembler, or
26615 the Python Pygments package.
26617 @value{GDBN}'s first choice will be to use the builtin disassembler
26618 for styling, this usually provides better results, being able to style
26619 different types of instruction operands differently. However, the
26620 builtin disassembler is not able to style all architectures.
26622 For architectures that the builtin disassembler is unable to style,
26623 @value{GDBN} will fall back to use the Python Pygments package where
26624 possible. In order to use the Python Pygments package, @value{GDBN}
26625 must be built with Python support, and the Pygments package must be
26628 If neither of these options are available then @value{GDBN} will
26629 produce unstyled disassembler output, even when this setting is
26632 To discover if the current architecture supports styling using the
26633 builtin disassembler library see @ref{maint_libopcodes_styling,,@kbd{maint
26634 show libopcodes-styling enabled}}.
26636 @item show style disassembler enabled
26637 Show the current state of disassembler styling.
26641 Subcommands of @code{set style} control specific forms of styling.
26642 These subcommands all follow the same pattern: each style-able object
26643 can be styled with a foreground color, a background color, and an
26646 For example, the style of file names can be controlled using the
26647 @code{set style filename} group of commands:
26650 @item set style filename background @var{color}
26651 Set the background to @var{color}. Valid colors are @samp{none}
26652 (meaning the terminal's default color), @samp{black}, @samp{red},
26653 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26656 @item set style filename foreground @var{color}
26657 Set the foreground to @var{color}. Valid colors are @samp{none}
26658 (meaning the terminal's default color), @samp{black}, @samp{red},
26659 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26662 @item set style filename intensity @var{value}
26663 Set the intensity to @var{value}. Valid intensities are @samp{normal}
26664 (the default), @samp{bold}, and @samp{dim}.
26667 The @code{show style} command and its subcommands are styling
26668 a style name in their output using its own style.
26669 So, use @command{show style} to see the complete list of styles,
26670 their characteristics and the visual aspect of each style.
26672 The style-able objects are:
26675 Control the styling of file names and URLs. By default, this style's
26676 foreground color is green.
26679 Control the styling of function names. These are managed with the
26680 @code{set style function} family of commands. By default, this
26681 style's foreground color is yellow.
26683 This style is also used for symbol names in styled disassembler output
26684 if @value{GDBN} is using its builtin disassembler library for styling
26685 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
26689 Control the styling of variable names. These are managed with the
26690 @code{set style variable} family of commands. By default, this style's
26691 foreground color is cyan.
26694 Control the styling of addresses. These are managed with the
26695 @code{set style address} family of commands. By default, this style's
26696 foreground color is blue.
26698 This style is also used for addresses in styled disassembler output
26699 if @value{GDBN} is using its builtin disassembler library for styling
26700 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
26704 Control the styling of @value{GDBN}'s version number text. By
26705 default, this style's foreground color is magenta and it has bold
26706 intensity. The version number is displayed in two places, the output
26707 of @command{show version}, and when @value{GDBN} starts up.
26709 In order to control how @value{GDBN} styles the version number at
26710 startup, add the @code{set style version} family of commands to the
26711 early initialization command file (@pxref{Initialization
26715 Control the styling of titles. These are managed with the
26716 @code{set style title} family of commands. By default, this style's
26717 intensity is bold. Commands are using the title style to improve
26718 the readability of large output. For example, the commands
26719 @command{apropos} and @command{help} are using the title style
26720 for the command names.
26723 Control the styling of highlightings. These are managed with the
26724 @code{set style highlight} family of commands. By default, this style's
26725 foreground color is red. Commands are using the highlight style to draw
26726 the user attention to some specific parts of their output. For example,
26727 the command @command{apropos -v REGEXP} uses the highlight style to
26728 mark the documentation parts matching @var{regexp}.
26731 Control the styling of data annotations added by @value{GDBN} to data
26732 it displays. By default, this style's intensity is dim. Metadata
26733 annotations include the @samp{repeats @var{n} times} annotation for
26734 suppressed display of repeated array elements (@pxref{Print Settings}),
26735 @samp{<unavailable>} and @w{@samp{<error @var{descr}>}} annotations
26736 for errors and @samp{<optimized-out>} annotations for optimized-out
26737 values in displaying stack frame information in backtraces
26738 (@pxref{Backtrace}), etc.
26741 Control the styling of the TUI border. Note that, unlike other
26742 styling options, only the color of the border can be controlled via
26743 @code{set style}. This was done for compatibility reasons, as TUI
26744 controls to set the border's intensity predated the addition of
26745 general styling to @value{GDBN}. @xref{TUI Configuration}.
26747 @item tui-active-border
26748 Control the styling of the active TUI border; that is, the TUI window
26749 that has the focus.
26751 @item disassembler comment
26752 Control the styling of comments in the disassembler output. These are
26753 managed with the @code{set style disassembler comment} family of
26754 commands. This style is only used when @value{GDBN} is styling using
26755 its builtin disassembler library
26756 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
26757 enabled}}). By default, this style's intensity is dim, and its
26758 foreground color is white.
26760 @item disassembler immediate
26761 Control the styling of numeric operands in the disassembler output.
26762 These are managed with the @code{set style disassembler immediate}
26763 family of commands. This style is not used for instruction operands
26764 that represent addresses, in that case the @samp{disassembler address}
26765 style is used. This style is only used when @value{GDBN} is styling
26766 using its builtin disassembler library. By default, this style's
26767 foreground color is blue.
26769 @item disassembler address
26770 Control the styling of address operands in the disassembler output.
26771 This is an alias for the @samp{address} style.
26773 @item disassembler symbol
26774 Control the styling of symbol names in the disassembler output. This
26775 is an alias for the @samp{function} style.
26777 @item disassembler mnemonic
26778 Control the styling of instruction mnemonics in the disassembler
26779 output. These are managed with the @code{set style disassembler
26780 mnemonic} family of commands. This style is also used for assembler
26781 directives, e.g.@: @code{.byte}, @code{.word}, etc. This style is
26782 only used when @value{GDBN} is styling using its builtin disassembler
26783 library. By default, this style's foreground color is green.
26785 @item disassembler register
26786 Control the styling of register operands in the disassembler output.
26787 These are managed with the @code{set style disassembler register}
26788 family of commands. This style is only used when @value{GDBN} is
26789 styling using its builtin disassembler library. By default, this style's
26790 foreground color is red.
26796 @cindex number representation
26797 @cindex entering numbers
26799 You can always enter numbers in octal, decimal, or hexadecimal in
26800 @value{GDBN} by the usual conventions: octal numbers begin with
26801 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
26802 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
26803 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
26804 10; likewise, the default display for numbers---when no particular
26805 format is specified---is base 10. You can change the default base for
26806 both input and output with the commands described below.
26809 @kindex set input-radix
26810 @item set input-radix @var{base}
26811 Set the default base for numeric input. Supported choices
26812 for @var{base} are decimal 8, 10, or 16. The base must itself be
26813 specified either unambiguously or using the current input radix; for
26817 set input-radix 012
26818 set input-radix 10.
26819 set input-radix 0xa
26823 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
26824 leaves the input radix unchanged, no matter what it was, since
26825 @samp{10}, being without any leading or trailing signs of its base, is
26826 interpreted in the current radix. Thus, if the current radix is 16,
26827 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
26830 @kindex set output-radix
26831 @item set output-radix @var{base}
26832 Set the default base for numeric display. Supported choices
26833 for @var{base} are decimal 8, 10, or 16. The base must itself be
26834 specified either unambiguously or using the current input radix.
26836 @kindex show input-radix
26837 @item show input-radix
26838 Display the current default base for numeric input.
26840 @kindex show output-radix
26841 @item show output-radix
26842 Display the current default base for numeric display.
26844 @item set radix @r{[}@var{base}@r{]}
26848 These commands set and show the default base for both input and output
26849 of numbers. @code{set radix} sets the radix of input and output to
26850 the same base; without an argument, it resets the radix back to its
26851 default value of 10.
26856 @section Configuring the Current ABI
26858 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
26859 application automatically. However, sometimes you need to override its
26860 conclusions. Use these commands to manage @value{GDBN}'s view of the
26866 @cindex Newlib OS ABI and its influence on the longjmp handling
26868 One @value{GDBN} configuration can debug binaries for multiple operating
26869 system targets, either via remote debugging or native emulation.
26870 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
26871 but you can override its conclusion using the @code{set osabi} command.
26872 One example where this is useful is in debugging of binaries which use
26873 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
26874 not have the same identifying marks that the standard C library for your
26877 When @value{GDBN} is debugging the AArch64 architecture, it provides a
26878 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
26879 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
26880 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
26884 Show the OS ABI currently in use.
26887 With no argument, show the list of registered available OS ABI's.
26889 @item set osabi @var{abi}
26890 Set the current OS ABI to @var{abi}.
26893 @cindex float promotion
26895 Generally, the way that an argument of type @code{float} is passed to a
26896 function depends on whether the function is prototyped. For a prototyped
26897 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
26898 according to the architecture's convention for @code{float}. For unprototyped
26899 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
26900 @code{double} and then passed.
26902 Unfortunately, some forms of debug information do not reliably indicate whether
26903 a function is prototyped. If @value{GDBN} calls a function that is not marked
26904 as prototyped, it consults @kbd{set coerce-float-to-double}.
26907 @kindex set coerce-float-to-double
26908 @item set coerce-float-to-double
26909 @itemx set coerce-float-to-double on
26910 Arguments of type @code{float} will be promoted to @code{double} when passed
26911 to an unprototyped function. This is the default setting.
26913 @item set coerce-float-to-double off
26914 Arguments of type @code{float} will be passed directly to unprototyped
26917 @kindex show coerce-float-to-double
26918 @item show coerce-float-to-double
26919 Show the current setting of promoting @code{float} to @code{double}.
26923 @kindex show cp-abi
26924 @value{GDBN} needs to know the ABI used for your program's C@t{++}
26925 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
26926 used to build your application. @value{GDBN} only fully supports
26927 programs with a single C@t{++} ABI; if your program contains code using
26928 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
26929 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
26930 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
26931 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
26932 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
26933 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
26938 Show the C@t{++} ABI currently in use.
26941 With no argument, show the list of supported C@t{++} ABI's.
26943 @item set cp-abi @var{abi}
26944 @itemx set cp-abi auto
26945 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
26949 @section Automatically loading associated files
26950 @cindex auto-loading
26952 @value{GDBN} sometimes reads files with commands and settings automatically,
26953 without being explicitly told so by the user. We call this feature
26954 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
26955 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
26956 results or introduce security risks (e.g., if the file comes from untrusted
26959 There are various kinds of files @value{GDBN} can automatically load.
26960 In addition to these files, @value{GDBN} supports auto-loading code written
26961 in various extension languages. @xref{Auto-loading extensions}.
26963 Note that loading of these associated files (including the local @file{.gdbinit}
26964 file) requires accordingly configured @code{auto-load safe-path}
26965 (@pxref{Auto-loading safe path}).
26967 For these reasons, @value{GDBN} includes commands and options to let you
26968 control when to auto-load files and which files should be auto-loaded.
26971 @anchor{set auto-load off}
26972 @kindex set auto-load off
26973 @item set auto-load off
26974 Globally disable loading of all auto-loaded files.
26975 You may want to use this command with the @samp{-iex} option
26976 (@pxref{Option -init-eval-command}) such as:
26978 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
26981 Be aware that system init file (@pxref{System-wide configuration})
26982 and init files from your home directory (@pxref{Home Directory Init File})
26983 still get read (as they come from generally trusted directories).
26984 To prevent @value{GDBN} from auto-loading even those init files, use the
26985 @option{-nx} option (@pxref{Mode Options}), in addition to
26986 @code{set auto-load no}.
26988 @anchor{show auto-load}
26989 @kindex show auto-load
26990 @item show auto-load
26991 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
26995 (gdb) show auto-load
26996 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
26997 libthread-db: Auto-loading of inferior specific libthread_db is on.
26998 local-gdbinit: Auto-loading of .gdbinit script from current directory
27000 python-scripts: Auto-loading of Python scripts is on.
27001 safe-path: List of directories from which it is safe to auto-load files
27002 is $debugdir:$datadir/auto-load.
27003 scripts-directory: List of directories from which to load auto-loaded scripts
27004 is $debugdir:$datadir/auto-load.
27007 @anchor{info auto-load}
27008 @kindex info auto-load
27009 @item info auto-load
27010 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
27014 (gdb) info auto-load
27017 Yes /home/user/gdb/gdb-gdb.gdb
27018 libthread-db: No auto-loaded libthread-db.
27019 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
27023 Yes /home/user/gdb/gdb-gdb.py
27027 These are @value{GDBN} control commands for the auto-loading:
27029 @multitable @columnfractions .5 .5
27030 @item @xref{set auto-load off}.
27031 @tab Disable auto-loading globally.
27032 @item @xref{show auto-load}.
27033 @tab Show setting of all kinds of files.
27034 @item @xref{info auto-load}.
27035 @tab Show state of all kinds of files.
27036 @item @xref{set auto-load gdb-scripts}.
27037 @tab Control for @value{GDBN} command scripts.
27038 @item @xref{show auto-load gdb-scripts}.
27039 @tab Show setting of @value{GDBN} command scripts.
27040 @item @xref{info auto-load gdb-scripts}.
27041 @tab Show state of @value{GDBN} command scripts.
27042 @item @xref{set auto-load python-scripts}.
27043 @tab Control for @value{GDBN} Python scripts.
27044 @item @xref{show auto-load python-scripts}.
27045 @tab Show setting of @value{GDBN} Python scripts.
27046 @item @xref{info auto-load python-scripts}.
27047 @tab Show state of @value{GDBN} Python scripts.
27048 @item @xref{set auto-load guile-scripts}.
27049 @tab Control for @value{GDBN} Guile scripts.
27050 @item @xref{show auto-load guile-scripts}.
27051 @tab Show setting of @value{GDBN} Guile scripts.
27052 @item @xref{info auto-load guile-scripts}.
27053 @tab Show state of @value{GDBN} Guile scripts.
27054 @item @xref{set auto-load scripts-directory}.
27055 @tab Control for @value{GDBN} auto-loaded scripts location.
27056 @item @xref{show auto-load scripts-directory}.
27057 @tab Show @value{GDBN} auto-loaded scripts location.
27058 @item @xref{add-auto-load-scripts-directory}.
27059 @tab Add directory for auto-loaded scripts location list.
27060 @item @xref{set auto-load local-gdbinit}.
27061 @tab Control for init file in the current directory.
27062 @item @xref{show auto-load local-gdbinit}.
27063 @tab Show setting of init file in the current directory.
27064 @item @xref{info auto-load local-gdbinit}.
27065 @tab Show state of init file in the current directory.
27066 @item @xref{set auto-load libthread-db}.
27067 @tab Control for thread debugging library.
27068 @item @xref{show auto-load libthread-db}.
27069 @tab Show setting of thread debugging library.
27070 @item @xref{info auto-load libthread-db}.
27071 @tab Show state of thread debugging library.
27072 @item @xref{set auto-load safe-path}.
27073 @tab Control directories trusted for automatic loading.
27074 @item @xref{show auto-load safe-path}.
27075 @tab Show directories trusted for automatic loading.
27076 @item @xref{add-auto-load-safe-path}.
27077 @tab Add directory trusted for automatic loading.
27081 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
27082 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
27084 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
27085 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
27088 @node Init File in the Current Directory
27089 @subsection Automatically loading init file in the current directory
27090 @cindex auto-loading init file in the current directory
27092 By default, @value{GDBN} reads and executes the canned sequences of commands
27093 from init file (if any) in the current working directory,
27094 see @ref{Init File in the Current Directory during Startup}.
27096 Note that loading of this local @file{.gdbinit} file also requires accordingly
27097 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27100 @anchor{set auto-load local-gdbinit}
27101 @kindex set auto-load local-gdbinit
27102 @item set auto-load local-gdbinit [on|off]
27103 Enable or disable the auto-loading of canned sequences of commands
27104 (@pxref{Sequences}) found in init file in the current directory.
27106 @anchor{show auto-load local-gdbinit}
27107 @kindex show auto-load local-gdbinit
27108 @item show auto-load local-gdbinit
27109 Show whether auto-loading of canned sequences of commands from init file in the
27110 current directory is enabled or disabled.
27112 @anchor{info auto-load local-gdbinit}
27113 @kindex info auto-load local-gdbinit
27114 @item info auto-load local-gdbinit
27115 Print whether canned sequences of commands from init file in the
27116 current directory have been auto-loaded.
27119 @node libthread_db.so.1 file
27120 @subsection Automatically loading thread debugging library
27121 @cindex auto-loading libthread_db.so.1
27123 This feature is currently present only on @sc{gnu}/Linux native hosts.
27125 @value{GDBN} reads in some cases thread debugging library from places specific
27126 to the inferior (@pxref{set libthread-db-search-path}).
27128 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
27129 without checking this @samp{set auto-load libthread-db} switch as system
27130 libraries have to be trusted in general. In all other cases of
27131 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
27132 auto-load libthread-db} is enabled before trying to open such thread debugging
27135 Note that loading of this debugging library also requires accordingly configured
27136 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27139 @anchor{set auto-load libthread-db}
27140 @kindex set auto-load libthread-db
27141 @item set auto-load libthread-db [on|off]
27142 Enable or disable the auto-loading of inferior specific thread debugging library.
27144 @anchor{show auto-load libthread-db}
27145 @kindex show auto-load libthread-db
27146 @item show auto-load libthread-db
27147 Show whether auto-loading of inferior specific thread debugging library is
27148 enabled or disabled.
27150 @anchor{info auto-load libthread-db}
27151 @kindex info auto-load libthread-db
27152 @item info auto-load libthread-db
27153 Print the list of all loaded inferior specific thread debugging libraries and
27154 for each such library print list of inferior @var{pid}s using it.
27157 @node Auto-loading safe path
27158 @subsection Security restriction for auto-loading
27159 @cindex auto-loading safe-path
27161 As the files of inferior can come from untrusted source (such as submitted by
27162 an application user) @value{GDBN} does not always load any files automatically.
27163 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
27164 directories trusted for loading files not explicitly requested by user.
27165 Each directory can also be a shell wildcard pattern.
27167 If the path is not set properly you will see a warning and the file will not
27172 Reading symbols from /home/user/gdb/gdb...
27173 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
27174 declined by your `auto-load safe-path' set
27175 to "$debugdir:$datadir/auto-load".
27176 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
27177 declined by your `auto-load safe-path' set
27178 to "$debugdir:$datadir/auto-load".
27182 To instruct @value{GDBN} to go ahead and use the init files anyway,
27183 invoke @value{GDBN} like this:
27186 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
27189 The list of trusted directories is controlled by the following commands:
27192 @anchor{set auto-load safe-path}
27193 @kindex set auto-load safe-path
27194 @item set auto-load safe-path @r{[}@var{directories}@r{]}
27195 Set the list of directories (and their subdirectories) trusted for automatic
27196 loading and execution of scripts. You can also enter a specific trusted file.
27197 Each directory can also be a shell wildcard pattern; wildcards do not match
27198 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
27199 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
27200 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
27201 its default value as specified during @value{GDBN} compilation.
27203 The list of directories uses path separator (@samp{:} on GNU and Unix
27204 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27205 to the @env{PATH} environment variable.
27207 @anchor{show auto-load safe-path}
27208 @kindex show auto-load safe-path
27209 @item show auto-load safe-path
27210 Show the list of directories trusted for automatic loading and execution of
27213 @anchor{add-auto-load-safe-path}
27214 @kindex add-auto-load-safe-path
27215 @item add-auto-load-safe-path
27216 Add an entry (or list of entries) to the list of directories trusted for
27217 automatic loading and execution of scripts. Multiple entries may be delimited
27218 by the host platform path separator in use.
27221 This variable defaults to what @code{--with-auto-load-dir} has been configured
27222 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
27223 substitution applies the same as for @ref{set auto-load scripts-directory}.
27224 The default @code{set auto-load safe-path} value can be also overriden by
27225 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
27227 Setting this variable to @file{/} disables this security protection,
27228 corresponding @value{GDBN} configuration option is
27229 @option{--without-auto-load-safe-path}.
27230 This variable is supposed to be set to the system directories writable by the
27231 system superuser only. Users can add their source directories in init files in
27232 their home directories (@pxref{Home Directory Init File}). See also deprecated
27233 init file in the current directory
27234 (@pxref{Init File in the Current Directory during Startup}).
27236 To force @value{GDBN} to load the files it declined to load in the previous
27237 example, you could use one of the following ways:
27240 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
27241 Specify this trusted directory (or a file) as additional component of the list.
27242 You have to specify also any existing directories displayed by
27243 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
27245 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
27246 Specify this directory as in the previous case but just for a single
27247 @value{GDBN} session.
27249 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
27250 Disable auto-loading safety for a single @value{GDBN} session.
27251 This assumes all the files you debug during this @value{GDBN} session will come
27252 from trusted sources.
27254 @item @kbd{./configure --without-auto-load-safe-path}
27255 During compilation of @value{GDBN} you may disable any auto-loading safety.
27256 This assumes all the files you will ever debug with this @value{GDBN} come from
27260 On the other hand you can also explicitly forbid automatic files loading which
27261 also suppresses any such warning messages:
27264 @item @kbd{gdb -iex "set auto-load no" @dots{}}
27265 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
27267 @item @file{~/.gdbinit}: @samp{set auto-load no}
27268 Disable auto-loading globally for the user
27269 (@pxref{Home Directory Init File}). While it is improbable, you could also
27270 use system init file instead (@pxref{System-wide configuration}).
27273 This setting applies to the file names as entered by user. If no entry matches
27274 @value{GDBN} tries as a last resort to also resolve all the file names into
27275 their canonical form (typically resolving symbolic links) and compare the
27276 entries again. @value{GDBN} already canonicalizes most of the filenames on its
27277 own before starting the comparison so a canonical form of directories is
27278 recommended to be entered.
27280 @node Auto-loading verbose mode
27281 @subsection Displaying files tried for auto-load
27282 @cindex auto-loading verbose mode
27284 For better visibility of all the file locations where you can place scripts to
27285 be auto-loaded with inferior --- or to protect yourself against accidental
27286 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
27287 all the files attempted to be loaded. Both existing and non-existing files may
27290 For example the list of directories from which it is safe to auto-load files
27291 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
27292 may not be too obvious while setting it up.
27295 (gdb) set debug auto-load on
27296 (gdb) file ~/src/t/true
27297 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
27298 for objfile "/tmp/true".
27299 auto-load: Updating directories of "/usr:/opt".
27300 auto-load: Using directory "/usr".
27301 auto-load: Using directory "/opt".
27302 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
27303 by your `auto-load safe-path' set to "/usr:/opt".
27307 @anchor{set debug auto-load}
27308 @kindex set debug auto-load
27309 @item set debug auto-load [on|off]
27310 Set whether to print the filenames attempted to be auto-loaded.
27312 @anchor{show debug auto-load}
27313 @kindex show debug auto-load
27314 @item show debug auto-load
27315 Show whether printing of the filenames attempted to be auto-loaded is turned
27319 @node Messages/Warnings
27320 @section Optional Warnings and Messages
27322 @cindex verbose operation
27323 @cindex optional warnings
27324 By default, @value{GDBN} is silent about its inner workings. If you are
27325 running on a slow machine, you may want to use the @code{set verbose}
27326 command. This makes @value{GDBN} tell you when it does a lengthy
27327 internal operation, so you will not think it has crashed.
27329 Currently, the messages controlled by @code{set verbose} are those
27330 which announce that the symbol table for a source file is being read;
27331 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
27334 @kindex set verbose
27335 @item set verbose on
27336 Enables @value{GDBN} output of certain informational messages.
27338 @item set verbose off
27339 Disables @value{GDBN} output of certain informational messages.
27341 @kindex show verbose
27343 Displays whether @code{set verbose} is on or off.
27346 By default, if @value{GDBN} encounters bugs in the symbol table of an
27347 object file, it is silent; but if you are debugging a compiler, you may
27348 find this information useful (@pxref{Symbol Errors, ,Errors Reading
27353 @kindex set complaints
27354 @item set complaints @var{limit}
27355 Permits @value{GDBN} to output @var{limit} complaints about each type of
27356 unusual symbols before becoming silent about the problem. Set
27357 @var{limit} to zero to suppress all complaints; set it to a large number
27358 to prevent complaints from being suppressed.
27360 @kindex show complaints
27361 @item show complaints
27362 Displays how many symbol complaints @value{GDBN} is permitted to produce.
27366 @anchor{confirmation requests}
27367 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
27368 lot of stupid questions to confirm certain commands. For example, if
27369 you try to run a program which is already running:
27373 The program being debugged has been started already.
27374 Start it from the beginning? (y or n)
27377 If you are willing to unflinchingly face the consequences of your own
27378 commands, you can disable this ``feature'':
27382 @kindex set confirm
27384 @cindex confirmation
27385 @cindex stupid questions
27386 @item set confirm off
27387 Disables confirmation requests. Note that running @value{GDBN} with
27388 the @option{--batch} option (@pxref{Mode Options, -batch}) also
27389 automatically disables confirmation requests.
27391 @item set confirm on
27392 Enables confirmation requests (the default).
27394 @kindex show confirm
27396 Displays state of confirmation requests.
27400 @cindex command tracing
27401 If you need to debug user-defined commands or sourced files you may find it
27402 useful to enable @dfn{command tracing}. In this mode each command will be
27403 printed as it is executed, prefixed with one or more @samp{+} symbols, the
27404 quantity denoting the call depth of each command.
27407 @kindex set trace-commands
27408 @cindex command scripts, debugging
27409 @item set trace-commands on
27410 Enable command tracing.
27411 @item set trace-commands off
27412 Disable command tracing.
27413 @item show trace-commands
27414 Display the current state of command tracing.
27417 @node Debugging Output
27418 @section Optional Messages about Internal Happenings
27419 @cindex optional debugging messages
27421 @value{GDBN} has commands that enable optional debugging messages from
27422 various @value{GDBN} subsystems; normally these commands are of
27423 interest to @value{GDBN} maintainers, or when reporting a bug. This
27424 section documents those commands.
27427 @kindex set exec-done-display
27428 @item set exec-done-display
27429 Turns on or off the notification of asynchronous commands'
27430 completion. When on, @value{GDBN} will print a message when an
27431 asynchronous command finishes its execution. The default is off.
27432 @kindex show exec-done-display
27433 @item show exec-done-display
27434 Displays the current setting of asynchronous command completion
27438 @cindex ARM AArch64
27439 @item set debug aarch64
27440 Turns on or off display of debugging messages related to ARM AArch64.
27441 The default is off.
27443 @item show debug aarch64
27444 Displays the current state of displaying debugging messages related to
27447 @cindex gdbarch debugging info
27448 @cindex architecture debugging info
27449 @item set debug arch
27450 Turns on or off display of gdbarch debugging info. The default is off
27451 @item show debug arch
27452 Displays the current state of displaying gdbarch debugging info.
27454 @item set debug aix-solib
27455 @cindex AIX shared library debugging
27456 Control display of debugging messages from the AIX shared library
27457 support module. The default is off.
27458 @item show debug aix-solib
27459 Show the current state of displaying AIX shared library debugging messages.
27461 @item set debug aix-thread
27462 @cindex AIX threads
27463 Display debugging messages about inner workings of the AIX thread
27465 @item show debug aix-thread
27466 Show the current state of AIX thread debugging info display.
27468 @item set debug check-physname
27470 Check the results of the ``physname'' computation. When reading DWARF
27471 debugging information for C@t{++}, @value{GDBN} attempts to compute
27472 each entity's name. @value{GDBN} can do this computation in two
27473 different ways, depending on exactly what information is present.
27474 When enabled, this setting causes @value{GDBN} to compute the names
27475 both ways and display any discrepancies.
27476 @item show debug check-physname
27477 Show the current state of ``physname'' checking.
27479 @item set debug coff-pe-read
27480 @cindex COFF/PE exported symbols
27481 Control display of debugging messages related to reading of COFF/PE
27482 exported symbols. The default is off.
27483 @item show debug coff-pe-read
27484 Displays the current state of displaying debugging messages related to
27485 reading of COFF/PE exported symbols.
27487 @item set debug dwarf-die
27489 Dump DWARF DIEs after they are read in.
27490 The value is the number of nesting levels to print.
27491 A value of zero turns off the display.
27492 @item show debug dwarf-die
27493 Show the current state of DWARF DIE debugging.
27495 @item set debug dwarf-line
27496 @cindex DWARF Line Tables
27497 Turns on or off display of debugging messages related to reading
27498 DWARF line tables. The default is 0 (off).
27499 A value of 1 provides basic information.
27500 A value greater than 1 provides more verbose information.
27501 @item show debug dwarf-line
27502 Show the current state of DWARF line table debugging.
27504 @item set debug dwarf-read
27505 @cindex DWARF Reading
27506 Turns on or off display of debugging messages related to reading
27507 DWARF debug info. The default is 0 (off).
27508 A value of 1 provides basic information.
27509 A value greater than 1 provides more verbose information.
27510 @item show debug dwarf-read
27511 Show the current state of DWARF reader debugging.
27513 @item set debug displaced
27514 @cindex displaced stepping debugging info
27515 Turns on or off display of @value{GDBN} debugging info for the
27516 displaced stepping support. The default is off.
27517 @item show debug displaced
27518 Displays the current state of displaying @value{GDBN} debugging info
27519 related to displaced stepping.
27521 @item set debug event
27522 @cindex event debugging info
27523 Turns on or off display of @value{GDBN} event debugging info. The
27525 @item show debug event
27526 Displays the current state of displaying @value{GDBN} event debugging
27529 @item set debug event-loop
27530 @cindex event-loop debugging
27531 Controls output of debugging info about the event loop. The possible
27532 values are @samp{off}, @samp{all} (shows all debugging info) and
27533 @samp{all-except-ui} (shows all debugging info except those about
27534 UI-related events).
27535 @item show debug event-loop
27536 Shows the current state of displaying debugging info about the event
27539 @item set debug expression
27540 @cindex expression debugging info
27541 Turns on or off display of debugging info about @value{GDBN}
27542 expression parsing. The default is off.
27543 @item show debug expression
27544 Displays the current state of displaying debugging info about
27545 @value{GDBN} expression parsing.
27547 @item set debug fbsd-lwp
27548 @cindex FreeBSD LWP debug messages
27549 Turns on or off debugging messages from the FreeBSD LWP debug support.
27550 @item show debug fbsd-lwp
27551 Show the current state of FreeBSD LWP debugging messages.
27553 @item set debug fbsd-nat
27554 @cindex FreeBSD native target debug messages
27555 Turns on or off debugging messages from the FreeBSD native target.
27556 @item show debug fbsd-nat
27557 Show the current state of FreeBSD native target debugging messages.
27559 @item set debug fortran-array-slicing
27560 @cindex fortran array slicing debugging info
27561 Turns on or off display of @value{GDBN} Fortran array slicing
27562 debugging info. The default is off.
27564 @item show debug fortran-array-slicing
27565 Displays the current state of displaying @value{GDBN} Fortran array
27566 slicing debugging info.
27568 @item set debug frame
27569 @cindex frame debugging info
27570 Turns on or off display of @value{GDBN} frame debugging info. The
27572 @item show debug frame
27573 Displays the current state of displaying @value{GDBN} frame debugging
27576 @item set debug gnu-nat
27577 @cindex @sc{gnu}/Hurd debug messages
27578 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
27579 @item show debug gnu-nat
27580 Show the current state of @sc{gnu}/Hurd debugging messages.
27582 @item set debug infrun
27583 @cindex inferior debugging info
27584 Turns on or off display of @value{GDBN} debugging info for running the inferior.
27585 The default is off. @file{infrun.c} contains GDB's runtime state machine used
27586 for implementing operations such as single-stepping the inferior.
27587 @item show debug infrun
27588 Displays the current state of @value{GDBN} inferior debugging.
27590 @item set debug jit
27591 @cindex just-in-time compilation, debugging messages
27592 Turn on or off debugging messages from JIT debug support.
27593 @item show debug jit
27594 Displays the current state of @value{GDBN} JIT debugging.
27596 @item set debug linux-nat @r{[}on@r{|}off@r{]}
27597 @cindex @sc{gnu}/Linux native target debug messages
27598 @cindex Linux native targets
27599 Turn on or off debugging messages from the Linux native target debug support.
27600 @item show debug linux-nat
27601 Show the current state of Linux native target debugging messages.
27603 @item set debug linux-namespaces
27604 @cindex @sc{gnu}/Linux namespaces debug messages
27605 Turn on or off debugging messages from the Linux namespaces debug support.
27606 @item show debug linux-namespaces
27607 Show the current state of Linux namespaces debugging messages.
27609 @item set debug mach-o
27610 @cindex Mach-O symbols processing
27611 Control display of debugging messages related to Mach-O symbols
27612 processing. The default is off.
27613 @item show debug mach-o
27614 Displays the current state of displaying debugging messages related to
27615 reading of COFF/PE exported symbols.
27617 @item set debug notification
27618 @cindex remote async notification debugging info
27619 Turn on or off debugging messages about remote async notification.
27620 The default is off.
27621 @item show debug notification
27622 Displays the current state of remote async notification debugging messages.
27624 @item set debug observer
27625 @cindex observer debugging info
27626 Turns on or off display of @value{GDBN} observer debugging. This
27627 includes info such as the notification of observable events.
27628 @item show debug observer
27629 Displays the current state of observer debugging.
27631 @item set debug overload
27632 @cindex C@t{++} overload debugging info
27633 Turns on or off display of @value{GDBN} C@t{++} overload debugging
27634 info. This includes info such as ranking of functions, etc. The default
27636 @item show debug overload
27637 Displays the current state of displaying @value{GDBN} C@t{++} overload
27640 @cindex expression parser, debugging info
27641 @cindex debug expression parser
27642 @item set debug parser
27643 Turns on or off the display of expression parser debugging output.
27644 Internally, this sets the @code{yydebug} variable in the expression
27645 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
27646 details. The default is off.
27647 @item show debug parser
27648 Show the current state of expression parser debugging.
27650 @cindex packets, reporting on stdout
27651 @cindex serial connections, debugging
27652 @cindex debug remote protocol
27653 @cindex remote protocol debugging
27654 @cindex display remote packets
27655 @item set debug remote
27656 Turns on or off display of reports on all packets sent back and forth across
27657 the serial line to the remote machine. The info is printed on the
27658 @value{GDBN} standard output stream. The default is off.
27659 @item show debug remote
27660 Displays the state of display of remote packets.
27662 @item set debug remote-packet-max-chars
27663 Sets the maximum number of characters to display for each remote packet when
27664 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
27665 displaying lengthy remote packets and polluting the console.
27667 The default value is @code{512}, which means @value{GDBN} will truncate each
27668 remote packet after 512 bytes.
27670 Setting this option to @code{unlimited} will disable truncation and will output
27671 the full length of the remote packets.
27672 @item show debug remote-packet-max-chars
27673 Displays the number of bytes to output for remote packet debugging.
27675 @item set debug separate-debug-file
27676 Turns on or off display of debug output about separate debug file search.
27677 @item show debug separate-debug-file
27678 Displays the state of separate debug file search debug output.
27680 @item set debug serial
27681 Turns on or off display of @value{GDBN} serial debugging info. The
27683 @item show debug serial
27684 Displays the current state of displaying @value{GDBN} serial debugging
27687 @item set debug solib-frv
27688 @cindex FR-V shared-library debugging
27689 Turn on or off debugging messages for FR-V shared-library code.
27690 @item show debug solib-frv
27691 Display the current state of FR-V shared-library code debugging
27694 @item set debug symbol-lookup
27695 @cindex symbol lookup
27696 Turns on or off display of debugging messages related to symbol lookup.
27697 The default is 0 (off).
27698 A value of 1 provides basic information.
27699 A value greater than 1 provides more verbose information.
27700 @item show debug symbol-lookup
27701 Show the current state of symbol lookup debugging messages.
27703 @item set debug symfile
27704 @cindex symbol file functions
27705 Turns on or off display of debugging messages related to symbol file functions.
27706 The default is off. @xref{Files}.
27707 @item show debug symfile
27708 Show the current state of symbol file debugging messages.
27710 @item set debug symtab-create
27711 @cindex symbol table creation
27712 Turns on or off display of debugging messages related to symbol table creation.
27713 The default is 0 (off).
27714 A value of 1 provides basic information.
27715 A value greater than 1 provides more verbose information.
27716 @item show debug symtab-create
27717 Show the current state of symbol table creation debugging.
27719 @item set debug target
27720 @cindex target debugging info
27721 Turns on or off display of @value{GDBN} target debugging info. This info
27722 includes what is going on at the target level of GDB, as it happens. The
27723 default is 0. Set it to 1 to track events, and to 2 to also track the
27724 value of large memory transfers.
27725 @item show debug target
27726 Displays the current state of displaying @value{GDBN} target debugging
27729 @item set debug timestamp
27730 @cindex timestamping debugging info
27731 Turns on or off display of timestamps with @value{GDBN} debugging info.
27732 When enabled, seconds and microseconds are displayed before each debugging
27734 @item show debug timestamp
27735 Displays the current state of displaying timestamps with @value{GDBN}
27738 @item set debug varobj
27739 @cindex variable object debugging info
27740 Turns on or off display of @value{GDBN} variable object debugging
27741 info. The default is off.
27742 @item show debug varobj
27743 Displays the current state of displaying @value{GDBN} variable object
27746 @item set debug xml
27747 @cindex XML parser debugging
27748 Turn on or off debugging messages for built-in XML parsers.
27749 @item show debug xml
27750 Displays the current state of XML debugging messages.
27753 @node Other Misc Settings
27754 @section Other Miscellaneous Settings
27755 @cindex miscellaneous settings
27758 @kindex set interactive-mode
27759 @item set interactive-mode
27760 If @code{on}, forces @value{GDBN} to assume that GDB was started
27761 in a terminal. In practice, this means that @value{GDBN} should wait
27762 for the user to answer queries generated by commands entered at
27763 the command prompt. If @code{off}, forces @value{GDBN} to operate
27764 in the opposite mode, and it uses the default answers to all queries.
27765 If @code{auto} (the default), @value{GDBN} tries to determine whether
27766 its standard input is a terminal, and works in interactive-mode if it
27767 is, non-interactively otherwise.
27769 In the vast majority of cases, the debugger should be able to guess
27770 correctly which mode should be used. But this setting can be useful
27771 in certain specific cases, such as running a MinGW @value{GDBN}
27772 inside a cygwin window.
27774 @kindex show interactive-mode
27775 @item show interactive-mode
27776 Displays whether the debugger is operating in interactive mode or not.
27780 @kindex set suppress-cli-notifications
27781 @item set suppress-cli-notifications
27782 If @code{on}, command-line-interface (CLI) notifications that are
27783 printed by @value{GDBN} are suppressed. If @code{off}, the
27784 notifications are printed as usual. The default value is @code{off}.
27785 CLI notifications occur when you change the selected context or when
27786 the program being debugged stops, as detailed below.
27789 @item User-selected context changes:
27790 When you change the selected context (i.e.@: the current inferior,
27791 thread and/or the frame), @value{GDBN} prints information about the
27792 new context. For example, the default behavior is below:
27796 [Switching to inferior 1 [process 634] (/tmp/test)]
27797 [Switching to thread 1 (process 634)]
27798 #0 main () at test.c:3
27803 When the notifications are suppressed, the new context is not printed:
27806 (gdb) set suppress-cli-notifications on
27811 @item The program being debugged stops:
27812 When the program you are debugging stops (e.g.@: because of hitting a
27813 breakpoint, completing source-stepping, an interrupt, etc.),
27814 @value{GDBN} prints information about the stop event. For example,
27815 below is a breakpoint hit:
27818 (gdb) break test.c:3
27819 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27823 Breakpoint 2, main () at test.c:3
27828 When the notifications are suppressed, the output becomes:
27831 (gdb) break test.c:3
27832 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27833 (gdb) set suppress-cli-notifications on
27839 Suppressing CLI notifications may be useful in scripts to obtain a
27840 reduced output from a list of commands.
27843 @kindex show suppress-cli-notifications
27844 @item show suppress-cli-notifications
27845 Displays whether printing CLI notifications is suppressed or not.
27848 @node Extending GDB
27849 @chapter Extending @value{GDBN}
27850 @cindex extending GDB
27852 @value{GDBN} provides several mechanisms for extension.
27853 @value{GDBN} also provides the ability to automatically load
27854 extensions when it reads a file for debugging. This allows the
27855 user to automatically customize @value{GDBN} for the program
27858 To facilitate the use of extension languages, @value{GDBN} is capable
27859 of evaluating the contents of a file. When doing so, @value{GDBN}
27860 can recognize which extension language is being used by looking at
27861 the filename extension. Files with an unrecognized filename extension
27862 are always treated as a @value{GDBN} Command Files.
27863 @xref{Command Files,, Command files}.
27865 You can control how @value{GDBN} evaluates these files with the following
27869 @kindex set script-extension
27870 @kindex show script-extension
27871 @item set script-extension off
27872 All scripts are always evaluated as @value{GDBN} Command Files.
27874 @item set script-extension soft
27875 The debugger determines the scripting language based on filename
27876 extension. If this scripting language is supported, @value{GDBN}
27877 evaluates the script using that language. Otherwise, it evaluates
27878 the file as a @value{GDBN} Command File.
27880 @item set script-extension strict
27881 The debugger determines the scripting language based on filename
27882 extension, and evaluates the script using that language. If the
27883 language is not supported, then the evaluation fails.
27885 @item show script-extension
27886 Display the current value of the @code{script-extension} option.
27890 @ifset SYSTEM_GDBINIT_DIR
27891 This setting is not used for files in the system-wide gdbinit directory.
27892 Files in that directory must have an extension matching their language,
27893 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
27894 commands. @xref{Startup}.
27898 * Sequences:: Canned Sequences of @value{GDBN} Commands
27899 * Aliases:: Command Aliases
27900 * Python:: Extending @value{GDBN} using Python
27901 * Guile:: Extending @value{GDBN} using Guile
27902 * Auto-loading extensions:: Automatically loading extensions
27903 * Multiple Extension Languages:: Working with multiple extension languages
27907 @section Canned Sequences of Commands
27909 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
27910 Command Lists}), @value{GDBN} provides two ways to store sequences of
27911 commands for execution as a unit: user-defined commands and command
27915 * Define:: How to define your own commands
27916 * Hooks:: Hooks for user-defined commands
27917 * Command Files:: How to write scripts of commands to be stored in a file
27918 * Output:: Commands for controlled output
27919 * Auto-loading sequences:: Controlling auto-loaded command files
27923 @subsection User-defined Commands
27925 @cindex user-defined command
27926 @cindex arguments, to user-defined commands
27927 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
27928 which you assign a new name as a command. This is done with the
27929 @code{define} command. User commands may accept an unlimited number of arguments
27930 separated by whitespace. Arguments are accessed within the user command
27931 via @code{$arg0@dots{}$argN}. A trivial example:
27935 print $arg0 + $arg1 + $arg2
27940 To execute the command use:
27947 This defines the command @code{adder}, which prints the sum of
27948 its three arguments. Note the arguments are text substitutions, so they may
27949 reference variables, use complex expressions, or even perform inferior
27952 @cindex argument count in user-defined commands
27953 @cindex how many arguments (user-defined commands)
27954 In addition, @code{$argc} may be used to find out how many arguments have
27960 print $arg0 + $arg1
27963 print $arg0 + $arg1 + $arg2
27968 Combining with the @code{eval} command (@pxref{eval}) makes it easier
27969 to process a variable number of arguments:
27976 eval "set $sum = $sum + $arg%d", $i
27986 @item define @var{commandname}
27987 Define a command named @var{commandname}. If there is already a command
27988 by that name, you are asked to confirm that you want to redefine it.
27989 The argument @var{commandname} may be a bare command name consisting of letters,
27990 numbers, dashes, dots, and underscores. It may also start with any
27991 predefined or user-defined prefix command.
27992 For example, @samp{define target my-target} creates
27993 a user-defined @samp{target my-target} command.
27995 The definition of the command is made up of other @value{GDBN} command lines,
27996 which are given following the @code{define} command. The end of these
27997 commands is marked by a line containing @code{end}.
28000 @kindex end@r{ (user-defined commands)}
28001 @item document @var{commandname}
28002 Document the user-defined command @var{commandname}, so that it can be
28003 accessed by @code{help}. The command @var{commandname} must already be
28004 defined. This command reads lines of documentation just as @code{define}
28005 reads the lines of the command definition, ending with @code{end}.
28006 After the @code{document} command is finished, @code{help} on command
28007 @var{commandname} displays the documentation you have written.
28009 You may use the @code{document} command again to change the
28010 documentation of a command. Redefining the command with @code{define}
28011 does not change the documentation.
28013 It is also possible to document user-defined aliases. The alias documentation
28014 will then be used by the @code{help} and @code{apropos} commands
28015 instead of the documentation of the aliased command.
28016 Documenting a user-defined alias is particularly useful when defining
28017 an alias as a set of nested @code{with} commands
28018 (@pxref{Command aliases default args}).
28020 @kindex define-prefix
28021 @item define-prefix @var{commandname}
28022 Define or mark the command @var{commandname} as a user-defined prefix
28023 command. Once marked, @var{commandname} can be used as prefix command
28024 by the @code{define} command.
28025 Note that @code{define-prefix} can be used with a not yet defined
28026 @var{commandname}. In such a case, @var{commandname} is defined as
28027 an empty user-defined command.
28028 In case you redefine a command that was marked as a user-defined
28029 prefix command, the subcommands of the redefined command are kept
28030 (and @value{GDBN} indicates so to the user).
28034 (gdb) define-prefix abc
28035 (gdb) define-prefix abc def
28036 (gdb) define abc def
28037 Type commands for definition of "abc def".
28038 End with a line saying just "end".
28039 >echo command initial def\n
28041 (gdb) define abc def ghi
28042 Type commands for definition of "abc def ghi".
28043 End with a line saying just "end".
28044 >echo command ghi\n
28046 (gdb) define abc def
28047 Keeping subcommands of prefix command "def".
28048 Redefine command "def"? (y or n) y
28049 Type commands for definition of "abc def".
28050 End with a line saying just "end".
28051 >echo command def\n
28060 @kindex dont-repeat
28061 @cindex don't repeat command
28063 Used inside a user-defined command, this tells @value{GDBN} that this
28064 command should not be repeated when the user hits @key{RET}
28065 (@pxref{Command Syntax, repeat last command}).
28067 @kindex help user-defined
28068 @item help user-defined
28069 List all user-defined commands and all python commands defined in class
28070 COMMAND_USER. The first line of the documentation or docstring is
28075 @itemx show user @var{commandname}
28076 Display the @value{GDBN} commands used to define @var{commandname} (but
28077 not its documentation). If no @var{commandname} is given, display the
28078 definitions for all user-defined commands.
28079 This does not work for user-defined python commands.
28081 @cindex infinite recursion in user-defined commands
28082 @kindex show max-user-call-depth
28083 @kindex set max-user-call-depth
28084 @item show max-user-call-depth
28085 @itemx set max-user-call-depth
28086 The value of @code{max-user-call-depth} controls how many recursion
28087 levels are allowed in user-defined commands before @value{GDBN} suspects an
28088 infinite recursion and aborts the command.
28089 This does not apply to user-defined python commands.
28092 In addition to the above commands, user-defined commands frequently
28093 use control flow commands, described in @ref{Command Files}.
28095 When user-defined commands are executed, the
28096 commands of the definition are not printed. An error in any command
28097 stops execution of the user-defined command.
28099 If used interactively, commands that would ask for confirmation proceed
28100 without asking when used inside a user-defined command. Many @value{GDBN}
28101 commands that normally print messages to say what they are doing omit the
28102 messages when used in a user-defined command.
28105 @subsection User-defined Command Hooks
28106 @cindex command hooks
28107 @cindex hooks, for commands
28108 @cindex hooks, pre-command
28111 You may define @dfn{hooks}, which are a special kind of user-defined
28112 command. Whenever you run the command @samp{foo}, if the user-defined
28113 command @samp{hook-foo} exists, it is executed (with no arguments)
28114 before that command.
28116 @cindex hooks, post-command
28118 A hook may also be defined which is run after the command you executed.
28119 Whenever you run the command @samp{foo}, if the user-defined command
28120 @samp{hookpost-foo} exists, it is executed (with no arguments) after
28121 that command. Post-execution hooks may exist simultaneously with
28122 pre-execution hooks, for the same command.
28124 It is valid for a hook to call the command which it hooks. If this
28125 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
28127 @c It would be nice if hookpost could be passed a parameter indicating
28128 @c if the command it hooks executed properly or not. FIXME!
28130 @kindex stop@r{, a pseudo-command}
28131 In addition, a pseudo-command, @samp{stop} exists. Defining
28132 (@samp{hook-stop}) makes the associated commands execute every time
28133 execution stops in your program: before breakpoint commands are run,
28134 displays are printed, or the stack frame is printed.
28136 For example, to ignore @code{SIGALRM} signals while
28137 single-stepping, but treat them normally during normal execution,
28142 handle SIGALRM nopass
28146 handle SIGALRM pass
28149 define hook-continue
28150 handle SIGALRM pass
28154 As a further example, to hook at the beginning and end of the @code{echo}
28155 command, and to add extra text to the beginning and end of the message,
28163 define hookpost-echo
28167 (@value{GDBP}) echo Hello World
28168 <<<---Hello World--->>>
28173 You can define a hook for any single-word command in @value{GDBN}, but
28174 not for command aliases; you should define a hook for the basic command
28175 name, e.g.@: @code{backtrace} rather than @code{bt}.
28176 @c FIXME! So how does Joe User discover whether a command is an alias
28178 You can hook a multi-word command by adding @code{hook-} or
28179 @code{hookpost-} to the last word of the command, e.g.@:
28180 @samp{define target hook-remote} to add a hook to @samp{target remote}.
28182 If an error occurs during the execution of your hook, execution of
28183 @value{GDBN} commands stops and @value{GDBN} issues a prompt
28184 (before the command that you actually typed had a chance to run).
28186 If you try to define a hook which does not match any known command, you
28187 get a warning from the @code{define} command.
28189 @node Command Files
28190 @subsection Command Files
28192 @cindex command files
28193 @cindex scripting commands
28194 A command file for @value{GDBN} is a text file made of lines that are
28195 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
28196 also be included. An empty line in a command file does nothing; it
28197 does not mean to repeat the last command, as it would from the
28200 You can request the execution of a command file with the @code{source}
28201 command. Note that the @code{source} command is also used to evaluate
28202 scripts that are not Command Files. The exact behavior can be configured
28203 using the @code{script-extension} setting.
28204 @xref{Extending GDB,, Extending GDB}.
28208 @cindex execute commands from a file
28209 @item source [-s] [-v] @var{filename}
28210 Execute the command file @var{filename}.
28213 The lines in a command file are generally executed sequentially,
28214 unless the order of execution is changed by one of the
28215 @emph{flow-control commands} described below. The commands are not
28216 printed as they are executed. An error in any command terminates
28217 execution of the command file and control is returned to the console.
28219 @value{GDBN} first searches for @var{filename} in the current directory.
28220 If the file is not found there, and @var{filename} does not specify a
28221 directory, then @value{GDBN} also looks for the file on the source search path
28222 (specified with the @samp{directory} command);
28223 except that @file{$cdir} is not searched because the compilation directory
28224 is not relevant to scripts.
28226 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
28227 on the search path even if @var{filename} specifies a directory.
28228 The search is done by appending @var{filename} to each element of the
28229 search path. So, for example, if @var{filename} is @file{mylib/myscript}
28230 and the search path contains @file{/home/user} then @value{GDBN} will
28231 look for the script @file{/home/user/mylib/myscript}.
28232 The search is also done if @var{filename} is an absolute path.
28233 For example, if @var{filename} is @file{/tmp/myscript} and
28234 the search path contains @file{/home/user} then @value{GDBN} will
28235 look for the script @file{/home/user/tmp/myscript}.
28236 For DOS-like systems, if @var{filename} contains a drive specification,
28237 it is stripped before concatenation. For example, if @var{filename} is
28238 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
28239 will look for the script @file{c:/tmp/myscript}.
28241 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
28242 each command as it is executed. The option must be given before
28243 @var{filename}, and is interpreted as part of the filename anywhere else.
28245 Commands that would ask for confirmation if used interactively proceed
28246 without asking when used in a command file. Many @value{GDBN} commands that
28247 normally print messages to say what they are doing omit the messages
28248 when called from command files.
28250 @value{GDBN} also accepts command input from standard input. In this
28251 mode, normal output goes to standard output and error output goes to
28252 standard error. Errors in a command file supplied on standard input do
28253 not terminate execution of the command file---execution continues with
28257 gdb < cmds > log 2>&1
28260 (The syntax above will vary depending on the shell used.) This example
28261 will execute commands from the file @file{cmds}. All output and errors
28262 would be directed to @file{log}.
28264 Since commands stored on command files tend to be more general than
28265 commands typed interactively, they frequently need to deal with
28266 complicated situations, such as different or unexpected values of
28267 variables and symbols, changes in how the program being debugged is
28268 built, etc. @value{GDBN} provides a set of flow-control commands to
28269 deal with these complexities. Using these commands, you can write
28270 complex scripts that loop over data structures, execute commands
28271 conditionally, etc.
28278 This command allows to include in your script conditionally executed
28279 commands. The @code{if} command takes a single argument, which is an
28280 expression to evaluate. It is followed by a series of commands that
28281 are executed only if the expression is true (its value is nonzero).
28282 There can then optionally be an @code{else} line, followed by a series
28283 of commands that are only executed if the expression was false. The
28284 end of the list is marked by a line containing @code{end}.
28288 This command allows to write loops. Its syntax is similar to
28289 @code{if}: the command takes a single argument, which is an expression
28290 to evaluate, and must be followed by the commands to execute, one per
28291 line, terminated by an @code{end}. These commands are called the
28292 @dfn{body} of the loop. The commands in the body of @code{while} are
28293 executed repeatedly as long as the expression evaluates to true.
28297 This command exits the @code{while} loop in whose body it is included.
28298 Execution of the script continues after that @code{while}s @code{end}
28301 @kindex loop_continue
28302 @item loop_continue
28303 This command skips the execution of the rest of the body of commands
28304 in the @code{while} loop in whose body it is included. Execution
28305 branches to the beginning of the @code{while} loop, where it evaluates
28306 the controlling expression.
28308 @kindex end@r{ (if/else/while commands)}
28310 Terminate the block of commands that are the body of @code{if},
28311 @code{else}, or @code{while} flow-control commands.
28316 @subsection Commands for Controlled Output
28318 During the execution of a command file or a user-defined command, normal
28319 @value{GDBN} output is suppressed; the only output that appears is what is
28320 explicitly printed by the commands in the definition. This section
28321 describes three commands useful for generating exactly the output you
28326 @item echo @var{text}
28327 @c I do not consider backslash-space a standard C escape sequence
28328 @c because it is not in ANSI.
28329 Print @var{text}. Nonprinting characters can be included in
28330 @var{text} using C escape sequences, such as @samp{\n} to print a
28331 newline. @strong{No newline is printed unless you specify one.}
28332 In addition to the standard C escape sequences, a backslash followed
28333 by a space stands for a space. This is useful for displaying a
28334 string with spaces at the beginning or the end, since leading and
28335 trailing spaces are otherwise trimmed from all arguments.
28336 To print @samp{@w{ }and foo =@w{ }}, use the command
28337 @samp{echo \@w{ }and foo = \@w{ }}.
28339 A backslash at the end of @var{text} can be used, as in C, to continue
28340 the command onto subsequent lines. For example,
28343 echo This is some text\n\
28344 which is continued\n\
28345 onto several lines.\n
28348 produces the same output as
28351 echo This is some text\n
28352 echo which is continued\n
28353 echo onto several lines.\n
28357 @item output @var{expression}
28358 Print the value of @var{expression} and nothing but that value: no
28359 newlines, no @samp{$@var{nn} = }. The value is not entered in the
28360 value history either. @xref{Expressions, ,Expressions}, for more information
28363 @item output/@var{fmt} @var{expression}
28364 Print the value of @var{expression} in format @var{fmt}. You can use
28365 the same formats as for @code{print}. @xref{Output Formats,,Output
28366 Formats}, for more information.
28369 @item printf @var{template}, @var{expressions}@dots{}
28370 Print the values of one or more @var{expressions} under the control of
28371 the string @var{template}. To print several values, make
28372 @var{expressions} be a comma-separated list of individual expressions,
28373 which may be either numbers or pointers. Their values are printed as
28374 specified by @var{template}, exactly as a C program would do by
28375 executing the code below:
28378 printf (@var{template}, @var{expressions}@dots{});
28381 As in @code{C} @code{printf}, ordinary characters in @var{template}
28382 are printed verbatim, while @dfn{conversion specification} introduced
28383 by the @samp{%} character cause subsequent @var{expressions} to be
28384 evaluated, their values converted and formatted according to type and
28385 style information encoded in the conversion specifications, and then
28388 For example, you can print two values in hex like this:
28391 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
28394 @code{printf} supports all the standard @code{C} conversion
28395 specifications, including the flags and modifiers between the @samp{%}
28396 character and the conversion letter, with the following exceptions:
28400 The argument-ordering modifiers, such as @samp{2$}, are not supported.
28403 The modifier @samp{*} is not supported for specifying precision or
28407 The @samp{'} flag (for separation of digits into groups according to
28408 @code{LC_NUMERIC'}) is not supported.
28411 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
28415 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
28418 The conversion letters @samp{a} and @samp{A} are not supported.
28422 Note that the @samp{ll} type modifier is supported only if the
28423 underlying @code{C} implementation used to build @value{GDBN} supports
28424 the @code{long long int} type, and the @samp{L} type modifier is
28425 supported only if @code{long double} type is available.
28427 As in @code{C}, @code{printf} supports simple backslash-escape
28428 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
28429 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
28430 single character. Octal and hexadecimal escape sequences are not
28433 Additionally, @code{printf} supports conversion specifications for DFP
28434 (@dfn{Decimal Floating Point}) types using the following length modifiers
28435 together with a floating point specifier.
28440 @samp{H} for printing @code{Decimal32} types.
28443 @samp{D} for printing @code{Decimal64} types.
28446 @samp{DD} for printing @code{Decimal128} types.
28449 If the underlying @code{C} implementation used to build @value{GDBN} has
28450 support for the three length modifiers for DFP types, other modifiers
28451 such as width and precision will also be available for @value{GDBN} to use.
28453 In case there is no such @code{C} support, no additional modifiers will be
28454 available and the value will be printed in the standard way.
28456 Here's an example of printing DFP types using the above conversion letters:
28458 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
28463 @item eval @var{template}, @var{expressions}@dots{}
28464 Convert the values of one or more @var{expressions} under the control of
28465 the string @var{template} to a command line, and call it.
28469 @node Auto-loading sequences
28470 @subsection Controlling auto-loading native @value{GDBN} scripts
28471 @cindex native script auto-loading
28473 When a new object file is read (for example, due to the @code{file}
28474 command, or because the inferior has loaded a shared library),
28475 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
28476 @xref{Auto-loading extensions}.
28478 Auto-loading can be enabled or disabled,
28479 and the list of auto-loaded scripts can be printed.
28482 @anchor{set auto-load gdb-scripts}
28483 @kindex set auto-load gdb-scripts
28484 @item set auto-load gdb-scripts [on|off]
28485 Enable or disable the auto-loading of canned sequences of commands scripts.
28487 @anchor{show auto-load gdb-scripts}
28488 @kindex show auto-load gdb-scripts
28489 @item show auto-load gdb-scripts
28490 Show whether auto-loading of canned sequences of commands scripts is enabled or
28493 @anchor{info auto-load gdb-scripts}
28494 @kindex info auto-load gdb-scripts
28495 @cindex print list of auto-loaded canned sequences of commands scripts
28496 @item info auto-load gdb-scripts [@var{regexp}]
28497 Print the list of all canned sequences of commands scripts that @value{GDBN}
28501 If @var{regexp} is supplied only canned sequences of commands scripts with
28502 matching names are printed.
28505 @section Command Aliases
28506 @cindex aliases for commands
28508 Aliases allow you to define alternate spellings for existing commands.
28509 For example, if a new @value{GDBN} command defined in Python
28510 (@pxref{Python}) has a long name, it is handy to have an abbreviated
28511 version of it that involves less typing.
28513 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
28514 of the @samp{step} command even though it is otherwise an ambiguous
28515 abbreviation of other commands like @samp{set} and @samp{show}.
28517 Aliases are also used to provide shortened or more common versions
28518 of multi-word commands. For example, @value{GDBN} provides the
28519 @samp{tty} alias of the @samp{set inferior-tty} command.
28521 You can define a new alias with the @samp{alias} command.
28526 @item alias [-a] [--] @var{alias} = @var{command} [@var{default-args}]
28530 @var{alias} specifies the name of the new alias. Each word of
28531 @var{alias} must consist of letters, numbers, dashes and underscores.
28533 @var{command} specifies the name of an existing command
28534 that is being aliased.
28536 @var{command} can also be the name of an existing alias. In this
28537 case, @var{command} cannot be an alias that has default arguments.
28539 The @samp{-a} option specifies that the new alias is an abbreviation
28540 of the command. Abbreviations are not used in command completion.
28542 The @samp{--} option specifies the end of options,
28543 and is useful when @var{alias} begins with a dash.
28545 You can specify @var{default-args} for your alias. These
28546 @var{default-args} will be automatically added before the alias
28547 arguments typed explicitly on the command line.
28549 For example, the below defines an alias @code{btfullall} that shows all local
28550 variables and all frame arguments:
28552 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
28555 For more information about @var{default-args}, see @ref{Command
28556 aliases default args, ,Default Arguments}.
28558 Here is a simple example showing how to make an abbreviation of a
28559 command so that there is less to type. Suppose you were tired of
28560 typing @samp{disas}, the current shortest unambiguous abbreviation of
28561 the @samp{disassemble} command and you wanted an even shorter version
28562 named @samp{di}. The following will accomplish this.
28565 (gdb) alias -a di = disas
28568 Note that aliases are different from user-defined commands. With a
28569 user-defined command, you also need to write documentation for it with
28570 the @samp{document} command. An alias automatically picks up the
28571 documentation of the existing command.
28573 Here is an example where we make @samp{elms} an abbreviation of
28574 @samp{elements} in the @samp{set print elements} command.
28575 This is to show that you can make an abbreviation of any part
28579 (gdb) alias -a set print elms = set print elements
28580 (gdb) alias -a show print elms = show print elements
28581 (gdb) set p elms 200
28583 Limit on string chars or array elements to print is 200.
28586 Note that if you are defining an alias of a @samp{set} command,
28587 and you want to have an alias for the corresponding @samp{show}
28588 command, then you need to define the latter separately.
28590 Unambiguously abbreviated commands are allowed in @var{command} and
28591 @var{alias}, just as they are normally.
28594 (gdb) alias -a set pr elms = set p ele
28597 Finally, here is an example showing the creation of a one word
28598 alias for a more complex command.
28599 This creates alias @samp{spe} of the command @samp{set print elements}.
28602 (gdb) alias spe = set print elements
28607 * Command aliases default args:: Default arguments for aliases
28610 @node Command aliases default args
28611 @subsection Default Arguments
28612 @cindex aliases for commands, default arguments
28614 You can tell @value{GDBN} to always prepend some default arguments to
28615 the list of arguments provided explicitly by the user when using a
28616 user-defined alias.
28618 If you repeatedly use the same arguments or options for a command, you
28619 can define an alias for this command and tell @value{GDBN} to
28620 automatically prepend these arguments or options to the list of
28621 arguments you type explicitly when using the alias@footnote{@value{GDBN}
28622 could easily accept default arguments for pre-defined commands and aliases,
28623 but it was deemed this would be confusing, and so is not allowed.}.
28625 For example, if you often use the command @code{thread apply all}
28626 specifying to work on the threads in ascending order and to continue in case it
28627 encounters an error, you can tell @value{GDBN} to automatically preprend
28628 the @code{-ascending} and @code{-c} options by using:
28631 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
28634 Once you have defined this alias with its default args, any time you type
28635 the @code{thread apply asc-all} followed by @code{some arguments},
28636 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
28638 To have even less to type, you can also define a one word alias:
28640 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
28643 As usual, unambiguous abbreviations can be used for @var{alias}
28644 and @var{default-args}.
28646 The different aliases of a command do not share their default args.
28647 For example, you define a new alias @code{bt_ALL} showing all possible
28648 information and another alias @code{bt_SMALL} showing very limited information
28651 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
28652 -past-main -past-entry -full
28653 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
28654 -past-main off -past-entry off
28657 (For more on using the @code{alias} command, see @ref{Aliases}.)
28659 Default args are not limited to the arguments and options of @var{command},
28660 but can specify nested commands if @var{command} accepts such a nested command
28662 For example, the below defines @code{faalocalsoftype} that lists the
28663 frames having locals of a certain type, together with the matching
28666 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
28667 (@value{GDBP}) faalocalsoftype int
28668 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
28673 This is also very useful to define an alias for a set of nested @code{with}
28674 commands to have a particular combination of temporary settings. For example,
28675 the below defines the alias @code{pp10} that pretty prints an expression
28676 argument, with a maximum of 10 elements if the expression is a string or
28679 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
28681 This defines the alias @code{pp10} as being a sequence of 3 commands.
28682 The first part @code{with print pretty --} temporarily activates the setting
28683 @code{set print pretty}, then launches the command that follows the separator
28685 The command following the first part is also a @code{with} command that
28686 temporarily changes the setting @code{set print elements} to 10, then
28687 launches the command that follows the second separator @code{--}.
28688 The third part @code{print} is the command the @code{pp10} alias will launch,
28689 using the temporary values of the settings and the arguments explicitly given
28691 For more information about the @code{with} command usage,
28692 see @ref{Command Settings}.
28694 By default, asking the help for an alias shows the documentation of
28695 the aliased command. When the alias is a set of nested commands, @code{help}
28696 of an alias shows the documentation of the first command. This help
28697 is not particularly useful for an alias such as @code{pp10}.
28698 For such an alias, it is useful to give a specific documentation
28699 using the @code{document} command (@pxref{Define, document}).
28702 @c Python docs live in a separate file.
28703 @include python.texi
28705 @c Guile docs live in a separate file.
28706 @include guile.texi
28708 @node Auto-loading extensions
28709 @section Auto-loading extensions
28710 @cindex auto-loading extensions
28712 @value{GDBN} provides two mechanisms for automatically loading
28713 extensions when a new object file is read (for example, due to the
28714 @code{file} command, or because the inferior has loaded a shared
28715 library): @file{@var{objfile}-gdb.@var{ext}} (@pxref{objfile-gdbdotext
28716 file,,The @file{@var{objfile}-gdb.@var{ext}} file}) and the
28717 @code{.debug_gdb_scripts} section of modern file formats like ELF
28718 (@pxref{dotdebug_gdb_scripts section,,The @code{.debug_gdb_scripts}
28719 section}). For a discussion of the differences between these two
28720 approaches see @ref{Which flavor to choose?}.
28722 The auto-loading feature is useful for supplying application-specific
28723 debugging commands and features.
28725 Auto-loading can be enabled or disabled,
28726 and the list of auto-loaded scripts can be printed.
28727 See the @samp{auto-loading} section of each extension language
28728 for more information.
28729 For @value{GDBN} command files see @ref{Auto-loading sequences}.
28730 For Python files see @ref{Python Auto-loading}.
28732 Note that loading of this script file also requires accordingly configured
28733 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28736 * objfile-gdbdotext file:: The @file{@var{objfile}-gdb.@var{ext}} file
28737 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
28738 * Which flavor to choose?:: Choosing between these approaches
28741 @node objfile-gdbdotext file
28742 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
28743 @cindex @file{@var{objfile}-gdb.gdb}
28744 @cindex @file{@var{objfile}-gdb.py}
28745 @cindex @file{@var{objfile}-gdb.scm}
28747 When a new object file is read, @value{GDBN} looks for a file named
28748 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
28749 where @var{objfile} is the object file's name and
28750 where @var{ext} is the file extension for the extension language:
28753 @item @file{@var{objfile}-gdb.gdb}
28754 GDB's own command language
28755 @item @file{@var{objfile}-gdb.py}
28757 @item @file{@var{objfile}-gdb.scm}
28761 @var{script-name} is formed by ensuring that the file name of @var{objfile}
28762 is absolute, following all symlinks, and resolving @code{.} and @code{..}
28763 components, and appending the @file{-gdb.@var{ext}} suffix.
28764 If this file exists and is readable, @value{GDBN} will evaluate it as a
28765 script in the specified extension language.
28767 If this file does not exist, then @value{GDBN} will look for
28768 @var{script-name} file in all of the directories as specified below.
28769 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
28770 directories is converted to a one-letter subdirectory, i.e.@:
28771 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
28772 filesystems disallow colons in file names.)
28774 Note that loading of these files requires an accordingly configured
28775 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28777 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
28778 scripts normally according to its @file{.exe} filename. But if no scripts are
28779 found @value{GDBN} also tries script filenames matching the object file without
28780 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
28781 is attempted on any platform. This makes the script filenames compatible
28782 between Unix and MS-Windows hosts.
28785 @anchor{set auto-load scripts-directory}
28786 @kindex set auto-load scripts-directory
28787 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
28788 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
28789 may be delimited by the host platform path separator in use
28790 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
28792 Each entry here needs to be covered also by the security setting
28793 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
28795 @anchor{with-auto-load-dir}
28796 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
28797 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
28798 configuration option @option{--with-auto-load-dir}.
28800 Any reference to @file{$debugdir} will get replaced by
28801 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
28802 reference to @file{$datadir} will get replaced by @var{data-directory} which is
28803 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
28804 @file{$datadir} must be placed as a directory component --- either alone or
28805 delimited by @file{/} or @file{\} directory separators, depending on the host
28808 The list of directories uses path separator (@samp{:} on GNU and Unix
28809 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
28810 to the @env{PATH} environment variable.
28812 @anchor{show auto-load scripts-directory}
28813 @kindex show auto-load scripts-directory
28814 @item show auto-load scripts-directory
28815 Show @value{GDBN} auto-loaded scripts location.
28817 @anchor{add-auto-load-scripts-directory}
28818 @kindex add-auto-load-scripts-directory
28819 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
28820 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
28821 Multiple entries may be delimited by the host platform path separator in use.
28824 @value{GDBN} does not track which files it has already auto-loaded this way.
28825 @value{GDBN} will load the associated script every time the corresponding
28826 @var{objfile} is opened.
28827 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
28828 is evaluated more than once.
28830 @node dotdebug_gdb_scripts section
28831 @subsection The @code{.debug_gdb_scripts} section
28832 @cindex @code{.debug_gdb_scripts} section
28834 For systems using file formats like ELF and COFF,
28835 when @value{GDBN} loads a new object file
28836 it will look for a special section named @code{.debug_gdb_scripts}.
28837 If this section exists, its contents is a list of null-terminated entries
28838 specifying scripts to load. Each entry begins with a non-null prefix byte that
28839 specifies the kind of entry, typically the extension language and whether the
28840 script is in a file or inlined in @code{.debug_gdb_scripts}.
28842 The following entries are supported:
28845 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
28846 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
28847 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
28848 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
28851 @subsubsection Script File Entries
28853 If the entry specifies a file, @value{GDBN} will look for the file first
28854 in the current directory and then along the source search path
28855 (@pxref{Source Path, ,Specifying Source Directories}),
28856 except that @file{$cdir} is not searched, since the compilation
28857 directory is not relevant to scripts.
28859 File entries can be placed in section @code{.debug_gdb_scripts} with,
28860 for example, this GCC macro for Python scripts.
28863 /* Note: The "MS" section flags are to remove duplicates. */
28864 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28866 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28867 .byte 1 /* Python */\n\
28868 .asciz \"" script_name "\"\n\
28874 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
28875 Then one can reference the macro in a header or source file like this:
28878 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28881 The script name may include directories if desired.
28883 Note that loading of this script file also requires accordingly configured
28884 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28886 If the macro invocation is put in a header, any application or library
28887 using this header will get a reference to the specified script,
28888 and with the use of @code{"MS"} attributes on the section, the linker
28889 will remove duplicates.
28891 @subsubsection Script Text Entries
28893 Script text entries allow to put the executable script in the entry
28894 itself instead of loading it from a file.
28895 The first line of the entry, everything after the prefix byte and up to
28896 the first newline (@code{0xa}) character, is the script name, and must not
28897 contain any kind of space character, e.g., spaces or tabs.
28898 The rest of the entry, up to the trailing null byte, is the script to
28899 execute in the specified language. The name needs to be unique among
28900 all script names, as @value{GDBN} executes each script only once based
28903 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
28907 #include "symcat.h"
28908 #include "gdb/section-scripts.h"
28910 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
28911 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
28912 ".ascii \"gdb.inlined-script\\n\"\n"
28913 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
28914 ".ascii \" def __init__ (self):\\n\"\n"
28915 ".ascii \" super (test_cmd, self).__init__ ("
28916 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
28917 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
28918 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
28919 ".ascii \"test_cmd ()\\n\"\n"
28925 Loading of inlined scripts requires a properly configured
28926 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28927 The path to specify in @code{auto-load safe-path} is the path of the file
28928 containing the @code{.debug_gdb_scripts} section.
28930 @node Which flavor to choose?
28931 @subsection Which flavor to choose?
28933 Given the multiple ways of auto-loading extensions, it might not always
28934 be clear which one to choose. This section provides some guidance.
28937 Benefits of the @file{-gdb.@var{ext}} way:
28941 Can be used with file formats that don't support multiple sections.
28944 Ease of finding scripts for public libraries.
28946 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
28947 in the source search path.
28948 For publicly installed libraries, e.g., @file{libstdc++}, there typically
28949 isn't a source directory in which to find the script.
28952 Doesn't require source code additions.
28956 Benefits of the @code{.debug_gdb_scripts} way:
28960 Works with static linking.
28962 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
28963 trigger their loading. When an application is statically linked the only
28964 objfile available is the executable, and it is cumbersome to attach all the
28965 scripts from all the input libraries to the executable's
28966 @file{-gdb.@var{ext}} script.
28969 Works with classes that are entirely inlined.
28971 Some classes can be entirely inlined, and thus there may not be an associated
28972 shared library to attach a @file{-gdb.@var{ext}} script to.
28975 Scripts needn't be copied out of the source tree.
28977 In some circumstances, apps can be built out of large collections of internal
28978 libraries, and the build infrastructure necessary to install the
28979 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
28980 cumbersome. It may be easier to specify the scripts in the
28981 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
28982 top of the source tree to the source search path.
28985 @node Multiple Extension Languages
28986 @section Multiple Extension Languages
28988 The Guile and Python extension languages do not share any state,
28989 and generally do not interfere with each other.
28990 There are some things to be aware of, however.
28992 @subsection Python comes first
28994 Python was @value{GDBN}'s first extension language, and to avoid breaking
28995 existing behaviour Python comes first. This is generally solved by the
28996 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
28997 extension languages, and when it makes a call to an extension language,
28998 (say to pretty-print a value), it tries each in turn until an extension
28999 language indicates it has performed the request (e.g., has returned the
29000 pretty-printed form of a value).
29001 This extends to errors while performing such requests: If an error happens
29002 while, for example, trying to pretty-print an object then the error is
29003 reported and any following extension languages are not tried.
29006 @chapter Command Interpreters
29007 @cindex command interpreters
29009 @value{GDBN} supports multiple command interpreters, and some command
29010 infrastructure to allow users or user interface writers to switch
29011 between interpreters or run commands in other interpreters.
29013 @value{GDBN} currently supports two command interpreters, the console
29014 interpreter (sometimes called the command-line interpreter or @sc{cli})
29015 and the machine interface interpreter (or @sc{gdb/mi}). This manual
29016 describes both of these interfaces in great detail.
29018 By default, @value{GDBN} will start with the console interpreter.
29019 However, the user may choose to start @value{GDBN} with another
29020 interpreter by specifying the @option{-i} or @option{--interpreter}
29021 startup options. Defined interpreters include:
29025 @cindex console interpreter
29026 The traditional console or command-line interpreter. This is the most often
29027 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
29028 @value{GDBN} will use this interpreter.
29031 @cindex mi interpreter
29032 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
29033 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
29034 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
29038 @cindex mi3 interpreter
29039 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
29042 @cindex mi2 interpreter
29043 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
29046 @cindex mi1 interpreter
29047 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
29051 @cindex invoke another interpreter
29053 @kindex interpreter-exec
29054 You may execute commands in any interpreter from the current
29055 interpreter using the appropriate command. If you are running the
29056 console interpreter, simply use the @code{interpreter-exec} command:
29059 interpreter-exec mi "-data-list-register-names"
29062 @sc{gdb/mi} has a similar command, although it is only available in versions of
29063 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
29065 Note that @code{interpreter-exec} only changes the interpreter for the
29066 duration of the specified command. It does not change the interpreter
29069 @cindex start a new independent interpreter
29071 Although you may only choose a single interpreter at startup, it is
29072 possible to run an independent interpreter on a specified input/output
29073 device (usually a tty).
29075 For example, consider a debugger GUI or IDE that wants to provide a
29076 @value{GDBN} console view. It may do so by embedding a terminal
29077 emulator widget in its GUI, starting @value{GDBN} in the traditional
29078 command-line mode with stdin/stdout/stderr redirected to that
29079 terminal, and then creating an MI interpreter running on a specified
29080 input/output device. The console interpreter created by @value{GDBN}
29081 at startup handles commands the user types in the terminal widget,
29082 while the GUI controls and synchronizes state with @value{GDBN} using
29083 the separate MI interpreter.
29085 To start a new secondary @dfn{user interface} running MI, use the
29086 @code{new-ui} command:
29089 @cindex new user interface
29091 new-ui @var{interpreter} @var{tty}
29094 The @var{interpreter} parameter specifies the interpreter to run.
29095 This accepts the same values as the @code{interpreter-exec} command.
29096 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
29097 @var{tty} parameter specifies the name of the bidirectional file the
29098 interpreter uses for input/output, usually the name of a
29099 pseudoterminal slave on Unix systems. For example:
29102 (@value{GDBP}) new-ui mi /dev/pts/9
29106 runs an MI interpreter on @file{/dev/pts/9}.
29109 @chapter @value{GDBN} Text User Interface
29111 @cindex Text User Interface
29113 The @value{GDBN} Text User Interface (TUI) is a terminal
29114 interface which uses the @code{curses} library to show the source
29115 file, the assembly output, the program registers and @value{GDBN}
29116 commands in separate text windows. The TUI mode is supported only
29117 on platforms where a suitable version of the @code{curses} library
29120 The TUI mode is enabled by default when you invoke @value{GDBN} as
29121 @samp{@value{GDBP} -tui}.
29122 You can also switch in and out of TUI mode while @value{GDBN} runs by
29123 using various TUI commands and key bindings, such as @command{tui
29124 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
29125 @ref{TUI Keys, ,TUI Key Bindings}.
29128 * TUI Overview:: TUI overview
29129 * TUI Keys:: TUI key bindings
29130 * TUI Single Key Mode:: TUI single key mode
29131 * TUI Mouse Support:: TUI mouse support
29132 * TUI Commands:: TUI-specific commands
29133 * TUI Configuration:: TUI configuration variables
29137 @section TUI Overview
29139 In TUI mode, @value{GDBN} can display several text windows:
29143 This window is the @value{GDBN} command window with the @value{GDBN}
29144 prompt and the @value{GDBN} output. The @value{GDBN} input is still
29145 managed using readline.
29148 The source window shows the source file of the program. The current
29149 line and active breakpoints are displayed in this window.
29152 The assembly window shows the disassembly output of the program.
29155 This window shows the processor registers. Registers are highlighted
29156 when their values change.
29159 The source and assembly windows show the current program position
29160 by highlighting the current line and marking it with a @samp{>} marker.
29161 Breakpoints are indicated with two markers. The first marker
29162 indicates the breakpoint type:
29166 Breakpoint which was hit at least once.
29169 Breakpoint which was never hit.
29172 Hardware breakpoint which was hit at least once.
29175 Hardware breakpoint which was never hit.
29178 The second marker indicates whether the breakpoint is enabled or not:
29182 Breakpoint is enabled.
29185 Breakpoint is disabled.
29188 The source, assembly and register windows are updated when the current
29189 thread changes, when the frame changes, or when the program counter
29192 These windows are not all visible at the same time. The command
29193 window is always visible. The others can be arranged in several
29204 source and assembly,
29207 source and registers, or
29210 assembly and registers.
29213 These are the standard layouts, but other layouts can be defined.
29215 A status line above the command window shows the following information:
29219 Indicates the current @value{GDBN} target.
29220 (@pxref{Targets, ,Specifying a Debugging Target}).
29223 Gives the current process or thread number.
29224 When no process is being debugged, this field is set to @code{No process}.
29227 Gives the current function name for the selected frame.
29228 The name is demangled if demangling is turned on (@pxref{Print Settings}).
29229 When there is no symbol corresponding to the current program counter,
29230 the string @code{??} is displayed.
29233 Indicates the current line number for the selected frame.
29234 When the current line number is not known, the string @code{??} is displayed.
29237 Indicates the current program counter address.
29241 @section TUI Key Bindings
29242 @cindex TUI key bindings
29244 The TUI installs several key bindings in the readline keymaps
29245 @ifset SYSTEM_READLINE
29246 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
29248 @ifclear SYSTEM_READLINE
29249 (@pxref{Command Line Editing}).
29251 The following key bindings are installed for both TUI mode and the
29252 @value{GDBN} standard mode.
29261 Enter or leave the TUI mode. When leaving the TUI mode,
29262 the curses window management stops and @value{GDBN} operates using
29263 its standard mode, writing on the terminal directly. When reentering
29264 the TUI mode, control is given back to the curses windows.
29265 The screen is then refreshed.
29267 This key binding uses the bindable Readline function
29268 @code{tui-switch-mode}.
29272 Use a TUI layout with only one window. The layout will
29273 either be @samp{source} or @samp{assembly}. When the TUI mode
29274 is not active, it will switch to the TUI mode.
29276 Think of this key binding as the Emacs @kbd{C-x 1} binding.
29278 This key binding uses the bindable Readline function
29279 @code{tui-delete-other-windows}.
29283 Use a TUI layout with at least two windows. When the current
29284 layout already has two windows, the next layout with two windows is used.
29285 When a new layout is chosen, one window will always be common to the
29286 previous layout and the new one.
29288 Think of it as the Emacs @kbd{C-x 2} binding.
29290 This key binding uses the bindable Readline function
29291 @code{tui-change-windows}.
29295 Change the active window. The TUI associates several key bindings
29296 (like scrolling and arrow keys) with the active window. This command
29297 gives the focus to the next TUI window.
29299 Think of it as the Emacs @kbd{C-x o} binding.
29301 This key binding uses the bindable Readline function
29302 @code{tui-other-window}.
29306 Switch in and out of the TUI SingleKey mode that binds single
29307 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
29309 This key binding uses the bindable Readline function
29310 @code{next-keymap}.
29313 The following key bindings only work in the TUI mode:
29318 Scroll the active window one page up.
29322 Scroll the active window one page down.
29326 Scroll the active window one line up.
29330 Scroll the active window one line down.
29334 Scroll the active window one column left.
29338 Scroll the active window one column right.
29342 Refresh the screen.
29345 Because the arrow keys scroll the active window in the TUI mode, they
29346 are not available for their normal use by readline unless the command
29347 window has the focus. When another window is active, you must use
29348 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
29349 and @kbd{C-f} to control the command window.
29351 @node TUI Single Key Mode
29352 @section TUI Single Key Mode
29353 @cindex TUI single key mode
29355 The TUI also provides a @dfn{SingleKey} mode, which binds several
29356 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
29357 switch into this mode, where the following key bindings are used:
29360 @kindex c @r{(SingleKey TUI key)}
29364 @kindex d @r{(SingleKey TUI key)}
29368 @kindex f @r{(SingleKey TUI key)}
29372 @kindex n @r{(SingleKey TUI key)}
29376 @kindex o @r{(SingleKey TUI key)}
29378 nexti. The shortcut letter @samp{o} stands for ``step Over''.
29380 @kindex q @r{(SingleKey TUI key)}
29382 exit the SingleKey mode.
29384 @kindex r @r{(SingleKey TUI key)}
29388 @kindex s @r{(SingleKey TUI key)}
29392 @kindex i @r{(SingleKey TUI key)}
29394 stepi. The shortcut letter @samp{i} stands for ``step Into''.
29396 @kindex u @r{(SingleKey TUI key)}
29400 @kindex v @r{(SingleKey TUI key)}
29404 @kindex w @r{(SingleKey TUI key)}
29409 Other keys temporarily switch to the @value{GDBN} command prompt.
29410 The key that was pressed is inserted in the editing buffer so that
29411 it is possible to type most @value{GDBN} commands without interaction
29412 with the TUI SingleKey mode. Once the command is entered the TUI
29413 SingleKey mode is restored. The only way to permanently leave
29414 this mode is by typing @kbd{q} or @kbd{C-x s}.
29416 @cindex SingleKey keymap name
29417 If @value{GDBN} was built with Readline 8.0 or later, the TUI
29418 SingleKey keymap will be named @samp{SingleKey}. This can be used in
29419 @file{.inputrc} to add additional bindings to this keymap.
29421 @node TUI Mouse Support
29422 @section TUI Mouse Support
29423 @cindex TUI mouse support
29425 If the curses library supports the mouse, the TUI supports mouse
29428 The mouse wheel scrolls the appropriate window under the mouse cursor.
29430 The TUI itself does not directly support copying/pasting with the
29431 mouse. However, on Unix terminals, you can typically press and hold
29432 the @key{SHIFT} key on your keyboard to temporarily bypass
29433 @value{GDBN}'s TUI and access the terminal's native mouse copy/paste
29434 functionality (commonly, click-drag-release or double-click to select
29435 text, middle-click to paste). This copy/paste works with the
29436 terminal's selection buffer, as opposed to the TUI's buffer.
29439 @section TUI-specific Commands
29440 @cindex TUI commands
29442 The TUI has specific commands to control the text windows.
29443 These commands are always available, even when @value{GDBN} is not in
29444 the TUI mode. When @value{GDBN} is in the standard mode, most
29445 of these commands will automatically switch to the TUI mode.
29447 Note that if @value{GDBN}'s @code{stdout} is not connected to a
29448 terminal, or @value{GDBN} has been started with the machine interface
29449 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
29450 these commands will fail with an error, because it would not be
29451 possible or desirable to enable curses window management.
29456 Activate TUI mode. The last active TUI window layout will be used if
29457 TUI mode has previously been used in the current debugging session,
29458 otherwise a default layout is used.
29461 @kindex tui disable
29462 Disable TUI mode, returning to the console interpreter.
29464 @anchor{info_win_command}
29467 List the names and sizes of all currently displayed windows.
29469 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
29470 @kindex tui new-layout
29471 Create a new TUI layout. The new layout will be named @var{name}, and
29472 can be accessed using the @code{layout} command (see below).
29474 Each @var{window} parameter is either the name of a window to display,
29475 or a window description. The windows will be displayed from top to
29476 bottom in the order listed.
29478 The names of the windows are the same as the ones given to the
29479 @code{focus} command (see below); additional, the @code{status}
29480 window can be specified. Note that, because it is of fixed height,
29481 the weight assigned to the status window is of no importance. It is
29482 conventional to use @samp{0} here.
29484 A window description looks a bit like an invocation of @code{tui
29485 new-layout}, and is of the form
29486 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
29488 This specifies a sub-layout. If @code{-horizontal} is given, the
29489 windows in this description will be arranged side-by-side, rather than
29492 Each @var{weight} is an integer. It is the weight of this window
29493 relative to all the other windows in the layout. These numbers are
29494 used to calculate how much of the screen is given to each window.
29499 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
29502 Here, the new layout is called @samp{example}. It shows the source
29503 and register windows, followed by the status window, and then finally
29504 the command window. The non-status windows all have the same weight,
29505 so the terminal will be split into three roughly equal sections.
29507 Here is a more complex example, showing a horizontal layout:
29510 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
29513 This will result in side-by-side source and assembly windows; with the
29514 status and command window being beneath these, filling the entire
29515 width of the terminal. Because they have weight 2, the source and
29516 assembly windows will be twice the height of the command window.
29520 @item tui layout @var{name}
29521 @itemx layout @var{name}
29522 Changes which TUI windows are displayed. The @var{name} parameter
29523 controls which layout is shown. It can be either one of the built-in
29524 layout names, or the name of a layout defined by the user using
29525 @code{tui new-layout}.
29527 The built-in layouts are as follows:
29531 Display the next layout.
29534 Display the previous layout.
29537 Display the source and command windows.
29540 Display the assembly and command windows.
29543 Display the source, assembly, and command windows.
29546 When in @code{src} layout display the register, source, and command
29547 windows. When in @code{asm} or @code{split} layout display the
29548 register, assembler, and command windows.
29552 @item tui focus @var{name}
29553 @itemx focus @var{name}
29554 Changes which TUI window is currently active for scrolling. The
29555 @var{name} parameter can be any of the following:
29559 Make the next window active for scrolling.
29562 Make the previous window active for scrolling.
29565 Make the source window active for scrolling.
29568 Make the assembly window active for scrolling.
29571 Make the register window active for scrolling.
29574 Make the command window active for scrolling.
29577 @kindex tui refresh
29581 Refresh the screen. This is similar to typing @kbd{C-L}.
29583 @item tui reg @var{group}
29585 Changes the register group displayed in the tui register window to
29586 @var{group}. If the register window is not currently displayed this
29587 command will cause the register window to be displayed. The list of
29588 register groups, as well as their order is target specific. The
29589 following groups are available on most targets:
29592 Repeatedly selecting this group will cause the display to cycle
29593 through all of the available register groups.
29596 Repeatedly selecting this group will cause the display to cycle
29597 through all of the available register groups in the reverse order to
29601 Display the general registers.
29603 Display the floating point registers.
29605 Display the system registers.
29607 Display the vector registers.
29609 Display all registers.
29614 Update the source window and the current execution point.
29616 @kindex tui window height
29618 @item tui window height @var{name} +@var{count}
29619 @itemx tui window height @var{name} -@var{count}
29620 @itemx winheight @var{name} +@var{count}
29621 @itemx winheight @var{name} -@var{count}
29622 Change the height of the window @var{name} by @var{count} lines.
29623 Positive counts increase the height, while negative counts decrease
29624 it. The @var{name} parameter can be the name of any currently visible
29625 window. The names of the currently visible windows can be discovered
29626 using @kbd{info win} (@pxref{info_win_command,,info win}).
29628 The set of currently visible windows must always fill the terminal,
29629 and so, it is only possible to resize on window if there are other
29630 visible windows that can either give or receive the extra terminal
29633 @kindex tui window width
29635 @item tui window width @var{name} +@var{count}
29636 @itemx tui window width @var{name} -@var{count}
29637 @itemx winwidth @var{name} +@var{count}
29638 @itemx winwidth @var{name} -@var{count}
29639 Change the width of the window @var{name} by @var{count} columns.
29640 Positive counts increase the width, while negative counts decrease it.
29641 The @var{name} parameter can be the name of any currently visible
29642 window. The names of the currently visible windows can be discovered
29643 using @code{info win} (@pxref{info_win_command,,info win}).
29645 The set of currently visible windows must always fill the terminal,
29646 and so, it is only possible to resize on window if there are other
29647 visible windows that can either give or receive the extra terminal
29651 @node TUI Configuration
29652 @section TUI Configuration Variables
29653 @cindex TUI configuration variables
29655 Several configuration variables control the appearance of TUI windows.
29658 @item set tui border-kind @var{kind}
29659 @kindex set tui border-kind
29660 Select the border appearance for the source, assembly and register windows.
29661 The possible values are the following:
29664 Use a space character to draw the border.
29667 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
29670 Use the Alternate Character Set to draw the border. The border is
29671 drawn using character line graphics if the terminal supports them.
29674 @item set tui border-mode @var{mode}
29675 @kindex set tui border-mode
29676 @itemx set tui active-border-mode @var{mode}
29677 @kindex set tui active-border-mode
29678 Select the display attributes for the borders of the inactive windows
29679 or the active window. The @var{mode} can be one of the following:
29682 Use normal attributes to display the border.
29688 Use reverse video mode.
29691 Use half bright mode.
29693 @item half-standout
29694 Use half bright and standout mode.
29697 Use extra bright or bold mode.
29699 @item bold-standout
29700 Use extra bright or bold and standout mode.
29703 @item set tui tab-width @var{nchars}
29704 @kindex set tui tab-width
29706 Set the width of tab stops to be @var{nchars} characters. This
29707 setting affects the display of TAB characters in the source and
29710 @item set tui compact-source @r{[}on@r{|}off@r{]}
29711 @kindex set tui compact-source
29712 Set whether the TUI source window is displayed in ``compact'' form.
29713 The default display uses more space for line numbers and starts the
29714 source text at the next tab stop; the compact display uses only as
29715 much space as is needed for the line numbers in the current file, and
29716 only a single space to separate the line numbers from the source.
29718 @kindex set debug tui
29719 @item set debug tui @r{[}on|off@r{]}
29720 Turn on or off display of @value{GDBN} internal debug messages relating
29723 @kindex show debug tui
29724 @item show debug tui
29725 Show the current status of displaying @value{GDBN} internal debug
29726 messages relating to the TUI.
29730 Note that the colors of the TUI borders can be controlled using the
29731 appropriate @code{set style} commands. @xref{Output Styling}.
29734 @chapter Using @value{GDBN} under @sc{gnu} Emacs
29737 @cindex @sc{gnu} Emacs
29738 A special interface allows you to use @sc{gnu} Emacs to view (and
29739 edit) the source files for the program you are debugging with
29742 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
29743 executable file you want to debug as an argument. This command starts
29744 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
29745 created Emacs buffer.
29746 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
29748 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
29753 All ``terminal'' input and output goes through an Emacs buffer, called
29756 This applies both to @value{GDBN} commands and their output, and to the input
29757 and output done by the program you are debugging.
29759 This is useful because it means that you can copy the text of previous
29760 commands and input them again; you can even use parts of the output
29763 All the facilities of Emacs' Shell mode are available for interacting
29764 with your program. In particular, you can send signals the usual
29765 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
29769 @value{GDBN} displays source code through Emacs.
29771 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
29772 source file for that frame and puts an arrow (@samp{=>}) at the
29773 left margin of the current line. Emacs uses a separate buffer for
29774 source display, and splits the screen to show both your @value{GDBN} session
29777 Explicit @value{GDBN} @code{list} or search commands still produce output as
29778 usual, but you probably have no reason to use them from Emacs.
29781 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
29782 a graphical mode, enabled by default, which provides further buffers
29783 that can control the execution and describe the state of your program.
29784 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
29786 If you specify an absolute file name when prompted for the @kbd{M-x
29787 gdb} argument, then Emacs sets your current working directory to where
29788 your program resides. If you only specify the file name, then Emacs
29789 sets your current working directory to the directory associated
29790 with the previous buffer. In this case, @value{GDBN} may find your
29791 program by searching your environment's @env{PATH} variable, but on
29792 some operating systems it might not find the source. So, although the
29793 @value{GDBN} input and output session proceeds normally, the auxiliary
29794 buffer does not display the current source and line of execution.
29796 The initial working directory of @value{GDBN} is printed on the top
29797 line of the GUD buffer and this serves as a default for the commands
29798 that specify files for @value{GDBN} to operate on. @xref{Files,
29799 ,Commands to Specify Files}.
29801 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
29802 need to call @value{GDBN} by a different name (for example, if you
29803 keep several configurations around, with different names) you can
29804 customize the Emacs variable @code{gud-gdb-command-name} to run the
29807 In the GUD buffer, you can use these special Emacs commands in
29808 addition to the standard Shell mode commands:
29812 Describe the features of Emacs' GUD Mode.
29815 Execute to another source line, like the @value{GDBN} @code{step} command; also
29816 update the display window to show the current file and location.
29819 Execute to next source line in this function, skipping all function
29820 calls, like the @value{GDBN} @code{next} command. Then update the display window
29821 to show the current file and location.
29824 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
29825 display window accordingly.
29828 Execute until exit from the selected stack frame, like the @value{GDBN}
29829 @code{finish} command.
29832 Continue execution of your program, like the @value{GDBN} @code{continue}
29836 Go up the number of frames indicated by the numeric argument
29837 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
29838 like the @value{GDBN} @code{up} command.
29841 Go down the number of frames indicated by the numeric argument, like the
29842 @value{GDBN} @code{down} command.
29845 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
29846 tells @value{GDBN} to set a breakpoint on the source line point is on.
29848 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
29849 separate frame which shows a backtrace when the GUD buffer is current.
29850 Move point to any frame in the stack and type @key{RET} to make it
29851 become the current frame and display the associated source in the
29852 source buffer. Alternatively, click @kbd{Mouse-2} to make the
29853 selected frame become the current one. In graphical mode, the
29854 speedbar displays watch expressions.
29856 If you accidentally delete the source-display buffer, an easy way to get
29857 it back is to type the command @code{f} in the @value{GDBN} buffer, to
29858 request a frame display; when you run under Emacs, this recreates
29859 the source buffer if necessary to show you the context of the current
29862 The source files displayed in Emacs are in ordinary Emacs buffers
29863 which are visiting the source files in the usual way. You can edit
29864 the files with these buffers if you wish; but keep in mind that @value{GDBN}
29865 communicates with Emacs in terms of line numbers. If you add or
29866 delete lines from the text, the line numbers that @value{GDBN} knows cease
29867 to correspond properly with the code.
29869 A more detailed description of Emacs' interaction with @value{GDBN} is
29870 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
29874 @chapter The @sc{gdb/mi} Interface
29876 @unnumberedsec Function and Purpose
29878 @cindex @sc{gdb/mi}, its purpose
29879 @sc{gdb/mi} is a line based machine oriented text interface to
29880 @value{GDBN} and is activated by specifying using the
29881 @option{--interpreter} command line option (@pxref{Mode Options}). It
29882 is specifically intended to support the development of systems which
29883 use the debugger as just one small component of a larger system.
29885 This chapter is a specification of the @sc{gdb/mi} interface. It is written
29886 in the form of a reference manual.
29888 Note that @sc{gdb/mi} is still under construction, so some of the
29889 features described below are incomplete and subject to change
29890 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
29892 @unnumberedsec Notation and Terminology
29894 @cindex notational conventions, for @sc{gdb/mi}
29895 This chapter uses the following notation:
29899 @code{|} separates two alternatives.
29902 @code{[ @var{something} ]} indicates that @var{something} is optional:
29903 it may or may not be given.
29906 @code{( @var{group} )*} means that @var{group} inside the parentheses
29907 may repeat zero or more times.
29910 @code{( @var{group} )+} means that @var{group} inside the parentheses
29911 may repeat one or more times.
29914 @code{"@var{string}"} means a literal @var{string}.
29918 @heading Dependencies
29922 * GDB/MI General Design::
29923 * GDB/MI Command Syntax::
29924 * GDB/MI Compatibility with CLI::
29925 * GDB/MI Development and Front Ends::
29926 * GDB/MI Output Records::
29927 * GDB/MI Simple Examples::
29928 * GDB/MI Command Description Format::
29929 * GDB/MI Breakpoint Commands::
29930 * GDB/MI Catchpoint Commands::
29931 * GDB/MI Program Context::
29932 * GDB/MI Thread Commands::
29933 * GDB/MI Ada Tasking Commands::
29934 * GDB/MI Program Execution::
29935 * GDB/MI Stack Manipulation::
29936 * GDB/MI Variable Objects::
29937 * GDB/MI Data Manipulation::
29938 * GDB/MI Tracepoint Commands::
29939 * GDB/MI Symbol Query::
29940 * GDB/MI File Commands::
29942 * GDB/MI Kod Commands::
29943 * GDB/MI Memory Overlay Commands::
29944 * GDB/MI Signal Handling Commands::
29946 * GDB/MI Target Manipulation::
29947 * GDB/MI File Transfer Commands::
29948 * GDB/MI Ada Exceptions Commands::
29949 * GDB/MI Support Commands::
29950 * GDB/MI Miscellaneous Commands::
29953 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29954 @node GDB/MI General Design
29955 @section @sc{gdb/mi} General Design
29956 @cindex GDB/MI General Design
29958 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
29959 parts---commands sent to @value{GDBN}, responses to those commands
29960 and notifications. Each command results in exactly one response,
29961 indicating either successful completion of the command, or an error.
29962 For the commands that do not resume the target, the response contains the
29963 requested information. For the commands that resume the target, the
29964 response only indicates whether the target was successfully resumed.
29965 Notifications is the mechanism for reporting changes in the state of the
29966 target, or in @value{GDBN} state, that cannot conveniently be associated with
29967 a command and reported as part of that command response.
29969 The important examples of notifications are:
29973 Exec notifications. These are used to report changes in
29974 target state---when a target is resumed, or stopped. It would not
29975 be feasible to include this information in response of resuming
29976 commands, because one resume commands can result in multiple events in
29977 different threads. Also, quite some time may pass before any event
29978 happens in the target, while a frontend needs to know whether the resuming
29979 command itself was successfully executed.
29982 Console output, and status notifications. Console output
29983 notifications are used to report output of CLI commands, as well as
29984 diagnostics for other commands. Status notifications are used to
29985 report the progress of a long-running operation. Naturally, including
29986 this information in command response would mean no output is produced
29987 until the command is finished, which is undesirable.
29990 General notifications. Commands may have various side effects on
29991 the @value{GDBN} or target state beyond their official purpose. For example,
29992 a command may change the selected thread. Although such changes can
29993 be included in command response, using notification allows for more
29994 orthogonal frontend design.
29998 There's no guarantee that whenever an MI command reports an error,
29999 @value{GDBN} or the target are in any specific state, and especially,
30000 the state is not reverted to the state before the MI command was
30001 processed. Therefore, whenever an MI command results in an error,
30002 we recommend that the frontend refreshes all the information shown in
30003 the user interface.
30007 * Context management::
30008 * Asynchronous and non-stop modes::
30012 @node Context management
30013 @subsection Context management
30015 @subsubsection Threads and Frames
30017 In most cases when @value{GDBN} accesses the target, this access is
30018 done in context of a specific thread and frame (@pxref{Frames}).
30019 Often, even when accessing global data, the target requires that a thread
30020 be specified. The CLI interface maintains the selected thread and frame,
30021 and supplies them to target on each command. This is convenient,
30022 because a command line user would not want to specify that information
30023 explicitly on each command, and because user interacts with
30024 @value{GDBN} via a single terminal, so no confusion is possible as
30025 to what thread and frame are the current ones.
30027 In the case of MI, the concept of selected thread and frame is less
30028 useful. First, a frontend can easily remember this information
30029 itself. Second, a graphical frontend can have more than one window,
30030 each one used for debugging a different thread, and the frontend might
30031 want to access additional threads for internal purposes. This
30032 increases the risk that by relying on implicitly selected thread, the
30033 frontend may be operating on a wrong one. Therefore, each MI command
30034 should explicitly specify which thread and frame to operate on. To
30035 make it possible, each MI command accepts the @samp{--thread} and
30036 @samp{--frame} options, the value to each is @value{GDBN} global
30037 identifier for thread and frame to operate on.
30039 Usually, each top-level window in a frontend allows the user to select
30040 a thread and a frame, and remembers the user selection for further
30041 operations. However, in some cases @value{GDBN} may suggest that the
30042 current thread or frame be changed. For example, when stopping on a
30043 breakpoint it is reasonable to switch to the thread where breakpoint is
30044 hit. For another example, if the user issues the CLI @samp{thread} or
30045 @samp{frame} commands via the frontend, it is desirable to change the
30046 frontend's selection to the one specified by user. @value{GDBN}
30047 communicates the suggestion to change current thread and frame using the
30048 @samp{=thread-selected} notification.
30050 Note that historically, MI shares the selected thread with CLI, so
30051 frontends used the @code{-thread-select} to execute commands in the
30052 right context. However, getting this to work right is cumbersome. The
30053 simplest way is for frontend to emit @code{-thread-select} command
30054 before every command. This doubles the number of commands that need
30055 to be sent. The alternative approach is to suppress @code{-thread-select}
30056 if the selected thread in @value{GDBN} is supposed to be identical to the
30057 thread the frontend wants to operate on. However, getting this
30058 optimization right can be tricky. In particular, if the frontend
30059 sends several commands to @value{GDBN}, and one of the commands changes the
30060 selected thread, then the behaviour of subsequent commands will
30061 change. So, a frontend should either wait for response from such
30062 problematic commands, or explicitly add @code{-thread-select} for
30063 all subsequent commands. No frontend is known to do this exactly
30064 right, so it is suggested to just always pass the @samp{--thread} and
30065 @samp{--frame} options.
30067 @subsubsection Language
30069 The execution of several commands depends on which language is selected.
30070 By default, the current language (@pxref{show language}) is used.
30071 But for commands known to be language-sensitive, it is recommended
30072 to use the @samp{--language} option. This option takes one argument,
30073 which is the name of the language to use while executing the command.
30077 -data-evaluate-expression --language c "sizeof (void*)"
30082 The valid language names are the same names accepted by the
30083 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
30084 @samp{local} or @samp{unknown}.
30086 @node Asynchronous and non-stop modes
30087 @subsection Asynchronous command execution and non-stop mode
30089 On some targets, @value{GDBN} is capable of processing MI commands
30090 even while the target is running. This is called @dfn{asynchronous
30091 command execution} (@pxref{Background Execution}). The frontend may
30092 specify a preference for asynchronous execution using the
30093 @code{-gdb-set mi-async 1} command, which should be emitted before
30094 either running the executable or attaching to the target. After the
30095 frontend has started the executable or attached to the target, it can
30096 find if asynchronous execution is enabled using the
30097 @code{-list-target-features} command.
30100 @cindex foreground execution
30101 @cindex background execution
30102 @cindex asynchronous execution
30103 @cindex execution, foreground, background and asynchronous
30104 @kindex set mi-async
30105 @item -gdb-set mi-async @r{[}on@r{|}off@r{]}
30106 Set whether MI is in asynchronous mode.
30108 When @code{off}, which is the default, MI execution commands (e.g.,
30109 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
30110 for the program to stop before processing further commands.
30112 When @code{on}, MI execution commands are background execution
30113 commands (e.g., @code{-exec-continue} becomes the equivalent of the
30114 @code{c&} CLI command), and so @value{GDBN} is capable of processing
30115 MI commands even while the target is running.
30117 @kindex show mi-async
30118 @item -gdb-show mi-async
30119 Show whether MI asynchronous mode is enabled.
30122 Note: In @value{GDBN} version 7.7 and earlier, this option was called
30123 @code{target-async} instead of @code{mi-async}, and it had the effect
30124 of both putting MI in asynchronous mode and making CLI background
30125 commands possible. CLI background commands are now always possible
30126 ``out of the box'' if the target supports them. The old spelling is
30127 kept as a deprecated alias for backwards compatibility.
30129 Even if @value{GDBN} can accept a command while target is running,
30130 many commands that access the target do not work when the target is
30131 running. Therefore, asynchronous command execution is most useful
30132 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
30133 it is possible to examine the state of one thread, while other threads
30136 When a given thread is running, MI commands that try to access the
30137 target in the context of that thread may not work, or may work only on
30138 some targets. In particular, commands that try to operate on thread's
30139 stack will not work, on any target. Commands that read memory, or
30140 modify breakpoints, may work or not work, depending on the target. Note
30141 that even commands that operate on global state, such as @code{print},
30142 @code{set}, and breakpoint commands, still access the target in the
30143 context of a specific thread, so frontend should try to find a
30144 stopped thread and perform the operation on that thread (using the
30145 @samp{--thread} option).
30147 Which commands will work in the context of a running thread is
30148 highly target dependent. However, the two commands
30149 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
30150 to find the state of a thread, will always work.
30152 @node Thread groups
30153 @subsection Thread groups
30154 @value{GDBN} may be used to debug several processes at the same time.
30155 On some platforms, @value{GDBN} may support debugging of several
30156 hardware systems, each one having several cores with several different
30157 processes running on each core. This section describes the MI
30158 mechanism to support such debugging scenarios.
30160 The key observation is that regardless of the structure of the
30161 target, MI can have a global list of threads, because most commands that
30162 accept the @samp{--thread} option do not need to know what process that
30163 thread belongs to. Therefore, it is not necessary to introduce
30164 neither additional @samp{--process} option, nor an notion of the
30165 current process in the MI interface. The only strictly new feature
30166 that is required is the ability to find how the threads are grouped
30169 To allow the user to discover such grouping, and to support arbitrary
30170 hierarchy of machines/cores/processes, MI introduces the concept of a
30171 @dfn{thread group}. Thread group is a collection of threads and other
30172 thread groups. A thread group always has a string identifier, a type,
30173 and may have additional attributes specific to the type. A new
30174 command, @code{-list-thread-groups}, returns the list of top-level
30175 thread groups, which correspond to processes that @value{GDBN} is
30176 debugging at the moment. By passing an identifier of a thread group
30177 to the @code{-list-thread-groups} command, it is possible to obtain
30178 the members of specific thread group.
30180 To allow the user to easily discover processes, and other objects, he
30181 wishes to debug, a concept of @dfn{available thread group} is
30182 introduced. Available thread group is an thread group that
30183 @value{GDBN} is not debugging, but that can be attached to, using the
30184 @code{-target-attach} command. The list of available top-level thread
30185 groups can be obtained using @samp{-list-thread-groups --available}.
30186 In general, the content of a thread group may be only retrieved only
30187 after attaching to that thread group.
30189 Thread groups are related to inferiors (@pxref{Inferiors Connections and
30190 Programs}). Each inferior corresponds to a thread group of a special
30191 type @samp{process}, and some additional operations are permitted on
30192 such thread groups.
30194 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30195 @node GDB/MI Command Syntax
30196 @section @sc{gdb/mi} Command Syntax
30199 * GDB/MI Input Syntax::
30200 * GDB/MI Output Syntax::
30203 @node GDB/MI Input Syntax
30204 @subsection @sc{gdb/mi} Input Syntax
30206 @cindex input syntax for @sc{gdb/mi}
30207 @cindex @sc{gdb/mi}, input syntax
30209 @item @var{command} @expansion{}
30210 @code{@var{cli-command} | @var{mi-command}}
30212 @item @var{cli-command} @expansion{}
30213 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
30214 @var{cli-command} is any existing @value{GDBN} CLI command.
30216 @item @var{mi-command} @expansion{}
30217 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
30218 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
30220 @item @var{token} @expansion{}
30221 "any sequence of digits"
30223 @item @var{option} @expansion{}
30224 @code{"-" @var{parameter} [ " " @var{parameter} ]}
30226 @item @var{parameter} @expansion{}
30227 @code{@var{non-blank-sequence} | @var{c-string}}
30229 @item @var{operation} @expansion{}
30230 @emph{any of the operations described in this chapter}
30232 @item @var{non-blank-sequence} @expansion{}
30233 @emph{anything, provided it doesn't contain special characters such as
30234 "-", @var{nl}, """ and of course " "}
30236 @item @var{c-string} @expansion{}
30237 @code{""" @var{seven-bit-iso-c-string-content} """}
30239 @item @var{nl} @expansion{}
30248 The CLI commands are still handled by the @sc{mi} interpreter; their
30249 output is described below.
30252 The @code{@var{token}}, when present, is passed back when the command
30256 Some @sc{mi} commands accept optional arguments as part of the parameter
30257 list. Each option is identified by a leading @samp{-} (dash) and may be
30258 followed by an optional argument parameter. Options occur first in the
30259 parameter list and can be delimited from normal parameters using
30260 @samp{--} (this is useful when some parameters begin with a dash).
30267 We want easy access to the existing CLI syntax (for debugging).
30270 We want it to be easy to spot a @sc{mi} operation.
30273 @node GDB/MI Output Syntax
30274 @subsection @sc{gdb/mi} Output Syntax
30276 @cindex output syntax of @sc{gdb/mi}
30277 @cindex @sc{gdb/mi}, output syntax
30278 The output from @sc{gdb/mi} consists of zero or more out-of-band records
30279 followed, optionally, by a single result record. This result record
30280 is for the most recent command. The sequence of output records is
30281 terminated by @samp{(gdb)}.
30283 If an input command was prefixed with a @code{@var{token}} then the
30284 corresponding output for that command will also be prefixed by that same
30288 @item @var{output} @expansion{}
30289 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
30291 @item @var{result-record} @expansion{}
30292 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
30294 @item @var{out-of-band-record} @expansion{}
30295 @code{@var{async-record} | @var{stream-record}}
30297 @item @var{async-record} @expansion{}
30298 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
30300 @item @var{exec-async-output} @expansion{}
30301 @code{[ @var{token} ] "*" @var{async-output nl}}
30303 @item @var{status-async-output} @expansion{}
30304 @code{[ @var{token} ] "+" @var{async-output nl}}
30306 @item @var{notify-async-output} @expansion{}
30307 @code{[ @var{token} ] "=" @var{async-output nl}}
30309 @item @var{async-output} @expansion{}
30310 @code{@var{async-class} ( "," @var{result} )*}
30312 @item @var{result-class} @expansion{}
30313 @code{"done" | "running" | "connected" | "error" | "exit"}
30315 @item @var{async-class} @expansion{}
30316 @code{"stopped" | @var{others}} (where @var{others} will be added
30317 depending on the needs---this is still in development).
30319 @item @var{result} @expansion{}
30320 @code{ @var{variable} "=" @var{value}}
30322 @item @var{variable} @expansion{}
30323 @code{ @var{string} }
30325 @item @var{value} @expansion{}
30326 @code{ @var{const} | @var{tuple} | @var{list} }
30328 @item @var{const} @expansion{}
30329 @code{@var{c-string}}
30331 @item @var{tuple} @expansion{}
30332 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
30334 @item @var{list} @expansion{}
30335 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
30336 @var{result} ( "," @var{result} )* "]" }
30338 @item @var{stream-record} @expansion{}
30339 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
30341 @item @var{console-stream-output} @expansion{}
30342 @code{"~" @var{c-string nl}}
30344 @item @var{target-stream-output} @expansion{}
30345 @code{"@@" @var{c-string nl}}
30347 @item @var{log-stream-output} @expansion{}
30348 @code{"&" @var{c-string nl}}
30350 @item @var{nl} @expansion{}
30353 @item @var{token} @expansion{}
30354 @emph{any sequence of digits}.
30362 All output sequences end in a single line containing a period.
30365 The @code{@var{token}} is from the corresponding request. Note that
30366 for all async output, while the token is allowed by the grammar and
30367 may be output by future versions of @value{GDBN} for select async
30368 output messages, it is generally omitted. Frontends should treat
30369 all async output as reporting general changes in the state of the
30370 target and there should be no need to associate async output to any
30374 @cindex status output in @sc{gdb/mi}
30375 @var{status-async-output} contains on-going status information about the
30376 progress of a slow operation. It can be discarded. All status output is
30377 prefixed by @samp{+}.
30380 @cindex async output in @sc{gdb/mi}
30381 @var{exec-async-output} contains asynchronous state change on the target
30382 (stopped, started, disappeared). All async output is prefixed by
30386 @cindex notify output in @sc{gdb/mi}
30387 @var{notify-async-output} contains supplementary information that the
30388 client should handle (e.g., a new breakpoint information). All notify
30389 output is prefixed by @samp{=}.
30392 @cindex console output in @sc{gdb/mi}
30393 @var{console-stream-output} is output that should be displayed as is in the
30394 console. It is the textual response to a CLI command. All the console
30395 output is prefixed by @samp{~}.
30398 @cindex target output in @sc{gdb/mi}
30399 @var{target-stream-output} is the output produced by the target program.
30400 All the target output is prefixed by @samp{@@}.
30403 @cindex log output in @sc{gdb/mi}
30404 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
30405 instance messages that should be displayed as part of an error log. All
30406 the log output is prefixed by @samp{&}.
30409 @cindex list output in @sc{gdb/mi}
30410 New @sc{gdb/mi} commands should only output @var{lists} containing
30416 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
30417 details about the various output records.
30419 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30420 @node GDB/MI Compatibility with CLI
30421 @section @sc{gdb/mi} Compatibility with CLI
30423 @cindex compatibility, @sc{gdb/mi} and CLI
30424 @cindex @sc{gdb/mi}, compatibility with CLI
30426 For the developers convenience CLI commands can be entered directly,
30427 but there may be some unexpected behaviour. For example, commands
30428 that query the user will behave as if the user replied yes, breakpoint
30429 command lists are not executed and some CLI commands, such as
30430 @code{if}, @code{when} and @code{define}, prompt for further input with
30431 @samp{>}, which is not valid MI output.
30433 This feature may be removed at some stage in the future and it is
30434 recommended that front ends use the @code{-interpreter-exec} command
30435 (@pxref{-interpreter-exec}).
30437 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30438 @node GDB/MI Development and Front Ends
30439 @section @sc{gdb/mi} Development and Front Ends
30440 @cindex @sc{gdb/mi} development
30442 The application which takes the MI output and presents the state of the
30443 program being debugged to the user is called a @dfn{front end}.
30445 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
30446 to the MI interface may break existing usage. This section describes how the
30447 protocol changes and how to request previous version of the protocol when it
30450 Some changes in MI need not break a carefully designed front end, and
30451 for these the MI version will remain unchanged. The following is a
30452 list of changes that may occur within one level, so front ends should
30453 parse MI output in a way that can handle them:
30457 New MI commands may be added.
30460 New fields may be added to the output of any MI command.
30463 The range of values for fields with specified values, e.g.,
30464 @code{in_scope} (@pxref{-var-update}) may be extended.
30466 @c The format of field's content e.g type prefix, may change so parse it
30467 @c at your own risk. Yes, in general?
30469 @c The order of fields may change? Shouldn't really matter but it might
30470 @c resolve inconsistencies.
30473 If the changes are likely to break front ends, the MI version level
30474 will be increased by one. The new versions of the MI protocol are not compatible
30475 with the old versions. Old versions of MI remain available, allowing front ends
30476 to keep using them until they are modified to use the latest MI version.
30478 Since @code{--interpreter=mi} always points to the latest MI version, it is
30479 recommended that front ends request a specific version of MI when launching
30480 @value{GDBN} (e.g.@: @code{--interpreter=mi2}) to make sure they get an
30481 interpreter with the MI version they expect.
30483 The following table gives a summary of the released versions of the MI
30484 interface: the version number, the version of GDB in which it first appeared
30485 and the breaking changes compared to the previous version.
30487 @multitable @columnfractions .1 .1 .8
30488 @headitem MI version @tab GDB version @tab Breaking changes
30505 The @code{-environment-pwd}, @code{-environment-directory} and
30506 @code{-environment-path} commands now returns values using the MI output
30507 syntax, rather than CLI output syntax.
30510 @code{-var-list-children}'s @code{children} result field is now a list, rather
30514 @code{-var-update}'s @code{changelist} result field is now a list, rather than
30526 The output of information about multi-location breakpoints has changed in the
30527 responses to the @code{-break-insert} and @code{-break-info} commands, as well
30528 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
30529 The multiple locations are now placed in a @code{locations} field, whose value
30541 The syntax of the "script" field in breakpoint output has changed in the
30542 responses to the @code{-break-insert} and @code{-break-info} commands, as
30543 well as the @code{=breakpoint-created} and @code{=breakpoint-modified}
30544 events. The previous output was syntactically invalid. The new output is
30550 If your front end cannot yet migrate to a more recent version of the
30551 MI protocol, you can nevertheless selectively enable specific features
30552 available in those recent MI versions, using the following commands:
30556 @item -fix-multi-location-breakpoint-output
30557 Use the output for multi-location breakpoints which was introduced by
30558 MI 3, even when using MI versions below 3. This command has no
30559 effect when using MI version 3 or later.
30561 @item -fix-breakpoint-script-output
30562 Use the output for the breakpoint "script" field which was introduced by
30563 MI 4, even when using MI versions below 4. This command has no effect when
30564 using MI version 4 or later.
30568 The best way to avoid unexpected changes in MI that might break your front
30569 end is to make your project known to @value{GDBN} developers and
30570 follow development on @email{gdb@@sourceware.org} and
30571 @email{gdb-patches@@sourceware.org}.
30572 @cindex mailing lists
30574 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30575 @node GDB/MI Output Records
30576 @section @sc{gdb/mi} Output Records
30579 * GDB/MI Result Records::
30580 * GDB/MI Stream Records::
30581 * GDB/MI Async Records::
30582 * GDB/MI Breakpoint Information::
30583 * GDB/MI Frame Information::
30584 * GDB/MI Thread Information::
30585 * GDB/MI Ada Exception Information::
30588 @node GDB/MI Result Records
30589 @subsection @sc{gdb/mi} Result Records
30591 @cindex result records in @sc{gdb/mi}
30592 @cindex @sc{gdb/mi}, result records
30593 In addition to a number of out-of-band notifications, the response to a
30594 @sc{gdb/mi} command includes one of the following result indications:
30598 @item "^done" [ "," @var{results} ]
30599 The synchronous operation was successful, @code{@var{results}} are the return
30604 This result record is equivalent to @samp{^done}. Historically, it
30605 was output instead of @samp{^done} if the command has resumed the
30606 target. This behaviour is maintained for backward compatibility, but
30607 all frontends should treat @samp{^done} and @samp{^running}
30608 identically and rely on the @samp{*running} output record to determine
30609 which threads are resumed.
30613 @value{GDBN} has connected to a remote target.
30615 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
30617 The operation failed. The @code{msg=@var{c-string}} variable contains
30618 the corresponding error message.
30620 If present, the @code{code=@var{c-string}} variable provides an error
30621 code on which consumers can rely on to detect the corresponding
30622 error condition. At present, only one error code is defined:
30625 @item "undefined-command"
30626 Indicates that the command causing the error does not exist.
30631 @value{GDBN} has terminated.
30635 @node GDB/MI Stream Records
30636 @subsection @sc{gdb/mi} Stream Records
30638 @cindex @sc{gdb/mi}, stream records
30639 @cindex stream records in @sc{gdb/mi}
30640 @value{GDBN} internally maintains a number of output streams: the console, the
30641 target, and the log. The output intended for each of these streams is
30642 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
30644 Each stream record begins with a unique @dfn{prefix character} which
30645 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
30646 Syntax}). In addition to the prefix, each stream record contains a
30647 @code{@var{string-output}}. This is either raw text (with an implicit new
30648 line) or a quoted C string (which does not contain an implicit newline).
30651 @item "~" @var{string-output}
30652 The console output stream contains text that should be displayed in the
30653 CLI console window. It contains the textual responses to CLI commands.
30655 @item "@@" @var{string-output}
30656 The target output stream contains any textual output from the running
30657 target. This is only present when GDB's event loop is truly
30658 asynchronous, which is currently only the case for remote targets.
30660 @item "&" @var{string-output}
30661 The log stream contains debugging messages being produced by @value{GDBN}'s
30665 @node GDB/MI Async Records
30666 @subsection @sc{gdb/mi} Async Records
30668 @cindex async records in @sc{gdb/mi}
30669 @cindex @sc{gdb/mi}, async records
30670 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
30671 additional changes that have occurred. Those changes can either be a
30672 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
30673 target activity (e.g., target stopped).
30675 The following is the list of possible async records:
30679 @item *running,thread-id="@var{thread}"
30680 The target is now running. The @var{thread} field can be the global
30681 thread ID of the thread that is now running, and it can be
30682 @samp{all} if all threads are running. The frontend should assume
30683 that no interaction with a running thread is possible after this
30684 notification is produced. The frontend should not assume that this
30685 notification is output only once for any command. @value{GDBN} may
30686 emit this notification several times, either for different threads,
30687 because it cannot resume all threads together, or even for a single
30688 thread, if the thread must be stepped though some code before letting
30691 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
30692 The target has stopped. The @var{reason} field can have one of the
30696 @item breakpoint-hit
30697 A breakpoint was reached.
30698 @item watchpoint-trigger
30699 A watchpoint was triggered.
30700 @item read-watchpoint-trigger
30701 A read watchpoint was triggered.
30702 @item access-watchpoint-trigger
30703 An access watchpoint was triggered.
30704 @item function-finished
30705 An -exec-finish or similar CLI command was accomplished.
30706 @item location-reached
30707 An -exec-until or similar CLI command was accomplished.
30708 @item watchpoint-scope
30709 A watchpoint has gone out of scope.
30710 @item end-stepping-range
30711 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
30712 similar CLI command was accomplished.
30713 @item exited-signalled
30714 The inferior exited because of a signal.
30716 The inferior exited.
30717 @item exited-normally
30718 The inferior exited normally.
30719 @item signal-received
30720 A signal was received by the inferior.
30722 The inferior has stopped due to a library being loaded or unloaded.
30723 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
30724 set or when a @code{catch load} or @code{catch unload} catchpoint is
30725 in use (@pxref{Set Catchpoints}).
30727 The inferior has forked. This is reported when @code{catch fork}
30728 (@pxref{Set Catchpoints}) has been used.
30730 The inferior has vforked. This is reported in when @code{catch vfork}
30731 (@pxref{Set Catchpoints}) has been used.
30732 @item syscall-entry
30733 The inferior entered a system call. This is reported when @code{catch
30734 syscall} (@pxref{Set Catchpoints}) has been used.
30735 @item syscall-return
30736 The inferior returned from a system call. This is reported when
30737 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
30739 The inferior called @code{exec}. This is reported when @code{catch exec}
30740 (@pxref{Set Catchpoints}) has been used.
30743 The @var{id} field identifies the global thread ID of the thread
30744 that directly caused the stop -- for example by hitting a breakpoint.
30745 Depending on whether all-stop
30746 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
30747 stop all threads, or only the thread that directly triggered the stop.
30748 If all threads are stopped, the @var{stopped} field will have the
30749 value of @code{"all"}. Otherwise, the value of the @var{stopped}
30750 field will be a list of thread identifiers. Presently, this list will
30751 always include a single thread, but frontend should be prepared to see
30752 several threads in the list. The @var{core} field reports the
30753 processor core on which the stop event has happened. This field may be absent
30754 if such information is not available.
30756 @item =thread-group-added,id="@var{id}"
30757 @itemx =thread-group-removed,id="@var{id}"
30758 A thread group was either added or removed. The @var{id} field
30759 contains the @value{GDBN} identifier of the thread group. When a thread
30760 group is added, it generally might not be associated with a running
30761 process. When a thread group is removed, its id becomes invalid and
30762 cannot be used in any way.
30764 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
30765 A thread group became associated with a running program,
30766 either because the program was just started or the thread group
30767 was attached to a program. The @var{id} field contains the
30768 @value{GDBN} identifier of the thread group. The @var{pid} field
30769 contains process identifier, specific to the operating system.
30771 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
30772 A thread group is no longer associated with a running program,
30773 either because the program has exited, or because it was detached
30774 from. The @var{id} field contains the @value{GDBN} identifier of the
30775 thread group. The @var{code} field is the exit code of the inferior; it exists
30776 only when the inferior exited with some code.
30778 @item =thread-created,id="@var{id}",group-id="@var{gid}"
30779 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
30780 A thread either was created, or has exited. The @var{id} field
30781 contains the global @value{GDBN} identifier of the thread. The @var{gid}
30782 field identifies the thread group this thread belongs to.
30784 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
30785 Informs that the selected thread or frame were changed. This notification
30786 is not emitted as result of the @code{-thread-select} or
30787 @code{-stack-select-frame} commands, but is emitted whenever an MI command
30788 that is not documented to change the selected thread and frame actually
30789 changes them. In particular, invoking, directly or indirectly
30790 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
30791 will generate this notification. Changing the thread or frame from another
30792 user interface (see @ref{Interpreters}) will also generate this notification.
30794 The @var{frame} field is only present if the newly selected thread is
30795 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
30797 We suggest that in response to this notification, front ends
30798 highlight the selected thread and cause subsequent commands to apply to
30801 @item =library-loaded,...
30802 Reports that a new library file was loaded by the program. This
30803 notification has 5 fields---@var{id}, @var{target-name},
30804 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
30805 opaque identifier of the library. For remote debugging case,
30806 @var{target-name} and @var{host-name} fields give the name of the
30807 library file on the target, and on the host respectively. For native
30808 debugging, both those fields have the same value. The
30809 @var{symbols-loaded} field is emitted only for backward compatibility
30810 and should not be relied on to convey any useful information. The
30811 @var{thread-group} field, if present, specifies the id of the thread
30812 group in whose context the library was loaded. If the field is
30813 absent, it means the library was loaded in the context of all present
30814 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
30817 @item =library-unloaded,...
30818 Reports that a library was unloaded by the program. This notification
30819 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
30820 the same meaning as for the @code{=library-loaded} notification.
30821 The @var{thread-group} field, if present, specifies the id of the
30822 thread group in whose context the library was unloaded. If the field is
30823 absent, it means the library was unloaded in the context of all present
30826 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
30827 @itemx =traceframe-changed,end
30828 Reports that the trace frame was changed and its new number is
30829 @var{tfnum}. The number of the tracepoint associated with this trace
30830 frame is @var{tpnum}.
30832 @item =tsv-created,name=@var{name},initial=@var{initial}
30833 Reports that the new trace state variable @var{name} is created with
30834 initial value @var{initial}.
30836 @item =tsv-deleted,name=@var{name}
30837 @itemx =tsv-deleted
30838 Reports that the trace state variable @var{name} is deleted or all
30839 trace state variables are deleted.
30841 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
30842 Reports that the trace state variable @var{name} is modified with
30843 the initial value @var{initial}. The current value @var{current} of
30844 trace state variable is optional and is reported if the current
30845 value of trace state variable is known.
30847 @item =breakpoint-created,bkpt=@{...@}
30848 @itemx =breakpoint-modified,bkpt=@{...@}
30849 @itemx =breakpoint-deleted,id=@var{number}
30850 Reports that a breakpoint was created, modified, or deleted,
30851 respectively. Only user-visible breakpoints are reported to the MI
30854 The @var{bkpt} argument is of the same form as returned by the various
30855 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
30856 @var{number} is the ordinal number of the breakpoint.
30858 Note that if a breakpoint is emitted in the result record of a
30859 command, then it will not also be emitted in an async record.
30861 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
30862 @itemx =record-stopped,thread-group="@var{id}"
30863 Execution log recording was either started or stopped on an
30864 inferior. The @var{id} is the @value{GDBN} identifier of the thread
30865 group corresponding to the affected inferior.
30867 The @var{method} field indicates the method used to record execution. If the
30868 method in use supports multiple recording formats, @var{format} will be present
30869 and contain the currently used format. @xref{Process Record and Replay},
30870 for existing method and format values.
30872 @item =cmd-param-changed,param=@var{param},value=@var{value}
30873 Reports that a parameter of the command @code{set @var{param}} is
30874 changed to @var{value}. In the multi-word @code{set} command,
30875 the @var{param} is the whole parameter list to @code{set} command.
30876 For example, In command @code{set check type on}, @var{param}
30877 is @code{check type} and @var{value} is @code{on}.
30879 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
30880 Reports that bytes from @var{addr} to @var{data} + @var{len} were
30881 written in an inferior. The @var{id} is the identifier of the
30882 thread group corresponding to the affected inferior. The optional
30883 @code{type="code"} part is reported if the memory written to holds
30887 @node GDB/MI Breakpoint Information
30888 @subsection @sc{gdb/mi} Breakpoint Information
30890 When @value{GDBN} reports information about a breakpoint, a
30891 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
30896 The breakpoint number.
30899 The type of the breakpoint. For ordinary breakpoints this will be
30900 @samp{breakpoint}, but many values are possible.
30903 If the type of the breakpoint is @samp{catchpoint}, then this
30904 indicates the exact type of catchpoint.
30907 This is the breakpoint disposition---either @samp{del}, meaning that
30908 the breakpoint will be deleted at the next stop, or @samp{keep},
30909 meaning that the breakpoint will not be deleted.
30912 This indicates whether the breakpoint is enabled, in which case the
30913 value is @samp{y}, or disabled, in which case the value is @samp{n}.
30914 Note that this is not the same as the field @code{enable}.
30917 The address of the breakpoint. This may be a hexidecimal number,
30918 giving the address; or the string @samp{<PENDING>}, for a pending
30919 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
30920 multiple locations. This field will not be present if no address can
30921 be determined. For example, a watchpoint does not have an address.
30924 Optional field containing any flags related to the address. These flags are
30925 architecture-dependent; see @ref{Architectures} for their meaning for a
30929 If known, the function in which the breakpoint appears.
30930 If not known, this field is not present.
30933 The name of the source file which contains this function, if known.
30934 If not known, this field is not present.
30937 The full file name of the source file which contains this function, if
30938 known. If not known, this field is not present.
30941 The line number at which this breakpoint appears, if known.
30942 If not known, this field is not present.
30945 If the source file is not known, this field may be provided. If
30946 provided, this holds the address of the breakpoint, possibly followed
30950 If this breakpoint is pending, this field is present and holds the
30951 text used to set the breakpoint, as entered by the user.
30954 Where this breakpoint's condition is evaluated, either @samp{host} or
30958 If this is a thread-specific breakpoint, then this identifies the
30959 thread in which the breakpoint can trigger.
30962 If this breakpoint is restricted to a particular Ada task, then this
30963 field will hold the task identifier.
30966 If the breakpoint is conditional, this is the condition expression.
30969 The ignore count of the breakpoint.
30972 The enable count of the breakpoint.
30974 @item traceframe-usage
30977 @item static-tracepoint-marker-string-id
30978 For a static tracepoint, the name of the static tracepoint marker.
30981 For a masked watchpoint, this is the mask.
30984 A tracepoint's pass count.
30986 @item original-location
30987 The location of the breakpoint as originally specified by the user.
30988 This field is optional.
30991 The number of times the breakpoint has been hit.
30994 This field is only given for tracepoints. This is either @samp{y},
30995 meaning that the tracepoint is installed, or @samp{n}, meaning that it
30999 Some extra data, the exact contents of which are type-dependent.
31002 This field is present if the breakpoint has multiple locations. It is also
31003 exceptionally present if the breakpoint is enabled and has a single, disabled
31006 The value is a list of locations. The format of a location is described below.
31010 A location in a multi-location breakpoint is represented as a tuple with the
31016 The location number as a dotted pair, like @samp{1.2}. The first digit is the
31017 number of the parent breakpoint. The second digit is the number of the
31018 location within that breakpoint.
31021 There are three possible values, with the following meanings:
31024 The location is enabled.
31026 The location is disabled by the user.
31028 The location is disabled because the breakpoint condition is invalid
31033 The address of this location as an hexidecimal number.
31036 Optional field containing any flags related to the address. These flags are
31037 architecture-dependent; see @ref{Architectures} for their meaning for a
31041 If known, the function in which the location appears.
31042 If not known, this field is not present.
31045 The name of the source file which contains this location, if known.
31046 If not known, this field is not present.
31049 The full file name of the source file which contains this location, if
31050 known. If not known, this field is not present.
31053 The line number at which this location appears, if known.
31054 If not known, this field is not present.
31056 @item thread-groups
31057 The thread groups this location is in.
31061 For example, here is what the output of @code{-break-insert}
31062 (@pxref{GDB/MI Breakpoint Commands}) might be:
31065 -> -break-insert main
31066 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31067 enabled="y",addr="0x08048564",func="main",file="myprog.c",
31068 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
31073 @node GDB/MI Frame Information
31074 @subsection @sc{gdb/mi} Frame Information
31076 Response from many MI commands includes an information about stack
31077 frame. This information is a tuple that may have the following
31082 The level of the stack frame. The innermost frame has the level of
31083 zero. This field is always present.
31086 The name of the function corresponding to the frame. This field may
31087 be absent if @value{GDBN} is unable to determine the function name.
31090 The code address for the frame. This field is always present.
31093 Optional field containing any flags related to the address. These flags are
31094 architecture-dependent; see @ref{Architectures} for their meaning for a
31098 The name of the source files that correspond to the frame's code
31099 address. This field may be absent.
31102 The source line corresponding to the frames' code address. This field
31106 The name of the binary file (either executable or shared library) the
31107 corresponds to the frame's code address. This field may be absent.
31111 @node GDB/MI Thread Information
31112 @subsection @sc{gdb/mi} Thread Information
31114 Whenever @value{GDBN} has to report an information about a thread, it
31115 uses a tuple with the following fields. The fields are always present unless
31120 The global numeric id assigned to the thread by @value{GDBN}.
31123 The target-specific string identifying the thread.
31126 Additional information about the thread provided by the target.
31127 It is supposed to be human-readable and not interpreted by the
31128 frontend. This field is optional.
31131 The name of the thread. If the user specified a name using the
31132 @code{thread name} command, then this name is given. Otherwise, if
31133 @value{GDBN} can extract the thread name from the target, then that
31134 name is given. If @value{GDBN} cannot find the thread name, then this
31138 The execution state of the thread, either @samp{stopped} or @samp{running},
31139 depending on whether the thread is presently running.
31142 The stack frame currently executing in the thread. This field is only present
31143 if the thread is stopped. Its format is documented in
31144 @ref{GDB/MI Frame Information}.
31147 The value of this field is an integer number of the processor core the
31148 thread was last seen on. This field is optional.
31151 @node GDB/MI Ada Exception Information
31152 @subsection @sc{gdb/mi} Ada Exception Information
31154 Whenever a @code{*stopped} record is emitted because the program
31155 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
31156 @value{GDBN} provides the name of the exception that was raised via
31157 the @code{exception-name} field. Also, for exceptions that were raised
31158 with an exception message, @value{GDBN} provides that message via
31159 the @code{exception-message} field.
31161 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31162 @node GDB/MI Simple Examples
31163 @section Simple Examples of @sc{gdb/mi} Interaction
31164 @cindex @sc{gdb/mi}, simple examples
31166 This subsection presents several simple examples of interaction using
31167 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
31168 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
31169 the output received from @sc{gdb/mi}.
31171 Note the line breaks shown in the examples are here only for
31172 readability, they don't appear in the real output.
31174 @subheading Setting a Breakpoint
31176 Setting a breakpoint generates synchronous output which contains detailed
31177 information of the breakpoint.
31180 -> -break-insert main
31181 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31182 enabled="y",addr="0x08048564",func="main",file="myprog.c",
31183 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
31188 @subheading Program Execution
31190 Program execution generates asynchronous records and MI gives the
31191 reason that execution stopped.
31197 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31198 frame=@{addr="0x08048564",func="main",
31199 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
31200 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
31201 arch="i386:x86_64"@}
31206 <- *stopped,reason="exited-normally"
31210 @subheading Quitting @value{GDBN}
31212 Quitting @value{GDBN} just prints the result class @samp{^exit}.
31220 Please note that @samp{^exit} is printed immediately, but it might
31221 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
31222 performs necessary cleanups, including killing programs being debugged
31223 or disconnecting from debug hardware, so the frontend should wait till
31224 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
31225 fails to exit in reasonable time.
31227 @subheading A Bad Command
31229 Here's what happens if you pass a non-existent command:
31233 <- ^error,msg="Undefined MI command: rubbish"
31238 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31239 @node GDB/MI Command Description Format
31240 @section @sc{gdb/mi} Command Description Format
31242 The remaining sections describe blocks of commands. Each block of
31243 commands is laid out in a fashion similar to this section.
31245 @subheading Motivation
31247 The motivation for this collection of commands.
31249 @subheading Introduction
31251 A brief introduction to this collection of commands as a whole.
31253 @subheading Commands
31255 For each command in the block, the following is described:
31257 @subsubheading Synopsis
31260 -command @var{args}@dots{}
31263 @subsubheading Result
31265 @subsubheading @value{GDBN} Command
31267 The corresponding @value{GDBN} CLI command(s), if any.
31269 @subsubheading Example
31271 Example(s) formatted for readability. Some of the described commands have
31272 not been implemented yet and these are labeled N.A.@: (not available).
31275 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31276 @node GDB/MI Breakpoint Commands
31277 @section @sc{gdb/mi} Breakpoint Commands
31279 @cindex breakpoint commands for @sc{gdb/mi}
31280 @cindex @sc{gdb/mi}, breakpoint commands
31281 This section documents @sc{gdb/mi} commands for manipulating
31284 @subheading The @code{-break-after} Command
31285 @findex -break-after
31287 @subsubheading Synopsis
31290 -break-after @var{number} @var{count}
31293 The breakpoint number @var{number} is not in effect until it has been
31294 hit @var{count} times. To see how this is reflected in the output of
31295 the @samp{-break-list} command, see the description of the
31296 @samp{-break-list} command below.
31298 @subsubheading @value{GDBN} Command
31300 The corresponding @value{GDBN} command is @samp{ignore}.
31302 @subsubheading Example
31307 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31308 enabled="y",addr="0x000100d0",func="main",file="hello.c",
31309 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
31317 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31318 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31319 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31320 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31321 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31322 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31323 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31324 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31325 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31326 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
31331 @subheading The @code{-break-catch} Command
31332 @findex -break-catch
31335 @subheading The @code{-break-commands} Command
31336 @findex -break-commands
31338 @subsubheading Synopsis
31341 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
31344 Specifies the CLI commands that should be executed when breakpoint
31345 @var{number} is hit. The parameters @var{command1} to @var{commandN}
31346 are the commands. If no command is specified, any previously-set
31347 commands are cleared. @xref{Break Commands}. Typical use of this
31348 functionality is tracing a program, that is, printing of values of
31349 some variables whenever breakpoint is hit and then continuing.
31351 @subsubheading @value{GDBN} Command
31353 The corresponding @value{GDBN} command is @samp{commands}.
31355 @subsubheading Example
31360 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31361 enabled="y",addr="0x000100d0",func="main",file="hello.c",
31362 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
31365 -break-commands 1 "print v" "continue"
31370 @subheading The @code{-break-condition} Command
31371 @findex -break-condition
31373 @subsubheading Synopsis
31376 -break-condition [ --force ] @var{number} [ @var{expr} ]
31379 Breakpoint @var{number} will stop the program only if the condition in
31380 @var{expr} is true. The condition becomes part of the
31381 @samp{-break-list} output (see the description of the @samp{-break-list}
31382 command below). If the @samp{--force} flag is passed, the condition
31383 is forcibly defined even when it is invalid for all locations of
31384 breakpoint @var{number}. If the @var{expr} argument is omitted,
31385 breakpoint @var{number} becomes unconditional.
31387 @subsubheading @value{GDBN} Command
31389 The corresponding @value{GDBN} command is @samp{condition}.
31391 @subsubheading Example
31395 -break-condition 1 1
31399 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31400 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31401 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31402 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31403 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31404 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31405 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31406 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31407 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31408 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
31412 @subheading The @code{-break-delete} Command
31413 @findex -break-delete
31415 @subsubheading Synopsis
31418 -break-delete ( @var{breakpoint} )+
31421 Delete the breakpoint(s) whose number(s) are specified in the argument
31422 list. This is obviously reflected in the breakpoint list.
31424 @subsubheading @value{GDBN} Command
31426 The corresponding @value{GDBN} command is @samp{delete}.
31428 @subsubheading Example
31436 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31437 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31438 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31439 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31440 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31441 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31442 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31447 @subheading The @code{-break-disable} Command
31448 @findex -break-disable
31450 @subsubheading Synopsis
31453 -break-disable ( @var{breakpoint} )+
31456 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
31457 break list is now set to @samp{n} for the named @var{breakpoint}(s).
31459 @subsubheading @value{GDBN} Command
31461 The corresponding @value{GDBN} command is @samp{disable}.
31463 @subsubheading Example
31471 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31472 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31473 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31474 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31475 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31476 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31477 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31478 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
31479 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31480 line="5",thread-groups=["i1"],times="0"@}]@}
31484 @subheading The @code{-break-enable} Command
31485 @findex -break-enable
31487 @subsubheading Synopsis
31490 -break-enable ( @var{breakpoint} )+
31493 Enable (previously disabled) @var{breakpoint}(s).
31495 @subsubheading @value{GDBN} Command
31497 The corresponding @value{GDBN} command is @samp{enable}.
31499 @subsubheading Example
31507 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31508 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31509 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31510 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31511 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31512 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31513 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31514 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31515 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31516 line="5",thread-groups=["i1"],times="0"@}]@}
31520 @subheading The @code{-break-info} Command
31521 @findex -break-info
31523 @subsubheading Synopsis
31526 -break-info @var{breakpoint}
31530 Get information about a single breakpoint.
31532 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
31533 Information}, for details on the format of each breakpoint in the
31536 @subsubheading @value{GDBN} Command
31538 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
31540 @subsubheading Example
31543 @subheading The @code{-break-insert} Command
31544 @findex -break-insert
31545 @anchor{-break-insert}
31547 @subsubheading Synopsis
31550 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
31551 [ -c @var{condition} ] [ --force-condition ] [ -i @var{ignore-count} ]
31552 [ -p @var{thread-id} ] [ @var{locspec} ]
31556 If specified, @var{locspec}, can be one of:
31559 @item linespec location
31560 A linespec location. @xref{Linespec Locations}.
31562 @item explicit location
31563 An explicit location. @sc{gdb/mi} explicit locations are
31564 analogous to the CLI's explicit locations using the option names
31565 listed below. @xref{Explicit Locations}.
31568 @item --source @var{filename}
31569 The source file name of the location. This option requires the use
31570 of either @samp{--function} or @samp{--line}.
31572 @item --function @var{function}
31573 The name of a function or method.
31575 @item --label @var{label}
31576 The name of a label.
31578 @item --line @var{lineoffset}
31579 An absolute or relative line offset from the start of the location.
31582 @item address location
31583 An address location, *@var{address}. @xref{Address Locations}.
31587 The possible optional parameters of this command are:
31591 Insert a temporary breakpoint.
31593 Insert a hardware breakpoint.
31595 If @var{locspec} cannot be resolved (for example if it
31596 refers to unknown files or functions), create a pending
31597 breakpoint. Without this flag, @value{GDBN} will report
31598 an error, and won't create a breakpoint, if @var{locspec}
31601 Create a disabled breakpoint.
31603 Create a tracepoint. @xref{Tracepoints}. When this parameter
31604 is used together with @samp{-h}, a fast tracepoint is created.
31605 @item -c @var{condition}
31606 Make the breakpoint conditional on @var{condition}.
31607 @item --force-condition
31608 Forcibly define the breakpoint even if the condition is invalid at
31609 all of the breakpoint locations.
31610 @item -i @var{ignore-count}
31611 Initialize the @var{ignore-count}.
31612 @item -p @var{thread-id}
31613 Restrict the breakpoint to the thread with the specified global
31616 This option makes @value{GDBN} interpret a function name specified as
31617 a complete fully-qualified name.
31620 @subsubheading Result
31622 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31623 resulting breakpoint.
31625 Note: this format is open to change.
31626 @c An out-of-band breakpoint instead of part of the result?
31628 @subsubheading @value{GDBN} Command
31630 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
31631 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
31633 @subsubheading Example
31638 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
31639 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
31642 -break-insert -t foo
31643 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
31644 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
31648 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31649 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31650 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31651 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31652 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31653 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31654 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31655 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31656 addr="0x0001072c", func="main",file="recursive2.c",
31657 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
31659 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
31660 addr="0x00010774",func="foo",file="recursive2.c",
31661 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
31666 @subheading The @code{-dprintf-insert} Command
31667 @findex -dprintf-insert
31669 @subsubheading Synopsis
31672 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
31673 [ -c @var{condition} ] [--force-condition] [ -i @var{ignore-count} ]
31674 [ -p @var{thread-id} ] [ @var{locspec} ] [ @var{format} ]
31679 If supplied, @var{locspec} and @code{--qualified} may be specified
31680 the same way as for the @code{-break-insert} command.
31681 @xref{-break-insert}.
31683 The possible optional parameters of this command are:
31687 Insert a temporary breakpoint.
31689 If @var{locspec} cannot be parsed (for example, if it
31690 refers to unknown files or functions), create a pending
31691 breakpoint. Without this flag, @value{GDBN} will report
31692 an error, and won't create a breakpoint, if @var{locspec}
31695 Create a disabled breakpoint.
31696 @item -c @var{condition}
31697 Make the breakpoint conditional on @var{condition}.
31698 @item --force-condition
31699 Forcibly define the breakpoint even if the condition is invalid at
31700 all of the breakpoint locations.
31701 @item -i @var{ignore-count}
31702 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
31703 to @var{ignore-count}.
31704 @item -p @var{thread-id}
31705 Restrict the breakpoint to the thread with the specified global
31709 @subsubheading Result
31711 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31712 resulting breakpoint.
31714 @c An out-of-band breakpoint instead of part of the result?
31716 @subsubheading @value{GDBN} Command
31718 The corresponding @value{GDBN} command is @samp{dprintf}.
31720 @subsubheading Example
31724 4-dprintf-insert foo "At foo entry\n"
31725 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
31726 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
31727 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
31728 times="0",script=["printf \"At foo entry\\n\"","continue"],
31729 original-location="foo"@}
31731 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
31732 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
31733 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
31734 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
31735 times="0",script=["printf \"arg=%d, g=%d\\n\", arg, g","continue"],
31736 original-location="mi-dprintf.c:26"@}
31740 @subheading The @code{-break-list} Command
31741 @findex -break-list
31743 @subsubheading Synopsis
31749 Displays the list of inserted breakpoints, showing the following fields:
31753 number of the breakpoint
31755 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
31757 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
31760 is the breakpoint enabled or no: @samp{y} or @samp{n}
31762 memory location at which the breakpoint is set
31764 logical location of the breakpoint, expressed by function name, file
31766 @item Thread-groups
31767 list of thread groups to which this breakpoint applies
31769 number of times the breakpoint has been hit
31772 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
31773 @code{body} field is an empty list.
31775 @subsubheading @value{GDBN} Command
31777 The corresponding @value{GDBN} command is @samp{info break}.
31779 @subsubheading Example
31784 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31785 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31786 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31787 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31788 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31789 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31790 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31791 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31792 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
31794 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31795 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
31796 line="13",thread-groups=["i1"],times="0"@}]@}
31800 Here's an example of the result when there are no breakpoints:
31805 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31806 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31807 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31808 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31809 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31810 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31811 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31816 @subheading The @code{-break-passcount} Command
31817 @findex -break-passcount
31819 @subsubheading Synopsis
31822 -break-passcount @var{tracepoint-number} @var{passcount}
31825 Set the passcount for tracepoint @var{tracepoint-number} to
31826 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
31827 is not a tracepoint, error is emitted. This corresponds to CLI
31828 command @samp{passcount}.
31830 @subheading The @code{-break-watch} Command
31831 @findex -break-watch
31833 @subsubheading Synopsis
31836 -break-watch [ -a | -r ]
31839 Create a watchpoint. With the @samp{-a} option it will create an
31840 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
31841 read from or on a write to the memory location. With the @samp{-r}
31842 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
31843 trigger only when the memory location is accessed for reading. Without
31844 either of the options, the watchpoint created is a regular watchpoint,
31845 i.e., it will trigger when the memory location is accessed for writing.
31846 @xref{Set Watchpoints, , Setting Watchpoints}.
31848 Note that @samp{-break-list} will report a single list of watchpoints and
31849 breakpoints inserted.
31851 @subsubheading @value{GDBN} Command
31853 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
31856 @subsubheading Example
31858 Setting a watchpoint on a variable in the @code{main} function:
31863 ^done,wpt=@{number="2",exp="x"@}
31868 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
31869 value=@{old="-268439212",new="55"@},
31870 frame=@{func="main",args=[],file="recursive2.c",
31871 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
31875 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
31876 the program execution twice: first for the variable changing value, then
31877 for the watchpoint going out of scope.
31882 ^done,wpt=@{number="5",exp="C"@}
31887 *stopped,reason="watchpoint-trigger",
31888 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
31889 frame=@{func="callee4",args=[],
31890 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31891 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31892 arch="i386:x86_64"@}
31897 *stopped,reason="watchpoint-scope",wpnum="5",
31898 frame=@{func="callee3",args=[@{name="strarg",
31899 value="0x11940 \"A string argument.\""@}],
31900 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31901 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31902 arch="i386:x86_64"@}
31906 Listing breakpoints and watchpoints, at different points in the program
31907 execution. Note that once the watchpoint goes out of scope, it is
31913 ^done,wpt=@{number="2",exp="C"@}
31916 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31917 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31918 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31919 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31920 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31921 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31922 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31923 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31924 addr="0x00010734",func="callee4",
31925 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31926 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
31928 bkpt=@{number="2",type="watchpoint",disp="keep",
31929 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
31934 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
31935 value=@{old="-276895068",new="3"@},
31936 frame=@{func="callee4",args=[],
31937 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31938 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31939 arch="i386:x86_64"@}
31942 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31943 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31944 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31945 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31946 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31947 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31948 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31949 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31950 addr="0x00010734",func="callee4",
31951 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31952 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
31954 bkpt=@{number="2",type="watchpoint",disp="keep",
31955 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
31959 ^done,reason="watchpoint-scope",wpnum="2",
31960 frame=@{func="callee3",args=[@{name="strarg",
31961 value="0x11940 \"A string argument.\""@}],
31962 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31963 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31964 arch="i386:x86_64"@}
31967 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31968 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31969 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31970 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31971 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31972 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31973 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31974 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31975 addr="0x00010734",func="callee4",
31976 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31977 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31978 thread-groups=["i1"],times="1"@}]@}
31983 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31984 @node GDB/MI Catchpoint Commands
31985 @section @sc{gdb/mi} Catchpoint Commands
31987 This section documents @sc{gdb/mi} commands for manipulating
31991 * Shared Library GDB/MI Catchpoint Commands::
31992 * Ada Exception GDB/MI Catchpoint Commands::
31993 * C++ Exception GDB/MI Catchpoint Commands::
31996 @node Shared Library GDB/MI Catchpoint Commands
31997 @subsection Shared Library @sc{gdb/mi} Catchpoints
31999 @subheading The @code{-catch-load} Command
32000 @findex -catch-load
32002 @subsubheading Synopsis
32005 -catch-load [ -t ] [ -d ] @var{regexp}
32008 Add a catchpoint for library load events. If the @samp{-t} option is used,
32009 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
32010 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
32011 in a disabled state. The @samp{regexp} argument is a regular
32012 expression used to match the name of the loaded library.
32015 @subsubheading @value{GDBN} Command
32017 The corresponding @value{GDBN} command is @samp{catch load}.
32019 @subsubheading Example
32022 -catch-load -t foo.so
32023 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
32024 what="load of library matching foo.so",catch-type="load",times="0"@}
32029 @subheading The @code{-catch-unload} Command
32030 @findex -catch-unload
32032 @subsubheading Synopsis
32035 -catch-unload [ -t ] [ -d ] @var{regexp}
32038 Add a catchpoint for library unload events. If the @samp{-t} option is
32039 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
32040 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
32041 created in a disabled state. The @samp{regexp} argument is a regular
32042 expression used to match the name of the unloaded library.
32044 @subsubheading @value{GDBN} Command
32046 The corresponding @value{GDBN} command is @samp{catch unload}.
32048 @subsubheading Example
32051 -catch-unload -d bar.so
32052 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
32053 what="load of library matching bar.so",catch-type="unload",times="0"@}
32057 @node Ada Exception GDB/MI Catchpoint Commands
32058 @subsection Ada Exception @sc{gdb/mi} Catchpoints
32060 The following @sc{gdb/mi} commands can be used to create catchpoints
32061 that stop the execution when Ada exceptions are being raised.
32063 @subheading The @code{-catch-assert} Command
32064 @findex -catch-assert
32066 @subsubheading Synopsis
32069 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
32072 Add a catchpoint for failed Ada assertions.
32074 The possible optional parameters for this command are:
32077 @item -c @var{condition}
32078 Make the catchpoint conditional on @var{condition}.
32080 Create a disabled catchpoint.
32082 Create a temporary catchpoint.
32085 @subsubheading @value{GDBN} Command
32087 The corresponding @value{GDBN} command is @samp{catch assert}.
32089 @subsubheading Example
32093 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
32094 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
32095 thread-groups=["i1"],times="0",
32096 original-location="__gnat_debug_raise_assert_failure"@}
32100 @subheading The @code{-catch-exception} Command
32101 @findex -catch-exception
32103 @subsubheading Synopsis
32106 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
32110 Add a catchpoint stopping when Ada exceptions are raised.
32111 By default, the command stops the program when any Ada exception
32112 gets raised. But it is also possible, by using some of the
32113 optional parameters described below, to create more selective
32116 The possible optional parameters for this command are:
32119 @item -c @var{condition}
32120 Make the catchpoint conditional on @var{condition}.
32122 Create a disabled catchpoint.
32123 @item -e @var{exception-name}
32124 Only stop when @var{exception-name} is raised. This option cannot
32125 be used combined with @samp{-u}.
32127 Create a temporary catchpoint.
32129 Stop only when an unhandled exception gets raised. This option
32130 cannot be used combined with @samp{-e}.
32133 @subsubheading @value{GDBN} Command
32135 The corresponding @value{GDBN} commands are @samp{catch exception}
32136 and @samp{catch exception unhandled}.
32138 @subsubheading Example
32141 -catch-exception -e Program_Error
32142 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
32143 enabled="y",addr="0x0000000000404874",
32144 what="`Program_Error' Ada exception", thread-groups=["i1"],
32145 times="0",original-location="__gnat_debug_raise_exception"@}
32149 @subheading The @code{-catch-handlers} Command
32150 @findex -catch-handlers
32152 @subsubheading Synopsis
32155 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
32159 Add a catchpoint stopping when Ada exceptions are handled.
32160 By default, the command stops the program when any Ada exception
32161 gets handled. But it is also possible, by using some of the
32162 optional parameters described below, to create more selective
32165 The possible optional parameters for this command are:
32168 @item -c @var{condition}
32169 Make the catchpoint conditional on @var{condition}.
32171 Create a disabled catchpoint.
32172 @item -e @var{exception-name}
32173 Only stop when @var{exception-name} is handled.
32175 Create a temporary catchpoint.
32178 @subsubheading @value{GDBN} Command
32180 The corresponding @value{GDBN} command is @samp{catch handlers}.
32182 @subsubheading Example
32185 -catch-handlers -e Constraint_Error
32186 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
32187 enabled="y",addr="0x0000000000402f68",
32188 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
32189 times="0",original-location="__gnat_begin_handler"@}
32193 @node C++ Exception GDB/MI Catchpoint Commands
32194 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
32196 The following @sc{gdb/mi} commands can be used to create catchpoints
32197 that stop the execution when C@t{++} exceptions are being throw, rethrown,
32200 @subheading The @code{-catch-throw} Command
32201 @findex -catch-throw
32203 @subsubheading Synopsis
32206 -catch-throw [ -t ] [ -r @var{regexp}]
32209 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
32210 given, then only exceptions whose type matches the regular expression
32213 If @samp{-t} is given, then the catchpoint is enabled only for one
32214 stop, the catchpoint is automatically deleted after stopping once for
32217 @subsubheading @value{GDBN} Command
32219 The corresponding @value{GDBN} commands are @samp{catch throw}
32220 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
32222 @subsubheading Example
32225 -catch-throw -r exception_type
32226 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32227 what="exception throw",catch-type="throw",
32228 thread-groups=["i1"],
32229 regexp="exception_type",times="0"@}
32235 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
32236 in __cxa_throw () from /lib64/libstdc++.so.6\n"
32237 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32238 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
32239 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32240 thread-id="1",stopped-threads="all",core="6"
32244 @subheading The @code{-catch-rethrow} Command
32245 @findex -catch-rethrow
32247 @subsubheading Synopsis
32250 -catch-rethrow [ -t ] [ -r @var{regexp}]
32253 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
32254 then only exceptions whose type matches the regular expression will be
32257 If @samp{-t} is given, then the catchpoint is enabled only for one
32258 stop, the catchpoint is automatically deleted after the first event is
32261 @subsubheading @value{GDBN} Command
32263 The corresponding @value{GDBN} commands are @samp{catch rethrow}
32264 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
32266 @subsubheading Example
32269 -catch-rethrow -r exception_type
32270 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32271 what="exception rethrow",catch-type="rethrow",
32272 thread-groups=["i1"],
32273 regexp="exception_type",times="0"@}
32279 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
32280 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
32281 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32282 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
32283 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32284 thread-id="1",stopped-threads="all",core="6"
32288 @subheading The @code{-catch-catch} Command
32289 @findex -catch-catch
32291 @subsubheading Synopsis
32294 -catch-catch [ -t ] [ -r @var{regexp}]
32297 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
32298 is given, then only exceptions whose type matches the regular
32299 expression will be caught.
32301 If @samp{-t} is given, then the catchpoint is enabled only for one
32302 stop, the catchpoint is automatically deleted after the first event is
32305 @subsubheading @value{GDBN} Command
32307 The corresponding @value{GDBN} commands are @samp{catch catch}
32308 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
32310 @subsubheading Example
32313 -catch-catch -r exception_type
32314 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32315 what="exception catch",catch-type="catch",
32316 thread-groups=["i1"],
32317 regexp="exception_type",times="0"@}
32323 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
32324 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
32325 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32326 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
32327 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32328 thread-id="1",stopped-threads="all",core="6"
32332 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32333 @node GDB/MI Program Context
32334 @section @sc{gdb/mi} Program Context
32336 @subheading The @code{-exec-arguments} Command
32337 @findex -exec-arguments
32340 @subsubheading Synopsis
32343 -exec-arguments @var{args}
32346 Set the inferior program arguments, to be used in the next
32349 @subsubheading @value{GDBN} Command
32351 The corresponding @value{GDBN} command is @samp{set args}.
32353 @subsubheading Example
32357 -exec-arguments -v word
32364 @subheading The @code{-exec-show-arguments} Command
32365 @findex -exec-show-arguments
32367 @subsubheading Synopsis
32370 -exec-show-arguments
32373 Print the arguments of the program.
32375 @subsubheading @value{GDBN} Command
32377 The corresponding @value{GDBN} command is @samp{show args}.
32379 @subsubheading Example
32384 @subheading The @code{-environment-cd} Command
32385 @findex -environment-cd
32387 @subsubheading Synopsis
32390 -environment-cd @var{pathdir}
32393 Set @value{GDBN}'s working directory.
32395 @subsubheading @value{GDBN} Command
32397 The corresponding @value{GDBN} command is @samp{cd}.
32399 @subsubheading Example
32403 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
32409 @subheading The @code{-environment-directory} Command
32410 @findex -environment-directory
32412 @subsubheading Synopsis
32415 -environment-directory [ -r ] [ @var{pathdir} ]+
32418 Add directories @var{pathdir} to beginning of search path for source files.
32419 If the @samp{-r} option is used, the search path is reset to the default
32420 search path. If directories @var{pathdir} are supplied in addition to the
32421 @samp{-r} option, the search path is first reset and then addition
32423 Multiple directories may be specified, separated by blanks. Specifying
32424 multiple directories in a single command
32425 results in the directories added to the beginning of the
32426 search path in the same order they were presented in the command.
32427 If blanks are needed as
32428 part of a directory name, double-quotes should be used around
32429 the name. In the command output, the path will show up separated
32430 by the system directory-separator character. The directory-separator
32431 character must not be used
32432 in any directory name.
32433 If no directories are specified, the current search path is displayed.
32435 @subsubheading @value{GDBN} Command
32437 The corresponding @value{GDBN} command is @samp{dir}.
32439 @subsubheading Example
32443 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
32444 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
32446 -environment-directory ""
32447 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
32449 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
32450 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
32452 -environment-directory -r
32453 ^done,source-path="$cdir:$cwd"
32458 @subheading The @code{-environment-path} Command
32459 @findex -environment-path
32461 @subsubheading Synopsis
32464 -environment-path [ -r ] [ @var{pathdir} ]+
32467 Add directories @var{pathdir} to beginning of search path for object files.
32468 If the @samp{-r} option is used, the search path is reset to the original
32469 search path that existed at gdb start-up. If directories @var{pathdir} are
32470 supplied in addition to the
32471 @samp{-r} option, the search path is first reset and then addition
32473 Multiple directories may be specified, separated by blanks. Specifying
32474 multiple directories in a single command
32475 results in the directories added to the beginning of the
32476 search path in the same order they were presented in the command.
32477 If blanks are needed as
32478 part of a directory name, double-quotes should be used around
32479 the name. In the command output, the path will show up separated
32480 by the system directory-separator character. The directory-separator
32481 character must not be used
32482 in any directory name.
32483 If no directories are specified, the current path is displayed.
32486 @subsubheading @value{GDBN} Command
32488 The corresponding @value{GDBN} command is @samp{path}.
32490 @subsubheading Example
32495 ^done,path="/usr/bin"
32497 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
32498 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
32500 -environment-path -r /usr/local/bin
32501 ^done,path="/usr/local/bin:/usr/bin"
32506 @subheading The @code{-environment-pwd} Command
32507 @findex -environment-pwd
32509 @subsubheading Synopsis
32515 Show the current working directory.
32517 @subsubheading @value{GDBN} Command
32519 The corresponding @value{GDBN} command is @samp{pwd}.
32521 @subsubheading Example
32526 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
32530 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32531 @node GDB/MI Thread Commands
32532 @section @sc{gdb/mi} Thread Commands
32535 @subheading The @code{-thread-info} Command
32536 @findex -thread-info
32538 @subsubheading Synopsis
32541 -thread-info [ @var{thread-id} ]
32544 Reports information about either a specific thread, if the
32545 @var{thread-id} parameter is present, or about all threads.
32546 @var{thread-id} is the thread's global thread ID. When printing
32547 information about all threads, also reports the global ID of the
32550 @subsubheading @value{GDBN} Command
32552 The @samp{info thread} command prints the same information
32555 @subsubheading Result
32557 The result contains the following attributes:
32561 A list of threads. The format of the elements of the list is described in
32562 @ref{GDB/MI Thread Information}.
32564 @item current-thread-id
32565 The global id of the currently selected thread. This field is omitted if there
32566 is no selected thread (for example, when the selected inferior is not running,
32567 and therefore has no threads) or if a @var{thread-id} argument was passed to
32572 @subsubheading Example
32577 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32578 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
32579 args=[]@},state="running"@},
32580 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32581 frame=@{level="0",addr="0x0804891f",func="foo",
32582 args=[@{name="i",value="10"@}],
32583 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
32584 state="running"@}],
32585 current-thread-id="1"
32589 @subheading The @code{-thread-list-ids} Command
32590 @findex -thread-list-ids
32592 @subsubheading Synopsis
32598 Produces a list of the currently known global @value{GDBN} thread ids.
32599 At the end of the list it also prints the total number of such
32602 This command is retained for historical reasons, the
32603 @code{-thread-info} command should be used instead.
32605 @subsubheading @value{GDBN} Command
32607 Part of @samp{info threads} supplies the same information.
32609 @subsubheading Example
32614 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32615 current-thread-id="1",number-of-threads="3"
32620 @subheading The @code{-thread-select} Command
32621 @findex -thread-select
32623 @subsubheading Synopsis
32626 -thread-select @var{thread-id}
32629 Make thread with global thread number @var{thread-id} the current
32630 thread. It prints the number of the new current thread, and the
32631 topmost frame for that thread.
32633 This command is deprecated in favor of explicitly using the
32634 @samp{--thread} option to each command.
32636 @subsubheading @value{GDBN} Command
32638 The corresponding @value{GDBN} command is @samp{thread}.
32640 @subsubheading Example
32647 *stopped,reason="end-stepping-range",thread-id="2",line="187",
32648 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
32652 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32653 number-of-threads="3"
32656 ^done,new-thread-id="3",
32657 frame=@{level="0",func="vprintf",
32658 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
32659 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
32663 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32664 @node GDB/MI Ada Tasking Commands
32665 @section @sc{gdb/mi} Ada Tasking Commands
32667 @subheading The @code{-ada-task-info} Command
32668 @findex -ada-task-info
32670 @subsubheading Synopsis
32673 -ada-task-info [ @var{task-id} ]
32676 Reports information about either a specific Ada task, if the
32677 @var{task-id} parameter is present, or about all Ada tasks.
32679 @subsubheading @value{GDBN} Command
32681 The @samp{info tasks} command prints the same information
32682 about all Ada tasks (@pxref{Ada Tasks}).
32684 @subsubheading Result
32686 The result is a table of Ada tasks. The following columns are
32687 defined for each Ada task:
32691 This field exists only for the current thread. It has the value @samp{*}.
32694 The identifier that @value{GDBN} uses to refer to the Ada task.
32697 The identifier that the target uses to refer to the Ada task.
32700 The global thread identifier of the thread corresponding to the Ada
32703 This field should always exist, as Ada tasks are always implemented
32704 on top of a thread. But if @value{GDBN} cannot find this corresponding
32705 thread for any reason, the field is omitted.
32708 This field exists only when the task was created by another task.
32709 In this case, it provides the ID of the parent task.
32712 The base priority of the task.
32715 The current state of the task. For a detailed description of the
32716 possible states, see @ref{Ada Tasks}.
32719 The name of the task.
32723 @subsubheading Example
32727 ^done,tasks=@{nr_rows="3",nr_cols="8",
32728 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
32729 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
32730 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
32731 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
32732 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
32733 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
32734 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
32735 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
32736 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
32737 state="Child Termination Wait",name="main_task"@}]@}
32741 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32742 @node GDB/MI Program Execution
32743 @section @sc{gdb/mi} Program Execution
32745 These are the asynchronous commands which generate the out-of-band
32746 record @samp{*stopped}. Currently @value{GDBN} only really executes
32747 asynchronously with remote targets and this interaction is mimicked in
32750 @subheading The @code{-exec-continue} Command
32751 @findex -exec-continue
32753 @subsubheading Synopsis
32756 -exec-continue [--reverse] [--all|--thread-group N]
32759 Resumes the execution of the inferior program, which will continue
32760 to execute until it reaches a debugger stop event. If the
32761 @samp{--reverse} option is specified, execution resumes in reverse until
32762 it reaches a stop event. Stop events may include
32765 breakpoints or watchpoints
32767 signals or exceptions
32769 the end of the process (or its beginning under @samp{--reverse})
32771 the end or beginning of a replay log if one is being used.
32773 In all-stop mode (@pxref{All-Stop
32774 Mode}), may resume only one thread, or all threads, depending on the
32775 value of the @samp{scheduler-locking} variable. If @samp{--all} is
32776 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
32777 ignored in all-stop mode. If the @samp{--thread-group} options is
32778 specified, then all threads in that thread group are resumed.
32780 @subsubheading @value{GDBN} Command
32782 The corresponding @value{GDBN} corresponding is @samp{continue}.
32784 @subsubheading Example
32791 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
32792 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
32793 line="13",arch="i386:x86_64"@}
32798 @subheading The @code{-exec-finish} Command
32799 @findex -exec-finish
32801 @subsubheading Synopsis
32804 -exec-finish [--reverse]
32807 Resumes the execution of the inferior program until the current
32808 function is exited. Displays the results returned by the function.
32809 If the @samp{--reverse} option is specified, resumes the reverse
32810 execution of the inferior program until the point where current
32811 function was called.
32813 @subsubheading @value{GDBN} Command
32815 The corresponding @value{GDBN} command is @samp{finish}.
32817 @subsubheading Example
32819 Function returning @code{void}.
32826 *stopped,reason="function-finished",frame=@{func="main",args=[],
32827 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
32831 Function returning other than @code{void}. The name of the internal
32832 @value{GDBN} variable storing the result is printed, together with the
32839 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
32840 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
32841 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32842 arch="i386:x86_64"@},
32843 gdb-result-var="$1",return-value="0"
32848 @subheading The @code{-exec-interrupt} Command
32849 @findex -exec-interrupt
32851 @subsubheading Synopsis
32854 -exec-interrupt [--all|--thread-group N]
32857 Interrupts the background execution of the target. Note how the token
32858 associated with the stop message is the one for the execution command
32859 that has been interrupted. The token for the interrupt itself only
32860 appears in the @samp{^done} output. If the user is trying to
32861 interrupt a non-running program, an error message will be printed.
32863 Note that when asynchronous execution is enabled, this command is
32864 asynchronous just like other execution commands. That is, first the
32865 @samp{^done} response will be printed, and the target stop will be
32866 reported after that using the @samp{*stopped} notification.
32868 In non-stop mode, only the context thread is interrupted by default.
32869 All threads (in all inferiors) will be interrupted if the
32870 @samp{--all} option is specified. If the @samp{--thread-group}
32871 option is specified, all threads in that group will be interrupted.
32873 @subsubheading @value{GDBN} Command
32875 The corresponding @value{GDBN} command is @samp{interrupt}.
32877 @subsubheading Example
32888 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
32889 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
32890 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
32895 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
32899 @subheading The @code{-exec-jump} Command
32902 @subsubheading Synopsis
32905 -exec-jump @var{locspec}
32908 Resumes execution of the inferior program at the address to
32909 which @var{locspec} resolves. @xref{Location Specifications},
32910 for a description of the different forms of @var{locspec}.
32912 @subsubheading @value{GDBN} Command
32914 The corresponding @value{GDBN} command is @samp{jump}.
32916 @subsubheading Example
32919 -exec-jump foo.c:10
32920 *running,thread-id="all"
32925 @subheading The @code{-exec-next} Command
32928 @subsubheading Synopsis
32931 -exec-next [--reverse]
32934 Resumes execution of the inferior program, stopping when the beginning
32935 of the next source line is reached.
32937 If the @samp{--reverse} option is specified, resumes reverse execution
32938 of the inferior program, stopping at the beginning of the previous
32939 source line. If you issue this command on the first line of a
32940 function, it will take you back to the caller of that function, to the
32941 source line where the function was called.
32944 @subsubheading @value{GDBN} Command
32946 The corresponding @value{GDBN} command is @samp{next}.
32948 @subsubheading Example
32954 *stopped,reason="end-stepping-range",line="8",file="hello.c"
32959 @subheading The @code{-exec-next-instruction} Command
32960 @findex -exec-next-instruction
32962 @subsubheading Synopsis
32965 -exec-next-instruction [--reverse]
32968 Executes one machine instruction. If the instruction is a function
32969 call, continues until the function returns. If the program stops at an
32970 instruction in the middle of a source line, the address will be
32973 If the @samp{--reverse} option is specified, resumes reverse execution
32974 of the inferior program, stopping at the previous instruction. If the
32975 previously executed instruction was a return from another function,
32976 it will continue to execute in reverse until the call to that function
32977 (from the current stack frame) is reached.
32979 @subsubheading @value{GDBN} Command
32981 The corresponding @value{GDBN} command is @samp{nexti}.
32983 @subsubheading Example
32987 -exec-next-instruction
32991 *stopped,reason="end-stepping-range",
32992 addr="0x000100d4",line="5",file="hello.c"
32997 @subheading The @code{-exec-return} Command
32998 @findex -exec-return
33000 @subsubheading Synopsis
33006 Makes current function return immediately. Doesn't execute the inferior.
33007 Displays the new current frame.
33009 @subsubheading @value{GDBN} Command
33011 The corresponding @value{GDBN} command is @samp{return}.
33013 @subsubheading Example
33017 200-break-insert callee4
33018 200^done,bkpt=@{number="1",addr="0x00010734",
33019 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
33024 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
33025 frame=@{func="callee4",args=[],
33026 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33027 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
33028 arch="i386:x86_64"@}
33034 111^done,frame=@{level="0",func="callee3",
33035 args=[@{name="strarg",
33036 value="0x11940 \"A string argument.\""@}],
33037 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33038 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
33039 arch="i386:x86_64"@}
33044 @subheading The @code{-exec-run} Command
33047 @subsubheading Synopsis
33050 -exec-run [ --all | --thread-group N ] [ --start ]
33053 Starts execution of the inferior from the beginning. The inferior
33054 executes until either a breakpoint is encountered or the program
33055 exits. In the latter case the output will include an exit code, if
33056 the program has exited exceptionally.
33058 When neither the @samp{--all} nor the @samp{--thread-group} option
33059 is specified, the current inferior is started. If the
33060 @samp{--thread-group} option is specified, it should refer to a thread
33061 group of type @samp{process}, and that thread group will be started.
33062 If the @samp{--all} option is specified, then all inferiors will be started.
33064 Using the @samp{--start} option instructs the debugger to stop
33065 the execution at the start of the inferior's main subprogram,
33066 following the same behavior as the @code{start} command
33067 (@pxref{Starting}).
33069 @subsubheading @value{GDBN} Command
33071 The corresponding @value{GDBN} command is @samp{run}.
33073 @subsubheading Examples
33078 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
33083 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
33084 frame=@{func="main",args=[],file="recursive2.c",
33085 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
33090 Program exited normally:
33098 *stopped,reason="exited-normally"
33103 Program exited exceptionally:
33111 *stopped,reason="exited",exit-code="01"
33115 Another way the program can terminate is if it receives a signal such as
33116 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
33120 *stopped,reason="exited-signalled",signal-name="SIGINT",
33121 signal-meaning="Interrupt"
33125 @c @subheading -exec-signal
33128 @subheading The @code{-exec-step} Command
33131 @subsubheading Synopsis
33134 -exec-step [--reverse]
33137 Resumes execution of the inferior program, stopping when the beginning
33138 of the next source line is reached, if the next source line is not a
33139 function call. If it is, stop at the first instruction of the called
33140 function. If the @samp{--reverse} option is specified, resumes reverse
33141 execution of the inferior program, stopping at the beginning of the
33142 previously executed source line.
33144 @subsubheading @value{GDBN} Command
33146 The corresponding @value{GDBN} command is @samp{step}.
33148 @subsubheading Example
33150 Stepping into a function:
33156 *stopped,reason="end-stepping-range",
33157 frame=@{func="foo",args=[@{name="a",value="10"@},
33158 @{name="b",value="0"@}],file="recursive2.c",
33159 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
33169 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
33174 @subheading The @code{-exec-step-instruction} Command
33175 @findex -exec-step-instruction
33177 @subsubheading Synopsis
33180 -exec-step-instruction [--reverse]
33183 Resumes the inferior which executes one machine instruction. If the
33184 @samp{--reverse} option is specified, resumes reverse execution of the
33185 inferior program, stopping at the previously executed instruction.
33186 The output, once @value{GDBN} has stopped, will vary depending on
33187 whether we have stopped in the middle of a source line or not. In the
33188 former case, the address at which the program stopped will be printed
33191 @subsubheading @value{GDBN} Command
33193 The corresponding @value{GDBN} command is @samp{stepi}.
33195 @subsubheading Example
33199 -exec-step-instruction
33203 *stopped,reason="end-stepping-range",
33204 frame=@{func="foo",args=[],file="try.c",
33205 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
33207 -exec-step-instruction
33211 *stopped,reason="end-stepping-range",
33212 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
33213 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
33218 @subheading The @code{-exec-until} Command
33219 @findex -exec-until
33221 @subsubheading Synopsis
33224 -exec-until [ @var{locspec} ]
33227 Executes the inferior until it reaches the address to which
33228 @var{locspec} resolves. If there is no argument, the inferior
33229 executes until it reaches a source line greater than the current one.
33230 The reason for stopping in this case will be @samp{location-reached}.
33232 @subsubheading @value{GDBN} Command
33234 The corresponding @value{GDBN} command is @samp{until}.
33236 @subsubheading Example
33240 -exec-until recursive2.c:6
33244 *stopped,reason="location-reached",frame=@{func="main",args=[],
33245 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
33246 arch="i386:x86_64"@}
33251 @subheading -file-clear
33252 Is this going away????
33255 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33256 @node GDB/MI Stack Manipulation
33257 @section @sc{gdb/mi} Stack Manipulation Commands
33259 @subheading The @code{-enable-frame-filters} Command
33260 @findex -enable-frame-filters
33263 -enable-frame-filters
33266 @value{GDBN} allows Python-based frame filters to affect the output of
33267 the MI commands relating to stack traces. As there is no way to
33268 implement this in a fully backward-compatible way, a front end must
33269 request that this functionality be enabled.
33271 Once enabled, this feature cannot be disabled.
33273 Note that if Python support has not been compiled into @value{GDBN},
33274 this command will still succeed (and do nothing).
33276 @subheading The @code{-stack-info-frame} Command
33277 @findex -stack-info-frame
33279 @subsubheading Synopsis
33285 Get info on the selected frame.
33287 @subsubheading @value{GDBN} Command
33289 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
33290 (without arguments).
33292 @subsubheading Example
33297 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
33298 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33299 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
33300 arch="i386:x86_64"@}
33304 @subheading The @code{-stack-info-depth} Command
33305 @findex -stack-info-depth
33307 @subsubheading Synopsis
33310 -stack-info-depth [ @var{max-depth} ]
33313 Return the depth of the stack. If the integer argument @var{max-depth}
33314 is specified, do not count beyond @var{max-depth} frames.
33316 @subsubheading @value{GDBN} Command
33318 There's no equivalent @value{GDBN} command.
33320 @subsubheading Example
33322 For a stack with frame levels 0 through 11:
33329 -stack-info-depth 4
33332 -stack-info-depth 12
33335 -stack-info-depth 11
33338 -stack-info-depth 13
33343 @anchor{-stack-list-arguments}
33344 @subheading The @code{-stack-list-arguments} Command
33345 @findex -stack-list-arguments
33347 @subsubheading Synopsis
33350 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33351 [ @var{low-frame} @var{high-frame} ]
33354 Display a list of the arguments for the frames between @var{low-frame}
33355 and @var{high-frame} (inclusive). If @var{low-frame} and
33356 @var{high-frame} are not provided, list the arguments for the whole
33357 call stack. If the two arguments are equal, show the single frame
33358 at the corresponding level. It is an error if @var{low-frame} is
33359 larger than the actual number of frames. On the other hand,
33360 @var{high-frame} may be larger than the actual number of frames, in
33361 which case only existing frames will be returned.
33363 If @var{print-values} is 0 or @code{--no-values}, print only the names of
33364 the variables; if it is 1 or @code{--all-values}, print also their
33365 values; and if it is 2 or @code{--simple-values}, print the name,
33366 type and value for simple data types, and the name and type for arrays,
33367 structures and unions. If the option @code{--no-frame-filters} is
33368 supplied, then Python frame filters will not be executed.
33370 If the @code{--skip-unavailable} option is specified, arguments that
33371 are not available are not listed. Partially available arguments
33372 are still displayed, however.
33374 Use of this command to obtain arguments in a single frame is
33375 deprecated in favor of the @samp{-stack-list-variables} command.
33377 @subsubheading @value{GDBN} Command
33379 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
33380 @samp{gdb_get_args} command which partially overlaps with the
33381 functionality of @samp{-stack-list-arguments}.
33383 @subsubheading Example
33390 frame=@{level="0",addr="0x00010734",func="callee4",
33391 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33392 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
33393 arch="i386:x86_64"@},
33394 frame=@{level="1",addr="0x0001076c",func="callee3",
33395 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33396 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
33397 arch="i386:x86_64"@},
33398 frame=@{level="2",addr="0x0001078c",func="callee2",
33399 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33400 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
33401 arch="i386:x86_64"@},
33402 frame=@{level="3",addr="0x000107b4",func="callee1",
33403 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33404 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
33405 arch="i386:x86_64"@},
33406 frame=@{level="4",addr="0x000107e0",func="main",
33407 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33408 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
33409 arch="i386:x86_64"@}]
33411 -stack-list-arguments 0
33414 frame=@{level="0",args=[]@},
33415 frame=@{level="1",args=[name="strarg"]@},
33416 frame=@{level="2",args=[name="intarg",name="strarg"]@},
33417 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
33418 frame=@{level="4",args=[]@}]
33420 -stack-list-arguments 1
33423 frame=@{level="0",args=[]@},
33425 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
33426 frame=@{level="2",args=[
33427 @{name="intarg",value="2"@},
33428 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
33429 @{frame=@{level="3",args=[
33430 @{name="intarg",value="2"@},
33431 @{name="strarg",value="0x11940 \"A string argument.\""@},
33432 @{name="fltarg",value="3.5"@}]@},
33433 frame=@{level="4",args=[]@}]
33435 -stack-list-arguments 0 2 2
33436 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
33438 -stack-list-arguments 1 2 2
33439 ^done,stack-args=[frame=@{level="2",
33440 args=[@{name="intarg",value="2"@},
33441 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
33445 @c @subheading -stack-list-exception-handlers
33448 @anchor{-stack-list-frames}
33449 @subheading The @code{-stack-list-frames} Command
33450 @findex -stack-list-frames
33452 @subsubheading Synopsis
33455 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
33458 List the frames currently on the stack. For each frame it displays the
33463 The frame number, 0 being the topmost frame, i.e., the innermost function.
33465 The @code{$pc} value for that frame.
33469 File name of the source file where the function lives.
33470 @item @var{fullname}
33471 The full file name of the source file where the function lives.
33473 Line number corresponding to the @code{$pc}.
33475 The shared library where this function is defined. This is only given
33476 if the frame's function is not known.
33478 Frame's architecture.
33481 If invoked without arguments, this command prints a backtrace for the
33482 whole stack. If given two integer arguments, it shows the frames whose
33483 levels are between the two arguments (inclusive). If the two arguments
33484 are equal, it shows the single frame at the corresponding level. It is
33485 an error if @var{low-frame} is larger than the actual number of
33486 frames. On the other hand, @var{high-frame} may be larger than the
33487 actual number of frames, in which case only existing frames will be
33488 returned. If the option @code{--no-frame-filters} is supplied, then
33489 Python frame filters will not be executed.
33491 @subsubheading @value{GDBN} Command
33493 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
33495 @subsubheading Example
33497 Full stack backtrace:
33503 [frame=@{level="0",addr="0x0001076c",func="foo",
33504 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
33505 arch="i386:x86_64"@},
33506 frame=@{level="1",addr="0x000107a4",func="foo",
33507 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33508 arch="i386:x86_64"@},
33509 frame=@{level="2",addr="0x000107a4",func="foo",
33510 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33511 arch="i386:x86_64"@},
33512 frame=@{level="3",addr="0x000107a4",func="foo",
33513 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33514 arch="i386:x86_64"@},
33515 frame=@{level="4",addr="0x000107a4",func="foo",
33516 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33517 arch="i386:x86_64"@},
33518 frame=@{level="5",addr="0x000107a4",func="foo",
33519 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33520 arch="i386:x86_64"@},
33521 frame=@{level="6",addr="0x000107a4",func="foo",
33522 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33523 arch="i386:x86_64"@},
33524 frame=@{level="7",addr="0x000107a4",func="foo",
33525 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33526 arch="i386:x86_64"@},
33527 frame=@{level="8",addr="0x000107a4",func="foo",
33528 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33529 arch="i386:x86_64"@},
33530 frame=@{level="9",addr="0x000107a4",func="foo",
33531 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33532 arch="i386:x86_64"@},
33533 frame=@{level="10",addr="0x000107a4",func="foo",
33534 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33535 arch="i386:x86_64"@},
33536 frame=@{level="11",addr="0x00010738",func="main",
33537 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
33538 arch="i386:x86_64"@}]
33542 Show frames between @var{low_frame} and @var{high_frame}:
33546 -stack-list-frames 3 5
33548 [frame=@{level="3",addr="0x000107a4",func="foo",
33549 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33550 arch="i386:x86_64"@},
33551 frame=@{level="4",addr="0x000107a4",func="foo",
33552 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33553 arch="i386:x86_64"@},
33554 frame=@{level="5",addr="0x000107a4",func="foo",
33555 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33556 arch="i386:x86_64"@}]
33560 Show a single frame:
33564 -stack-list-frames 3 3
33566 [frame=@{level="3",addr="0x000107a4",func="foo",
33567 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33568 arch="i386:x86_64"@}]
33573 @subheading The @code{-stack-list-locals} Command
33574 @findex -stack-list-locals
33575 @anchor{-stack-list-locals}
33577 @subsubheading Synopsis
33580 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33583 Display the local variable names for the selected frame. If
33584 @var{print-values} is 0 or @code{--no-values}, print only the names of
33585 the variables; if it is 1 or @code{--all-values}, print also their
33586 values; and if it is 2 or @code{--simple-values}, print the name,
33587 type and value for simple data types, and the name and type for arrays,
33588 structures and unions. In this last case, a frontend can immediately
33589 display the value of simple data types and create variable objects for
33590 other data types when the user wishes to explore their values in
33591 more detail. If the option @code{--no-frame-filters} is supplied, then
33592 Python frame filters will not be executed.
33594 If the @code{--skip-unavailable} option is specified, local variables
33595 that are not available are not listed. Partially available local
33596 variables are still displayed, however.
33598 This command is deprecated in favor of the
33599 @samp{-stack-list-variables} command.
33601 @subsubheading @value{GDBN} Command
33603 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
33605 @subsubheading Example
33609 -stack-list-locals 0
33610 ^done,locals=[name="A",name="B",name="C"]
33612 -stack-list-locals --all-values
33613 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
33614 @{name="C",value="@{1, 2, 3@}"@}]
33615 -stack-list-locals --simple-values
33616 ^done,locals=[@{name="A",type="int",value="1"@},
33617 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
33621 @anchor{-stack-list-variables}
33622 @subheading The @code{-stack-list-variables} Command
33623 @findex -stack-list-variables
33625 @subsubheading Synopsis
33628 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33631 Display the names of local variables and function arguments for the selected frame. If
33632 @var{print-values} is 0 or @code{--no-values}, print only the names of
33633 the variables; if it is 1 or @code{--all-values}, print also their
33634 values; and if it is 2 or @code{--simple-values}, print the name,
33635 type and value for simple data types, and the name and type for arrays,
33636 structures and unions. If the option @code{--no-frame-filters} is
33637 supplied, then Python frame filters will not be executed.
33639 If the @code{--skip-unavailable} option is specified, local variables
33640 and arguments that are not available are not listed. Partially
33641 available arguments and local variables are still displayed, however.
33643 @subsubheading Example
33647 -stack-list-variables --thread 1 --frame 0 --all-values
33648 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
33653 @subheading The @code{-stack-select-frame} Command
33654 @findex -stack-select-frame
33656 @subsubheading Synopsis
33659 -stack-select-frame @var{framenum}
33662 Change the selected frame. Select a different frame @var{framenum} on
33665 This command in deprecated in favor of passing the @samp{--frame}
33666 option to every command.
33668 @subsubheading @value{GDBN} Command
33670 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
33671 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
33673 @subsubheading Example
33677 -stack-select-frame 2
33682 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33683 @node GDB/MI Variable Objects
33684 @section @sc{gdb/mi} Variable Objects
33688 @subheading Motivation for Variable Objects in @sc{gdb/mi}
33690 For the implementation of a variable debugger window (locals, watched
33691 expressions, etc.), we are proposing the adaptation of the existing code
33692 used by @code{Insight}.
33694 The two main reasons for that are:
33698 It has been proven in practice (it is already on its second generation).
33701 It will shorten development time (needless to say how important it is
33705 The original interface was designed to be used by Tcl code, so it was
33706 slightly changed so it could be used through @sc{gdb/mi}. This section
33707 describes the @sc{gdb/mi} operations that will be available and gives some
33708 hints about their use.
33710 @emph{Note}: In addition to the set of operations described here, we
33711 expect the @sc{gui} implementation of a variable window to require, at
33712 least, the following operations:
33715 @item @code{-gdb-show} @code{output-radix}
33716 @item @code{-stack-list-arguments}
33717 @item @code{-stack-list-locals}
33718 @item @code{-stack-select-frame}
33723 @subheading Introduction to Variable Objects
33725 @cindex variable objects in @sc{gdb/mi}
33727 Variable objects are "object-oriented" MI interface for examining and
33728 changing values of expressions. Unlike some other MI interfaces that
33729 work with expressions, variable objects are specifically designed for
33730 simple and efficient presentation in the frontend. A variable object
33731 is identified by string name. When a variable object is created, the
33732 frontend specifies the expression for that variable object. The
33733 expression can be a simple variable, or it can be an arbitrary complex
33734 expression, and can even involve CPU registers. After creating a
33735 variable object, the frontend can invoke other variable object
33736 operations---for example to obtain or change the value of a variable
33737 object, or to change display format.
33739 Variable objects have hierarchical tree structure. Any variable object
33740 that corresponds to a composite type, such as structure in C, has
33741 a number of child variable objects, for example corresponding to each
33742 element of a structure. A child variable object can itself have
33743 children, recursively. Recursion ends when we reach
33744 leaf variable objects, which always have built-in types. Child variable
33745 objects are created only by explicit request, so if a frontend
33746 is not interested in the children of a particular variable object, no
33747 child will be created.
33749 For a leaf variable object it is possible to obtain its value as a
33750 string, or set the value from a string. String value can be also
33751 obtained for a non-leaf variable object, but it's generally a string
33752 that only indicates the type of the object, and does not list its
33753 contents. Assignment to a non-leaf variable object is not allowed.
33755 A frontend does not need to read the values of all variable objects each time
33756 the program stops. Instead, MI provides an update command that lists all
33757 variable objects whose values has changed since the last update
33758 operation. This considerably reduces the amount of data that must
33759 be transferred to the frontend. As noted above, children variable
33760 objects are created on demand, and only leaf variable objects have a
33761 real value. As result, gdb will read target memory only for leaf
33762 variables that frontend has created.
33764 The automatic update is not always desirable. For example, a frontend
33765 might want to keep a value of some expression for future reference,
33766 and never update it. For another example, fetching memory is
33767 relatively slow for embedded targets, so a frontend might want
33768 to disable automatic update for the variables that are either not
33769 visible on the screen, or ``closed''. This is possible using so
33770 called ``frozen variable objects''. Such variable objects are never
33771 implicitly updated.
33773 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
33774 fixed variable object, the expression is parsed when the variable
33775 object is created, including associating identifiers to specific
33776 variables. The meaning of expression never changes. For a floating
33777 variable object the values of variables whose names appear in the
33778 expressions are re-evaluated every time in the context of the current
33779 frame. Consider this example:
33784 struct work_state state;
33791 If a fixed variable object for the @code{state} variable is created in
33792 this function, and we enter the recursive call, the variable
33793 object will report the value of @code{state} in the top-level
33794 @code{do_work} invocation. On the other hand, a floating variable
33795 object will report the value of @code{state} in the current frame.
33797 If an expression specified when creating a fixed variable object
33798 refers to a local variable, the variable object becomes bound to the
33799 thread and frame in which the variable object is created. When such
33800 variable object is updated, @value{GDBN} makes sure that the
33801 thread/frame combination the variable object is bound to still exists,
33802 and re-evaluates the variable object in context of that thread/frame.
33804 The following is the complete set of @sc{gdb/mi} operations defined to
33805 access this functionality:
33807 @multitable @columnfractions .4 .6
33808 @item @strong{Operation}
33809 @tab @strong{Description}
33811 @item @code{-enable-pretty-printing}
33812 @tab enable Python-based pretty-printing
33813 @item @code{-var-create}
33814 @tab create a variable object
33815 @item @code{-var-delete}
33816 @tab delete the variable object and/or its children
33817 @item @code{-var-set-format}
33818 @tab set the display format of this variable
33819 @item @code{-var-show-format}
33820 @tab show the display format of this variable
33821 @item @code{-var-info-num-children}
33822 @tab tells how many children this object has
33823 @item @code{-var-list-children}
33824 @tab return a list of the object's children
33825 @item @code{-var-info-type}
33826 @tab show the type of this variable object
33827 @item @code{-var-info-expression}
33828 @tab print parent-relative expression that this variable object represents
33829 @item @code{-var-info-path-expression}
33830 @tab print full expression that this variable object represents
33831 @item @code{-var-show-attributes}
33832 @tab is this variable editable? does it exist here?
33833 @item @code{-var-evaluate-expression}
33834 @tab get the value of this variable
33835 @item @code{-var-assign}
33836 @tab set the value of this variable
33837 @item @code{-var-update}
33838 @tab update the variable and its children
33839 @item @code{-var-set-frozen}
33840 @tab set frozenness attribute
33841 @item @code{-var-set-update-range}
33842 @tab set range of children to display on update
33845 In the next subsection we describe each operation in detail and suggest
33846 how it can be used.
33848 @subheading Description And Use of Operations on Variable Objects
33850 @subheading The @code{-enable-pretty-printing} Command
33851 @findex -enable-pretty-printing
33854 -enable-pretty-printing
33857 @value{GDBN} allows Python-based visualizers to affect the output of the
33858 MI variable object commands. However, because there was no way to
33859 implement this in a fully backward-compatible way, a front end must
33860 request that this functionality be enabled.
33862 Once enabled, this feature cannot be disabled.
33864 Note that if Python support has not been compiled into @value{GDBN},
33865 this command will still succeed (and do nothing).
33867 @subheading The @code{-var-create} Command
33868 @findex -var-create
33870 @subsubheading Synopsis
33873 -var-create @{@var{name} | "-"@}
33874 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
33877 This operation creates a variable object, which allows the monitoring of
33878 a variable, the result of an expression, a memory cell or a CPU
33881 The @var{name} parameter is the string by which the object can be
33882 referenced. It must be unique. If @samp{-} is specified, the varobj
33883 system will generate a string ``varNNNNNN'' automatically. It will be
33884 unique provided that one does not specify @var{name} of that format.
33885 The command fails if a duplicate name is found.
33887 The frame under which the expression should be evaluated can be
33888 specified by @var{frame-addr}. A @samp{*} indicates that the current
33889 frame should be used. A @samp{@@} indicates that a floating variable
33890 object must be created.
33892 @var{expression} is any expression valid on the current language set (must not
33893 begin with a @samp{*}), or one of the following:
33897 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
33900 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
33903 @samp{$@var{regname}} --- a CPU register name
33906 @cindex dynamic varobj
33907 A varobj's contents may be provided by a Python-based pretty-printer. In this
33908 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
33909 have slightly different semantics in some cases. If the
33910 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
33911 will never create a dynamic varobj. This ensures backward
33912 compatibility for existing clients.
33914 @subsubheading Result
33916 This operation returns attributes of the newly-created varobj. These
33921 The name of the varobj.
33924 The number of children of the varobj. This number is not necessarily
33925 reliable for a dynamic varobj. Instead, you must examine the
33926 @samp{has_more} attribute.
33929 The varobj's scalar value. For a varobj whose type is some sort of
33930 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
33931 will not be interesting.
33934 The varobj's type. This is a string representation of the type, as
33935 would be printed by the @value{GDBN} CLI. If @samp{print object}
33936 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33937 @emph{actual} (derived) type of the object is shown rather than the
33938 @emph{declared} one.
33941 If a variable object is bound to a specific thread, then this is the
33942 thread's global identifier.
33945 For a dynamic varobj, this indicates whether there appear to be any
33946 children available. For a non-dynamic varobj, this will be 0.
33949 This attribute will be present and have the value @samp{1} if the
33950 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33951 then this attribute will not be present.
33954 A dynamic varobj can supply a display hint to the front end. The
33955 value comes directly from the Python pretty-printer object's
33956 @code{display_hint} method. @xref{Pretty Printing API}.
33959 Typical output will look like this:
33962 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
33963 has_more="@var{has_more}"
33967 @subheading The @code{-var-delete} Command
33968 @findex -var-delete
33970 @subsubheading Synopsis
33973 -var-delete [ -c ] @var{name}
33976 Deletes a previously created variable object and all of its children.
33977 With the @samp{-c} option, just deletes the children.
33979 Returns an error if the object @var{name} is not found.
33982 @subheading The @code{-var-set-format} Command
33983 @findex -var-set-format
33985 @subsubheading Synopsis
33988 -var-set-format @var{name} @var{format-spec}
33991 Sets the output format for the value of the object @var{name} to be
33994 @anchor{-var-set-format}
33995 The syntax for the @var{format-spec} is as follows:
33998 @var{format-spec} @expansion{}
33999 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
34002 The natural format is the default format choosen automatically
34003 based on the variable type (like decimal for an @code{int}, hex
34004 for pointers, etc.).
34006 The zero-hexadecimal format has a representation similar to hexadecimal
34007 but with padding zeroes to the left of the value. For example, a 32-bit
34008 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
34009 zero-hexadecimal format.
34011 For a variable with children, the format is set only on the
34012 variable itself, and the children are not affected.
34014 @subheading The @code{-var-show-format} Command
34015 @findex -var-show-format
34017 @subsubheading Synopsis
34020 -var-show-format @var{name}
34023 Returns the format used to display the value of the object @var{name}.
34026 @var{format} @expansion{}
34031 @subheading The @code{-var-info-num-children} Command
34032 @findex -var-info-num-children
34034 @subsubheading Synopsis
34037 -var-info-num-children @var{name}
34040 Returns the number of children of a variable object @var{name}:
34046 Note that this number is not completely reliable for a dynamic varobj.
34047 It will return the current number of children, but more children may
34051 @subheading The @code{-var-list-children} Command
34052 @findex -var-list-children
34054 @subsubheading Synopsis
34057 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
34059 @anchor{-var-list-children}
34061 Return a list of the children of the specified variable object and
34062 create variable objects for them, if they do not already exist. With
34063 a single argument or if @var{print-values} has a value of 0 or
34064 @code{--no-values}, print only the names of the variables; if
34065 @var{print-values} is 1 or @code{--all-values}, also print their
34066 values; and if it is 2 or @code{--simple-values} print the name and
34067 value for simple data types and just the name for arrays, structures
34070 @var{from} and @var{to}, if specified, indicate the range of children
34071 to report. If @var{from} or @var{to} is less than zero, the range is
34072 reset and all children will be reported. Otherwise, children starting
34073 at @var{from} (zero-based) and up to and excluding @var{to} will be
34076 If a child range is requested, it will only affect the current call to
34077 @code{-var-list-children}, but not future calls to @code{-var-update}.
34078 For this, you must instead use @code{-var-set-update-range}. The
34079 intent of this approach is to enable a front end to implement any
34080 update approach it likes; for example, scrolling a view may cause the
34081 front end to request more children with @code{-var-list-children}, and
34082 then the front end could call @code{-var-set-update-range} with a
34083 different range to ensure that future updates are restricted to just
34086 For each child the following results are returned:
34091 Name of the variable object created for this child.
34094 The expression to be shown to the user by the front end to designate this child.
34095 For example this may be the name of a structure member.
34097 For a dynamic varobj, this value cannot be used to form an
34098 expression. There is no way to do this at all with a dynamic varobj.
34100 For C/C@t{++} structures there are several pseudo children returned to
34101 designate access qualifiers. For these pseudo children @var{exp} is
34102 @samp{public}, @samp{private}, or @samp{protected}. In this case the
34103 type and value are not present.
34105 A dynamic varobj will not report the access qualifying
34106 pseudo-children, regardless of the language. This information is not
34107 available at all with a dynamic varobj.
34110 Number of children this child has. For a dynamic varobj, this will be
34114 The type of the child. If @samp{print object}
34115 (@pxref{Print Settings, set print object}) is set to @code{on}, the
34116 @emph{actual} (derived) type of the object is shown rather than the
34117 @emph{declared} one.
34120 If values were requested, this is the value.
34123 If this variable object is associated with a thread, this is the
34124 thread's global thread id. Otherwise this result is not present.
34127 If the variable object is frozen, this variable will be present with a value of 1.
34130 A dynamic varobj can supply a display hint to the front end. The
34131 value comes directly from the Python pretty-printer object's
34132 @code{display_hint} method. @xref{Pretty Printing API}.
34135 This attribute will be present and have the value @samp{1} if the
34136 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
34137 then this attribute will not be present.
34141 The result may have its own attributes:
34145 A dynamic varobj can supply a display hint to the front end. The
34146 value comes directly from the Python pretty-printer object's
34147 @code{display_hint} method. @xref{Pretty Printing API}.
34150 This is an integer attribute which is nonzero if there are children
34151 remaining after the end of the selected range.
34154 @subsubheading Example
34158 -var-list-children n
34159 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
34160 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
34162 -var-list-children --all-values n
34163 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
34164 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
34168 @subheading The @code{-var-info-type} Command
34169 @findex -var-info-type
34171 @subsubheading Synopsis
34174 -var-info-type @var{name}
34177 Returns the type of the specified variable @var{name}. The type is
34178 returned as a string in the same format as it is output by the
34182 type=@var{typename}
34186 @subheading The @code{-var-info-expression} Command
34187 @findex -var-info-expression
34189 @subsubheading Synopsis
34192 -var-info-expression @var{name}
34195 Returns a string that is suitable for presenting this
34196 variable object in user interface. The string is generally
34197 not valid expression in the current language, and cannot be evaluated.
34199 For example, if @code{a} is an array, and variable object
34200 @code{A} was created for @code{a}, then we'll get this output:
34203 (gdb) -var-info-expression A.1
34204 ^done,lang="C",exp="1"
34208 Here, the value of @code{lang} is the language name, which can be
34209 found in @ref{Supported Languages}.
34211 Note that the output of the @code{-var-list-children} command also
34212 includes those expressions, so the @code{-var-info-expression} command
34215 @subheading The @code{-var-info-path-expression} Command
34216 @findex -var-info-path-expression
34218 @subsubheading Synopsis
34221 -var-info-path-expression @var{name}
34224 Returns an expression that can be evaluated in the current
34225 context and will yield the same value that a variable object has.
34226 Compare this with the @code{-var-info-expression} command, which
34227 result can be used only for UI presentation. Typical use of
34228 the @code{-var-info-path-expression} command is creating a
34229 watchpoint from a variable object.
34231 This command is currently not valid for children of a dynamic varobj,
34232 and will give an error when invoked on one.
34234 For example, suppose @code{C} is a C@t{++} class, derived from class
34235 @code{Base}, and that the @code{Base} class has a member called
34236 @code{m_size}. Assume a variable @code{c} is has the type of
34237 @code{C} and a variable object @code{C} was created for variable
34238 @code{c}. Then, we'll get this output:
34240 (gdb) -var-info-path-expression C.Base.public.m_size
34241 ^done,path_expr=((Base)c).m_size)
34244 @subheading The @code{-var-show-attributes} Command
34245 @findex -var-show-attributes
34247 @subsubheading Synopsis
34250 -var-show-attributes @var{name}
34253 List attributes of the specified variable object @var{name}:
34256 status=@var{attr} [ ( ,@var{attr} )* ]
34260 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
34262 @subheading The @code{-var-evaluate-expression} Command
34263 @findex -var-evaluate-expression
34265 @subsubheading Synopsis
34268 -var-evaluate-expression [-f @var{format-spec}] @var{name}
34271 Evaluates the expression that is represented by the specified variable
34272 object and returns its value as a string. The format of the string
34273 can be specified with the @samp{-f} option. The possible values of
34274 this option are the same as for @code{-var-set-format}
34275 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
34276 the current display format will be used. The current display format
34277 can be changed using the @code{-var-set-format} command.
34283 Note that one must invoke @code{-var-list-children} for a variable
34284 before the value of a child variable can be evaluated.
34286 @subheading The @code{-var-assign} Command
34287 @findex -var-assign
34289 @subsubheading Synopsis
34292 -var-assign @var{name} @var{expression}
34295 Assigns the value of @var{expression} to the variable object specified
34296 by @var{name}. The object must be @samp{editable}. If the variable's
34297 value is altered by the assign, the variable will show up in any
34298 subsequent @code{-var-update} list.
34300 @subsubheading Example
34308 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
34312 @subheading The @code{-var-update} Command
34313 @findex -var-update
34315 @subsubheading Synopsis
34318 -var-update [@var{print-values}] @{@var{name} | "*"@}
34321 Reevaluate the expressions corresponding to the variable object
34322 @var{name} and all its direct and indirect children, and return the
34323 list of variable objects whose values have changed; @var{name} must
34324 be a root variable object. Here, ``changed'' means that the result of
34325 @code{-var-evaluate-expression} before and after the
34326 @code{-var-update} is different. If @samp{*} is used as the variable
34327 object names, all existing variable objects are updated, except
34328 for frozen ones (@pxref{-var-set-frozen}). The option
34329 @var{print-values} determines whether both names and values, or just
34330 names are printed. The possible values of this option are the same
34331 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
34332 recommended to use the @samp{--all-values} option, to reduce the
34333 number of MI commands needed on each program stop.
34335 With the @samp{*} parameter, if a variable object is bound to a
34336 currently running thread, it will not be updated, without any
34339 If @code{-var-set-update-range} was previously used on a varobj, then
34340 only the selected range of children will be reported.
34342 @code{-var-update} reports all the changed varobjs in a tuple named
34345 Each item in the change list is itself a tuple holding:
34349 The name of the varobj.
34352 If values were requested for this update, then this field will be
34353 present and will hold the value of the varobj.
34356 @anchor{-var-update}
34357 This field is a string which may take one of three values:
34361 The variable object's current value is valid.
34364 The variable object does not currently hold a valid value but it may
34365 hold one in the future if its associated expression comes back into
34369 The variable object no longer holds a valid value.
34370 This can occur when the executable file being debugged has changed,
34371 either through recompilation or by using the @value{GDBN} @code{file}
34372 command. The front end should normally choose to delete these variable
34376 In the future new values may be added to this list so the front should
34377 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
34380 This is only present if the varobj is still valid. If the type
34381 changed, then this will be the string @samp{true}; otherwise it will
34384 When a varobj's type changes, its children are also likely to have
34385 become incorrect. Therefore, the varobj's children are automatically
34386 deleted when this attribute is @samp{true}. Also, the varobj's update
34387 range, when set using the @code{-var-set-update-range} command, is
34391 If the varobj's type changed, then this field will be present and will
34394 @item new_num_children
34395 For a dynamic varobj, if the number of children changed, or if the
34396 type changed, this will be the new number of children.
34398 The @samp{numchild} field in other varobj responses is generally not
34399 valid for a dynamic varobj -- it will show the number of children that
34400 @value{GDBN} knows about, but because dynamic varobjs lazily
34401 instantiate their children, this will not reflect the number of
34402 children which may be available.
34404 The @samp{new_num_children} attribute only reports changes to the
34405 number of children known by @value{GDBN}. This is the only way to
34406 detect whether an update has removed children (which necessarily can
34407 only happen at the end of the update range).
34410 The display hint, if any.
34413 This is an integer value, which will be 1 if there are more children
34414 available outside the varobj's update range.
34417 This attribute will be present and have the value @samp{1} if the
34418 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
34419 then this attribute will not be present.
34422 If new children were added to a dynamic varobj within the selected
34423 update range (as set by @code{-var-set-update-range}), then they will
34424 be listed in this attribute.
34427 @subsubheading Example
34434 -var-update --all-values var1
34435 ^done,changelist=[@{name="var1",value="3",in_scope="true",
34436 type_changed="false"@}]
34440 @subheading The @code{-var-set-frozen} Command
34441 @findex -var-set-frozen
34442 @anchor{-var-set-frozen}
34444 @subsubheading Synopsis
34447 -var-set-frozen @var{name} @var{flag}
34450 Set the frozenness flag on the variable object @var{name}. The
34451 @var{flag} parameter should be either @samp{1} to make the variable
34452 frozen or @samp{0} to make it unfrozen. If a variable object is
34453 frozen, then neither itself, nor any of its children, are
34454 implicitly updated by @code{-var-update} of
34455 a parent variable or by @code{-var-update *}. Only
34456 @code{-var-update} of the variable itself will update its value and
34457 values of its children. After a variable object is unfrozen, it is
34458 implicitly updated by all subsequent @code{-var-update} operations.
34459 Unfreezing a variable does not update it, only subsequent
34460 @code{-var-update} does.
34462 @subsubheading Example
34466 -var-set-frozen V 1
34471 @subheading The @code{-var-set-update-range} command
34472 @findex -var-set-update-range
34473 @anchor{-var-set-update-range}
34475 @subsubheading Synopsis
34478 -var-set-update-range @var{name} @var{from} @var{to}
34481 Set the range of children to be returned by future invocations of
34482 @code{-var-update}.
34484 @var{from} and @var{to} indicate the range of children to report. If
34485 @var{from} or @var{to} is less than zero, the range is reset and all
34486 children will be reported. Otherwise, children starting at @var{from}
34487 (zero-based) and up to and excluding @var{to} will be reported.
34489 @subsubheading Example
34493 -var-set-update-range V 1 2
34497 @subheading The @code{-var-set-visualizer} command
34498 @findex -var-set-visualizer
34499 @anchor{-var-set-visualizer}
34501 @subsubheading Synopsis
34504 -var-set-visualizer @var{name} @var{visualizer}
34507 Set a visualizer for the variable object @var{name}.
34509 @var{visualizer} is the visualizer to use. The special value
34510 @samp{None} means to disable any visualizer in use.
34512 If not @samp{None}, @var{visualizer} must be a Python expression.
34513 This expression must evaluate to a callable object which accepts a
34514 single argument. @value{GDBN} will call this object with the value of
34515 the varobj @var{name} as an argument (this is done so that the same
34516 Python pretty-printing code can be used for both the CLI and MI).
34517 When called, this object must return an object which conforms to the
34518 pretty-printing interface (@pxref{Pretty Printing API}).
34520 The pre-defined function @code{gdb.default_visualizer} may be used to
34521 select a visualizer by following the built-in process
34522 (@pxref{Selecting Pretty-Printers}). This is done automatically when
34523 a varobj is created, and so ordinarily is not needed.
34525 This feature is only available if Python support is enabled. The MI
34526 command @code{-list-features} (@pxref{GDB/MI Support Commands})
34527 can be used to check this.
34529 @subsubheading Example
34531 Resetting the visualizer:
34535 -var-set-visualizer V None
34539 Reselecting the default (type-based) visualizer:
34543 -var-set-visualizer V gdb.default_visualizer
34547 Suppose @code{SomeClass} is a visualizer class. A lambda expression
34548 can be used to instantiate this class for a varobj:
34552 -var-set-visualizer V "lambda val: SomeClass()"
34556 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34557 @node GDB/MI Data Manipulation
34558 @section @sc{gdb/mi} Data Manipulation
34560 @cindex data manipulation, in @sc{gdb/mi}
34561 @cindex @sc{gdb/mi}, data manipulation
34562 This section describes the @sc{gdb/mi} commands that manipulate data:
34563 examine memory and registers, evaluate expressions, etc.
34565 For details about what an addressable memory unit is,
34566 @pxref{addressable memory unit}.
34568 @c REMOVED FROM THE INTERFACE.
34569 @c @subheading -data-assign
34570 @c Change the value of a program variable. Plenty of side effects.
34571 @c @subsubheading GDB Command
34573 @c @subsubheading Example
34576 @subheading The @code{-data-disassemble} Command
34577 @findex -data-disassemble
34579 @subsubheading Synopsis
34583 [ -s @var{start-addr} -e @var{end-addr} ]
34584 | [ -a @var{addr} ]
34585 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
34593 @item @var{start-addr}
34594 is the beginning address (or @code{$pc})
34595 @item @var{end-addr}
34598 is an address anywhere within (or the name of) the function to
34599 disassemble. If an address is specified, the whole function
34600 surrounding that address will be disassembled. If a name is
34601 specified, the whole function with that name will be disassembled.
34602 @item @var{filename}
34603 is the name of the file to disassemble
34604 @item @var{linenum}
34605 is the line number to disassemble around
34607 is the number of disassembly lines to be produced. If it is -1,
34608 the whole function will be disassembled, in case no @var{end-addr} is
34609 specified. If @var{end-addr} is specified as a non-zero value, and
34610 @var{lines} is lower than the number of disassembly lines between
34611 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
34612 displayed; if @var{lines} is higher than the number of lines between
34613 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
34618 @item 0 disassembly only
34619 @item 1 mixed source and disassembly (deprecated)
34620 @item 2 disassembly with raw opcodes
34621 @item 3 mixed source and disassembly with raw opcodes (deprecated)
34622 @item 4 mixed source and disassembly
34623 @item 5 mixed source and disassembly with raw opcodes
34626 Modes 1 and 3 are deprecated. The output is ``source centric''
34627 which hasn't proved useful in practice.
34628 @xref{Machine Code}, for a discussion of the difference between
34629 @code{/m} and @code{/s} output of the @code{disassemble} command.
34632 @subsubheading Result
34634 The result of the @code{-data-disassemble} command will be a list named
34635 @samp{asm_insns}, the contents of this list depend on the @var{mode}
34636 used with the @code{-data-disassemble} command.
34638 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
34643 The address at which this instruction was disassembled.
34646 The name of the function this instruction is within.
34649 The decimal offset in bytes from the start of @samp{func-name}.
34652 The text disassembly for this @samp{address}.
34655 This field is only present for modes 2, 3 and 5. This contains the
34656 raw opcode bytes for the @samp{inst} field. The bytes are formatted
34657 as single bytes, in hex, in ascending address order, with a single
34658 space between each byte.
34662 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
34663 @samp{src_and_asm_line}, each of which has the following fields:
34667 The line number within @samp{file}.
34670 The file name from the compilation unit. This might be an absolute
34671 file name or a relative file name depending on the compile command
34675 Absolute file name of @samp{file}. It is converted to a canonical form
34676 using the source file search path
34677 (@pxref{Source Path, ,Specifying Source Directories})
34678 and after resolving all the symbolic links.
34680 If the source file is not found this field will contain the path as
34681 present in the debug information.
34683 @item line_asm_insn
34684 This is a list of tuples containing the disassembly for @samp{line} in
34685 @samp{file}. The fields of each tuple are the same as for
34686 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
34687 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
34692 Note that whatever included in the @samp{inst} field, is not
34693 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
34696 @subsubheading @value{GDBN} Command
34698 The corresponding @value{GDBN} command is @samp{disassemble}.
34700 @subsubheading Example
34702 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
34706 -data-disassemble -s $pc -e "$pc + 20" -- 0
34709 @{address="0x000107c0",func-name="main",offset="4",
34710 inst="mov 2, %o0"@},
34711 @{address="0x000107c4",func-name="main",offset="8",
34712 inst="sethi %hi(0x11800), %o2"@},
34713 @{address="0x000107c8",func-name="main",offset="12",
34714 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
34715 @{address="0x000107cc",func-name="main",offset="16",
34716 inst="sethi %hi(0x11800), %o2"@},
34717 @{address="0x000107d0",func-name="main",offset="20",
34718 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
34722 Disassemble the whole @code{main} function. Line 32 is part of
34726 -data-disassemble -f basics.c -l 32 -- 0
34728 @{address="0x000107bc",func-name="main",offset="0",
34729 inst="save %sp, -112, %sp"@},
34730 @{address="0x000107c0",func-name="main",offset="4",
34731 inst="mov 2, %o0"@},
34732 @{address="0x000107c4",func-name="main",offset="8",
34733 inst="sethi %hi(0x11800), %o2"@},
34735 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
34736 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
34740 Disassemble 3 instructions from the start of @code{main}:
34744 -data-disassemble -f basics.c -l 32 -n 3 -- 0
34746 @{address="0x000107bc",func-name="main",offset="0",
34747 inst="save %sp, -112, %sp"@},
34748 @{address="0x000107c0",func-name="main",offset="4",
34749 inst="mov 2, %o0"@},
34750 @{address="0x000107c4",func-name="main",offset="8",
34751 inst="sethi %hi(0x11800), %o2"@}]
34755 Disassemble 3 instructions from the start of @code{main} in mixed mode:
34759 -data-disassemble -f basics.c -l 32 -n 3 -- 1
34761 src_and_asm_line=@{line="31",
34762 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34763 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34764 line_asm_insn=[@{address="0x000107bc",
34765 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
34766 src_and_asm_line=@{line="32",
34767 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34768 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34769 line_asm_insn=[@{address="0x000107c0",
34770 func-name="main",offset="4",inst="mov 2, %o0"@},
34771 @{address="0x000107c4",func-name="main",offset="8",
34772 inst="sethi %hi(0x11800), %o2"@}]@}]
34777 @subheading The @code{-data-evaluate-expression} Command
34778 @findex -data-evaluate-expression
34780 @subsubheading Synopsis
34783 -data-evaluate-expression @var{expr}
34786 Evaluate @var{expr} as an expression. The expression could contain an
34787 inferior function call. The function call will execute synchronously.
34788 If the expression contains spaces, it must be enclosed in double quotes.
34790 @subsubheading @value{GDBN} Command
34792 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
34793 @samp{call}. In @code{gdbtk} only, there's a corresponding
34794 @samp{gdb_eval} command.
34796 @subsubheading Example
34798 In the following example, the numbers that precede the commands are the
34799 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
34800 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
34804 211-data-evaluate-expression A
34807 311-data-evaluate-expression &A
34808 311^done,value="0xefffeb7c"
34810 411-data-evaluate-expression A+3
34813 511-data-evaluate-expression "A + 3"
34819 @subheading The @code{-data-list-changed-registers} Command
34820 @findex -data-list-changed-registers
34822 @subsubheading Synopsis
34825 -data-list-changed-registers
34828 Display a list of the registers that have changed.
34830 @subsubheading @value{GDBN} Command
34832 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
34833 has the corresponding command @samp{gdb_changed_register_list}.
34835 @subsubheading Example
34837 On a PPC MBX board:
34845 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
34846 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
34847 line="5",arch="powerpc"@}
34849 -data-list-changed-registers
34850 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
34851 "10","11","13","14","15","16","17","18","19","20","21","22","23",
34852 "24","25","26","27","28","30","31","64","65","66","67","69"]
34857 @subheading The @code{-data-list-register-names} Command
34858 @findex -data-list-register-names
34860 @subsubheading Synopsis
34863 -data-list-register-names [ ( @var{regno} )+ ]
34866 Show a list of register names for the current target. If no arguments
34867 are given, it shows a list of the names of all the registers. If
34868 integer numbers are given as arguments, it will print a list of the
34869 names of the registers corresponding to the arguments. To ensure
34870 consistency between a register name and its number, the output list may
34871 include empty register names.
34873 @subsubheading @value{GDBN} Command
34875 @value{GDBN} does not have a command which corresponds to
34876 @samp{-data-list-register-names}. In @code{gdbtk} there is a
34877 corresponding command @samp{gdb_regnames}.
34879 @subsubheading Example
34881 For the PPC MBX board:
34884 -data-list-register-names
34885 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
34886 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
34887 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
34888 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
34889 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
34890 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
34891 "", "pc","ps","cr","lr","ctr","xer"]
34893 -data-list-register-names 1 2 3
34894 ^done,register-names=["r1","r2","r3"]
34898 @subheading The @code{-data-list-register-values} Command
34899 @findex -data-list-register-values
34901 @subsubheading Synopsis
34904 -data-list-register-values
34905 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
34908 Display the registers' contents. The format according to which the
34909 registers' contents are to be returned is given by @var{fmt}, followed
34910 by an optional list of numbers specifying the registers to display. A
34911 missing list of numbers indicates that the contents of all the
34912 registers must be returned. The @code{--skip-unavailable} option
34913 indicates that only the available registers are to be returned.
34915 Allowed formats for @var{fmt} are:
34932 @subsubheading @value{GDBN} Command
34934 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
34935 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
34937 @subsubheading Example
34939 For a PPC MBX board (note: line breaks are for readability only, they
34940 don't appear in the actual output):
34944 -data-list-register-values r 64 65
34945 ^done,register-values=[@{number="64",value="0xfe00a300"@},
34946 @{number="65",value="0x00029002"@}]
34948 -data-list-register-values x
34949 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
34950 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
34951 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
34952 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
34953 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
34954 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
34955 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
34956 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
34957 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
34958 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
34959 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
34960 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
34961 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
34962 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
34963 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
34964 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
34965 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
34966 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
34967 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
34968 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
34969 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
34970 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
34971 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
34972 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
34973 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
34974 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
34975 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
34976 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
34977 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
34978 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
34979 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
34980 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
34981 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
34982 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
34983 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
34984 @{number="69",value="0x20002b03"@}]
34989 @subheading The @code{-data-read-memory} Command
34990 @findex -data-read-memory
34992 This command is deprecated, use @code{-data-read-memory-bytes} instead.
34994 @subsubheading Synopsis
34997 -data-read-memory [ -o @var{byte-offset} ]
34998 @var{address} @var{word-format} @var{word-size}
34999 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
35006 @item @var{address}
35007 An expression specifying the address of the first memory word to be
35008 read. Complex expressions containing embedded white space should be
35009 quoted using the C convention.
35011 @item @var{word-format}
35012 The format to be used to print the memory words. The notation is the
35013 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
35016 @item @var{word-size}
35017 The size of each memory word in bytes.
35019 @item @var{nr-rows}
35020 The number of rows in the output table.
35022 @item @var{nr-cols}
35023 The number of columns in the output table.
35026 If present, indicates that each row should include an @sc{ascii} dump. The
35027 value of @var{aschar} is used as a padding character when a byte is not a
35028 member of the printable @sc{ascii} character set (printable @sc{ascii}
35029 characters are those whose code is between 32 and 126, inclusively).
35031 @item @var{byte-offset}
35032 An offset to add to the @var{address} before fetching memory.
35035 This command displays memory contents as a table of @var{nr-rows} by
35036 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
35037 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
35038 (returned as @samp{total-bytes}). Should less than the requested number
35039 of bytes be returned by the target, the missing words are identified
35040 using @samp{N/A}. The number of bytes read from the target is returned
35041 in @samp{nr-bytes} and the starting address used to read memory in
35044 The address of the next/previous row or page is available in
35045 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
35048 @subsubheading @value{GDBN} Command
35050 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
35051 @samp{gdb_get_mem} memory read command.
35053 @subsubheading Example
35055 Read six bytes of memory starting at @code{bytes+6} but then offset by
35056 @code{-6} bytes. Format as three rows of two columns. One byte per
35057 word. Display each word in hex.
35061 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
35062 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
35063 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
35064 prev-page="0x0000138a",memory=[
35065 @{addr="0x00001390",data=["0x00","0x01"]@},
35066 @{addr="0x00001392",data=["0x02","0x03"]@},
35067 @{addr="0x00001394",data=["0x04","0x05"]@}]
35071 Read two bytes of memory starting at address @code{shorts + 64} and
35072 display as a single word formatted in decimal.
35076 5-data-read-memory shorts+64 d 2 1 1
35077 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
35078 next-row="0x00001512",prev-row="0x0000150e",
35079 next-page="0x00001512",prev-page="0x0000150e",memory=[
35080 @{addr="0x00001510",data=["128"]@}]
35084 Read thirty two bytes of memory starting at @code{bytes+16} and format
35085 as eight rows of four columns. Include a string encoding with @samp{x}
35086 used as the non-printable character.
35090 4-data-read-memory bytes+16 x 1 8 4 x
35091 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
35092 next-row="0x000013c0",prev-row="0x0000139c",
35093 next-page="0x000013c0",prev-page="0x00001380",memory=[
35094 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
35095 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
35096 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
35097 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
35098 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
35099 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
35100 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
35101 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
35105 @subheading The @code{-data-read-memory-bytes} Command
35106 @findex -data-read-memory-bytes
35108 @subsubheading Synopsis
35111 -data-read-memory-bytes [ -o @var{offset} ]
35112 @var{address} @var{count}
35119 @item @var{address}
35120 An expression specifying the address of the first addressable memory unit
35121 to be read. Complex expressions containing embedded white space should be
35122 quoted using the C convention.
35125 The number of addressable memory units to read. This should be an integer
35129 The offset relative to @var{address} at which to start reading. This
35130 should be an integer literal. This option is provided so that a frontend
35131 is not required to first evaluate address and then perform address
35132 arithmetics itself.
35136 This command attempts to read all accessible memory regions in the
35137 specified range. First, all regions marked as unreadable in the memory
35138 map (if one is defined) will be skipped. @xref{Memory Region
35139 Attributes}. Second, @value{GDBN} will attempt to read the remaining
35140 regions. For each one, if reading full region results in an errors,
35141 @value{GDBN} will try to read a subset of the region.
35143 In general, every single memory unit in the region may be readable or not,
35144 and the only way to read every readable unit is to try a read at
35145 every address, which is not practical. Therefore, @value{GDBN} will
35146 attempt to read all accessible memory units at either beginning or the end
35147 of the region, using a binary division scheme. This heuristic works
35148 well for reading across a memory map boundary. Note that if a region
35149 has a readable range that is neither at the beginning or the end,
35150 @value{GDBN} will not read it.
35152 The result record (@pxref{GDB/MI Result Records}) that is output of
35153 the command includes a field named @samp{memory} whose content is a
35154 list of tuples. Each tuple represent a successfully read memory block
35155 and has the following fields:
35159 The start address of the memory block, as hexadecimal literal.
35162 The end address of the memory block, as hexadecimal literal.
35165 The offset of the memory block, as hexadecimal literal, relative to
35166 the start address passed to @code{-data-read-memory-bytes}.
35169 The contents of the memory block, in hex.
35175 @subsubheading @value{GDBN} Command
35177 The corresponding @value{GDBN} command is @samp{x}.
35179 @subsubheading Example
35183 -data-read-memory-bytes &a 10
35184 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
35186 contents="01000000020000000300"@}]
35191 @subheading The @code{-data-write-memory-bytes} Command
35192 @findex -data-write-memory-bytes
35194 @subsubheading Synopsis
35197 -data-write-memory-bytes @var{address} @var{contents}
35198 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
35205 @item @var{address}
35206 An expression specifying the address of the first addressable memory unit
35207 to be written. Complex expressions containing embedded white space should
35208 be quoted using the C convention.
35210 @item @var{contents}
35211 The hex-encoded data to write. It is an error if @var{contents} does
35212 not represent an integral number of addressable memory units.
35215 Optional argument indicating the number of addressable memory units to be
35216 written. If @var{count} is greater than @var{contents}' length,
35217 @value{GDBN} will repeatedly write @var{contents} until it fills
35218 @var{count} memory units.
35222 @subsubheading @value{GDBN} Command
35224 There's no corresponding @value{GDBN} command.
35226 @subsubheading Example
35230 -data-write-memory-bytes &a "aabbccdd"
35237 -data-write-memory-bytes &a "aabbccdd" 16e
35242 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35243 @node GDB/MI Tracepoint Commands
35244 @section @sc{gdb/mi} Tracepoint Commands
35246 The commands defined in this section implement MI support for
35247 tracepoints. For detailed introduction, see @ref{Tracepoints}.
35249 @subheading The @code{-trace-find} Command
35250 @findex -trace-find
35252 @subsubheading Synopsis
35255 -trace-find @var{mode} [@var{parameters}@dots{}]
35258 Find a trace frame using criteria defined by @var{mode} and
35259 @var{parameters}. The following table lists permissible
35260 modes and their parameters. For details of operation, see @ref{tfind}.
35265 No parameters are required. Stops examining trace frames.
35268 An integer is required as parameter. Selects tracepoint frame with
35271 @item tracepoint-number
35272 An integer is required as parameter. Finds next
35273 trace frame that corresponds to tracepoint with the specified number.
35276 An address is required as parameter. Finds
35277 next trace frame that corresponds to any tracepoint at the specified
35280 @item pc-inside-range
35281 Two addresses are required as parameters. Finds next trace
35282 frame that corresponds to a tracepoint at an address inside the
35283 specified range. Both bounds are considered to be inside the range.
35285 @item pc-outside-range
35286 Two addresses are required as parameters. Finds
35287 next trace frame that corresponds to a tracepoint at an address outside
35288 the specified range. Both bounds are considered to be inside the range.
35291 Location specification is required as parameter. @xref{Location Specifications}.
35292 Finds next trace frame that corresponds to a tracepoint at
35293 the specified location.
35297 If @samp{none} was passed as @var{mode}, the response does not
35298 have fields. Otherwise, the response may have the following fields:
35302 This field has either @samp{0} or @samp{1} as the value, depending
35303 on whether a matching tracepoint was found.
35306 The index of the found traceframe. This field is present iff
35307 the @samp{found} field has value of @samp{1}.
35310 The index of the found tracepoint. This field is present iff
35311 the @samp{found} field has value of @samp{1}.
35314 The information about the frame corresponding to the found trace
35315 frame. This field is present only if a trace frame was found.
35316 @xref{GDB/MI Frame Information}, for description of this field.
35320 @subsubheading @value{GDBN} Command
35322 The corresponding @value{GDBN} command is @samp{tfind}.
35324 @subheading -trace-define-variable
35325 @findex -trace-define-variable
35327 @subsubheading Synopsis
35330 -trace-define-variable @var{name} [ @var{value} ]
35333 Create trace variable @var{name} if it does not exist. If
35334 @var{value} is specified, sets the initial value of the specified
35335 trace variable to that value. Note that the @var{name} should start
35336 with the @samp{$} character.
35338 @subsubheading @value{GDBN} Command
35340 The corresponding @value{GDBN} command is @samp{tvariable}.
35342 @subheading The @code{-trace-frame-collected} Command
35343 @findex -trace-frame-collected
35345 @subsubheading Synopsis
35348 -trace-frame-collected
35349 [--var-print-values @var{var_pval}]
35350 [--comp-print-values @var{comp_pval}]
35351 [--registers-format @var{regformat}]
35352 [--memory-contents]
35355 This command returns the set of collected objects, register names,
35356 trace state variable names, memory ranges and computed expressions
35357 that have been collected at a particular trace frame. The optional
35358 parameters to the command affect the output format in different ways.
35359 See the output description table below for more details.
35361 The reported names can be used in the normal manner to create
35362 varobjs and inspect the objects themselves. The items returned by
35363 this command are categorized so that it is clear which is a variable,
35364 which is a register, which is a trace state variable, which is a
35365 memory range and which is a computed expression.
35367 For instance, if the actions were
35369 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
35370 collect *(int*)0xaf02bef0@@40
35374 the object collected in its entirety would be @code{myVar}. The
35375 object @code{myArray} would be partially collected, because only the
35376 element at index @code{myIndex} would be collected. The remaining
35377 objects would be computed expressions.
35379 An example output would be:
35383 -trace-frame-collected
35385 explicit-variables=[@{name="myVar",value="1"@}],
35386 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
35387 @{name="myObj.field",value="0"@},
35388 @{name="myPtr->field",value="1"@},
35389 @{name="myCount + 2",value="3"@},
35390 @{name="$tvar1 + 1",value="43970027"@}],
35391 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
35392 @{number="1",value="0x0"@},
35393 @{number="2",value="0x4"@},
35395 @{number="125",value="0x0"@}],
35396 tvars=[@{name="$tvar1",current="43970026"@}],
35397 memory=[@{address="0x0000000000602264",length="4"@},
35398 @{address="0x0000000000615bc0",length="4"@}]
35405 @item explicit-variables
35406 The set of objects that have been collected in their entirety (as
35407 opposed to collecting just a few elements of an array or a few struct
35408 members). For each object, its name and value are printed.
35409 The @code{--var-print-values} option affects how or whether the value
35410 field is output. If @var{var_pval} is 0, then print only the names;
35411 if it is 1, print also their values; and if it is 2, print the name,
35412 type and value for simple data types, and the name and type for
35413 arrays, structures and unions.
35415 @item computed-expressions
35416 The set of computed expressions that have been collected at the
35417 current trace frame. The @code{--comp-print-values} option affects
35418 this set like the @code{--var-print-values} option affects the
35419 @code{explicit-variables} set. See above.
35422 The registers that have been collected at the current trace frame.
35423 For each register collected, the name and current value are returned.
35424 The value is formatted according to the @code{--registers-format}
35425 option. See the @command{-data-list-register-values} command for a
35426 list of the allowed formats. The default is @samp{x}.
35429 The trace state variables that have been collected at the current
35430 trace frame. For each trace state variable collected, the name and
35431 current value are returned.
35434 The set of memory ranges that have been collected at the current trace
35435 frame. Its content is a list of tuples. Each tuple represents a
35436 collected memory range and has the following fields:
35440 The start address of the memory range, as hexadecimal literal.
35443 The length of the memory range, as decimal literal.
35446 The contents of the memory block, in hex. This field is only present
35447 if the @code{--memory-contents} option is specified.
35453 @subsubheading @value{GDBN} Command
35455 There is no corresponding @value{GDBN} command.
35457 @subsubheading Example
35459 @subheading -trace-list-variables
35460 @findex -trace-list-variables
35462 @subsubheading Synopsis
35465 -trace-list-variables
35468 Return a table of all defined trace variables. Each element of the
35469 table has the following fields:
35473 The name of the trace variable. This field is always present.
35476 The initial value. This is a 64-bit signed integer. This
35477 field is always present.
35480 The value the trace variable has at the moment. This is a 64-bit
35481 signed integer. This field is absent iff current value is
35482 not defined, for example if the trace was never run, or is
35487 @subsubheading @value{GDBN} Command
35489 The corresponding @value{GDBN} command is @samp{tvariables}.
35491 @subsubheading Example
35495 -trace-list-variables
35496 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
35497 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
35498 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
35499 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
35500 body=[variable=@{name="$trace_timestamp",initial="0"@}
35501 variable=@{name="$foo",initial="10",current="15"@}]@}
35505 @subheading -trace-save
35506 @findex -trace-save
35508 @subsubheading Synopsis
35511 -trace-save [ -r ] [ -ctf ] @var{filename}
35514 Saves the collected trace data to @var{filename}. Without the
35515 @samp{-r} option, the data is downloaded from the target and saved
35516 in a local file. With the @samp{-r} option the target is asked
35517 to perform the save.
35519 By default, this command will save the trace in the tfile format. You can
35520 supply the optional @samp{-ctf} argument to save it the CTF format. See
35521 @ref{Trace Files} for more information about CTF.
35523 @subsubheading @value{GDBN} Command
35525 The corresponding @value{GDBN} command is @samp{tsave}.
35528 @subheading -trace-start
35529 @findex -trace-start
35531 @subsubheading Synopsis
35537 Starts a tracing experiment. The result of this command does not
35540 @subsubheading @value{GDBN} Command
35542 The corresponding @value{GDBN} command is @samp{tstart}.
35544 @subheading -trace-status
35545 @findex -trace-status
35547 @subsubheading Synopsis
35553 Obtains the status of a tracing experiment. The result may include
35554 the following fields:
35559 May have a value of either @samp{0}, when no tracing operations are
35560 supported, @samp{1}, when all tracing operations are supported, or
35561 @samp{file} when examining trace file. In the latter case, examining
35562 of trace frame is possible but new tracing experiement cannot be
35563 started. This field is always present.
35566 May have a value of either @samp{0} or @samp{1} depending on whether
35567 tracing experiement is in progress on target. This field is present
35568 if @samp{supported} field is not @samp{0}.
35571 Report the reason why the tracing was stopped last time. This field
35572 may be absent iff tracing was never stopped on target yet. The
35573 value of @samp{request} means the tracing was stopped as result of
35574 the @code{-trace-stop} command. The value of @samp{overflow} means
35575 the tracing buffer is full. The value of @samp{disconnection} means
35576 tracing was automatically stopped when @value{GDBN} has disconnected.
35577 The value of @samp{passcount} means tracing was stopped when a
35578 tracepoint was passed a maximal number of times for that tracepoint.
35579 This field is present if @samp{supported} field is not @samp{0}.
35581 @item stopping-tracepoint
35582 The number of tracepoint whose passcount as exceeded. This field is
35583 present iff the @samp{stop-reason} field has the value of
35587 @itemx frames-created
35588 The @samp{frames} field is a count of the total number of trace frames
35589 in the trace buffer, while @samp{frames-created} is the total created
35590 during the run, including ones that were discarded, such as when a
35591 circular trace buffer filled up. Both fields are optional.
35595 These fields tell the current size of the tracing buffer and the
35596 remaining space. These fields are optional.
35599 The value of the circular trace buffer flag. @code{1} means that the
35600 trace buffer is circular and old trace frames will be discarded if
35601 necessary to make room, @code{0} means that the trace buffer is linear
35605 The value of the disconnected tracing flag. @code{1} means that
35606 tracing will continue after @value{GDBN} disconnects, @code{0} means
35607 that the trace run will stop.
35610 The filename of the trace file being examined. This field is
35611 optional, and only present when examining a trace file.
35615 @subsubheading @value{GDBN} Command
35617 The corresponding @value{GDBN} command is @samp{tstatus}.
35619 @subheading -trace-stop
35620 @findex -trace-stop
35622 @subsubheading Synopsis
35628 Stops a tracing experiment. The result of this command has the same
35629 fields as @code{-trace-status}, except that the @samp{supported} and
35630 @samp{running} fields are not output.
35632 @subsubheading @value{GDBN} Command
35634 The corresponding @value{GDBN} command is @samp{tstop}.
35637 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35638 @node GDB/MI Symbol Query
35639 @section @sc{gdb/mi} Symbol Query Commands
35643 @subheading The @code{-symbol-info-address} Command
35644 @findex -symbol-info-address
35646 @subsubheading Synopsis
35649 -symbol-info-address @var{symbol}
35652 Describe where @var{symbol} is stored.
35654 @subsubheading @value{GDBN} Command
35656 The corresponding @value{GDBN} command is @samp{info address}.
35658 @subsubheading Example
35662 @subheading The @code{-symbol-info-file} Command
35663 @findex -symbol-info-file
35665 @subsubheading Synopsis
35671 Show the file for the symbol.
35673 @subsubheading @value{GDBN} Command
35675 There's no equivalent @value{GDBN} command. @code{gdbtk} has
35676 @samp{gdb_find_file}.
35678 @subsubheading Example
35682 @subheading The @code{-symbol-info-functions} Command
35683 @findex -symbol-info-functions
35684 @anchor{-symbol-info-functions}
35686 @subsubheading Synopsis
35689 -symbol-info-functions [--include-nondebug]
35690 [--type @var{type_regexp}]
35691 [--name @var{name_regexp}]
35692 [--max-results @var{limit}]
35696 Return a list containing the names and types for all global functions
35697 taken from the debug information. The functions are grouped by source
35698 file, and shown with the line number on which each function is
35701 The @code{--include-nondebug} option causes the output to include
35702 code symbols from the symbol table.
35704 The options @code{--type} and @code{--name} allow the symbols returned
35705 to be filtered based on either the name of the function, or the type
35706 signature of the function.
35708 The option @code{--max-results} restricts the command to return no
35709 more than @var{limit} results. If exactly @var{limit} results are
35710 returned then there might be additional results available if a higher
35713 @subsubheading @value{GDBN} Command
35715 The corresponding @value{GDBN} command is @samp{info functions}.
35717 @subsubheading Example
35721 -symbol-info-functions
35724 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35725 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35726 symbols=[@{line="36", name="f4", type="void (int *)",
35727 description="void f4(int *);"@},
35728 @{line="42", name="main", type="int ()",
35729 description="int main();"@},
35730 @{line="30", name="f1", type="my_int_t (int, int)",
35731 description="static my_int_t f1(int, int);"@}]@},
35732 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35733 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35734 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35735 description="float f2(another_float_t);"@},
35736 @{line="39", name="f3", type="int (another_int_t)",
35737 description="int f3(another_int_t);"@},
35738 @{line="27", name="f1", type="another_float_t (int)",
35739 description="static another_float_t f1(int);"@}]@}]@}
35743 -symbol-info-functions --name f1
35746 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35747 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35748 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
35749 description="static my_int_t f1(int, int);"@}]@},
35750 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35751 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35752 symbols=[@{line="27", name="f1", type="another_float_t (int)",
35753 description="static another_float_t f1(int);"@}]@}]@}
35757 -symbol-info-functions --type void
35760 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35761 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35762 symbols=[@{line="36", name="f4", type="void (int *)",
35763 description="void f4(int *);"@}]@}]@}
35767 -symbol-info-functions --include-nondebug
35770 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35771 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35772 symbols=[@{line="36", name="f4", type="void (int *)",
35773 description="void f4(int *);"@},
35774 @{line="42", name="main", type="int ()",
35775 description="int main();"@},
35776 @{line="30", name="f1", type="my_int_t (int, int)",
35777 description="static my_int_t f1(int, int);"@}]@},
35778 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35779 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35780 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35781 description="float f2(another_float_t);"@},
35782 @{line="39", name="f3", type="int (another_int_t)",
35783 description="int f3(another_int_t);"@},
35784 @{line="27", name="f1", type="another_float_t (int)",
35785 description="static another_float_t f1(int);"@}]@}],
35787 [@{address="0x0000000000400398",name="_init"@},
35788 @{address="0x00000000004003b0",name="_start"@},
35794 @subheading The @code{-symbol-info-module-functions} Command
35795 @findex -symbol-info-module-functions
35796 @anchor{-symbol-info-module-functions}
35798 @subsubheading Synopsis
35801 -symbol-info-module-functions [--module @var{module_regexp}]
35802 [--name @var{name_regexp}]
35803 [--type @var{type_regexp}]
35807 Return a list containing the names of all known functions within all
35808 know Fortran modules. The functions are grouped by source file and
35809 containing module, and shown with the line number on which each
35810 function is defined.
35812 The option @code{--module} only returns results for modules matching
35813 @var{module_regexp}. The option @code{--name} only returns functions
35814 whose name matches @var{name_regexp}, and @code{--type} only returns
35815 functions whose type matches @var{type_regexp}.
35817 @subsubheading @value{GDBN} Command
35819 The corresponding @value{GDBN} command is @samp{info module functions}.
35821 @subsubheading Example
35826 -symbol-info-module-functions
35829 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35830 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35831 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
35832 description="void mod1::check_all(void);"@}]@}]@},
35834 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35835 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35836 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
35837 description="void mod2::check_var_i(void);"@}]@}]@},
35839 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35840 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35841 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
35842 description="void mod3::check_all(void);"@},
35843 @{line="27",name="mod3::check_mod2",type="void (void)",
35844 description="void mod3::check_mod2(void);"@}]@}]@},
35845 @{module="modmany",
35846 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35847 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35848 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
35849 description="void modmany::check_some(void);"@}]@}]@},
35851 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35852 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35853 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
35854 description="void moduse::check_all(void);"@},
35855 @{line="49",name="moduse::check_var_x",type="void (void)",
35856 description="void moduse::check_var_x(void);"@}]@}]@}]
35860 @subheading The @code{-symbol-info-module-variables} Command
35861 @findex -symbol-info-module-variables
35862 @anchor{-symbol-info-module-variables}
35864 @subsubheading Synopsis
35867 -symbol-info-module-variables [--module @var{module_regexp}]
35868 [--name @var{name_regexp}]
35869 [--type @var{type_regexp}]
35873 Return a list containing the names of all known variables within all
35874 know Fortran modules. The variables are grouped by source file and
35875 containing module, and shown with the line number on which each
35876 variable is defined.
35878 The option @code{--module} only returns results for modules matching
35879 @var{module_regexp}. The option @code{--name} only returns variables
35880 whose name matches @var{name_regexp}, and @code{--type} only returns
35881 variables whose type matches @var{type_regexp}.
35883 @subsubheading @value{GDBN} Command
35885 The corresponding @value{GDBN} command is @samp{info module variables}.
35887 @subsubheading Example
35892 -symbol-info-module-variables
35895 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35896 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35897 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
35898 description="integer(kind=4) mod1::var_const;"@},
35899 @{line="17",name="mod1::var_i",type="integer(kind=4)",
35900 description="integer(kind=4) mod1::var_i;"@}]@}]@},
35902 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35903 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35904 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
35905 description="integer(kind=4) mod2::var_i;"@}]@}]@},
35907 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35908 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35909 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
35910 description="integer(kind=4) mod3::mod1;"@},
35911 @{line="17",name="mod3::mod2",type="integer(kind=4)",
35912 description="integer(kind=4) mod3::mod2;"@},
35913 @{line="19",name="mod3::var_i",type="integer(kind=4)",
35914 description="integer(kind=4) mod3::var_i;"@}]@}]@},
35915 @{module="modmany",
35916 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35917 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35918 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
35919 description="integer(kind=4) modmany::var_a;"@},
35920 @{line="33",name="modmany::var_b",type="integer(kind=4)",
35921 description="integer(kind=4) modmany::var_b;"@},
35922 @{line="33",name="modmany::var_c",type="integer(kind=4)",
35923 description="integer(kind=4) modmany::var_c;"@},
35924 @{line="33",name="modmany::var_i",type="integer(kind=4)",
35925 description="integer(kind=4) modmany::var_i;"@}]@}]@},
35927 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35928 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35929 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
35930 description="integer(kind=4) moduse::var_x;"@},
35931 @{line="42",name="moduse::var_y",type="integer(kind=4)",
35932 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
35936 @subheading The @code{-symbol-info-modules} Command
35937 @findex -symbol-info-modules
35938 @anchor{-symbol-info-modules}
35940 @subsubheading Synopsis
35943 -symbol-info-modules [--name @var{name_regexp}]
35944 [--max-results @var{limit}]
35949 Return a list containing the names of all known Fortran modules. The
35950 modules are grouped by source file, and shown with the line number on
35951 which each modules is defined.
35953 The option @code{--name} allows the modules returned to be filtered
35954 based the name of the module.
35956 The option @code{--max-results} restricts the command to return no
35957 more than @var{limit} results. If exactly @var{limit} results are
35958 returned then there might be additional results available if a higher
35961 @subsubheading @value{GDBN} Command
35963 The corresponding @value{GDBN} command is @samp{info modules}.
35965 @subsubheading Example
35969 -symbol-info-modules
35972 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35973 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35974 symbols=[@{line="16",name="mod1"@},
35975 @{line="22",name="mod2"@}]@},
35976 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35977 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35978 symbols=[@{line="16",name="mod3"@},
35979 @{line="22",name="modmany"@},
35980 @{line="26",name="moduse"@}]@}]@}
35984 -symbol-info-modules --name mod[123]
35987 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35988 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35989 symbols=[@{line="16",name="mod1"@},
35990 @{line="22",name="mod2"@}]@},
35991 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35992 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35993 symbols=[@{line="16",name="mod3"@}]@}]@}
35997 @subheading The @code{-symbol-info-types} Command
35998 @findex -symbol-info-types
35999 @anchor{-symbol-info-types}
36001 @subsubheading Synopsis
36004 -symbol-info-types [--name @var{name_regexp}]
36005 [--max-results @var{limit}]
36010 Return a list of all defined types. The types are grouped by source
36011 file, and shown with the line number on which each user defined type
36012 is defined. Some base types are not defined in the source code but
36013 are added to the debug information by the compiler, for example
36014 @code{int}, @code{float}, etc.; these types do not have an associated
36017 The option @code{--name} allows the list of types returned to be
36020 The option @code{--max-results} restricts the command to return no
36021 more than @var{limit} results. If exactly @var{limit} results are
36022 returned then there might be additional results available if a higher
36025 @subsubheading @value{GDBN} Command
36027 The corresponding @value{GDBN} command is @samp{info types}.
36029 @subsubheading Example
36036 [@{filename="gdb.mi/mi-sym-info-1.c",
36037 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36038 symbols=[@{name="float"@},
36040 @{line="27",name="typedef int my_int_t;"@}]@},
36041 @{filename="gdb.mi/mi-sym-info-2.c",
36042 fullname="/project/gdb.mi/mi-sym-info-2.c",
36043 symbols=[@{line="24",name="typedef float another_float_t;"@},
36044 @{line="23",name="typedef int another_int_t;"@},
36046 @{name="int"@}]@}]@}
36050 -symbol-info-types --name _int_
36053 [@{filename="gdb.mi/mi-sym-info-1.c",
36054 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36055 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
36056 @{filename="gdb.mi/mi-sym-info-2.c",
36057 fullname="/project/gdb.mi/mi-sym-info-2.c",
36058 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
36062 @subheading The @code{-symbol-info-variables} Command
36063 @findex -symbol-info-variables
36064 @anchor{-symbol-info-variables}
36066 @subsubheading Synopsis
36069 -symbol-info-variables [--include-nondebug]
36070 [--type @var{type_regexp}]
36071 [--name @var{name_regexp}]
36072 [--max-results @var{limit}]
36077 Return a list containing the names and types for all global variables
36078 taken from the debug information. The variables are grouped by source
36079 file, and shown with the line number on which each variable is
36082 The @code{--include-nondebug} option causes the output to include
36083 data symbols from the symbol table.
36085 The options @code{--type} and @code{--name} allow the symbols returned
36086 to be filtered based on either the name of the variable, or the type
36089 The option @code{--max-results} restricts the command to return no
36090 more than @var{limit} results. If exactly @var{limit} results are
36091 returned then there might be additional results available if a higher
36094 @subsubheading @value{GDBN} Command
36096 The corresponding @value{GDBN} command is @samp{info variables}.
36098 @subsubheading Example
36102 -symbol-info-variables
36105 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36106 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36107 symbols=[@{line="25",name="global_f1",type="float",
36108 description="static float global_f1;"@},
36109 @{line="24",name="global_i1",type="int",
36110 description="static int global_i1;"@}]@},
36111 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36112 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36113 symbols=[@{line="21",name="global_f2",type="int",
36114 description="int global_f2;"@},
36115 @{line="20",name="global_i2",type="int",
36116 description="int global_i2;"@},
36117 @{line="19",name="global_f1",type="float",
36118 description="static float global_f1;"@},
36119 @{line="18",name="global_i1",type="int",
36120 description="static int global_i1;"@}]@}]@}
36124 -symbol-info-variables --name f1
36127 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36128 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36129 symbols=[@{line="25",name="global_f1",type="float",
36130 description="static float global_f1;"@}]@},
36131 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36132 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36133 symbols=[@{line="19",name="global_f1",type="float",
36134 description="static float global_f1;"@}]@}]@}
36138 -symbol-info-variables --type float
36141 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36142 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36143 symbols=[@{line="25",name="global_f1",type="float",
36144 description="static float global_f1;"@}]@},
36145 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36146 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36147 symbols=[@{line="19",name="global_f1",type="float",
36148 description="static float global_f1;"@}]@}]@}
36152 -symbol-info-variables --include-nondebug
36155 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36156 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36157 symbols=[@{line="25",name="global_f1",type="float",
36158 description="static float global_f1;"@},
36159 @{line="24",name="global_i1",type="int",
36160 description="static int global_i1;"@}]@},
36161 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36162 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36163 symbols=[@{line="21",name="global_f2",type="int",
36164 description="int global_f2;"@},
36165 @{line="20",name="global_i2",type="int",
36166 description="int global_i2;"@},
36167 @{line="19",name="global_f1",type="float",
36168 description="static float global_f1;"@},
36169 @{line="18",name="global_i1",type="int",
36170 description="static int global_i1;"@}]@}],
36172 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
36173 @{address="0x00000000004005d8",name="__dso_handle"@}
36180 @subheading The @code{-symbol-info-line} Command
36181 @findex -symbol-info-line
36183 @subsubheading Synopsis
36189 Show the core addresses of the code for a source line.
36191 @subsubheading @value{GDBN} Command
36193 The corresponding @value{GDBN} command is @samp{info line}.
36194 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
36196 @subsubheading Example
36200 @subheading The @code{-symbol-info-symbol} Command
36201 @findex -symbol-info-symbol
36203 @subsubheading Synopsis
36206 -symbol-info-symbol @var{addr}
36209 Describe what symbol is at location @var{addr}.
36211 @subsubheading @value{GDBN} Command
36213 The corresponding @value{GDBN} command is @samp{info symbol}.
36215 @subsubheading Example
36219 @subheading The @code{-symbol-list-functions} Command
36220 @findex -symbol-list-functions
36222 @subsubheading Synopsis
36225 -symbol-list-functions
36228 List the functions in the executable.
36230 @subsubheading @value{GDBN} Command
36232 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
36233 @samp{gdb_search} in @code{gdbtk}.
36235 @subsubheading Example
36240 @subheading The @code{-symbol-list-lines} Command
36241 @findex -symbol-list-lines
36243 @subsubheading Synopsis
36246 -symbol-list-lines @var{filename}
36249 Print the list of lines that contain code and their associated program
36250 addresses for the given source filename. The entries are sorted in
36251 ascending PC order.
36253 @subsubheading @value{GDBN} Command
36255 There is no corresponding @value{GDBN} command.
36257 @subsubheading Example
36260 -symbol-list-lines basics.c
36261 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
36267 @subheading The @code{-symbol-list-types} Command
36268 @findex -symbol-list-types
36270 @subsubheading Synopsis
36276 List all the type names.
36278 @subsubheading @value{GDBN} Command
36280 The corresponding commands are @samp{info types} in @value{GDBN},
36281 @samp{gdb_search} in @code{gdbtk}.
36283 @subsubheading Example
36287 @subheading The @code{-symbol-list-variables} Command
36288 @findex -symbol-list-variables
36290 @subsubheading Synopsis
36293 -symbol-list-variables
36296 List all the global and static variable names.
36298 @subsubheading @value{GDBN} Command
36300 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
36302 @subsubheading Example
36306 @subheading The @code{-symbol-locate} Command
36307 @findex -symbol-locate
36309 @subsubheading Synopsis
36315 @subsubheading @value{GDBN} Command
36317 @samp{gdb_loc} in @code{gdbtk}.
36319 @subsubheading Example
36323 @subheading The @code{-symbol-type} Command
36324 @findex -symbol-type
36326 @subsubheading Synopsis
36329 -symbol-type @var{variable}
36332 Show type of @var{variable}.
36334 @subsubheading @value{GDBN} Command
36336 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
36337 @samp{gdb_obj_variable}.
36339 @subsubheading Example
36344 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36345 @node GDB/MI File Commands
36346 @section @sc{gdb/mi} File Commands
36348 This section describes the GDB/MI commands to specify executable file names
36349 and to read in and obtain symbol table information.
36351 @subheading The @code{-file-exec-and-symbols} Command
36352 @findex -file-exec-and-symbols
36354 @subsubheading Synopsis
36357 -file-exec-and-symbols @var{file}
36360 Specify the executable file to be debugged. This file is the one from
36361 which the symbol table is also read. If no file is specified, the
36362 command clears the executable and symbol information. If breakpoints
36363 are set when using this command with no arguments, @value{GDBN} will produce
36364 error messages. Otherwise, no output is produced, except a completion
36367 @subsubheading @value{GDBN} Command
36369 The corresponding @value{GDBN} command is @samp{file}.
36371 @subsubheading Example
36375 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36381 @subheading The @code{-file-exec-file} Command
36382 @findex -file-exec-file
36384 @subsubheading Synopsis
36387 -file-exec-file @var{file}
36390 Specify the executable file to be debugged. Unlike
36391 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
36392 from this file. If used without argument, @value{GDBN} clears the information
36393 about the executable file. No output is produced, except a completion
36396 @subsubheading @value{GDBN} Command
36398 The corresponding @value{GDBN} command is @samp{exec-file}.
36400 @subsubheading Example
36404 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36411 @subheading The @code{-file-list-exec-sections} Command
36412 @findex -file-list-exec-sections
36414 @subsubheading Synopsis
36417 -file-list-exec-sections
36420 List the sections of the current executable file.
36422 @subsubheading @value{GDBN} Command
36424 The @value{GDBN} command @samp{info file} shows, among the rest, the same
36425 information as this command. @code{gdbtk} has a corresponding command
36426 @samp{gdb_load_info}.
36428 @subsubheading Example
36433 @subheading The @code{-file-list-exec-source-file} Command
36434 @findex -file-list-exec-source-file
36436 @subsubheading Synopsis
36439 -file-list-exec-source-file
36442 List the line number, the current source file, and the absolute path
36443 to the current source file for the current executable. The macro
36444 information field has a value of @samp{1} or @samp{0} depending on
36445 whether or not the file includes preprocessor macro information.
36447 @subsubheading @value{GDBN} Command
36449 The @value{GDBN} equivalent is @samp{info source}
36451 @subsubheading Example
36455 123-file-list-exec-source-file
36456 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
36461 @subheading The @code{-file-list-exec-source-files} Command
36462 @kindex info sources
36463 @findex -file-list-exec-source-files
36465 @subsubheading Synopsis
36468 -file-list-exec-source-files @r{[} @var{--group-by-objfile} @r{]}
36469 @r{[} @var{--dirname} @r{|} @var{--basename} @r{]}
36471 @r{[} @var{regexp} @r{]}
36474 This command returns information about the source files @value{GDBN}
36475 knows about, it will output both the filename and fullname (absolute
36476 file name) of a source file, though the fullname can be elided if this
36477 information is not known to @value{GDBN}.
36479 With no arguments this command returns a list of source files. Each
36480 source file is represented by a tuple with the fields; @var{file},
36481 @var{fullname}, and @var{debug-fully-read}. The @var{file} is the
36482 display name for the file, while @var{fullname} is the absolute name
36483 of the file. The @var{fullname} field can be elided if the absolute
36484 name of the source file can't be computed. The field
36485 @var{debug-fully-read} will be a string, either @code{true} or
36486 @code{false}. When @code{true}, this indicates the full debug
36487 information for the compilation unit describing this file has been
36488 read in. When @code{false}, the full debug information has not yet
36489 been read in. While reading in the full debug information it is
36490 possible that @value{GDBN} could become aware of additional source
36493 The optional @var{regexp} can be used to filter the list of source
36494 files returned. The @var{regexp} will be matched against the full
36495 source file name. The matching is case-sensitive, except on operating
36496 systems that have case-insensitive filesystem (e.g.,
36497 MS-Windows). @samp{--} can be used before @var{regexp} to prevent
36498 @value{GDBN} interpreting @var{regexp} as a command option (e.g.@: if
36499 @var{regexp} starts with @samp{-}).
36501 If @code{--dirname} is provided, then @var{regexp} is matched only
36502 against the directory name of each source file. If @code{--basename}
36503 is provided, then @var{regexp} is matched against the basename of each
36504 source file. Only one of @code{--dirname} or @code{--basename} may be
36505 given, and if either is given then @var{regexp} is required.
36507 If @code{--group-by-objfile} is used then the format of the results is
36508 changed. The results will now be a list of tuples, with each tuple
36509 representing an object file (executable or shared library) loaded into
36510 @value{GDBN}. The fields of these tuples are; @var{filename},
36511 @var{debug-info}, and @var{sources}. The @var{filename} is the
36512 absolute name of the object file, @var{debug-info} is a string with
36513 one of the following values:
36517 This object file has no debug information.
36518 @item partially-read
36519 This object file has debug information, but it is not fully read in
36520 yet. When it is read in later, GDB might become aware of additional
36523 This object file has debug information, and this information is fully
36524 read into GDB. The list of source files is complete.
36527 The @var{sources} is a list or tuples, with each tuple describing a
36528 single source file with the same fields as described previously. The
36529 @var{sources} list can be empty for object files that have no debug
36532 @subsubheading @value{GDBN} Command
36534 The @value{GDBN} equivalent is @samp{info sources}.
36535 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
36537 @subsubheading Example
36540 -file-list-exec-source-files
36541 ^done,files=[@{file="foo.c",fullname="/home/foo.c",debug-fully-read="true"@},
36542 @{file="/home/bar.c",fullname="/home/bar.c",debug-fully-read="true"@},
36543 @{file="gdb_could_not_find_fullpath.c",debug-fully-read="true"@}]
36545 -file-list-exec-source-files
36546 ^done,files=[@{file="test.c",
36547 fullname="/tmp/info-sources/test.c",
36548 debug-fully-read="true"@},
36549 @{file="/usr/include/stdc-predef.h",
36550 fullname="/usr/include/stdc-predef.h",
36551 debug-fully-read="true"@},
36553 fullname="/tmp/info-sources/header.h",
36554 debug-fully-read="true"@},
36556 fullname="/tmp/info-sources/helper.c",
36557 debug-fully-read="true"@}]
36559 -file-list-exec-source-files -- \\.c
36560 ^done,files=[@{file="test.c",
36561 fullname="/tmp/info-sources/test.c",
36562 debug-fully-read="true"@},
36564 fullname="/tmp/info-sources/helper.c",
36565 debug-fully-read="true"@}]
36567 -file-list-exec-source-files --group-by-objfile
36568 ^done,files=[@{filename="/tmp/info-sources/test.x",
36569 debug-info="fully-read",
36570 sources=[@{file="test.c",
36571 fullname="/tmp/info-sources/test.c",
36572 debug-fully-read="true"@},
36573 @{file="/usr/include/stdc-predef.h",
36574 fullname="/usr/include/stdc-predef.h",
36575 debug-fully-read="true"@},
36577 fullname="/tmp/info-sources/header.h",
36578 debug-fully-read="true"@}]@},
36579 @{filename="/lib64/ld-linux-x86-64.so.2",
36582 @{filename="system-supplied DSO at 0x7ffff7fcf000",
36585 @{filename="/tmp/info-sources/libhelper.so",
36586 debug-info="fully-read",
36587 sources=[@{file="helper.c",
36588 fullname="/tmp/info-sources/helper.c",
36589 debug-fully-read="true"@},
36590 @{file="/usr/include/stdc-predef.h",
36591 fullname="/usr/include/stdc-predef.h",
36592 debug-fully-read="true"@},
36594 fullname="/tmp/info-sources/header.h",
36595 debug-fully-read="true"@}]@},
36596 @{filename="/lib64/libc.so.6",
36601 @subheading The @code{-file-list-shared-libraries} Command
36602 @findex -file-list-shared-libraries
36604 @subsubheading Synopsis
36607 -file-list-shared-libraries [ @var{regexp} ]
36610 List the shared libraries in the program.
36611 With a regular expression @var{regexp}, only those libraries whose
36612 names match @var{regexp} are listed.
36614 @subsubheading @value{GDBN} Command
36616 The corresponding @value{GDBN} command is @samp{info shared}. The fields
36617 have a similar meaning to the @code{=library-loaded} notification.
36618 The @code{ranges} field specifies the multiple segments belonging to this
36619 library. Each range has the following fields:
36623 The address defining the inclusive lower bound of the segment.
36625 The address defining the exclusive upper bound of the segment.
36628 @subsubheading Example
36631 -file-list-exec-source-files
36632 ^done,shared-libraries=[
36633 @{id="/lib/libfoo.so",target-name="/lib/libfoo.so",host-name="/lib/libfoo.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x72815989",to="0x728162c0"@}]@},
36634 @{id="/lib/libbar.so",target-name="/lib/libbar.so",host-name="/lib/libbar.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x76ee48c0",to="0x76ee9160"@}]@}]
36640 @subheading The @code{-file-list-symbol-files} Command
36641 @findex -file-list-symbol-files
36643 @subsubheading Synopsis
36646 -file-list-symbol-files
36651 @subsubheading @value{GDBN} Command
36653 The corresponding @value{GDBN} command is @samp{info file} (part of it).
36655 @subsubheading Example
36660 @subheading The @code{-file-symbol-file} Command
36661 @findex -file-symbol-file
36663 @subsubheading Synopsis
36666 -file-symbol-file @var{file}
36669 Read symbol table info from the specified @var{file} argument. When
36670 used without arguments, clears @value{GDBN}'s symbol table info. No output is
36671 produced, except for a completion notification.
36673 @subsubheading @value{GDBN} Command
36675 The corresponding @value{GDBN} command is @samp{symbol-file}.
36677 @subsubheading Example
36681 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36687 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36688 @node GDB/MI Memory Overlay Commands
36689 @section @sc{gdb/mi} Memory Overlay Commands
36691 The memory overlay commands are not implemented.
36693 @c @subheading -overlay-auto
36695 @c @subheading -overlay-list-mapping-state
36697 @c @subheading -overlay-list-overlays
36699 @c @subheading -overlay-map
36701 @c @subheading -overlay-off
36703 @c @subheading -overlay-on
36705 @c @subheading -overlay-unmap
36707 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36708 @node GDB/MI Signal Handling Commands
36709 @section @sc{gdb/mi} Signal Handling Commands
36711 Signal handling commands are not implemented.
36713 @c @subheading -signal-handle
36715 @c @subheading -signal-list-handle-actions
36717 @c @subheading -signal-list-signal-types
36721 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36722 @node GDB/MI Target Manipulation
36723 @section @sc{gdb/mi} Target Manipulation Commands
36726 @subheading The @code{-target-attach} Command
36727 @findex -target-attach
36729 @subsubheading Synopsis
36732 -target-attach @var{pid} | @var{gid} | @var{file}
36735 Attach to a process @var{pid} or a file @var{file} outside of
36736 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
36737 group, the id previously returned by
36738 @samp{-list-thread-groups --available} must be used.
36740 @subsubheading @value{GDBN} Command
36742 The corresponding @value{GDBN} command is @samp{attach}.
36744 @subsubheading Example
36748 =thread-created,id="1"
36749 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
36755 @subheading The @code{-target-compare-sections} Command
36756 @findex -target-compare-sections
36758 @subsubheading Synopsis
36761 -target-compare-sections [ @var{section} ]
36764 Compare data of section @var{section} on target to the exec file.
36765 Without the argument, all sections are compared.
36767 @subsubheading @value{GDBN} Command
36769 The @value{GDBN} equivalent is @samp{compare-sections}.
36771 @subsubheading Example
36776 @subheading The @code{-target-detach} Command
36777 @findex -target-detach
36779 @subsubheading Synopsis
36782 -target-detach [ @var{pid} | @var{gid} ]
36785 Detach from the remote target which normally resumes its execution.
36786 If either @var{pid} or @var{gid} is specified, detaches from either
36787 the specified process, or specified thread group. There's no output.
36789 @subsubheading @value{GDBN} Command
36791 The corresponding @value{GDBN} command is @samp{detach}.
36793 @subsubheading Example
36803 @subheading The @code{-target-disconnect} Command
36804 @findex -target-disconnect
36806 @subsubheading Synopsis
36812 Disconnect from the remote target. There's no output and the target is
36813 generally not resumed.
36815 @subsubheading @value{GDBN} Command
36817 The corresponding @value{GDBN} command is @samp{disconnect}.
36819 @subsubheading Example
36829 @subheading The @code{-target-download} Command
36830 @findex -target-download
36832 @subsubheading Synopsis
36838 Loads the executable onto the remote target.
36839 It prints out an update message every half second, which includes the fields:
36843 The name of the section.
36845 The size of what has been sent so far for that section.
36847 The size of the section.
36849 The total size of what was sent so far (the current and the previous sections).
36851 The size of the overall executable to download.
36855 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
36856 @sc{gdb/mi} Output Syntax}).
36858 In addition, it prints the name and size of the sections, as they are
36859 downloaded. These messages include the following fields:
36863 The name of the section.
36865 The size of the section.
36867 The size of the overall executable to download.
36871 At the end, a summary is printed.
36873 @subsubheading @value{GDBN} Command
36875 The corresponding @value{GDBN} command is @samp{load}.
36877 @subsubheading Example
36879 Note: each status message appears on a single line. Here the messages
36880 have been broken down so that they can fit onto a page.
36885 +download,@{section=".text",section-size="6668",total-size="9880"@}
36886 +download,@{section=".text",section-sent="512",section-size="6668",
36887 total-sent="512",total-size="9880"@}
36888 +download,@{section=".text",section-sent="1024",section-size="6668",
36889 total-sent="1024",total-size="9880"@}
36890 +download,@{section=".text",section-sent="1536",section-size="6668",
36891 total-sent="1536",total-size="9880"@}
36892 +download,@{section=".text",section-sent="2048",section-size="6668",
36893 total-sent="2048",total-size="9880"@}
36894 +download,@{section=".text",section-sent="2560",section-size="6668",
36895 total-sent="2560",total-size="9880"@}
36896 +download,@{section=".text",section-sent="3072",section-size="6668",
36897 total-sent="3072",total-size="9880"@}
36898 +download,@{section=".text",section-sent="3584",section-size="6668",
36899 total-sent="3584",total-size="9880"@}
36900 +download,@{section=".text",section-sent="4096",section-size="6668",
36901 total-sent="4096",total-size="9880"@}
36902 +download,@{section=".text",section-sent="4608",section-size="6668",
36903 total-sent="4608",total-size="9880"@}
36904 +download,@{section=".text",section-sent="5120",section-size="6668",
36905 total-sent="5120",total-size="9880"@}
36906 +download,@{section=".text",section-sent="5632",section-size="6668",
36907 total-sent="5632",total-size="9880"@}
36908 +download,@{section=".text",section-sent="6144",section-size="6668",
36909 total-sent="6144",total-size="9880"@}
36910 +download,@{section=".text",section-sent="6656",section-size="6668",
36911 total-sent="6656",total-size="9880"@}
36912 +download,@{section=".init",section-size="28",total-size="9880"@}
36913 +download,@{section=".fini",section-size="28",total-size="9880"@}
36914 +download,@{section=".data",section-size="3156",total-size="9880"@}
36915 +download,@{section=".data",section-sent="512",section-size="3156",
36916 total-sent="7236",total-size="9880"@}
36917 +download,@{section=".data",section-sent="1024",section-size="3156",
36918 total-sent="7748",total-size="9880"@}
36919 +download,@{section=".data",section-sent="1536",section-size="3156",
36920 total-sent="8260",total-size="9880"@}
36921 +download,@{section=".data",section-sent="2048",section-size="3156",
36922 total-sent="8772",total-size="9880"@}
36923 +download,@{section=".data",section-sent="2560",section-size="3156",
36924 total-sent="9284",total-size="9880"@}
36925 +download,@{section=".data",section-sent="3072",section-size="3156",
36926 total-sent="9796",total-size="9880"@}
36927 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
36934 @subheading The @code{-target-exec-status} Command
36935 @findex -target-exec-status
36937 @subsubheading Synopsis
36940 -target-exec-status
36943 Provide information on the state of the target (whether it is running or
36944 not, for instance).
36946 @subsubheading @value{GDBN} Command
36948 There's no equivalent @value{GDBN} command.
36950 @subsubheading Example
36954 @subheading The @code{-target-list-available-targets} Command
36955 @findex -target-list-available-targets
36957 @subsubheading Synopsis
36960 -target-list-available-targets
36963 List the possible targets to connect to.
36965 @subsubheading @value{GDBN} Command
36967 The corresponding @value{GDBN} command is @samp{help target}.
36969 @subsubheading Example
36973 @subheading The @code{-target-list-current-targets} Command
36974 @findex -target-list-current-targets
36976 @subsubheading Synopsis
36979 -target-list-current-targets
36982 Describe the current target.
36984 @subsubheading @value{GDBN} Command
36986 The corresponding information is printed by @samp{info file} (among
36989 @subsubheading Example
36993 @subheading The @code{-target-list-parameters} Command
36994 @findex -target-list-parameters
36996 @subsubheading Synopsis
36999 -target-list-parameters
37005 @subsubheading @value{GDBN} Command
37009 @subsubheading Example
37012 @subheading The @code{-target-flash-erase} Command
37013 @findex -target-flash-erase
37015 @subsubheading Synopsis
37018 -target-flash-erase
37021 Erases all known flash memory regions on the target.
37023 The corresponding @value{GDBN} command is @samp{flash-erase}.
37025 The output is a list of flash regions that have been erased, with starting
37026 addresses and memory region sizes.
37030 -target-flash-erase
37031 ^done,erased-regions=@{address="0x0",size="0x40000"@}
37035 @subheading The @code{-target-select} Command
37036 @findex -target-select
37038 @subsubheading Synopsis
37041 -target-select @var{type} @var{parameters @dots{}}
37044 Connect @value{GDBN} to the remote target. This command takes two args:
37048 The type of target, for instance @samp{remote}, etc.
37049 @item @var{parameters}
37050 Device names, host names and the like. @xref{Target Commands, ,
37051 Commands for Managing Targets}, for more details.
37054 The output is a connection notification, followed by the address at
37055 which the target program is, in the following form:
37058 ^connected,addr="@var{address}",func="@var{function name}",
37059 args=[@var{arg list}]
37062 @subsubheading @value{GDBN} Command
37064 The corresponding @value{GDBN} command is @samp{target}.
37066 @subsubheading Example
37070 -target-select remote /dev/ttya
37071 ^connected,addr="0xfe00a300",func="??",args=[]
37075 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37076 @node GDB/MI File Transfer Commands
37077 @section @sc{gdb/mi} File Transfer Commands
37080 @subheading The @code{-target-file-put} Command
37081 @findex -target-file-put
37083 @subsubheading Synopsis
37086 -target-file-put @var{hostfile} @var{targetfile}
37089 Copy file @var{hostfile} from the host system (the machine running
37090 @value{GDBN}) to @var{targetfile} on the target system.
37092 @subsubheading @value{GDBN} Command
37094 The corresponding @value{GDBN} command is @samp{remote put}.
37096 @subsubheading Example
37100 -target-file-put localfile remotefile
37106 @subheading The @code{-target-file-get} Command
37107 @findex -target-file-get
37109 @subsubheading Synopsis
37112 -target-file-get @var{targetfile} @var{hostfile}
37115 Copy file @var{targetfile} from the target system to @var{hostfile}
37116 on the host system.
37118 @subsubheading @value{GDBN} Command
37120 The corresponding @value{GDBN} command is @samp{remote get}.
37122 @subsubheading Example
37126 -target-file-get remotefile localfile
37132 @subheading The @code{-target-file-delete} Command
37133 @findex -target-file-delete
37135 @subsubheading Synopsis
37138 -target-file-delete @var{targetfile}
37141 Delete @var{targetfile} from the target system.
37143 @subsubheading @value{GDBN} Command
37145 The corresponding @value{GDBN} command is @samp{remote delete}.
37147 @subsubheading Example
37151 -target-file-delete remotefile
37157 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37158 @node GDB/MI Ada Exceptions Commands
37159 @section Ada Exceptions @sc{gdb/mi} Commands
37161 @subheading The @code{-info-ada-exceptions} Command
37162 @findex -info-ada-exceptions
37164 @subsubheading Synopsis
37167 -info-ada-exceptions [ @var{regexp}]
37170 List all Ada exceptions defined within the program being debugged.
37171 With a regular expression @var{regexp}, only those exceptions whose
37172 names match @var{regexp} are listed.
37174 @subsubheading @value{GDBN} Command
37176 The corresponding @value{GDBN} command is @samp{info exceptions}.
37178 @subsubheading Result
37180 The result is a table of Ada exceptions. The following columns are
37181 defined for each exception:
37185 The name of the exception.
37188 The address of the exception.
37192 @subsubheading Example
37195 -info-ada-exceptions aint
37196 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
37197 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
37198 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
37199 body=[@{name="constraint_error",address="0x0000000000613da0"@},
37200 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
37203 @subheading Catching Ada Exceptions
37205 The commands describing how to ask @value{GDBN} to stop when a program
37206 raises an exception are described at @ref{Ada Exception GDB/MI
37207 Catchpoint Commands}.
37210 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37211 @node GDB/MI Support Commands
37212 @section @sc{gdb/mi} Support Commands
37214 Since new commands and features get regularly added to @sc{gdb/mi},
37215 some commands are available to help front-ends query the debugger
37216 about support for these capabilities. Similarly, it is also possible
37217 to query @value{GDBN} about target support of certain features.
37219 @subheading The @code{-info-gdb-mi-command} Command
37220 @cindex @code{-info-gdb-mi-command}
37221 @findex -info-gdb-mi-command
37223 @subsubheading Synopsis
37226 -info-gdb-mi-command @var{cmd_name}
37229 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
37231 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
37232 is technically not part of the command name (@pxref{GDB/MI Input
37233 Syntax}), and thus should be omitted in @var{cmd_name}. However,
37234 for ease of use, this command also accepts the form with the leading
37237 @subsubheading @value{GDBN} Command
37239 There is no corresponding @value{GDBN} command.
37241 @subsubheading Result
37243 The result is a tuple. There is currently only one field:
37247 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
37248 @code{"false"} otherwise.
37252 @subsubheading Example
37254 Here is an example where the @sc{gdb/mi} command does not exist:
37257 -info-gdb-mi-command unsupported-command
37258 ^done,command=@{exists="false"@}
37262 And here is an example where the @sc{gdb/mi} command is known
37266 -info-gdb-mi-command symbol-list-lines
37267 ^done,command=@{exists="true"@}
37270 @subheading The @code{-list-features} Command
37271 @findex -list-features
37272 @cindex supported @sc{gdb/mi} features, list
37274 Returns a list of particular features of the MI protocol that
37275 this version of gdb implements. A feature can be a command,
37276 or a new field in an output of some command, or even an
37277 important bugfix. While a frontend can sometimes detect presence
37278 of a feature at runtime, it is easier to perform detection at debugger
37281 The command returns a list of strings, with each string naming an
37282 available feature. Each returned string is just a name, it does not
37283 have any internal structure. The list of possible feature names
37289 (gdb) -list-features
37290 ^done,result=["feature1","feature2"]
37293 The current list of features is:
37296 @item frozen-varobjs
37297 Indicates support for the @code{-var-set-frozen} command, as well
37298 as possible presence of the @code{frozen} field in the output
37299 of @code{-varobj-create}.
37300 @item pending-breakpoints
37301 Indicates support for the @option{-f} option to the @code{-break-insert}
37304 Indicates Python scripting support, Python-based
37305 pretty-printing commands, and possible presence of the
37306 @samp{display_hint} field in the output of @code{-var-list-children}
37308 Indicates support for the @code{-thread-info} command.
37309 @item data-read-memory-bytes
37310 Indicates support for the @code{-data-read-memory-bytes} and the
37311 @code{-data-write-memory-bytes} commands.
37312 @item breakpoint-notifications
37313 Indicates that changes to breakpoints and breakpoints created via the
37314 CLI will be announced via async records.
37315 @item ada-task-info
37316 Indicates support for the @code{-ada-task-info} command.
37317 @item language-option
37318 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
37319 option (@pxref{Context management}).
37320 @item info-gdb-mi-command
37321 Indicates support for the @code{-info-gdb-mi-command} command.
37322 @item undefined-command-error-code
37323 Indicates support for the "undefined-command" error code in error result
37324 records, produced when trying to execute an undefined @sc{gdb/mi} command
37325 (@pxref{GDB/MI Result Records}).
37326 @item exec-run-start-option
37327 Indicates that the @code{-exec-run} command supports the @option{--start}
37328 option (@pxref{GDB/MI Program Execution}).
37329 @item data-disassemble-a-option
37330 Indicates that the @code{-data-disassemble} command supports the @option{-a}
37331 option (@pxref{GDB/MI Data Manipulation}).
37334 @subheading The @code{-list-target-features} Command
37335 @findex -list-target-features
37337 Returns a list of particular features that are supported by the
37338 target. Those features affect the permitted MI commands, but
37339 unlike the features reported by the @code{-list-features} command, the
37340 features depend on which target GDB is using at the moment. Whenever
37341 a target can change, due to commands such as @code{-target-select},
37342 @code{-target-attach} or @code{-exec-run}, the list of target features
37343 may change, and the frontend should obtain it again.
37347 (gdb) -list-target-features
37348 ^done,result=["async"]
37351 The current list of features is:
37355 Indicates that the target is capable of asynchronous command
37356 execution, which means that @value{GDBN} will accept further commands
37357 while the target is running.
37360 Indicates that the target is capable of reverse execution.
37361 @xref{Reverse Execution}, for more information.
37365 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37366 @node GDB/MI Miscellaneous Commands
37367 @section Miscellaneous @sc{gdb/mi} Commands
37369 @c @subheading -gdb-complete
37371 @subheading The @code{-gdb-exit} Command
37374 @subsubheading Synopsis
37380 Exit @value{GDBN} immediately.
37382 @subsubheading @value{GDBN} Command
37384 Approximately corresponds to @samp{quit}.
37386 @subsubheading Example
37396 @subheading The @code{-exec-abort} Command
37397 @findex -exec-abort
37399 @subsubheading Synopsis
37405 Kill the inferior running program.
37407 @subsubheading @value{GDBN} Command
37409 The corresponding @value{GDBN} command is @samp{kill}.
37411 @subsubheading Example
37416 @subheading The @code{-gdb-set} Command
37419 @subsubheading Synopsis
37425 Set an internal @value{GDBN} variable.
37426 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
37428 @subsubheading @value{GDBN} Command
37430 The corresponding @value{GDBN} command is @samp{set}.
37432 @subsubheading Example
37442 @subheading The @code{-gdb-show} Command
37445 @subsubheading Synopsis
37451 Show the current value of a @value{GDBN} variable.
37453 @subsubheading @value{GDBN} Command
37455 The corresponding @value{GDBN} command is @samp{show}.
37457 @subsubheading Example
37466 @c @subheading -gdb-source
37469 @subheading The @code{-gdb-version} Command
37470 @findex -gdb-version
37472 @subsubheading Synopsis
37478 Show version information for @value{GDBN}. Used mostly in testing.
37480 @subsubheading @value{GDBN} Command
37482 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
37483 default shows this information when you start an interactive session.
37485 @subsubheading Example
37487 @c This example modifies the actual output from GDB to avoid overfull
37493 ~Copyright 2000 Free Software Foundation, Inc.
37494 ~GDB is free software, covered by the GNU General Public License, and
37495 ~you are welcome to change it and/or distribute copies of it under
37496 ~ certain conditions.
37497 ~Type "show copying" to see the conditions.
37498 ~There is absolutely no warranty for GDB. Type "show warranty" for
37500 ~This GDB was configured as
37501 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
37506 @subheading The @code{-list-thread-groups} Command
37507 @findex -list-thread-groups
37509 @subheading Synopsis
37512 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
37515 Lists thread groups (@pxref{Thread groups}). When a single thread
37516 group is passed as the argument, lists the children of that group.
37517 When several thread group are passed, lists information about those
37518 thread groups. Without any parameters, lists information about all
37519 top-level thread groups.
37521 Normally, thread groups that are being debugged are reported.
37522 With the @samp{--available} option, @value{GDBN} reports thread groups
37523 available on the target.
37525 The output of this command may have either a @samp{threads} result or
37526 a @samp{groups} result. The @samp{thread} result has a list of tuples
37527 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
37528 Information}). The @samp{groups} result has a list of tuples as value,
37529 each tuple describing a thread group. If top-level groups are
37530 requested (that is, no parameter is passed), or when several groups
37531 are passed, the output always has a @samp{groups} result. The format
37532 of the @samp{group} result is described below.
37534 To reduce the number of roundtrips it's possible to list thread groups
37535 together with their children, by passing the @samp{--recurse} option
37536 and the recursion depth. Presently, only recursion depth of 1 is
37537 permitted. If this option is present, then every reported thread group
37538 will also include its children, either as @samp{group} or
37539 @samp{threads} field.
37541 In general, any combination of option and parameters is permitted, with
37542 the following caveats:
37546 When a single thread group is passed, the output will typically
37547 be the @samp{threads} result. Because threads may not contain
37548 anything, the @samp{recurse} option will be ignored.
37551 When the @samp{--available} option is passed, limited information may
37552 be available. In particular, the list of threads of a process might
37553 be inaccessible. Further, specifying specific thread groups might
37554 not give any performance advantage over listing all thread groups.
37555 The frontend should assume that @samp{-list-thread-groups --available}
37556 is always an expensive operation and cache the results.
37560 The @samp{groups} result is a list of tuples, where each tuple may
37561 have the following fields:
37565 Identifier of the thread group. This field is always present.
37566 The identifier is an opaque string; frontends should not try to
37567 convert it to an integer, even though it might look like one.
37570 The type of the thread group. At present, only @samp{process} is a
37574 The target-specific process identifier. This field is only present
37575 for thread groups of type @samp{process} and only if the process exists.
37578 The exit code of this group's last exited thread, formatted in octal.
37579 This field is only present for thread groups of type @samp{process} and
37580 only if the process is not running.
37583 The number of children this thread group has. This field may be
37584 absent for an available thread group.
37587 This field has a list of tuples as value, each tuple describing a
37588 thread. It may be present if the @samp{--recurse} option is
37589 specified, and it's actually possible to obtain the threads.
37592 This field is a list of integers, each identifying a core that one
37593 thread of the group is running on. This field may be absent if
37594 such information is not available.
37597 The name of the executable file that corresponds to this thread group.
37598 The field is only present for thread groups of type @samp{process},
37599 and only if there is a corresponding executable file.
37603 @subheading Example
37607 -list-thread-groups
37608 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
37609 -list-thread-groups 17
37610 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
37611 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
37612 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
37613 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
37614 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
37615 -list-thread-groups --available
37616 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
37617 -list-thread-groups --available --recurse 1
37618 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37619 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37620 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
37621 -list-thread-groups --available --recurse 1 17 18
37622 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37623 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37624 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
37627 @subheading The @code{-info-os} Command
37630 @subsubheading Synopsis
37633 -info-os [ @var{type} ]
37636 If no argument is supplied, the command returns a table of available
37637 operating-system-specific information types. If one of these types is
37638 supplied as an argument @var{type}, then the command returns a table
37639 of data of that type.
37641 The types of information available depend on the target operating
37644 @subsubheading @value{GDBN} Command
37646 The corresponding @value{GDBN} command is @samp{info os}.
37648 @subsubheading Example
37650 When run on a @sc{gnu}/Linux system, the output will look something
37656 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
37657 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
37658 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
37659 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
37660 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
37662 item=@{col0="files",col1="Listing of all file descriptors",
37663 col2="File descriptors"@},
37664 item=@{col0="modules",col1="Listing of all loaded kernel modules",
37665 col2="Kernel modules"@},
37666 item=@{col0="msg",col1="Listing of all message queues",
37667 col2="Message queues"@},
37668 item=@{col0="processes",col1="Listing of all processes",
37669 col2="Processes"@},
37670 item=@{col0="procgroups",col1="Listing of all process groups",
37671 col2="Process groups"@},
37672 item=@{col0="semaphores",col1="Listing of all semaphores",
37673 col2="Semaphores"@},
37674 item=@{col0="shm",col1="Listing of all shared-memory regions",
37675 col2="Shared-memory regions"@},
37676 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
37678 item=@{col0="threads",col1="Listing of all threads",
37682 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
37683 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
37684 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
37685 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
37686 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
37687 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
37688 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
37689 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
37691 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
37692 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
37696 (Note that the MI output here includes a @code{"Title"} column that
37697 does not appear in command-line @code{info os}; this column is useful
37698 for MI clients that want to enumerate the types of data, such as in a
37699 popup menu, but is needless clutter on the command line, and
37700 @code{info os} omits it.)
37702 @subheading The @code{-add-inferior} Command
37703 @findex -add-inferior
37705 @subheading Synopsis
37708 -add-inferior [ --no-connection ]
37711 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
37712 inferior is not associated with any executable. Such association may
37713 be established with the @samp{-file-exec-and-symbols} command
37714 (@pxref{GDB/MI File Commands}).
37716 By default, the new inferior begins connected to the same target
37717 connection as the current inferior. For example, if the current
37718 inferior was connected to @code{gdbserver} with @code{target remote},
37719 then the new inferior will be connected to the same @code{gdbserver}
37720 instance. The @samp{--no-connection} option starts the new inferior
37721 with no connection yet. You can then for example use the
37722 @code{-target-select remote} command to connect to some other
37723 @code{gdbserver} instance, use @code{-exec-run} to spawn a local
37726 The command response always has a field, @var{inferior}, whose value
37727 is the identifier of the thread group corresponding to the new
37730 An additional section field, @var{connection}, is optional. This
37731 field will only exist if the new inferior has a target connection. If
37732 this field exists, then its value will be a tuple containing the
37737 The number of the connection used for the new inferior.
37740 The name of the connection type used for the new inferior.
37743 @subheading @value{GDBN} Command
37745 The corresponding @value{GDBN} command is @samp{add-inferior}
37746 (@pxref{add_inferior_cli,,@samp{add-inferior}}).
37748 @subheading Example
37753 ^done,inferior="i3"
37756 @subheading The @code{-interpreter-exec} Command
37757 @findex -interpreter-exec
37759 @subheading Synopsis
37762 -interpreter-exec @var{interpreter} @var{command}
37764 @anchor{-interpreter-exec}
37766 Execute the specified @var{command} in the given @var{interpreter}.
37768 @subheading @value{GDBN} Command
37770 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
37772 @subheading Example
37776 -interpreter-exec console "break main"
37777 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
37778 &"During symbol reading, bad structure-type format.\n"
37779 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
37784 @subheading The @code{-inferior-tty-set} Command
37785 @findex -inferior-tty-set
37787 @subheading Synopsis
37790 -inferior-tty-set /dev/pts/1
37793 Set terminal for future runs of the program being debugged.
37795 @subheading @value{GDBN} Command
37797 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
37799 @subheading Example
37803 -inferior-tty-set /dev/pts/1
37808 @subheading The @code{-inferior-tty-show} Command
37809 @findex -inferior-tty-show
37811 @subheading Synopsis
37817 Show terminal for future runs of program being debugged.
37819 @subheading @value{GDBN} Command
37821 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
37823 @subheading Example
37827 -inferior-tty-set /dev/pts/1
37831 ^done,inferior_tty_terminal="/dev/pts/1"
37835 @subheading The @code{-enable-timings} Command
37836 @findex -enable-timings
37838 @subheading Synopsis
37841 -enable-timings [yes | no]
37844 Toggle the printing of the wallclock, user and system times for an MI
37845 command as a field in its output. This command is to help frontend
37846 developers optimize the performance of their code. No argument is
37847 equivalent to @samp{yes}.
37849 @subheading @value{GDBN} Command
37853 @subheading Example
37861 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
37862 addr="0x080484ed",func="main",file="myprog.c",
37863 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
37865 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
37873 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
37874 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
37875 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
37876 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
37880 @subheading The @code{-complete} Command
37883 @subheading Synopsis
37886 -complete @var{command}
37889 Show a list of completions for partially typed CLI @var{command}.
37891 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
37892 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
37893 because @value{GDBN} is used remotely via a SSH connection.
37897 The result consists of two or three fields:
37901 This field contains the completed @var{command}. If @var{command}
37902 has no known completions, this field is omitted.
37905 This field contains a (possibly empty) array of matches. It is always present.
37907 @item max_completions_reached
37908 This field contains @code{1} if number of known completions is above
37909 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
37910 @code{0}. It is always present.
37914 @subheading @value{GDBN} Command
37916 The corresponding @value{GDBN} command is @samp{complete}.
37918 @subheading Example
37923 ^done,completion="break",
37924 matches=["break","break-range"],
37925 max_completions_reached="0"
37928 ^done,completion="b ma",
37929 matches=["b madvise","b main"],max_completions_reached="0"
37931 -complete "b push_b"
37932 ^done,completion="b push_back(",
37934 "b A::push_back(void*)",
37935 "b std::string::push_back(char)",
37936 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
37937 max_completions_reached="0"
37939 -complete "nonexist"
37940 ^done,matches=[],max_completions_reached="0"
37946 @chapter @value{GDBN} Annotations
37948 This chapter describes annotations in @value{GDBN}. Annotations were
37949 designed to interface @value{GDBN} to graphical user interfaces or other
37950 similar programs which want to interact with @value{GDBN} at a
37951 relatively high level.
37953 The annotation mechanism has largely been superseded by @sc{gdb/mi}
37957 This is Edition @value{EDITION}, @value{DATE}.
37961 * Annotations Overview:: What annotations are; the general syntax.
37962 * Server Prefix:: Issuing a command without affecting user state.
37963 * Prompting:: Annotations marking @value{GDBN}'s need for input.
37964 * Errors:: Annotations for error messages.
37965 * Invalidation:: Some annotations describe things now invalid.
37966 * Annotations for Running::
37967 Whether the program is running, how it stopped, etc.
37968 * Source Annotations:: Annotations describing source code.
37971 @node Annotations Overview
37972 @section What is an Annotation?
37973 @cindex annotations
37975 Annotations start with a newline character, two @samp{control-z}
37976 characters, and the name of the annotation. If there is no additional
37977 information associated with this annotation, the name of the annotation
37978 is followed immediately by a newline. If there is additional
37979 information, the name of the annotation is followed by a space, the
37980 additional information, and a newline. The additional information
37981 cannot contain newline characters.
37983 Any output not beginning with a newline and two @samp{control-z}
37984 characters denotes literal output from @value{GDBN}. Currently there is
37985 no need for @value{GDBN} to output a newline followed by two
37986 @samp{control-z} characters, but if there was such a need, the
37987 annotations could be extended with an @samp{escape} annotation which
37988 means those three characters as output.
37990 The annotation @var{level}, which is specified using the
37991 @option{--annotate} command line option (@pxref{Mode Options}), controls
37992 how much information @value{GDBN} prints together with its prompt,
37993 values of expressions, source lines, and other types of output. Level 0
37994 is for no annotations, level 1 is for use when @value{GDBN} is run as a
37995 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
37996 for programs that control @value{GDBN}, and level 2 annotations have
37997 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
37998 Interface, annotate, GDB's Obsolete Annotations}).
38001 @kindex set annotate
38002 @item set annotate @var{level}
38003 The @value{GDBN} command @code{set annotate} sets the level of
38004 annotations to the specified @var{level}.
38006 @item show annotate
38007 @kindex show annotate
38008 Show the current annotation level.
38011 This chapter describes level 3 annotations.
38013 A simple example of starting up @value{GDBN} with annotations is:
38016 $ @kbd{gdb --annotate=3}
38018 Copyright 2003 Free Software Foundation, Inc.
38019 GDB is free software, covered by the GNU General Public License,
38020 and you are welcome to change it and/or distribute copies of it
38021 under certain conditions.
38022 Type "show copying" to see the conditions.
38023 There is absolutely no warranty for GDB. Type "show warranty"
38025 This GDB was configured as "i386-pc-linux-gnu"
38036 Here @samp{quit} is input to @value{GDBN}; the rest is output from
38037 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
38038 denotes a @samp{control-z} character) are annotations; the rest is
38039 output from @value{GDBN}.
38041 @node Server Prefix
38042 @section The Server Prefix
38043 @cindex server prefix
38045 If you prefix a command with @samp{server } then it will not affect
38046 the command history, nor will it affect @value{GDBN}'s notion of which
38047 command to repeat if @key{RET} is pressed on a line by itself. This
38048 means that commands can be run behind a user's back by a front-end in
38049 a transparent manner.
38051 The @code{server } prefix does not affect the recording of values into
38052 the value history; to print a value without recording it into the
38053 value history, use the @code{output} command instead of the
38054 @code{print} command.
38056 Using this prefix also disables confirmation requests
38057 (@pxref{confirmation requests}).
38060 @section Annotation for @value{GDBN} Input
38062 @cindex annotations for prompts
38063 When @value{GDBN} prompts for input, it annotates this fact so it is possible
38064 to know when to send output, when the output from a given command is
38067 Different kinds of input each have a different @dfn{input type}. Each
38068 input type has three annotations: a @code{pre-} annotation, which
38069 denotes the beginning of any prompt which is being output, a plain
38070 annotation, which denotes the end of the prompt, and then a @code{post-}
38071 annotation which denotes the end of any echo which may (or may not) be
38072 associated with the input. For example, the @code{prompt} input type
38073 features the following annotations:
38081 The input types are
38084 @findex pre-prompt annotation
38085 @findex prompt annotation
38086 @findex post-prompt annotation
38088 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
38090 @findex pre-commands annotation
38091 @findex commands annotation
38092 @findex post-commands annotation
38094 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
38095 command. The annotations are repeated for each command which is input.
38097 @findex pre-overload-choice annotation
38098 @findex overload-choice annotation
38099 @findex post-overload-choice annotation
38100 @item overload-choice
38101 When @value{GDBN} wants the user to select between various overloaded functions.
38103 @findex pre-query annotation
38104 @findex query annotation
38105 @findex post-query annotation
38107 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
38109 @findex pre-prompt-for-continue annotation
38110 @findex prompt-for-continue annotation
38111 @findex post-prompt-for-continue annotation
38112 @item prompt-for-continue
38113 When @value{GDBN} is asking the user to press return to continue. Note: Don't
38114 expect this to work well; instead use @code{set height 0} to disable
38115 prompting. This is because the counting of lines is buggy in the
38116 presence of annotations.
38121 @cindex annotations for errors, warnings and interrupts
38123 @findex quit annotation
38128 This annotation occurs right before @value{GDBN} responds to an interrupt.
38130 @findex error annotation
38135 This annotation occurs right before @value{GDBN} responds to an error.
38137 Quit and error annotations indicate that any annotations which @value{GDBN} was
38138 in the middle of may end abruptly. For example, if a
38139 @code{value-history-begin} annotation is followed by a @code{error}, one
38140 cannot expect to receive the matching @code{value-history-end}. One
38141 cannot expect not to receive it either, however; an error annotation
38142 does not necessarily mean that @value{GDBN} is immediately returning all the way
38145 @findex error-begin annotation
38146 A quit or error annotation may be preceded by
38152 Any output between that and the quit or error annotation is the error
38155 Warning messages are not yet annotated.
38156 @c If we want to change that, need to fix warning(), type_error(),
38157 @c range_error(), and possibly other places.
38160 @section Invalidation Notices
38162 @cindex annotations for invalidation messages
38163 The following annotations say that certain pieces of state may have
38167 @findex frames-invalid annotation
38168 @item ^Z^Zframes-invalid
38170 The frames (for example, output from the @code{backtrace} command) may
38173 @findex breakpoints-invalid annotation
38174 @item ^Z^Zbreakpoints-invalid
38176 The breakpoints may have changed. For example, the user just added or
38177 deleted a breakpoint.
38180 @node Annotations for Running
38181 @section Running the Program
38182 @cindex annotations for running programs
38184 @findex starting annotation
38185 @findex stopping annotation
38186 When the program starts executing due to a @value{GDBN} command such as
38187 @code{step} or @code{continue},
38193 is output. When the program stops,
38199 is output. Before the @code{stopped} annotation, a variety of
38200 annotations describe how the program stopped.
38203 @findex exited annotation
38204 @item ^Z^Zexited @var{exit-status}
38205 The program exited, and @var{exit-status} is the exit status (zero for
38206 successful exit, otherwise nonzero).
38208 @findex signalled annotation
38209 @findex signal-name annotation
38210 @findex signal-name-end annotation
38211 @findex signal-string annotation
38212 @findex signal-string-end annotation
38213 @item ^Z^Zsignalled
38214 The program exited with a signal. After the @code{^Z^Zsignalled}, the
38215 annotation continues:
38221 ^Z^Zsignal-name-end
38225 ^Z^Zsignal-string-end
38230 where @var{name} is the name of the signal, such as @code{SIGILL} or
38231 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
38232 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
38233 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
38234 user's benefit and have no particular format.
38236 @findex signal annotation
38238 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
38239 just saying that the program received the signal, not that it was
38240 terminated with it.
38242 @findex breakpoint annotation
38243 @item ^Z^Zbreakpoint @var{number}
38244 The program hit breakpoint number @var{number}.
38246 @findex watchpoint annotation
38247 @item ^Z^Zwatchpoint @var{number}
38248 The program hit watchpoint number @var{number}.
38251 @node Source Annotations
38252 @section Displaying Source
38253 @cindex annotations for source display
38255 @findex source annotation
38256 The following annotation is used instead of displaying source code:
38259 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
38262 where @var{filename} is an absolute file name indicating which source
38263 file, @var{line} is the line number within that file (where 1 is the
38264 first line in the file), @var{character} is the character position
38265 within the file (where 0 is the first character in the file) (for most
38266 debug formats this will necessarily point to the beginning of a line),
38267 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
38268 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
38269 @var{addr} is the address in the target program associated with the
38270 source which is being displayed. The @var{addr} is in the form @samp{0x}
38271 followed by one or more lowercase hex digits (note that this does not
38272 depend on the language).
38274 @node JIT Interface
38275 @chapter JIT Compilation Interface
38276 @cindex just-in-time compilation
38277 @cindex JIT compilation interface
38279 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
38280 interface. A JIT compiler is a program or library that generates native
38281 executable code at runtime and executes it, usually in order to achieve good
38282 performance while maintaining platform independence.
38284 Programs that use JIT compilation are normally difficult to debug because
38285 portions of their code are generated at runtime, instead of being loaded from
38286 object files, which is where @value{GDBN} normally finds the program's symbols
38287 and debug information. In order to debug programs that use JIT compilation,
38288 @value{GDBN} has an interface that allows the program to register in-memory
38289 symbol files with @value{GDBN} at runtime.
38291 If you are using @value{GDBN} to debug a program that uses this interface, then
38292 it should work transparently so long as you have not stripped the binary. If
38293 you are developing a JIT compiler, then the interface is documented in the rest
38294 of this chapter. At this time, the only known client of this interface is the
38297 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
38298 JIT compiler communicates with @value{GDBN} by writing data into a global
38299 variable and calling a function at a well-known symbol. When @value{GDBN}
38300 attaches, it reads a linked list of symbol files from the global variable to
38301 find existing code, and puts a breakpoint in the function so that it can find
38302 out about additional code.
38305 * Declarations:: Relevant C struct declarations
38306 * Registering Code:: Steps to register code
38307 * Unregistering Code:: Steps to unregister code
38308 * Custom Debug Info:: Emit debug information in a custom format
38312 @section JIT Declarations
38314 These are the relevant struct declarations that a C program should include to
38315 implement the interface:
38325 struct jit_code_entry
38327 struct jit_code_entry *next_entry;
38328 struct jit_code_entry *prev_entry;
38329 const char *symfile_addr;
38330 uint64_t symfile_size;
38333 struct jit_descriptor
38336 /* This type should be jit_actions_t, but we use uint32_t
38337 to be explicit about the bitwidth. */
38338 uint32_t action_flag;
38339 struct jit_code_entry *relevant_entry;
38340 struct jit_code_entry *first_entry;
38343 /* GDB puts a breakpoint in this function. */
38344 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
38346 /* Make sure to specify the version statically, because the
38347 debugger may check the version before we can set it. */
38348 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
38351 If the JIT is multi-threaded, then it is important that the JIT synchronize any
38352 modifications to this global data properly, which can easily be done by putting
38353 a global mutex around modifications to these structures.
38355 @node Registering Code
38356 @section Registering Code
38358 To register code with @value{GDBN}, the JIT should follow this protocol:
38362 Generate an object file in memory with symbols and other desired debug
38363 information. The file must include the virtual addresses of the sections.
38366 Create a code entry for the file, which gives the start and size of the symbol
38370 Add it to the linked list in the JIT descriptor.
38373 Point the relevant_entry field of the descriptor at the entry.
38376 Set @code{action_flag} to @code{JIT_REGISTER} and call
38377 @code{__jit_debug_register_code}.
38380 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
38381 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
38382 new code. However, the linked list must still be maintained in order to allow
38383 @value{GDBN} to attach to a running process and still find the symbol files.
38385 @node Unregistering Code
38386 @section Unregistering Code
38388 If code is freed, then the JIT should use the following protocol:
38392 Remove the code entry corresponding to the code from the linked list.
38395 Point the @code{relevant_entry} field of the descriptor at the code entry.
38398 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
38399 @code{__jit_debug_register_code}.
38402 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
38403 and the JIT will leak the memory used for the associated symbol files.
38405 @node Custom Debug Info
38406 @section Custom Debug Info
38407 @cindex custom JIT debug info
38408 @cindex JIT debug info reader
38410 Generating debug information in platform-native file formats (like ELF
38411 or COFF) may be an overkill for JIT compilers; especially if all the
38412 debug info is used for is displaying a meaningful backtrace. The
38413 issue can be resolved by having the JIT writers decide on a debug info
38414 format and also provide a reader that parses the debug info generated
38415 by the JIT compiler. This section gives a brief overview on writing
38416 such a parser. More specific details can be found in the source file
38417 @file{gdb/jit-reader.in}, which is also installed as a header at
38418 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
38420 The reader is implemented as a shared object (so this functionality is
38421 not available on platforms which don't allow loading shared objects at
38422 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
38423 @code{jit-reader-unload} are provided, to be used to load and unload
38424 the readers from a preconfigured directory. Once loaded, the shared
38425 object is used the parse the debug information emitted by the JIT
38429 * Using JIT Debug Info Readers:: How to use supplied readers correctly
38430 * Writing JIT Debug Info Readers:: Creating a debug-info reader
38433 @node Using JIT Debug Info Readers
38434 @subsection Using JIT Debug Info Readers
38435 @kindex jit-reader-load
38436 @kindex jit-reader-unload
38438 Readers can be loaded and unloaded using the @code{jit-reader-load}
38439 and @code{jit-reader-unload} commands.
38442 @item jit-reader-load @var{reader}
38443 Load the JIT reader named @var{reader}, which is a shared
38444 object specified as either an absolute or a relative file name. In
38445 the latter case, @value{GDBN} will try to load the reader from a
38446 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
38447 system (here @var{libdir} is the system library directory, often
38448 @file{/usr/local/lib}).
38450 Only one reader can be active at a time; trying to load a second
38451 reader when one is already loaded will result in @value{GDBN}
38452 reporting an error. A new JIT reader can be loaded by first unloading
38453 the current one using @code{jit-reader-unload} and then invoking
38454 @code{jit-reader-load}.
38456 @item jit-reader-unload
38457 Unload the currently loaded JIT reader.
38461 @node Writing JIT Debug Info Readers
38462 @subsection Writing JIT Debug Info Readers
38463 @cindex writing JIT debug info readers
38465 As mentioned, a reader is essentially a shared object conforming to a
38466 certain ABI. This ABI is described in @file{jit-reader.h}.
38468 @file{jit-reader.h} defines the structures, macros and functions
38469 required to write a reader. It is installed (along with
38470 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
38471 the system include directory.
38473 Readers need to be released under a GPL compatible license. A reader
38474 can be declared as released under such a license by placing the macro
38475 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
38477 The entry point for readers is the symbol @code{gdb_init_reader},
38478 which is expected to be a function with the prototype
38480 @findex gdb_init_reader
38482 extern struct gdb_reader_funcs *gdb_init_reader (void);
38485 @cindex @code{struct gdb_reader_funcs}
38487 @code{struct gdb_reader_funcs} contains a set of pointers to callback
38488 functions. These functions are executed to read the debug info
38489 generated by the JIT compiler (@code{read}), to unwind stack frames
38490 (@code{unwind}) and to create canonical frame IDs
38491 (@code{get_frame_id}). It also has a callback that is called when the
38492 reader is being unloaded (@code{destroy}). The struct looks like this
38495 struct gdb_reader_funcs
38497 /* Must be set to GDB_READER_INTERFACE_VERSION. */
38498 int reader_version;
38500 /* For use by the reader. */
38503 gdb_read_debug_info *read;
38504 gdb_unwind_frame *unwind;
38505 gdb_get_frame_id *get_frame_id;
38506 gdb_destroy_reader *destroy;
38510 @cindex @code{struct gdb_symbol_callbacks}
38511 @cindex @code{struct gdb_unwind_callbacks}
38513 The callbacks are provided with another set of callbacks by
38514 @value{GDBN} to do their job. For @code{read}, these callbacks are
38515 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
38516 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
38517 @code{struct gdb_symbol_callbacks} has callbacks to create new object
38518 files and new symbol tables inside those object files. @code{struct
38519 gdb_unwind_callbacks} has callbacks to read registers off the current
38520 frame and to write out the values of the registers in the previous
38521 frame. Both have a callback (@code{target_read}) to read bytes off the
38522 target's address space.
38524 @node In-Process Agent
38525 @chapter In-Process Agent
38526 @cindex debugging agent
38527 The traditional debugging model is conceptually low-speed, but works fine,
38528 because most bugs can be reproduced in debugging-mode execution. However,
38529 as multi-core or many-core processors are becoming mainstream, and
38530 multi-threaded programs become more and more popular, there should be more
38531 and more bugs that only manifest themselves at normal-mode execution, for
38532 example, thread races, because debugger's interference with the program's
38533 timing may conceal the bugs. On the other hand, in some applications,
38534 it is not feasible for the debugger to interrupt the program's execution
38535 long enough for the developer to learn anything helpful about its behavior.
38536 If the program's correctness depends on its real-time behavior, delays
38537 introduced by a debugger might cause the program to fail, even when the
38538 code itself is correct. It is useful to be able to observe the program's
38539 behavior without interrupting it.
38541 Therefore, traditional debugging model is too intrusive to reproduce
38542 some bugs. In order to reduce the interference with the program, we can
38543 reduce the number of operations performed by debugger. The
38544 @dfn{In-Process Agent}, a shared library, is running within the same
38545 process with inferior, and is able to perform some debugging operations
38546 itself. As a result, debugger is only involved when necessary, and
38547 performance of debugging can be improved accordingly. Note that
38548 interference with program can be reduced but can't be removed completely,
38549 because the in-process agent will still stop or slow down the program.
38551 The in-process agent can interpret and execute Agent Expressions
38552 (@pxref{Agent Expressions}) during performing debugging operations. The
38553 agent expressions can be used for different purposes, such as collecting
38554 data in tracepoints, and condition evaluation in breakpoints.
38556 @anchor{Control Agent}
38557 You can control whether the in-process agent is used as an aid for
38558 debugging with the following commands:
38561 @kindex set agent on
38563 Causes the in-process agent to perform some operations on behalf of the
38564 debugger. Just which operations requested by the user will be done
38565 by the in-process agent depends on the its capabilities. For example,
38566 if you request to evaluate breakpoint conditions in the in-process agent,
38567 and the in-process agent has such capability as well, then breakpoint
38568 conditions will be evaluated in the in-process agent.
38570 @kindex set agent off
38571 @item set agent off
38572 Disables execution of debugging operations by the in-process agent. All
38573 of the operations will be performed by @value{GDBN}.
38577 Display the current setting of execution of debugging operations by
38578 the in-process agent.
38582 * In-Process Agent Protocol::
38585 @node In-Process Agent Protocol
38586 @section In-Process Agent Protocol
38587 @cindex in-process agent protocol
38589 The in-process agent is able to communicate with both @value{GDBN} and
38590 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
38591 used for communications between @value{GDBN} or GDBserver and the IPA.
38592 In general, @value{GDBN} or GDBserver sends commands
38593 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
38594 in-process agent replies back with the return result of the command, or
38595 some other information. The data sent to in-process agent is composed
38596 of primitive data types, such as 4-byte or 8-byte type, and composite
38597 types, which are called objects (@pxref{IPA Protocol Objects}).
38600 * IPA Protocol Objects::
38601 * IPA Protocol Commands::
38604 @node IPA Protocol Objects
38605 @subsection IPA Protocol Objects
38606 @cindex ipa protocol objects
38608 The commands sent to and results received from agent may contain some
38609 complex data types called @dfn{objects}.
38611 The in-process agent is running on the same machine with @value{GDBN}
38612 or GDBserver, so it doesn't have to handle as much differences between
38613 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
38614 However, there are still some differences of two ends in two processes:
38618 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
38619 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
38621 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
38622 GDBserver is compiled with one, and in-process agent is compiled with
38626 Here are the IPA Protocol Objects:
38630 agent expression object. It represents an agent expression
38631 (@pxref{Agent Expressions}).
38632 @anchor{agent expression object}
38634 tracepoint action object. It represents a tracepoint action
38635 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
38636 memory, static trace data and to evaluate expression.
38637 @anchor{tracepoint action object}
38639 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
38640 @anchor{tracepoint object}
38644 The following table describes important attributes of each IPA protocol
38647 @multitable @columnfractions .30 .20 .50
38648 @headitem Name @tab Size @tab Description
38649 @item @emph{agent expression object} @tab @tab
38650 @item length @tab 4 @tab length of bytes code
38651 @item byte code @tab @var{length} @tab contents of byte code
38652 @item @emph{tracepoint action for collecting memory} @tab @tab
38653 @item 'M' @tab 1 @tab type of tracepoint action
38654 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
38655 address of the lowest byte to collect, otherwise @var{addr} is the offset
38656 of @var{basereg} for memory collecting.
38657 @item len @tab 8 @tab length of memory for collecting
38658 @item basereg @tab 4 @tab the register number containing the starting
38659 memory address for collecting.
38660 @item @emph{tracepoint action for collecting registers} @tab @tab
38661 @item 'R' @tab 1 @tab type of tracepoint action
38662 @item @emph{tracepoint action for collecting static trace data} @tab @tab
38663 @item 'L' @tab 1 @tab type of tracepoint action
38664 @item @emph{tracepoint action for expression evaluation} @tab @tab
38665 @item 'X' @tab 1 @tab type of tracepoint action
38666 @item agent expression @tab length of @tab @ref{agent expression object}
38667 @item @emph{tracepoint object} @tab @tab
38668 @item number @tab 4 @tab number of tracepoint
38669 @item address @tab 8 @tab address of tracepoint inserted on
38670 @item type @tab 4 @tab type of tracepoint
38671 @item enabled @tab 1 @tab enable or disable of tracepoint
38672 @item step_count @tab 8 @tab step
38673 @item pass_count @tab 8 @tab pass
38674 @item numactions @tab 4 @tab number of tracepoint actions
38675 @item hit count @tab 8 @tab hit count
38676 @item trace frame usage @tab 8 @tab trace frame usage
38677 @item compiled_cond @tab 8 @tab compiled condition
38678 @item orig_size @tab 8 @tab orig size
38679 @item condition @tab 4 if condition is NULL otherwise length of
38680 @ref{agent expression object}
38681 @tab zero if condition is NULL, otherwise is
38682 @ref{agent expression object}
38683 @item actions @tab variable
38684 @tab numactions number of @ref{tracepoint action object}
38687 @node IPA Protocol Commands
38688 @subsection IPA Protocol Commands
38689 @cindex ipa protocol commands
38691 The spaces in each command are delimiters to ease reading this commands
38692 specification. They don't exist in real commands.
38696 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
38697 Installs a new fast tracepoint described by @var{tracepoint_object}
38698 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
38699 head of @dfn{jumppad}, which is used to jump to data collection routine
38704 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
38705 @var{target_address} is address of tracepoint in the inferior.
38706 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
38707 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
38708 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
38709 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
38716 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
38717 is about to kill inferiors.
38725 @item probe_marker_at:@var{address}
38726 Asks in-process agent to probe the marker at @var{address}.
38733 @item unprobe_marker_at:@var{address}
38734 Asks in-process agent to unprobe the marker at @var{address}.
38738 @chapter Reporting Bugs in @value{GDBN}
38739 @cindex bugs in @value{GDBN}
38740 @cindex reporting bugs in @value{GDBN}
38742 Your bug reports play an essential role in making @value{GDBN} reliable.
38744 Reporting a bug may help you by bringing a solution to your problem, or it
38745 may not. But in any case the principal function of a bug report is to help
38746 the entire community by making the next version of @value{GDBN} work better. Bug
38747 reports are your contribution to the maintenance of @value{GDBN}.
38749 In order for a bug report to serve its purpose, you must include the
38750 information that enables us to fix the bug.
38753 * Bug Criteria:: Have you found a bug?
38754 * Bug Reporting:: How to report bugs
38758 @section Have You Found a Bug?
38759 @cindex bug criteria
38761 If you are not sure whether you have found a bug, here are some guidelines:
38764 @cindex fatal signal
38765 @cindex debugger crash
38766 @cindex crash of debugger
38768 If the debugger gets a fatal signal, for any input whatever, that is a
38769 @value{GDBN} bug. Reliable debuggers never crash.
38771 @cindex error on valid input
38773 If @value{GDBN} produces an error message for valid input, that is a
38774 bug. (Note that if you're cross debugging, the problem may also be
38775 somewhere in the connection to the target.)
38777 @cindex invalid input
38779 If @value{GDBN} does not produce an error message for invalid input,
38780 that is a bug. However, you should note that your idea of
38781 ``invalid input'' might be our idea of ``an extension'' or ``support
38782 for traditional practice''.
38785 If you are an experienced user of debugging tools, your suggestions
38786 for improvement of @value{GDBN} are welcome in any case.
38789 @node Bug Reporting
38790 @section How to Report Bugs
38791 @cindex bug reports
38792 @cindex @value{GDBN} bugs, reporting
38794 A number of companies and individuals offer support for @sc{gnu} products.
38795 If you obtained @value{GDBN} from a support organization, we recommend you
38796 contact that organization first.
38798 You can find contact information for many support companies and
38799 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
38801 @c should add a web page ref...
38804 @ifset BUGURL_DEFAULT
38805 In any event, we also recommend that you submit bug reports for
38806 @value{GDBN}. The preferred method is to submit them directly using
38807 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
38808 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
38811 @strong{Do not send bug reports to @samp{info-gdb}, or to
38812 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
38813 not want to receive bug reports. Those that do have arranged to receive
38816 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
38817 serves as a repeater. The mailing list and the newsgroup carry exactly
38818 the same messages. Often people think of posting bug reports to the
38819 newsgroup instead of mailing them. This appears to work, but it has one
38820 problem which can be crucial: a newsgroup posting often lacks a mail
38821 path back to the sender. Thus, if we need to ask for more information,
38822 we may be unable to reach you. For this reason, it is better to send
38823 bug reports to the mailing list.
38825 @ifclear BUGURL_DEFAULT
38826 In any event, we also recommend that you submit bug reports for
38827 @value{GDBN} to @value{BUGURL}.
38831 The fundamental principle of reporting bugs usefully is this:
38832 @strong{report all the facts}. If you are not sure whether to state a
38833 fact or leave it out, state it!
38835 Often people omit facts because they think they know what causes the
38836 problem and assume that some details do not matter. Thus, you might
38837 assume that the name of the variable you use in an example does not matter.
38838 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
38839 stray memory reference which happens to fetch from the location where that
38840 name is stored in memory; perhaps, if the name were different, the contents
38841 of that location would fool the debugger into doing the right thing despite
38842 the bug. Play it safe and give a specific, complete example. That is the
38843 easiest thing for you to do, and the most helpful.
38845 Keep in mind that the purpose of a bug report is to enable us to fix the
38846 bug. It may be that the bug has been reported previously, but neither
38847 you nor we can know that unless your bug report is complete and
38850 Sometimes people give a few sketchy facts and ask, ``Does this ring a
38851 bell?'' Those bug reports are useless, and we urge everyone to
38852 @emph{refuse to respond to them} except to chide the sender to report
38855 To enable us to fix the bug, you should include all these things:
38859 The version of @value{GDBN}. @value{GDBN} announces it if you start
38860 with no arguments; you can also print it at any time using @code{show
38863 Without this, we will not know whether there is any point in looking for
38864 the bug in the current version of @value{GDBN}.
38867 The type of machine you are using, and the operating system name and
38871 The details of the @value{GDBN} build-time configuration.
38872 @value{GDBN} shows these details if you invoke it with the
38873 @option{--configuration} command-line option, or if you type
38874 @code{show configuration} at @value{GDBN}'s prompt.
38877 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
38878 ``@value{GCC}--2.8.1''.
38881 What compiler (and its version) was used to compile the program you are
38882 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
38883 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
38884 to get this information; for other compilers, see the documentation for
38888 The command arguments you gave the compiler to compile your example and
38889 observe the bug. For example, did you use @samp{-O}? To guarantee
38890 you will not omit something important, list them all. A copy of the
38891 Makefile (or the output from make) is sufficient.
38893 If we were to try to guess the arguments, we would probably guess wrong
38894 and then we might not encounter the bug.
38897 A complete input script, and all necessary source files, that will
38901 A description of what behavior you observe that you believe is
38902 incorrect. For example, ``It gets a fatal signal.''
38904 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
38905 will certainly notice it. But if the bug is incorrect output, we might
38906 not notice unless it is glaringly wrong. You might as well not give us
38907 a chance to make a mistake.
38909 Even if the problem you experience is a fatal signal, you should still
38910 say so explicitly. Suppose something strange is going on, such as, your
38911 copy of @value{GDBN} is out of synch, or you have encountered a bug in
38912 the C library on your system. (This has happened!) Your copy might
38913 crash and ours would not. If you told us to expect a crash, then when
38914 ours fails to crash, we would know that the bug was not happening for
38915 us. If you had not told us to expect a crash, then we would not be able
38916 to draw any conclusion from our observations.
38919 @cindex recording a session script
38920 To collect all this information, you can use a session recording program
38921 such as @command{script}, which is available on many Unix systems.
38922 Just run your @value{GDBN} session inside @command{script} and then
38923 include the @file{typescript} file with your bug report.
38925 Another way to record a @value{GDBN} session is to run @value{GDBN}
38926 inside Emacs and then save the entire buffer to a file.
38929 If you wish to suggest changes to the @value{GDBN} source, send us context
38930 diffs. If you even discuss something in the @value{GDBN} source, refer to
38931 it by context, not by line number.
38933 The line numbers in our development sources will not match those in your
38934 sources. Your line numbers would convey no useful information to us.
38938 Here are some things that are not necessary:
38942 A description of the envelope of the bug.
38944 Often people who encounter a bug spend a lot of time investigating
38945 which changes to the input file will make the bug go away and which
38946 changes will not affect it.
38948 This is often time consuming and not very useful, because the way we
38949 will find the bug is by running a single example under the debugger
38950 with breakpoints, not by pure deduction from a series of examples.
38951 We recommend that you save your time for something else.
38953 Of course, if you can find a simpler example to report @emph{instead}
38954 of the original one, that is a convenience for us. Errors in the
38955 output will be easier to spot, running under the debugger will take
38956 less time, and so on.
38958 However, simplification is not vital; if you do not want to do this,
38959 report the bug anyway and send us the entire test case you used.
38962 A patch for the bug.
38964 A patch for the bug does help us if it is a good one. But do not omit
38965 the necessary information, such as the test case, on the assumption that
38966 a patch is all we need. We might see problems with your patch and decide
38967 to fix the problem another way, or we might not understand it at all.
38969 Sometimes with a program as complicated as @value{GDBN} it is very hard to
38970 construct an example that will make the program follow a certain path
38971 through the code. If you do not send us the example, we will not be able
38972 to construct one, so we will not be able to verify that the bug is fixed.
38974 And if we cannot understand what bug you are trying to fix, or why your
38975 patch should be an improvement, we will not install it. A test case will
38976 help us to understand.
38979 A guess about what the bug is or what it depends on.
38981 Such guesses are usually wrong. Even we cannot guess right about such
38982 things without first using the debugger to find the facts.
38985 @c The readline documentation is distributed with the readline code
38986 @c and consists of the two following files:
38989 @c Use -I with makeinfo to point to the appropriate directory,
38990 @c environment var TEXINPUTS with TeX.
38991 @ifclear SYSTEM_READLINE
38992 @include rluser.texi
38993 @include hsuser.texi
38997 @appendix In Memoriam
38999 The @value{GDBN} project mourns the loss of the following long-time
39004 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
39005 to Free Software in general. Outside of @value{GDBN}, he was known in
39006 the Amiga world for his series of Fish Disks, and the GeekGadget project.
39008 @item Michael Snyder
39009 Michael was one of the Global Maintainers of the @value{GDBN} project,
39010 with contributions recorded as early as 1996, until 2011. In addition
39011 to his day to day participation, he was a large driving force behind
39012 adding Reverse Debugging to @value{GDBN}.
39015 Beyond their technical contributions to the project, they were also
39016 enjoyable members of the Free Software Community. We will miss them.
39018 @node Formatting Documentation
39019 @appendix Formatting Documentation
39021 @cindex @value{GDBN} reference card
39022 @cindex reference card
39023 The @value{GDBN} 4 release includes an already-formatted reference card, ready
39024 for printing with PostScript or Ghostscript, in the @file{gdb}
39025 subdirectory of the main source directory@footnote{In
39026 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
39027 release.}. If you can use PostScript or Ghostscript with your printer,
39028 you can print the reference card immediately with @file{refcard.ps}.
39030 The release also includes the source for the reference card. You
39031 can format it, using @TeX{}, by typing:
39037 The @value{GDBN} reference card is designed to print in @dfn{landscape}
39038 mode on US ``letter'' size paper;
39039 that is, on a sheet 11 inches wide by 8.5 inches
39040 high. You will need to specify this form of printing as an option to
39041 your @sc{dvi} output program.
39043 @cindex documentation
39045 All the documentation for @value{GDBN} comes as part of the machine-readable
39046 distribution. The documentation is written in Texinfo format, which is
39047 a documentation system that uses a single source file to produce both
39048 on-line information and a printed manual. You can use one of the Info
39049 formatting commands to create the on-line version of the documentation
39050 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
39052 @value{GDBN} includes an already formatted copy of the on-line Info
39053 version of this manual in the @file{gdb} subdirectory. The main Info
39054 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
39055 subordinate files matching @samp{gdb.info*} in the same directory. If
39056 necessary, you can print out these files, or read them with any editor;
39057 but they are easier to read using the @code{info} subsystem in @sc{gnu}
39058 Emacs or the standalone @code{info} program, available as part of the
39059 @sc{gnu} Texinfo distribution.
39061 If you want to format these Info files yourself, you need one of the
39062 Info formatting programs, such as @code{texinfo-format-buffer} or
39065 If you have @code{makeinfo} installed, and are in the top level
39066 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
39067 version @value{GDBVN}), you can make the Info file by typing:
39074 If you want to typeset and print copies of this manual, you need @TeX{},
39075 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
39076 Texinfo definitions file.
39078 @TeX{} is a typesetting program; it does not print files directly, but
39079 produces output files called @sc{dvi} files. To print a typeset
39080 document, you need a program to print @sc{dvi} files. If your system
39081 has @TeX{} installed, chances are it has such a program. The precise
39082 command to use depends on your system; @kbd{lpr -d} is common; another
39083 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
39084 require a file name without any extension or a @samp{.dvi} extension.
39086 @TeX{} also requires a macro definitions file called
39087 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
39088 written in Texinfo format. On its own, @TeX{} cannot either read or
39089 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
39090 and is located in the @file{gdb-@var{version-number}/texinfo}
39093 If you have @TeX{} and a @sc{dvi} printer program installed, you can
39094 typeset and print this manual. First switch to the @file{gdb}
39095 subdirectory of the main source directory (for example, to
39096 @file{gdb-@value{GDBVN}/gdb}) and type:
39102 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
39104 @node Installing GDB
39105 @appendix Installing @value{GDBN}
39106 @cindex installation
39109 * Requirements:: Requirements for building @value{GDBN}
39110 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
39111 * Separate Objdir:: Compiling @value{GDBN} in another directory
39112 * Config Names:: Specifying names for hosts and targets
39113 * Configure Options:: Summary of options for configure
39114 * System-wide configuration:: Having a system-wide init file
39118 @section Requirements for Building @value{GDBN}
39119 @cindex building @value{GDBN}, requirements for
39121 Building @value{GDBN} requires various tools and packages to be available.
39122 Other packages will be used only if they are found.
39124 @heading Tools/Packages Necessary for Building @value{GDBN}
39126 @item C@t{++}11 compiler
39127 @value{GDBN} is written in C@t{++}11. It should be buildable with any
39128 recent C@t{++}11 compiler, e.g.@: GCC.
39131 @value{GDBN}'s build system relies on features only found in the GNU
39132 make program. Other variants of @code{make} will not work.
39134 @item GMP (The GNU Multiple Precision Arithmetic Library)
39135 @value{GDBN} now uses GMP to perform some of its arithmetics.
39136 This library may be included with your operating system distribution;
39137 if it is not, you can get the latest version from
39138 @url{https://gmplib.org/}. If GMP is installed at an unusual path,
39139 you can use the @option{--with-libgmp-prefix} option to specify
39144 @heading Tools/Packages Optional for Building @value{GDBN}
39148 @value{GDBN} can use the Expat XML parsing library. This library may be
39149 included with your operating system distribution; if it is not, you
39150 can get the latest version from @url{http://expat.sourceforge.net}.
39151 The @file{configure} script will search for this library in several
39152 standard locations; if it is installed in an unusual path, you can
39153 use the @option{--with-libexpat-prefix} option to specify its location.
39159 Remote protocol memory maps (@pxref{Memory Map Format})
39161 Target descriptions (@pxref{Target Descriptions})
39163 Remote shared library lists (@xref{Library List Format},
39164 or alternatively @pxref{Library List Format for SVR4 Targets})
39166 MS-Windows shared libraries (@pxref{Shared Libraries})
39168 Traceframe info (@pxref{Traceframe Info Format})
39170 Branch trace (@pxref{Branch Trace Format},
39171 @pxref{Branch Trace Configuration Format})
39175 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
39176 default, @value{GDBN} will be compiled if the Guile libraries are
39177 installed and are found by @file{configure}. You can use the
39178 @code{--with-guile} option to request Guile, and pass either the Guile
39179 version number or the file name of the relevant @code{pkg-config}
39180 program to choose a particular version of Guile.
39183 @value{GDBN}'s features related to character sets (@pxref{Character
39184 Sets}) require a functioning @code{iconv} implementation. If you are
39185 on a GNU system, then this is provided by the GNU C Library. Some
39186 other systems also provide a working @code{iconv}.
39188 If @value{GDBN} is using the @code{iconv} program which is installed
39189 in a non-standard place, you will need to tell @value{GDBN} where to
39190 find it. This is done with @option{--with-iconv-bin} which specifies
39191 the directory that contains the @code{iconv} program. This program is
39192 run in order to make a list of the available character sets.
39194 On systems without @code{iconv}, you can install GNU Libiconv. If
39195 Libiconv is installed in a standard place, @value{GDBN} will
39196 automatically use it if it is needed. If you have previously
39197 installed Libiconv in a non-standard place, you can use the
39198 @option{--with-libiconv-prefix} option to @file{configure}.
39200 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
39201 arrange to build Libiconv if a directory named @file{libiconv} appears
39202 in the top-most source directory. If Libiconv is built this way, and
39203 if the operating system does not provide a suitable @code{iconv}
39204 implementation, then the just-built library will automatically be used
39205 by @value{GDBN}. One easy way to set this up is to download GNU
39206 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
39207 source tree, and then rename the directory holding the Libiconv source
39208 code to @samp{libiconv}.
39211 @value{GDBN} can support debugging sections that are compressed with
39212 the LZMA library. @xref{MiniDebugInfo}. If this library is not
39213 included with your operating system, you can find it in the xz package
39214 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
39215 the usual place, then the @file{configure} script will use it
39216 automatically. If it is installed in an unusual path, you can use the
39217 @option{--with-liblzma-prefix} option to specify its location.
39221 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
39222 library. This library may be included with your operating system
39223 distribution; if it is not, you can get the latest version from
39224 @url{http://www.mpfr.org}. The @file{configure} script will search
39225 for this library in several standard locations; if it is installed
39226 in an unusual path, you can use the @option{--with-libmpfr-prefix}
39227 option to specify its location.
39229 GNU MPFR is used to emulate target floating-point arithmetic during
39230 expression evaluation when the target uses different floating-point
39231 formats than the host. If GNU MPFR it is not available, @value{GDBN}
39232 will fall back to using host floating-point arithmetic.
39235 @value{GDBN} can be scripted using Python language. @xref{Python}.
39236 By default, @value{GDBN} will be compiled if the Python libraries are
39237 installed and are found by @file{configure}. You can use the
39238 @code{--with-python} option to request Python, and pass either the
39239 file name of the relevant @code{python} executable, or the name of the
39240 directory in which Python is installed, to choose a particular
39241 installation of Python.
39244 @cindex compressed debug sections
39245 @value{GDBN} will use the @samp{zlib} library, if available, to read
39246 compressed debug sections. Some linkers, such as GNU gold, are capable
39247 of producing binaries with compressed debug sections. If @value{GDBN}
39248 is compiled with @samp{zlib}, it will be able to read the debug
39249 information in such binaries.
39251 The @samp{zlib} library is likely included with your operating system
39252 distribution; if it is not, you can get the latest version from
39253 @url{http://zlib.net}.
39256 @node Running Configure
39257 @section Invoking the @value{GDBN} @file{configure} Script
39258 @cindex configuring @value{GDBN}
39259 @value{GDBN} comes with a @file{configure} script that automates the process
39260 of preparing @value{GDBN} for installation; you can then use @code{make} to
39261 build the @code{gdb} program.
39263 @c irrelevant in info file; it's as current as the code it lives with.
39264 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
39265 look at the @file{README} file in the sources; we may have improved the
39266 installation procedures since publishing this manual.}
39269 The @value{GDBN} distribution includes all the source code you need for
39270 @value{GDBN} in a single directory, whose name is usually composed by
39271 appending the version number to @samp{gdb}.
39273 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
39274 @file{gdb-@value{GDBVN}} directory. That directory contains:
39277 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
39278 script for configuring @value{GDBN} and all its supporting libraries
39280 @item gdb-@value{GDBVN}/gdb
39281 the source specific to @value{GDBN} itself
39283 @item gdb-@value{GDBVN}/bfd
39284 source for the Binary File Descriptor library
39286 @item gdb-@value{GDBVN}/include
39287 @sc{gnu} include files
39289 @item gdb-@value{GDBVN}/libiberty
39290 source for the @samp{-liberty} free software library
39292 @item gdb-@value{GDBVN}/opcodes
39293 source for the library of opcode tables and disassemblers
39295 @item gdb-@value{GDBVN}/readline
39296 source for the @sc{gnu} command-line interface
39299 There may be other subdirectories as well.
39301 The simplest way to configure and build @value{GDBN} is to run @file{configure}
39302 from the @file{gdb-@var{version-number}} source directory, which in
39303 this example is the @file{gdb-@value{GDBVN}} directory.
39305 First switch to the @file{gdb-@var{version-number}} source directory
39306 if you are not already in it; then run @file{configure}. Pass the
39307 identifier for the platform on which @value{GDBN} will run as an
39313 cd gdb-@value{GDBVN}
39318 Running @samp{configure} and then running @code{make} builds the
39319 included supporting libraries, then @code{gdb} itself. The configured
39320 source files, and the binaries, are left in the corresponding source
39324 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
39325 system does not recognize this automatically when you run a different
39326 shell, you may need to run @code{sh} on it explicitly:
39332 You should run the @file{configure} script from the top directory in the
39333 source tree, the @file{gdb-@var{version-number}} directory. If you run
39334 @file{configure} from one of the subdirectories, you will configure only
39335 that subdirectory. That is usually not what you want. In particular,
39336 if you run the first @file{configure} from the @file{gdb} subdirectory
39337 of the @file{gdb-@var{version-number}} directory, you will omit the
39338 configuration of @file{bfd}, @file{readline}, and other sibling
39339 directories of the @file{gdb} subdirectory. This leads to build errors
39340 about missing include files such as @file{bfd/bfd.h}.
39342 You can install @code{@value{GDBN}} anywhere. The best way to do this
39343 is to pass the @code{--prefix} option to @code{configure}, and then
39344 install it with @code{make install}.
39346 @node Separate Objdir
39347 @section Compiling @value{GDBN} in Another Directory
39349 If you want to run @value{GDBN} versions for several host or target machines,
39350 you need a different @code{gdb} compiled for each combination of
39351 host and target. @file{configure} is designed to make this easy by
39352 allowing you to generate each configuration in a separate subdirectory,
39353 rather than in the source directory. If your @code{make} program
39354 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
39355 @code{make} in each of these directories builds the @code{gdb}
39356 program specified there.
39358 To build @code{gdb} in a separate directory, run @file{configure}
39359 with the @samp{--srcdir} option to specify where to find the source.
39360 (You also need to specify a path to find @file{configure}
39361 itself from your working directory. If the path to @file{configure}
39362 would be the same as the argument to @samp{--srcdir}, you can leave out
39363 the @samp{--srcdir} option; it is assumed.)
39365 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
39366 separate directory for a Sun 4 like this:
39370 cd gdb-@value{GDBVN}
39373 ../gdb-@value{GDBVN}/configure
39378 When @file{configure} builds a configuration using a remote source
39379 directory, it creates a tree for the binaries with the same structure
39380 (and using the same names) as the tree under the source directory. In
39381 the example, you'd find the Sun 4 library @file{libiberty.a} in the
39382 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
39383 @file{gdb-sun4/gdb}.
39385 Make sure that your path to the @file{configure} script has just one
39386 instance of @file{gdb} in it. If your path to @file{configure} looks
39387 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
39388 one subdirectory of @value{GDBN}, not the whole package. This leads to
39389 build errors about missing include files such as @file{bfd/bfd.h}.
39391 One popular reason to build several @value{GDBN} configurations in separate
39392 directories is to configure @value{GDBN} for cross-compiling (where
39393 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
39394 programs that run on another machine---the @dfn{target}).
39395 You specify a cross-debugging target by
39396 giving the @samp{--target=@var{target}} option to @file{configure}.
39398 When you run @code{make} to build a program or library, you must run
39399 it in a configured directory---whatever directory you were in when you
39400 called @file{configure} (or one of its subdirectories).
39402 The @code{Makefile} that @file{configure} generates in each source
39403 directory also runs recursively. If you type @code{make} in a source
39404 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
39405 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
39406 will build all the required libraries, and then build GDB.
39408 When you have multiple hosts or targets configured in separate
39409 directories, you can run @code{make} on them in parallel (for example,
39410 if they are NFS-mounted on each of the hosts); they will not interfere
39414 @section Specifying Names for Hosts and Targets
39416 The specifications used for hosts and targets in the @file{configure}
39417 script are based on a three-part naming scheme, but some short predefined
39418 aliases are also supported. The full naming scheme encodes three pieces
39419 of information in the following pattern:
39422 @var{architecture}-@var{vendor}-@var{os}
39425 For example, you can use the alias @code{sun4} as a @var{host} argument,
39426 or as the value for @var{target} in a @code{--target=@var{target}}
39427 option. The equivalent full name is @samp{sparc-sun-sunos4}.
39429 The @file{configure} script accompanying @value{GDBN} does not provide
39430 any query facility to list all supported host and target names or
39431 aliases. @file{configure} calls the Bourne shell script
39432 @code{config.sub} to map abbreviations to full names; you can read the
39433 script, if you wish, or you can use it to test your guesses on
39434 abbreviations---for example:
39437 % sh config.sub i386-linux
39439 % sh config.sub alpha-linux
39440 alpha-unknown-linux-gnu
39441 % sh config.sub hp9k700
39443 % sh config.sub sun4
39444 sparc-sun-sunos4.1.1
39445 % sh config.sub sun3
39446 m68k-sun-sunos4.1.1
39447 % sh config.sub i986v
39448 Invalid configuration `i986v': machine `i986v' not recognized
39452 @code{config.sub} is also distributed in the @value{GDBN} source
39453 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
39455 @node Configure Options
39456 @section @file{configure} Options
39458 Here is a summary of the @file{configure} options and arguments that
39459 are most often useful for building @value{GDBN}. @file{configure}
39460 also has several other options not listed here. @xref{Running
39461 configure Scripts,,,autoconf}, for a full
39462 explanation of @file{configure}.
39465 configure @r{[}--help@r{]}
39466 @r{[}--prefix=@var{dir}@r{]}
39467 @r{[}--exec-prefix=@var{dir}@r{]}
39468 @r{[}--srcdir=@var{dirname}@r{]}
39469 @r{[}--target=@var{target}@r{]}
39473 You may introduce options with a single @samp{-} rather than
39474 @samp{--} if you prefer; but you may abbreviate option names if you use
39479 Display a quick summary of how to invoke @file{configure}.
39481 @item --prefix=@var{dir}
39482 Configure the source to install programs and files under directory
39485 @item --exec-prefix=@var{dir}
39486 Configure the source to install programs under directory
39489 @c avoid splitting the warning from the explanation:
39491 @item --srcdir=@var{dirname}
39492 Use this option to make configurations in directories separate from the
39493 @value{GDBN} source directories. Among other things, you can use this to
39494 build (or maintain) several configurations simultaneously, in separate
39495 directories. @file{configure} writes configuration-specific files in
39496 the current directory, but arranges for them to use the source in the
39497 directory @var{dirname}. @file{configure} creates directories under
39498 the working directory in parallel to the source directories below
39501 @item --target=@var{target}
39502 Configure @value{GDBN} for cross-debugging programs running on the specified
39503 @var{target}. Without this option, @value{GDBN} is configured to debug
39504 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
39506 There is no convenient way to generate a list of all available
39507 targets. Also see the @code{--enable-targets} option, below.
39510 There are many other options that are specific to @value{GDBN}. This
39511 lists just the most common ones; there are some very specialized
39512 options not described here.
39515 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
39516 @itemx --enable-targets=all
39517 Configure @value{GDBN} for cross-debugging programs running on the
39518 specified list of targets. The special value @samp{all} configures
39519 @value{GDBN} for debugging programs running on any target it supports.
39521 @item --with-gdb-datadir=@var{path}
39522 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
39523 here for certain supporting files or scripts. This defaults to the
39524 @file{gdb} subdirectory of @samp{datadir} (which can be set using
39527 @item --with-relocated-sources=@var{dir}
39528 Sets up the default source path substitution rule so that directory
39529 names recorded in debug information will be automatically adjusted for
39530 any directory under @var{dir}. @var{dir} should be a subdirectory of
39531 @value{GDBN}'s configured prefix, the one mentioned in the
39532 @code{--prefix} or @code{--exec-prefix} options to configure. This
39533 option is useful if GDB is supposed to be moved to a different place
39536 @item --enable-64-bit-bfd
39537 Enable 64-bit support in BFD on 32-bit hosts.
39539 @item --disable-gdbmi
39540 Build @value{GDBN} without the GDB/MI machine interface
39544 Build @value{GDBN} with the text-mode full-screen user interface
39545 (TUI). Requires a curses library (ncurses and cursesX are also
39548 @item --with-curses
39549 Use the curses library instead of the termcap library, for text-mode
39550 terminal operations.
39552 @item --with-debuginfod
39553 Build @value{GDBN} with @file{libdebuginfod}, the @code{debuginfod} client
39554 library. Used to automatically fetch ELF, DWARF and source files from
39555 @code{debuginfod} servers using build IDs associated with any missing
39556 files. Enabled by default if @file{libdebuginfod} is installed and found
39557 at configure time. For more information regarding @code{debuginfod} see
39560 @item --with-libunwind-ia64
39561 Use the libunwind library for unwinding function call stack on ia64
39562 target platforms. See http://www.nongnu.org/libunwind/index.html for
39565 @item --with-system-readline
39566 Use the readline library installed on the host, rather than the
39567 library supplied as part of @value{GDBN}. Readline 7 or newer is
39568 required; this is enforced by the build system.
39570 @item --with-system-zlib
39571 Use the zlib library installed on the host, rather than the library
39572 supplied as part of @value{GDBN}.
39575 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
39576 default if libexpat is installed and found at configure time.) This
39577 library is used to read XML files supplied with @value{GDBN}. If it
39578 is unavailable, some features, such as remote protocol memory maps,
39579 target descriptions, and shared library lists, that are based on XML
39580 files, will not be available in @value{GDBN}. If your host does not
39581 have libexpat installed, you can get the latest version from
39582 `http://expat.sourceforge.net'.
39584 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
39586 Build @value{GDBN} with GNU libiconv, a character set encoding
39587 conversion library. This is not done by default, as on GNU systems
39588 the @code{iconv} that is built in to the C library is sufficient. If
39589 your host does not have a working @code{iconv}, you can get the latest
39590 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
39592 @value{GDBN}'s build system also supports building GNU libiconv as
39593 part of the overall build. @xref{Requirements}.
39596 Build @value{GDBN} with LZMA, a compression library. (Done by default
39597 if liblzma is installed and found at configure time.) LZMA is used by
39598 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
39599 platforms using the ELF object file format. If your host does not
39600 have liblzma installed, you can get the latest version from
39601 `https://tukaani.org/xz/'.
39604 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
39605 floating-point computation with correct rounding. (Done by default if
39606 GNU MPFR is installed and found at configure time.) This library is
39607 used to emulate target floating-point arithmetic during expression
39608 evaluation when the target uses different floating-point formats than
39609 the host. If GNU MPFR is not available, @value{GDBN} will fall back
39610 to using host floating-point arithmetic. If your host does not have
39611 GNU MPFR installed, you can get the latest version from
39612 `http://www.mpfr.org'.
39614 @item --with-python@r{[}=@var{python}@r{]}
39615 Build @value{GDBN} with Python scripting support. (Done by default if
39616 libpython is present and found at configure time.) Python makes
39617 @value{GDBN} scripting much more powerful than the restricted CLI
39618 scripting language. If your host does not have Python installed, you
39619 can find it on `http://www.python.org/download/'. The oldest version
39620 of Python supported by GDB is 2.6. The optional argument @var{python}
39621 is used to find the Python headers and libraries. It can be either
39622 the name of a Python executable, or the name of the directory in which
39623 Python is installed.
39625 @item --with-guile[=GUILE]'
39626 Build @value{GDBN} with GNU Guile scripting support. (Done by default
39627 if libguile is present and found at configure time.) If your host
39628 does not have Guile installed, you can find it at
39629 `https://www.gnu.org/software/guile/'. The optional argument GUILE
39630 can be a version number, which will cause @code{configure} to try to
39631 use that version of Guile; or the file name of a @code{pkg-config}
39632 executable, which will be queried to find the information needed to
39633 compile and link against Guile.
39635 @item --without-included-regex
39636 Don't use the regex library included with @value{GDBN} (as part of the
39637 libiberty library). This is the default on hosts with version 2 of
39640 @item --with-sysroot=@var{dir}
39641 Use @var{dir} as the default system root directory for libraries whose
39642 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
39643 @var{dir} can be modified at run time by using the @command{set
39644 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
39645 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
39646 default system root will be automatically adjusted if and when
39647 @value{GDBN} is moved to a different location.
39649 @item --with-system-gdbinit=@var{file}
39650 Configure @value{GDBN} to automatically load a system-wide init file.
39651 @var{file} should be an absolute file name. If @var{file} is in a
39652 directory under the configured prefix, and @value{GDBN} is moved to
39653 another location after being built, the location of the system-wide
39654 init file will be adjusted accordingly.
39656 @item --with-system-gdbinit-dir=@var{directory}
39657 Configure @value{GDBN} to automatically load init files from a
39658 system-wide directory. @var{directory} should be an absolute directory
39659 name. If @var{directory} is in a directory under the configured
39660 prefix, and @value{GDBN} is moved to another location after being
39661 built, the location of the system-wide init directory will be
39662 adjusted accordingly.
39664 @item --enable-build-warnings
39665 When building the @value{GDBN} sources, ask the compiler to warn about
39666 any code which looks even vaguely suspicious. It passes many
39667 different warning flags, depending on the exact version of the
39668 compiler you are using.
39670 @item --enable-werror
39671 Treat compiler warnings as errors. It adds the @code{-Werror} flag
39672 to the compiler, which will fail the compilation if the compiler
39673 outputs any warning messages.
39675 @item --enable-ubsan
39676 Enable the GCC undefined behavior sanitizer. This is disabled by
39677 default, but passing @code{--enable-ubsan=yes} or
39678 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
39679 undefined behavior sanitizer checks for C@t{++} undefined behavior.
39680 It has a performance cost, so if you are looking at @value{GDBN}'s
39681 performance, you should disable it. The undefined behavior sanitizer
39682 was first introduced in GCC 4.9.
39685 @node System-wide configuration
39686 @section System-wide configuration and settings
39687 @cindex system-wide init file
39689 @value{GDBN} can be configured to have a system-wide init file and a
39690 system-wide init file directory; this file and files in that directory
39691 (if they have a recognized file extension) will be read and executed at
39692 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
39694 Here are the corresponding configure options:
39697 @item --with-system-gdbinit=@var{file}
39698 Specify that the default location of the system-wide init file is
39700 @item --with-system-gdbinit-dir=@var{directory}
39701 Specify that the default location of the system-wide init file directory
39702 is @var{directory}.
39705 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
39706 they may be subject to relocation. Two possible cases:
39710 If the default location of this init file/directory contains @file{$prefix},
39711 it will be subject to relocation. Suppose that the configure options
39712 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
39713 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
39714 init file is looked for as @file{$install/etc/gdbinit} instead of
39715 @file{$prefix/etc/gdbinit}.
39718 By contrast, if the default location does not contain the prefix,
39719 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
39720 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
39721 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
39722 wherever @value{GDBN} is installed.
39725 If the configured location of the system-wide init file (as given by the
39726 @option{--with-system-gdbinit} option at configure time) is in the
39727 data-directory (as specified by @option{--with-gdb-datadir} at configure
39728 time) or in one of its subdirectories, then @value{GDBN} will look for the
39729 system-wide init file in the directory specified by the
39730 @option{--data-directory} command-line option.
39731 Note that the system-wide init file is only read once, during @value{GDBN}
39732 initialization. If the data-directory is changed after @value{GDBN} has
39733 started with the @code{set data-directory} command, the file will not be
39736 This applies similarly to the system-wide directory specified in
39737 @option{--with-system-gdbinit-dir}.
39739 Any supported scripting language can be used for these init files, as long
39740 as the file extension matches the scripting language. To be interpreted
39741 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
39745 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
39748 @node System-wide Configuration Scripts
39749 @subsection Installed System-wide Configuration Scripts
39750 @cindex system-wide configuration scripts
39752 The @file{system-gdbinit} directory, located inside the data-directory
39753 (as specified by @option{--with-gdb-datadir} at configure time) contains
39754 a number of scripts which can be used as system-wide init files. To
39755 automatically source those scripts at startup, @value{GDBN} should be
39756 configured with @option{--with-system-gdbinit}. Otherwise, any user
39757 should be able to source them by hand as needed.
39759 The following scripts are currently available:
39762 @item @file{elinos.py}
39764 @cindex ELinOS system-wide configuration script
39765 This script is useful when debugging a program on an ELinOS target.
39766 It takes advantage of the environment variables defined in a standard
39767 ELinOS environment in order to determine the location of the system
39768 shared libraries, and then sets the @samp{solib-absolute-prefix}
39769 and @samp{solib-search-path} variables appropriately.
39771 @item @file{wrs-linux.py}
39772 @pindex wrs-linux.py
39773 @cindex Wind River Linux system-wide configuration script
39774 This script is useful when debugging a program on a target running
39775 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
39776 the host-side sysroot used by the target system.
39780 @node Maintenance Commands
39781 @appendix Maintenance Commands
39782 @cindex maintenance commands
39783 @cindex internal commands
39785 In addition to commands intended for @value{GDBN} users, @value{GDBN}
39786 includes a number of commands intended for @value{GDBN} developers,
39787 that are not documented elsewhere in this manual. These commands are
39788 provided here for reference. (For commands that turn on debugging
39789 messages, see @ref{Debugging Output}.)
39792 @kindex maint agent
39793 @kindex maint agent-eval
39794 @item maint agent @r{[}-at @var{linespec}@r{,}@r{]} @var{expression}
39795 @itemx maint agent-eval @r{[}-at @var{linespec}@r{,}@r{]} @var{expression}
39796 Translate the given @var{expression} into remote agent bytecodes.
39797 This command is useful for debugging the Agent Expression mechanism
39798 (@pxref{Agent Expressions}). The @samp{agent} version produces an
39799 expression useful for data collection, such as by tracepoints, while
39800 @samp{maint agent-eval} produces an expression that evaluates directly
39801 to a result. For instance, a collection expression for @code{globa +
39802 globb} will include bytecodes to record four bytes of memory at each
39803 of the addresses of @code{globa} and @code{globb}, while discarding
39804 the result of the addition, while an evaluation expression will do the
39805 addition and return the sum.
39806 If @code{-at} is given, generate remote agent bytecode for all the
39807 addresses to which @var{linespec} resolves (@pxref{Linespec
39809 If not, generate remote agent bytecode for current frame PC address.
39811 @kindex maint agent-printf
39812 @item maint agent-printf @var{format},@var{expr},...
39813 Translate the given format string and list of argument expressions
39814 into remote agent bytecodes and display them as a disassembled list.
39815 This command is useful for debugging the agent version of dynamic
39816 printf (@pxref{Dynamic Printf}).
39818 @kindex maint info breakpoints
39819 @item @anchor{maint info breakpoints}maint info breakpoints
39820 Using the same format as @samp{info breakpoints}, display both the
39821 breakpoints you've set explicitly, and those @value{GDBN} is using for
39822 internal purposes. Internal breakpoints are shown with negative
39823 breakpoint numbers. The type column identifies what kind of breakpoint
39828 Normal, explicitly set breakpoint.
39831 Normal, explicitly set watchpoint.
39834 Internal breakpoint, used to handle correctly stepping through
39835 @code{longjmp} calls.
39837 @item longjmp resume
39838 Internal breakpoint at the target of a @code{longjmp}.
39841 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
39844 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
39847 Shared library events.
39851 @kindex maint info btrace
39852 @item maint info btrace
39853 Pint information about raw branch tracing data.
39855 @kindex maint btrace packet-history
39856 @item maint btrace packet-history
39857 Print the raw branch trace packets that are used to compute the
39858 execution history for the @samp{record btrace} command. Both the
39859 information and the format in which it is printed depend on the btrace
39864 For the BTS recording format, print a list of blocks of sequential
39865 code. For each block, the following information is printed:
39869 Newer blocks have higher numbers. The oldest block has number zero.
39870 @item Lowest @samp{PC}
39871 @item Highest @samp{PC}
39875 For the Intel Processor Trace recording format, print a list of
39876 Intel Processor Trace packets. For each packet, the following
39877 information is printed:
39880 @item Packet number
39881 Newer packets have higher numbers. The oldest packet has number zero.
39883 The packet's offset in the trace stream.
39884 @item Packet opcode and payload
39888 @kindex maint btrace clear-packet-history
39889 @item maint btrace clear-packet-history
39890 Discards the cached packet history printed by the @samp{maint btrace
39891 packet-history} command. The history will be computed again when
39894 @kindex maint btrace clear
39895 @item maint btrace clear
39896 Discard the branch trace data. The data will be fetched anew and the
39897 branch trace will be recomputed when needed.
39899 This implicitly truncates the branch trace to a single branch trace
39900 buffer. When updating branch trace incrementally, the branch trace
39901 available to @value{GDBN} may be bigger than a single branch trace
39904 @kindex maint set btrace pt skip-pad
39905 @item maint set btrace pt skip-pad
39906 @kindex maint show btrace pt skip-pad
39907 @item maint show btrace pt skip-pad
39908 Control whether @value{GDBN} will skip PAD packets when computing the
39911 @kindex maint info jit
39912 @item maint info jit
39913 Print information about JIT code objects loaded in the current inferior.
39915 @anchor{maint info python-disassemblers}
39916 @kindex maint info python-disassemblers
39917 @item maint info python-disassemblers
39918 This command is defined within the @code{gdb.disassembler} Python
39919 module (@pxref{Disassembly In Python}), and will only be present after
39920 that module has been imported. To force the module to be imported do
39924 (@value{GDBP}) python import gdb.disassembler
39927 This command lists all the architectures for which a disassembler is
39928 currently registered, and the name of the disassembler. If a
39929 disassembler is registered for all architectures, then this is listed
39930 last against the @samp{GLOBAL} architecture.
39932 If one of the disassemblers would be selected for the architecture of
39933 the current inferior, then this disassembler will be marked.
39935 The following example shows a situation in which two disassemblers are
39936 registered, initially the @samp{i386} disassembler matches the current
39937 architecture, then the architecture is changed, now the @samp{GLOBAL}
39938 disassembler matches.
39942 (@value{GDBP}) show architecture
39943 The target architecture is set to "auto" (currently "i386").
39944 (@value{GDBP}) maint info python-disassemblers
39945 Architecture Disassember Name
39946 i386 Disassembler_1 (Matches current architecture)
39947 GLOBAL Disassembler_2
39950 (@value{GDBP}) set architecture arm
39951 The target architecture is set to "arm".
39952 (@value{GDBP}) maint info python-disassemblers
39954 Architecture Disassember Name
39955 i386 Disassembler_1
39956 GLOBAL Disassembler_2 (Matches current architecture)
39960 @kindex set displaced-stepping
39961 @kindex show displaced-stepping
39962 @cindex displaced stepping support
39963 @cindex out-of-line single-stepping
39964 @item set displaced-stepping
39965 @itemx show displaced-stepping
39966 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
39967 if the target supports it. Displaced stepping is a way to single-step
39968 over breakpoints without removing them from the inferior, by executing
39969 an out-of-line copy of the instruction that was originally at the
39970 breakpoint location. It is also known as out-of-line single-stepping.
39973 @item set displaced-stepping on
39974 If the target architecture supports it, @value{GDBN} will use
39975 displaced stepping to step over breakpoints.
39977 @item set displaced-stepping off
39978 @value{GDBN} will not use displaced stepping to step over breakpoints,
39979 even if such is supported by the target architecture.
39981 @cindex non-stop mode, and @samp{set displaced-stepping}
39982 @item set displaced-stepping auto
39983 This is the default mode. @value{GDBN} will use displaced stepping
39984 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
39985 architecture supports displaced stepping.
39988 @kindex maint check-psymtabs
39989 @item maint check-psymtabs
39990 Check the consistency of currently expanded psymtabs versus symtabs.
39991 Use this to check, for example, whether a symbol is in one but not the other.
39993 @kindex maint check-symtabs
39994 @item maint check-symtabs
39995 Check the consistency of currently expanded symtabs.
39997 @kindex maint expand-symtabs
39998 @item maint expand-symtabs [@var{regexp}]
39999 Expand symbol tables.
40000 If @var{regexp} is specified, only expand symbol tables for file
40001 names matching @var{regexp}.
40003 @kindex maint set catch-demangler-crashes
40004 @kindex maint show catch-demangler-crashes
40005 @cindex demangler crashes
40006 @item maint set catch-demangler-crashes [on|off]
40007 @itemx maint show catch-demangler-crashes
40008 Control whether @value{GDBN} should attempt to catch crashes in the
40009 symbol name demangler. The default is to attempt to catch crashes.
40010 If enabled, the first time a crash is caught, a core file is created,
40011 the offending symbol is displayed and the user is presented with the
40012 option to terminate the current session.
40014 @kindex maint cplus first_component
40015 @item maint cplus first_component @var{name}
40016 Print the first C@t{++} class/namespace component of @var{name}.
40018 @kindex maint cplus namespace
40019 @item maint cplus namespace
40020 Print the list of possible C@t{++} namespaces.
40022 @kindex maint deprecate
40023 @kindex maint undeprecate
40024 @cindex deprecated commands
40025 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
40026 @itemx maint undeprecate @var{command}
40027 Deprecate or undeprecate the named @var{command}. Deprecated commands
40028 cause @value{GDBN} to issue a warning when you use them. The optional
40029 argument @var{replacement} says which newer command should be used in
40030 favor of the deprecated one; if it is given, @value{GDBN} will mention
40031 the replacement as part of the warning.
40033 @kindex maint dump-me
40034 @item maint dump-me
40035 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
40036 Cause a fatal signal in the debugger and force it to dump its core.
40037 This is supported only on systems which support aborting a program
40038 with the @code{SIGQUIT} signal.
40040 @kindex maint internal-error
40041 @kindex maint internal-warning
40042 @kindex maint demangler-warning
40043 @cindex demangler crashes
40044 @item maint internal-error @r{[}@var{message-text}@r{]}
40045 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
40046 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
40048 Cause @value{GDBN} to call the internal function @code{internal_error},
40049 @code{internal_warning} or @code{demangler_warning} and hence behave
40050 as though an internal problem has been detected. In addition to
40051 reporting the internal problem, these functions give the user the
40052 opportunity to either quit @value{GDBN} or (for @code{internal_error}
40053 and @code{internal_warning}) create a core file of the current
40054 @value{GDBN} session.
40056 These commands take an optional parameter @var{message-text} that is
40057 used as the text of the error or warning message.
40059 Here's an example of using @code{internal-error}:
40062 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
40063 @dots{}/maint.c:121: internal-error: testing, 1, 2
40064 A problem internal to GDB has been detected. Further
40065 debugging may prove unreliable.
40066 Quit this debugging session? (y or n) @kbd{n}
40067 Create a core file? (y or n) @kbd{n}
40071 @cindex @value{GDBN} internal error
40072 @cindex internal errors, control of @value{GDBN} behavior
40073 @cindex demangler crashes
40075 @kindex maint set internal-error
40076 @kindex maint show internal-error
40077 @kindex maint set internal-warning
40078 @kindex maint show internal-warning
40079 @kindex maint set demangler-warning
40080 @kindex maint show demangler-warning
40081 @item maint set internal-error @var{action} [ask|yes|no]
40082 @itemx maint show internal-error @var{action}
40083 @itemx maint set internal-warning @var{action} [ask|yes|no]
40084 @itemx maint show internal-warning @var{action}
40085 @itemx maint set demangler-warning @var{action} [ask|yes|no]
40086 @itemx maint show demangler-warning @var{action}
40087 When @value{GDBN} reports an internal problem (error or warning) it
40088 gives the user the opportunity to both quit @value{GDBN} and create a
40089 core file of the current @value{GDBN} session. These commands let you
40090 override the default behaviour for each particular @var{action},
40091 described in the table below.
40095 You can specify that @value{GDBN} should always (yes) or never (no)
40096 quit. The default is to ask the user what to do.
40099 You can specify that @value{GDBN} should always (yes) or never (no)
40100 create a core file. The default is to ask the user what to do. Note
40101 that there is no @code{corefile} option for @code{demangler-warning}:
40102 demangler warnings always create a core file and this cannot be
40106 @kindex maint set internal-error
40107 @kindex maint show internal-error
40108 @kindex maint set internal-warning
40109 @kindex maint show internal-warning
40110 @item maint set internal-error backtrace @r{[}on|off@r{]}
40111 @itemx maint show internal-error backtrace
40112 @itemx maint set internal-warning backtrace @r{[}on|off@r{]}
40113 @itemx maint show internal-warning backtrace
40114 When @value{GDBN} reports an internal problem (error or warning) it is
40115 possible to have a backtrace of @value{GDBN} printed to the standard
40116 error stream. This is @samp{on} by default for @code{internal-error}
40117 and @samp{off} by default for @code{internal-warning}.
40119 @anchor{maint packet}
40120 @kindex maint packet
40121 @item maint packet @var{text}
40122 If @value{GDBN} is talking to an inferior via the serial protocol,
40123 then this command sends the string @var{text} to the inferior, and
40124 displays the response packet. @value{GDBN} supplies the initial
40125 @samp{$} character, the terminating @samp{#} character, and the
40128 Any non-printable characters in the reply are printed as escaped hex,
40129 e.g. @samp{\x00}, @samp{\x01}, etc.
40131 @kindex maint print architecture
40132 @item maint print architecture @r{[}@var{file}@r{]}
40133 Print the entire architecture configuration. The optional argument
40134 @var{file} names the file where the output goes.
40136 @kindex maint print c-tdesc
40137 @item maint print c-tdesc @r{[}-single-feature@r{]} @r{[}@var{file}@r{]}
40138 Print the target description (@pxref{Target Descriptions}) as
40139 a C source file. By default, the target description is for the current
40140 target, but if the optional argument @var{file} is provided, that file
40141 is used to produce the description. The @var{file} should be an XML
40142 document, of the form described in @ref{Target Description Format}.
40143 The created source file is built into @value{GDBN} when @value{GDBN} is
40144 built again. This command is used by developers after they add or
40145 modify XML target descriptions.
40147 When the optional flag @samp{-single-feature} is provided then the
40148 target description being processed (either the default, or from
40149 @var{file}) must only contain a single feature. The source file
40150 produced is different in this case.
40152 @kindex maint print xml-tdesc
40153 @item maint print xml-tdesc @r{[}@var{file}@r{]}
40154 Print the target description (@pxref{Target Descriptions}) as an XML
40155 file. By default print the target description for the current target,
40156 but if the optional argument @var{file} is provided, then that file is
40157 read in by GDB and then used to produce the description. The
40158 @var{file} should be an XML document, of the form described in
40159 @ref{Target Description Format}.
40161 @kindex maint check xml-descriptions
40162 @item maint check xml-descriptions @var{dir}
40163 Check that the target descriptions dynamically created by @value{GDBN}
40164 equal the descriptions created from XML files found in @var{dir}.
40166 @anchor{maint check libthread-db}
40167 @kindex maint check libthread-db
40168 @item maint check libthread-db
40169 Run integrity checks on the current inferior's thread debugging
40170 library. This exercises all @code{libthread_db} functionality used by
40171 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
40172 @code{proc_service} functions provided by @value{GDBN} that
40173 @code{libthread_db} uses. Note that parts of the test may be skipped
40174 on some platforms when debugging core files.
40176 @kindex maint print core-file-backed-mappings
40177 @cindex memory address space mappings
40178 @item maint print core-file-backed-mappings
40179 Print the file-backed mappings which were loaded from a core file note.
40180 This output represents state internal to @value{GDBN} and should be
40181 similar to the mappings displayed by the @code{info proc mappings}
40184 @kindex maint print dummy-frames
40185 @item maint print dummy-frames
40186 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
40189 (@value{GDBP}) @kbd{b add}
40191 (@value{GDBP}) @kbd{print add(2,3)}
40192 Breakpoint 2, add (a=2, b=3) at @dots{}
40194 The program being debugged stopped while in a function called from GDB.
40196 (@value{GDBP}) @kbd{maint print dummy-frames}
40197 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
40201 Takes an optional file parameter.
40203 @kindex maint print frame-id
40204 @item maint print frame-id
40205 @itemx maint print frame-id @var{level}
40206 Print @value{GDBN}'s internal frame-id for the frame at relative
40207 @var{level}, or for the currently selected frame when @var{level} is
40210 If used, @var{level} should be an integer, as displayed in the
40211 @command{backtrace} output.
40214 (@value{GDBP}) maint print frame-id
40215 frame-id for frame #0: @{stack=0x7fffffffac70,code=0x0000000000401106,!special@}
40216 (@value{GDBP}) maint print frame-id 2
40217 frame-id for frame #2: @{stack=0x7fffffffac90,code=0x000000000040111c,!special@}
40220 @kindex maint print registers
40221 @kindex maint print raw-registers
40222 @kindex maint print cooked-registers
40223 @kindex maint print register-groups
40224 @kindex maint print remote-registers
40225 @item maint print registers @r{[}@var{file}@r{]}
40226 @itemx maint print raw-registers @r{[}@var{file}@r{]}
40227 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
40228 @itemx maint print register-groups @r{[}@var{file}@r{]}
40229 @itemx maint print remote-registers @r{[}@var{file}@r{]}
40230 Print @value{GDBN}'s internal register data structures.
40232 The command @code{maint print raw-registers} includes the contents of
40233 the raw register cache; the command @code{maint print
40234 cooked-registers} includes the (cooked) value of all registers,
40235 including registers which aren't available on the target nor visible
40236 to user; the command @code{maint print register-groups} includes the
40237 groups that each register is a member of; and the command @code{maint
40238 print remote-registers} includes the remote target's register numbers
40239 and offsets in the `G' packets.
40241 These commands take an optional parameter, a file name to which to
40242 write the information.
40244 @kindex maint print reggroups
40245 @item maint print reggroups @r{[}@var{file}@r{]}
40246 Print @value{GDBN}'s internal register group data structures. The
40247 optional argument @var{file} tells to what file to write the
40250 The register groups info looks like this:
40253 (@value{GDBP}) @kbd{maint print reggroups}
40264 @kindex maint flush register-cache
40266 @cindex register cache, flushing
40267 @item maint flush register-cache
40269 Flush the contents of the register cache and as a consequence the
40270 frame cache. This command is useful when debugging issues related to
40271 register fetching, or frame unwinding. The command @code{flushregs}
40272 is deprecated in favor of @code{maint flush register-cache}.
40274 @kindex maint flush source-cache
40275 @cindex source code, caching
40276 @item maint flush source-cache
40277 Flush @value{GDBN}'s cache of source code file contents. After
40278 @value{GDBN} reads a source file, and optionally applies styling
40279 (@pxref{Output Styling}), the file contents are cached. This command
40280 clears that cache. The next time @value{GDBN} wants to show lines
40281 from a source file, the content will be re-read.
40283 This command is useful when debugging issues related to source code
40284 styling. After flushing the cache any source code displayed by
40285 @value{GDBN} will be re-read and re-styled.
40287 @kindex maint print objfiles
40288 @cindex info for known object files
40289 @item maint print objfiles @r{[}@var{regexp}@r{]}
40290 Print a dump of all known object files.
40291 If @var{regexp} is specified, only print object files whose names
40292 match @var{regexp}. For each object file, this command prints its name,
40293 address in memory, and all of its psymtabs and symtabs.
40295 @kindex maint print user-registers
40296 @cindex user registers
40297 @item maint print user-registers
40298 List all currently available @dfn{user registers}. User registers
40299 typically provide alternate names for actual hardware registers. They
40300 include the four ``standard'' registers @code{$fp}, @code{$pc},
40301 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
40302 registers can be used in expressions in the same way as the canonical
40303 register names, but only the latter are listed by the @code{info
40304 registers} and @code{maint print registers} commands.
40306 @kindex maint print section-scripts
40307 @cindex info for known .debug_gdb_scripts-loaded scripts
40308 @item maint print section-scripts [@var{regexp}]
40309 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
40310 If @var{regexp} is specified, only print scripts loaded by object files
40311 matching @var{regexp}.
40312 For each script, this command prints its name as specified in the objfile,
40313 and the full path if known.
40314 @xref{dotdebug_gdb_scripts section}.
40316 @kindex maint print statistics
40317 @cindex bcache statistics
40318 @item maint print statistics
40319 This command prints, for each object file in the program, various data
40320 about that object file followed by the byte cache (@dfn{bcache})
40321 statistics for the object file. The objfile data includes the number
40322 of minimal, partial, full, and stabs symbols, the number of types
40323 defined by the objfile, the number of as yet unexpanded psym tables,
40324 the number of line tables and string tables, and the amount of memory
40325 used by the various tables. The bcache statistics include the counts,
40326 sizes, and counts of duplicates of all and unique objects, max,
40327 average, and median entry size, total memory used and its overhead and
40328 savings, and various measures of the hash table size and chain
40331 @kindex maint print target-stack
40332 @cindex target stack description
40333 @item maint print target-stack
40334 A @dfn{target} is an interface between the debugger and a particular
40335 kind of file or process. Targets can be stacked in @dfn{strata},
40336 so that more than one target can potentially respond to a request.
40337 In particular, memory accesses will walk down the stack of targets
40338 until they find a target that is interested in handling that particular
40341 This command prints a short description of each layer that was pushed on
40342 the @dfn{target stack}, starting from the top layer down to the bottom one.
40344 @kindex maint print type
40345 @cindex type chain of a data type
40346 @item maint print type @var{expr}
40347 Print the type chain for a type specified by @var{expr}. The argument
40348 can be either a type name or a symbol. If it is a symbol, the type of
40349 that symbol is described. The type chain produced by this command is
40350 a recursive definition of the data type as stored in @value{GDBN}'s
40351 data structures, including its flags and contained types.
40353 @kindex maint selftest
40355 @item maint selftest @r{[}-verbose@r{]} @r{[}@var{filter}@r{]}
40356 Run any self tests that were compiled in to @value{GDBN}. This will
40357 print a message showing how many tests were run, and how many failed.
40358 If a @var{filter} is passed, only the tests with @var{filter} in their
40359 name will be ran. If @code{-verbose} is passed, the self tests can be
40362 @kindex maint set selftest verbose
40363 @kindex maint show selftest verbose
40365 @item maint set selftest verbose
40366 @item maint show selftest verbose
40367 Control whether self tests are run verbosely or not.
40369 @kindex maint info selftests
40371 @item maint info selftests
40372 List the selftests compiled in to @value{GDBN}.
40374 @kindex maint set dwarf always-disassemble
40375 @kindex maint show dwarf always-disassemble
40376 @item maint set dwarf always-disassemble
40377 @item maint show dwarf always-disassemble
40378 Control the behavior of @code{info address} when using DWARF debugging
40381 The default is @code{off}, which means that @value{GDBN} should try to
40382 describe a variable's location in an easily readable format. When
40383 @code{on}, @value{GDBN} will instead display the DWARF location
40384 expression in an assembly-like format. Note that some locations are
40385 too complex for @value{GDBN} to describe simply; in this case you will
40386 always see the disassembly form.
40388 Here is an example of the resulting disassembly:
40391 (gdb) info addr argc
40392 Symbol "argc" is a complex DWARF expression:
40396 For more information on these expressions, see
40397 @uref{http://www.dwarfstd.org/, the DWARF standard}.
40399 @kindex maint set dwarf max-cache-age
40400 @kindex maint show dwarf max-cache-age
40401 @item maint set dwarf max-cache-age
40402 @itemx maint show dwarf max-cache-age
40403 Control the DWARF compilation unit cache.
40405 @cindex DWARF compilation units cache
40406 In object files with inter-compilation-unit references, such as those
40407 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
40408 reader needs to frequently refer to previously read compilation units.
40409 This setting controls how long a compilation unit will remain in the
40410 cache if it is not referenced. A higher limit means that cached
40411 compilation units will be stored in memory longer, and more total
40412 memory will be used. Setting it to zero disables caching, which will
40413 slow down @value{GDBN} startup, but reduce memory consumption.
40415 @kindex maint set dwarf unwinders
40416 @kindex maint show dwarf unwinders
40417 @item maint set dwarf unwinders
40418 @itemx maint show dwarf unwinders
40419 Control use of the DWARF frame unwinders.
40421 @cindex DWARF frame unwinders
40422 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
40423 frame unwinders to build the backtrace. Many of these targets will
40424 also have a second mechanism for building the backtrace for use in
40425 cases where DWARF information is not available, this second mechanism
40426 is often an analysis of a function's prologue.
40428 In order to extend testing coverage of the second level stack
40429 unwinding mechanisms it is helpful to be able to disable the DWARF
40430 stack unwinders, this can be done with this switch.
40432 In normal use of @value{GDBN} disabling the DWARF unwinders is not
40433 advisable, there are cases that are better handled through DWARF than
40434 prologue analysis, and the debug experience is likely to be better
40435 with the DWARF frame unwinders enabled.
40437 If DWARF frame unwinders are not supported for a particular target
40438 architecture, then enabling this flag does not cause them to be used.
40440 @kindex maint set worker-threads
40441 @kindex maint show worker-threads
40442 @item maint set worker-threads
40443 @item maint show worker-threads
40444 Control the number of worker threads that may be used by @value{GDBN}.
40445 On capable hosts, @value{GDBN} may use multiple threads to speed up
40446 certain CPU-intensive operations, such as demangling symbol names.
40447 While the number of threads used by @value{GDBN} may vary, this
40448 command can be used to set an upper bound on this number. The default
40449 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
40450 number. Note that this only controls worker threads started by
40451 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
40454 @kindex maint set profile
40455 @kindex maint show profile
40456 @cindex profiling GDB
40457 @item maint set profile
40458 @itemx maint show profile
40459 Control profiling of @value{GDBN}.
40461 Profiling will be disabled until you use the @samp{maint set profile}
40462 command to enable it. When you enable profiling, the system will begin
40463 collecting timing and execution count data; when you disable profiling or
40464 exit @value{GDBN}, the results will be written to a log file. Remember that
40465 if you use profiling, @value{GDBN} will overwrite the profiling log file
40466 (often called @file{gmon.out}). If you have a record of important profiling
40467 data in a @file{gmon.out} file, be sure to move it to a safe location.
40469 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
40470 compiled with the @samp{-pg} compiler option.
40472 @kindex maint set show-debug-regs
40473 @kindex maint show show-debug-regs
40474 @cindex hardware debug registers
40475 @item maint set show-debug-regs
40476 @itemx maint show show-debug-regs
40477 Control whether to show variables that mirror the hardware debug
40478 registers. Use @code{on} to enable, @code{off} to disable. If
40479 enabled, the debug registers values are shown when @value{GDBN} inserts or
40480 removes a hardware breakpoint or watchpoint, and when the inferior
40481 triggers a hardware-assisted breakpoint or watchpoint.
40483 @kindex maint set show-all-tib
40484 @kindex maint show show-all-tib
40485 @item maint set show-all-tib
40486 @itemx maint show show-all-tib
40487 Control whether to show all non zero areas within a 1k block starting
40488 at thread local base, when using the @samp{info w32 thread-information-block}
40491 @kindex maint set target-async
40492 @kindex maint show target-async
40493 @item maint set target-async
40494 @itemx maint show target-async
40495 This controls whether @value{GDBN} targets operate in synchronous or
40496 asynchronous mode (@pxref{Background Execution}). Normally the
40497 default is asynchronous, if it is available; but this can be changed
40498 to more easily debug problems occurring only in synchronous mode.
40500 @kindex maint set target-non-stop @var{mode} [on|off|auto]
40501 @kindex maint show target-non-stop
40502 @item maint set target-non-stop
40503 @itemx maint show target-non-stop
40505 This controls whether @value{GDBN} targets always operate in non-stop
40506 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
40507 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
40508 if supported by the target.
40511 @item maint set target-non-stop auto
40512 This is the default mode. @value{GDBN} controls the target in
40513 non-stop mode if the target supports it.
40515 @item maint set target-non-stop on
40516 @value{GDBN} controls the target in non-stop mode even if the target
40517 does not indicate support.
40519 @item maint set target-non-stop off
40520 @value{GDBN} does not control the target in non-stop mode even if the
40521 target supports it.
40524 @kindex maint set tui-resize-message
40525 @kindex maint show tui-resize-message
40526 @item maint set tui-resize-message
40527 @item maint show tui-resize-message
40528 Control whether @value{GDBN} displays a message each time the terminal
40529 is resized when in TUI mode. The default is @code{off}, which means
40530 that @value{GDBN} is silent during resizes. When @code{on},
40531 @value{GDBN} will display a message after a resize is completed; the
40532 message will include a number indicating how many times the terminal
40533 has been resized. This setting is intended for use by the test suite,
40534 where it would otherwise be difficult to determine when a resize and
40535 refresh has been completed.
40537 @kindex maint set per-command
40538 @kindex maint show per-command
40539 @item maint set per-command
40540 @itemx maint show per-command
40541 @cindex resources used by commands
40543 @value{GDBN} can display the resources used by each command.
40544 This is useful in debugging performance problems.
40547 @item maint set per-command space [on|off]
40548 @itemx maint show per-command space
40549 Enable or disable the printing of the memory used by GDB for each command.
40550 If enabled, @value{GDBN} will display how much memory each command
40551 took, following the command's own output.
40552 This can also be requested by invoking @value{GDBN} with the
40553 @option{--statistics} command-line switch (@pxref{Mode Options}).
40555 @item maint set per-command time [on|off]
40556 @itemx maint show per-command time
40557 Enable or disable the printing of the execution time of @value{GDBN}
40559 If enabled, @value{GDBN} will display how much time it
40560 took to execute each command, following the command's own output.
40561 Both CPU time and wallclock time are printed.
40562 Printing both is useful when trying to determine whether the cost is
40563 CPU or, e.g., disk/network latency.
40564 Note that the CPU time printed is for @value{GDBN} only, it does not include
40565 the execution time of the inferior because there's no mechanism currently
40566 to compute how much time was spent by @value{GDBN} and how much time was
40567 spent by the program been debugged.
40568 This can also be requested by invoking @value{GDBN} with the
40569 @option{--statistics} command-line switch (@pxref{Mode Options}).
40571 @item maint set per-command symtab [on|off]
40572 @itemx maint show per-command symtab
40573 Enable or disable the printing of basic symbol table statistics
40575 If enabled, @value{GDBN} will display the following information:
40579 number of symbol tables
40581 number of primary symbol tables
40583 number of blocks in the blockvector
40587 @kindex maint set check-libthread-db
40588 @kindex maint show check-libthread-db
40589 @item maint set check-libthread-db [on|off]
40590 @itemx maint show check-libthread-db
40591 Control whether @value{GDBN} should run integrity checks on inferior
40592 specific thread debugging libraries as they are loaded. The default
40593 is not to perform such checks. If any check fails @value{GDBN} will
40594 unload the library and continue searching for a suitable candidate as
40595 described in @ref{set libthread-db-search-path}. For more information
40596 about the tests, see @ref{maint check libthread-db}.
40598 @kindex maint set gnu-source-highlight enabled
40599 @kindex maint show gnu-source-highlight enabled
40600 @item maint set gnu-source-highlight enabled @r{[}on|off@r{]}
40601 @itemx maint show gnu-source-highlight enabled
40602 Control whether @value{GDBN} should use the GNU Source Highlight
40603 library for applying styling to source code (@pxref{Output Styling}).
40604 This will be @samp{on} by default if the GNU Source Highlight library
40605 is available. If the GNU Source Highlight library is not available,
40606 then this will be @samp{off} by default, and attempting to change this
40607 value to @samp{on} will give an error.
40609 If the GNU Source Highlight library is not being used, then
40610 @value{GDBN} will use the Python Pygments package for source code
40611 styling, if it is available.
40613 This option is useful for debugging @value{GDBN}'s use of the Pygments
40614 library when @value{GDBN} is linked against the GNU Source Highlight
40617 @anchor{maint_libopcodes_styling}
40618 @kindex maint set libopcodes-styling enabled
40619 @kindex maint show libopcodes-styling enabled
40620 @item maint set libopcodes-styling enabled @r{[}on|off@r{]}
40621 @itemx maint show libopcodes-styling enabled
40622 Control whether @value{GDBN} should use its builtin disassembler
40623 (@file{libopcodes}) to style disassembler output (@pxref{Output
40624 Styling}). The builtin disassembler does not support styling for all
40627 When this option is @samp{off} the builtin disassembler will not be
40628 used for styling, @value{GDBN} will fall back to using the Python
40629 Pygments package if possible.
40631 Trying to set this option @samp{on} for an architecture that the
40632 builtin disassembler is unable to style will give an error, otherwise,
40633 the builtin disassembler will be used to style disassembler output.
40635 This option is @samp{on} by default for supported architectures.
40637 This option is useful for debugging @value{GDBN}'s use of the Pygments
40638 library when @value{GDBN} is built for an architecture that supports
40639 styling with the builtin disassembler
40640 @kindex maint space
40641 @cindex memory used by commands
40642 @item maint space @var{value}
40643 An alias for @code{maint set per-command space}.
40644 A non-zero value enables it, zero disables it.
40647 @cindex time of command execution
40648 @item maint time @var{value}
40649 An alias for @code{maint set per-command time}.
40650 A non-zero value enables it, zero disables it.
40652 @kindex maint translate-address
40653 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
40654 Find the symbol stored at the location specified by the address
40655 @var{addr} and an optional section name @var{section}. If found,
40656 @value{GDBN} prints the name of the closest symbol and an offset from
40657 the symbol's location to the specified address. This is similar to
40658 the @code{info address} command (@pxref{Symbols}), except that this
40659 command also allows to find symbols in other sections.
40661 If section was not specified, the section in which the symbol was found
40662 is also printed. For dynamically linked executables, the name of
40663 executable or shared library containing the symbol is printed as well.
40665 @kindex maint test-options
40666 @item maint test-options require-delimiter
40667 @itemx maint test-options unknown-is-error
40668 @itemx maint test-options unknown-is-operand
40669 These commands are used by the testsuite to validate the command
40670 options framework. The @code{require-delimiter} variant requires a
40671 double-dash delimiter to indicate end of options. The
40672 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
40673 @code{unknown-is-error} variant throws an error on unknown option,
40674 while @code{unknown-is-operand} treats unknown options as the start of
40675 the command's operands. When run, the commands output the result of
40676 the processed options. When completed, the commands store the
40677 internal result of completion in a variable exposed by the @code{maint
40678 show test-options-completion-result} command.
40680 @kindex maint show test-options-completion-result
40681 @item maint show test-options-completion-result
40682 Shows the result of completing the @code{maint test-options}
40683 subcommands. This is used by the testsuite to validate completion
40684 support in the command options framework.
40686 @kindex maint set test-settings
40687 @kindex maint show test-settings
40688 @item maint set test-settings @var{kind}
40689 @itemx maint show test-settings @var{kind}
40690 These are representative commands for each @var{kind} of setting type
40691 @value{GDBN} supports. They are used by the testsuite for exercising
40692 the settings infrastructure.
40694 @kindex maint set backtrace-on-fatal-signal
40695 @kindex maint show backtrace-on-fatal-signal
40696 @item maint set backtrace-on-fatal-signal [on|off]
40697 @itemx maint show backtrace-on-fatal-signal
40698 When this setting is @code{on}, if @value{GDBN} itself terminates with
40699 a fatal signal (e.g.@: SIGSEGV), then a limited backtrace will be
40700 printed to the standard error stream. This backtrace can be used to
40701 help diagnose crashes within @value{GDBN} in situations where a user
40702 is unable to share a corefile with the @value{GDBN} developers.
40704 If the functionality to provide this backtrace is not available for
40705 the platform on which GDB is running then this feature will be
40706 @code{off} by default, and attempting to turn this feature on will
40709 For platforms that do support creating the backtrace this feature is
40710 @code{on} by default.
40713 @item maint with @var{setting} [@var{value}] [-- @var{command}]
40714 Like the @code{with} command, but works with @code{maintenance set}
40715 variables. This is used by the testsuite to exercise the @code{with}
40716 command's infrastructure.
40720 The following command is useful for non-interactive invocations of
40721 @value{GDBN}, such as in the test suite.
40724 @item set watchdog @var{nsec}
40725 @kindex set watchdog
40726 @cindex watchdog timer
40727 @cindex timeout for commands
40728 Set the maximum number of seconds @value{GDBN} will wait for the
40729 target operation to finish. If this time expires, @value{GDBN}
40730 reports and error and the command is aborted.
40732 @item show watchdog
40733 Show the current setting of the target wait timeout.
40736 @node Remote Protocol
40737 @appendix @value{GDBN} Remote Serial Protocol
40742 * Stop Reply Packets::
40743 * General Query Packets::
40744 * Architecture-Specific Protocol Details::
40745 * Tracepoint Packets::
40746 * Host I/O Packets::
40748 * Notification Packets::
40749 * Remote Non-Stop::
40750 * Packet Acknowledgment::
40752 * File-I/O Remote Protocol Extension::
40753 * Library List Format::
40754 * Library List Format for SVR4 Targets::
40755 * Memory Map Format::
40756 * Thread List Format::
40757 * Traceframe Info Format::
40758 * Branch Trace Format::
40759 * Branch Trace Configuration Format::
40765 There may be occasions when you need to know something about the
40766 protocol---for example, if there is only one serial port to your target
40767 machine, you might want your program to do something special if it
40768 recognizes a packet meant for @value{GDBN}.
40770 In the examples below, @samp{->} and @samp{<-} are used to indicate
40771 transmitted and received data, respectively.
40773 @cindex protocol, @value{GDBN} remote serial
40774 @cindex serial protocol, @value{GDBN} remote
40775 @cindex remote serial protocol
40776 All @value{GDBN} commands and responses (other than acknowledgments
40777 and notifications, see @ref{Notification Packets}) are sent as a
40778 @var{packet}. A @var{packet} is introduced with the character
40779 @samp{$}, the actual @var{packet-data}, and the terminating character
40780 @samp{#} followed by a two-digit @var{checksum}:
40783 @code{$}@var{packet-data}@code{#}@var{checksum}
40787 @cindex checksum, for @value{GDBN} remote
40789 The two-digit @var{checksum} is computed as the modulo 256 sum of all
40790 characters between the leading @samp{$} and the trailing @samp{#} (an
40791 eight bit unsigned checksum).
40793 Implementors should note that prior to @value{GDBN} 5.0 the protocol
40794 specification also included an optional two-digit @var{sequence-id}:
40797 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
40800 @cindex sequence-id, for @value{GDBN} remote
40802 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
40803 has never output @var{sequence-id}s. Stubs that handle packets added
40804 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
40806 When either the host or the target machine receives a packet, the first
40807 response expected is an acknowledgment: either @samp{+} (to indicate
40808 the package was received correctly) or @samp{-} (to request
40812 -> @code{$}@var{packet-data}@code{#}@var{checksum}
40817 The @samp{+}/@samp{-} acknowledgments can be disabled
40818 once a connection is established.
40819 @xref{Packet Acknowledgment}, for details.
40821 The host (@value{GDBN}) sends @var{command}s, and the target (the
40822 debugging stub incorporated in your program) sends a @var{response}. In
40823 the case of step and continue @var{command}s, the response is only sent
40824 when the operation has completed, and the target has again stopped all
40825 threads in all attached processes. This is the default all-stop mode
40826 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
40827 execution mode; see @ref{Remote Non-Stop}, for details.
40829 @var{packet-data} consists of a sequence of characters with the
40830 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
40833 @cindex remote protocol, field separator
40834 Fields within the packet should be separated using @samp{,} @samp{;} or
40835 @samp{:}. Except where otherwise noted all numbers are represented in
40836 @sc{hex} with leading zeros suppressed.
40838 Implementors should note that prior to @value{GDBN} 5.0, the character
40839 @samp{:} could not appear as the third character in a packet (as it
40840 would potentially conflict with the @var{sequence-id}).
40842 @cindex remote protocol, binary data
40843 @anchor{Binary Data}
40844 Binary data in most packets is encoded either as two hexadecimal
40845 digits per byte of binary data. This allowed the traditional remote
40846 protocol to work over connections which were only seven-bit clean.
40847 Some packets designed more recently assume an eight-bit clean
40848 connection, and use a more efficient encoding to send and receive
40851 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
40852 as an escape character. Any escaped byte is transmitted as the escape
40853 character followed by the original character XORed with @code{0x20}.
40854 For example, the byte @code{0x7d} would be transmitted as the two
40855 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
40856 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
40857 @samp{@}}) must always be escaped. Responses sent by the stub
40858 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
40859 is not interpreted as the start of a run-length encoded sequence
40862 Response @var{data} can be run-length encoded to save space.
40863 Run-length encoding replaces runs of identical characters with one
40864 instance of the repeated character, followed by a @samp{*} and a
40865 repeat count. The repeat count is itself sent encoded, to avoid
40866 binary characters in @var{data}: a value of @var{n} is sent as
40867 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
40868 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
40869 code 32) for a repeat count of 3. (This is because run-length
40870 encoding starts to win for counts 3 or more.) Thus, for example,
40871 @samp{0* } is a run-length encoding of ``0000'': the space character
40872 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
40875 The printable characters @samp{#} and @samp{$} or with a numeric value
40876 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
40877 seven repeats (@samp{$}) can be expanded using a repeat count of only
40878 five (@samp{"}). For example, @samp{00000000} can be encoded as
40881 The error response returned for some packets includes a two character
40882 error number. That number is not well defined.
40884 @cindex empty response, for unsupported packets
40885 For any @var{command} not supported by the stub, an empty response
40886 (@samp{$#00}) should be returned. That way it is possible to extend the
40887 protocol. A newer @value{GDBN} can tell if a packet is supported based
40890 At a minimum, a stub is required to support the @samp{?} command to
40891 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
40892 commands for register access, and the @samp{m} and @samp{M} commands
40893 for memory access. Stubs that only control single-threaded targets
40894 can implement run control with the @samp{c} (continue) command, and if
40895 the target architecture supports hardware-assisted single-stepping,
40896 the @samp{s} (step) command. Stubs that support multi-threading
40897 targets should support the @samp{vCont} command. All other commands
40903 The following table provides a complete list of all currently defined
40904 @var{command}s and their corresponding response @var{data}.
40905 @xref{File-I/O Remote Protocol Extension}, for details about the File
40906 I/O extension of the remote protocol.
40908 Each packet's description has a template showing the packet's overall
40909 syntax, followed by an explanation of the packet's meaning. We
40910 include spaces in some of the templates for clarity; these are not
40911 part of the packet's syntax. No @value{GDBN} packet uses spaces to
40912 separate its components. For example, a template like @samp{foo
40913 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
40914 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
40915 @var{baz}. @value{GDBN} does not transmit a space character between the
40916 @samp{foo} and the @var{bar}, or between the @var{bar} and the
40919 @cindex @var{thread-id}, in remote protocol
40920 @anchor{thread-id syntax}
40921 Several packets and replies include a @var{thread-id} field to identify
40922 a thread. Normally these are positive numbers with a target-specific
40923 interpretation, formatted as big-endian hex strings. A @var{thread-id}
40924 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
40927 In addition, the remote protocol supports a multiprocess feature in
40928 which the @var{thread-id} syntax is extended to optionally include both
40929 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
40930 The @var{pid} (process) and @var{tid} (thread) components each have the
40931 format described above: a positive number with target-specific
40932 interpretation formatted as a big-endian hex string, literal @samp{-1}
40933 to indicate all processes or threads (respectively), or @samp{0} to
40934 indicate an arbitrary process or thread. Specifying just a process, as
40935 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
40936 error to specify all processes but a specific thread, such as
40937 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
40938 for those packets and replies explicitly documented to include a process
40939 ID, rather than a @var{thread-id}.
40941 The multiprocess @var{thread-id} syntax extensions are only used if both
40942 @value{GDBN} and the stub report support for the @samp{multiprocess}
40943 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
40946 Note that all packet forms beginning with an upper- or lower-case
40947 letter, other than those described here, are reserved for future use.
40949 Here are the packet descriptions.
40954 @cindex @samp{!} packet
40955 @anchor{extended mode}
40956 Enable extended mode. In extended mode, the remote server is made
40957 persistent. The @samp{R} packet is used to restart the program being
40963 The remote target both supports and has enabled extended mode.
40967 @cindex @samp{?} packet
40969 This is sent when connection is first established to query the reason
40970 the target halted. The reply is the same as for step and continue.
40971 This packet has a special interpretation when the target is in
40972 non-stop mode; see @ref{Remote Non-Stop}.
40975 @xref{Stop Reply Packets}, for the reply specifications.
40977 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
40978 @cindex @samp{A} packet
40979 Initialized @code{argv[]} array passed into program. @var{arglen}
40980 specifies the number of bytes in the hex encoded byte stream
40981 @var{arg}. See @code{gdbserver} for more details.
40986 The arguments were set.
40992 @cindex @samp{b} packet
40993 (Don't use this packet; its behavior is not well-defined.)
40994 Change the serial line speed to @var{baud}.
40996 JTC: @emph{When does the transport layer state change? When it's
40997 received, or after the ACK is transmitted. In either case, there are
40998 problems if the command or the acknowledgment packet is dropped.}
41000 Stan: @emph{If people really wanted to add something like this, and get
41001 it working for the first time, they ought to modify ser-unix.c to send
41002 some kind of out-of-band message to a specially-setup stub and have the
41003 switch happen "in between" packets, so that from remote protocol's point
41004 of view, nothing actually happened.}
41006 @item B @var{addr},@var{mode}
41007 @cindex @samp{B} packet
41008 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
41009 breakpoint at @var{addr}.
41011 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
41012 (@pxref{insert breakpoint or watchpoint packet}).
41014 @cindex @samp{bc} packet
41017 Backward continue. Execute the target system in reverse. No parameter.
41018 @xref{Reverse Execution}, for more information.
41021 @xref{Stop Reply Packets}, for the reply specifications.
41023 @cindex @samp{bs} packet
41026 Backward single step. Execute one instruction in reverse. No parameter.
41027 @xref{Reverse Execution}, for more information.
41030 @xref{Stop Reply Packets}, for the reply specifications.
41032 @item c @r{[}@var{addr}@r{]}
41033 @cindex @samp{c} packet
41034 Continue at @var{addr}, which is the address to resume. If @var{addr}
41035 is omitted, resume at current address.
41037 This packet is deprecated for multi-threading support. @xref{vCont
41041 @xref{Stop Reply Packets}, for the reply specifications.
41043 @item C @var{sig}@r{[};@var{addr}@r{]}
41044 @cindex @samp{C} packet
41045 Continue with signal @var{sig} (hex signal number). If
41046 @samp{;@var{addr}} is omitted, resume at same address.
41048 This packet is deprecated for multi-threading support. @xref{vCont
41052 @xref{Stop Reply Packets}, for the reply specifications.
41055 @cindex @samp{d} packet
41058 Don't use this packet; instead, define a general set packet
41059 (@pxref{General Query Packets}).
41063 @cindex @samp{D} packet
41064 The first form of the packet is used to detach @value{GDBN} from the
41065 remote system. It is sent to the remote target
41066 before @value{GDBN} disconnects via the @code{detach} command.
41068 The second form, including a process ID, is used when multiprocess
41069 protocol extensions are enabled (@pxref{multiprocess extensions}), to
41070 detach only a specific process. The @var{pid} is specified as a
41071 big-endian hex string.
41081 @item F @var{RC},@var{EE},@var{CF};@var{XX}
41082 @cindex @samp{F} packet
41083 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
41084 This is part of the File-I/O protocol extension. @xref{File-I/O
41085 Remote Protocol Extension}, for the specification.
41088 @anchor{read registers packet}
41089 @cindex @samp{g} packet
41090 Read general registers.
41094 @item @var{XX@dots{}}
41095 Each byte of register data is described by two hex digits. The bytes
41096 with the register are transmitted in target byte order. The size of
41097 each register and their position within the @samp{g} packet are
41098 determined by the @value{GDBN} internal gdbarch functions
41099 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
41101 When reading registers from a trace frame (@pxref{Analyze Collected
41102 Data,,Using the Collected Data}), the stub may also return a string of
41103 literal @samp{x}'s in place of the register data digits, to indicate
41104 that the corresponding register has not been collected, thus its value
41105 is unavailable. For example, for an architecture with 4 registers of
41106 4 bytes each, the following reply indicates to @value{GDBN} that
41107 registers 0 and 2 have not been collected, while registers 1 and 3
41108 have been collected, and both have zero value:
41112 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
41119 @item G @var{XX@dots{}}
41120 @cindex @samp{G} packet
41121 Write general registers. @xref{read registers packet}, for a
41122 description of the @var{XX@dots{}} data.
41132 @item H @var{op} @var{thread-id}
41133 @cindex @samp{H} packet
41134 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
41135 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
41136 should be @samp{c} for step and continue operations (note that this
41137 is deprecated, supporting the @samp{vCont} command is a better
41138 option), and @samp{g} for other operations. The thread designator
41139 @var{thread-id} has the format and interpretation described in
41140 @ref{thread-id syntax}.
41151 @c 'H': How restrictive (or permissive) is the thread model. If a
41152 @c thread is selected and stopped, are other threads allowed
41153 @c to continue to execute? As I mentioned above, I think the
41154 @c semantics of each command when a thread is selected must be
41155 @c described. For example:
41157 @c 'g': If the stub supports threads and a specific thread is
41158 @c selected, returns the register block from that thread;
41159 @c otherwise returns current registers.
41161 @c 'G' If the stub supports threads and a specific thread is
41162 @c selected, sets the registers of the register block of
41163 @c that thread; otherwise sets current registers.
41165 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
41166 @anchor{cycle step packet}
41167 @cindex @samp{i} packet
41168 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
41169 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
41170 step starting at that address.
41173 @cindex @samp{I} packet
41174 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
41178 @cindex @samp{k} packet
41181 The exact effect of this packet is not specified.
41183 For a bare-metal target, it may power cycle or reset the target
41184 system. For that reason, the @samp{k} packet has no reply.
41186 For a single-process target, it may kill that process if possible.
41188 A multiple-process target may choose to kill just one process, or all
41189 that are under @value{GDBN}'s control. For more precise control, use
41190 the vKill packet (@pxref{vKill packet}).
41192 If the target system immediately closes the connection in response to
41193 @samp{k}, @value{GDBN} does not consider the lack of packet
41194 acknowledgment to be an error, and assumes the kill was successful.
41196 If connected using @kbd{target extended-remote}, and the target does
41197 not close the connection in response to a kill request, @value{GDBN}
41198 probes the target state as if a new connection was opened
41199 (@pxref{? packet}).
41201 @item m @var{addr},@var{length}
41202 @cindex @samp{m} packet
41203 Read @var{length} addressable memory units starting at address @var{addr}
41204 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
41205 any particular boundary.
41207 The stub need not use any particular size or alignment when gathering
41208 data from memory for the response; even if @var{addr} is word-aligned
41209 and @var{length} is a multiple of the word size, the stub is free to
41210 use byte accesses, or not. For this reason, this packet may not be
41211 suitable for accessing memory-mapped I/O devices.
41212 @cindex alignment of remote memory accesses
41213 @cindex size of remote memory accesses
41214 @cindex memory, alignment and size of remote accesses
41218 @item @var{XX@dots{}}
41219 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
41220 The reply may contain fewer addressable memory units than requested if the
41221 server was able to read only part of the region of memory.
41226 @item M @var{addr},@var{length}:@var{XX@dots{}}
41227 @cindex @samp{M} packet
41228 Write @var{length} addressable memory units starting at address @var{addr}
41229 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
41230 byte is transmitted as a two-digit hexadecimal number.
41237 for an error (this includes the case where only part of the data was
41242 @cindex @samp{p} packet
41243 Read the value of register @var{n}; @var{n} is in hex.
41244 @xref{read registers packet}, for a description of how the returned
41245 register value is encoded.
41249 @item @var{XX@dots{}}
41250 the register's value
41254 Indicating an unrecognized @var{query}.
41257 @item P @var{n@dots{}}=@var{r@dots{}}
41258 @anchor{write register packet}
41259 @cindex @samp{P} packet
41260 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
41261 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
41262 digits for each byte in the register (target byte order).
41272 @item q @var{name} @var{params}@dots{}
41273 @itemx Q @var{name} @var{params}@dots{}
41274 @cindex @samp{q} packet
41275 @cindex @samp{Q} packet
41276 General query (@samp{q}) and set (@samp{Q}). These packets are
41277 described fully in @ref{General Query Packets}.
41280 @cindex @samp{r} packet
41281 Reset the entire system.
41283 Don't use this packet; use the @samp{R} packet instead.
41286 @cindex @samp{R} packet
41287 Restart the program being debugged. The @var{XX}, while needed, is ignored.
41288 This packet is only available in extended mode (@pxref{extended mode}).
41290 The @samp{R} packet has no reply.
41292 @item s @r{[}@var{addr}@r{]}
41293 @cindex @samp{s} packet
41294 Single step, resuming at @var{addr}. If
41295 @var{addr} is omitted, resume at same address.
41297 This packet is deprecated for multi-threading support. @xref{vCont
41301 @xref{Stop Reply Packets}, for the reply specifications.
41303 @item S @var{sig}@r{[};@var{addr}@r{]}
41304 @anchor{step with signal packet}
41305 @cindex @samp{S} packet
41306 Step with signal. This is analogous to the @samp{C} packet, but
41307 requests a single-step, rather than a normal resumption of execution.
41309 This packet is deprecated for multi-threading support. @xref{vCont
41313 @xref{Stop Reply Packets}, for the reply specifications.
41315 @item t @var{addr}:@var{PP},@var{MM}
41316 @cindex @samp{t} packet
41317 Search backwards starting at address @var{addr} for a match with pattern
41318 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
41319 There must be at least 3 digits in @var{addr}.
41321 @item T @var{thread-id}
41322 @cindex @samp{T} packet
41323 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
41328 thread is still alive
41334 Packets starting with @samp{v} are identified by a multi-letter name,
41335 up to the first @samp{;} or @samp{?} (or the end of the packet).
41337 @item vAttach;@var{pid}
41338 @cindex @samp{vAttach} packet
41339 Attach to a new process with the specified process ID @var{pid}.
41340 The process ID is a
41341 hexadecimal integer identifying the process. In all-stop mode, all
41342 threads in the attached process are stopped; in non-stop mode, it may be
41343 attached without being stopped if that is supported by the target.
41345 @c In non-stop mode, on a successful vAttach, the stub should set the
41346 @c current thread to a thread of the newly-attached process. After
41347 @c attaching, GDB queries for the attached process's thread ID with qC.
41348 @c Also note that, from a user perspective, whether or not the
41349 @c target is stopped on attach in non-stop mode depends on whether you
41350 @c use the foreground or background version of the attach command, not
41351 @c on what vAttach does; GDB does the right thing with respect to either
41352 @c stopping or restarting threads.
41354 This packet is only available in extended mode (@pxref{extended mode}).
41360 @item @r{Any stop packet}
41361 for success in all-stop mode (@pxref{Stop Reply Packets})
41363 for success in non-stop mode (@pxref{Remote Non-Stop})
41366 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
41367 @cindex @samp{vCont} packet
41368 @anchor{vCont packet}
41369 Resume the inferior, specifying different actions for each thread.
41371 For each inferior thread, the leftmost action with a matching
41372 @var{thread-id} is applied. Threads that don't match any action
41373 remain in their current state. Thread IDs are specified using the
41374 syntax described in @ref{thread-id syntax}. If multiprocess
41375 extensions (@pxref{multiprocess extensions}) are supported, actions
41376 can be specified to match all threads in a process by using the
41377 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
41378 @var{thread-id} matches all threads. Specifying no actions is an
41381 Currently supported actions are:
41387 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
41391 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
41394 @item r @var{start},@var{end}
41395 Step once, and then keep stepping as long as the thread stops at
41396 addresses between @var{start} (inclusive) and @var{end} (exclusive).
41397 The remote stub reports a stop reply when either the thread goes out
41398 of the range or is stopped due to an unrelated reason, such as hitting
41399 a breakpoint. @xref{range stepping}.
41401 If the range is empty (@var{start} == @var{end}), then the action
41402 becomes equivalent to the @samp{s} action. In other words,
41403 single-step once, and report the stop (even if the stepped instruction
41404 jumps to @var{start}).
41406 (A stop reply may be sent at any point even if the PC is still within
41407 the stepping range; for example, it is valid to implement this packet
41408 in a degenerate way as a single instruction step operation.)
41412 The optional argument @var{addr} normally associated with the
41413 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
41414 not supported in @samp{vCont}.
41416 The @samp{t} action is only relevant in non-stop mode
41417 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
41418 A stop reply should be generated for any affected thread not already stopped.
41419 When a thread is stopped by means of a @samp{t} action,
41420 the corresponding stop reply should indicate that the thread has stopped with
41421 signal @samp{0}, regardless of whether the target uses some other signal
41422 as an implementation detail.
41424 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
41425 @samp{r} actions for threads that are already running. Conversely,
41426 the server must ignore @samp{t} actions for threads that are already
41429 @emph{Note:} In non-stop mode, a thread is considered running until
41430 @value{GDBN} acknowledges an asynchronous stop notification for it with
41431 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
41433 The stub must support @samp{vCont} if it reports support for
41434 multiprocess extensions (@pxref{multiprocess extensions}).
41437 @xref{Stop Reply Packets}, for the reply specifications.
41440 @cindex @samp{vCont?} packet
41441 Request a list of actions supported by the @samp{vCont} packet.
41445 @item vCont@r{[};@var{action}@dots{}@r{]}
41446 The @samp{vCont} packet is supported. Each @var{action} is a supported
41447 command in the @samp{vCont} packet.
41449 The @samp{vCont} packet is not supported.
41452 @anchor{vCtrlC packet}
41454 @cindex @samp{vCtrlC} packet
41455 Interrupt remote target as if a control-C was pressed on the remote
41456 terminal. This is the equivalent to reacting to the @code{^C}
41457 (@samp{\003}, the control-C character) character in all-stop mode
41458 while the target is running, except this works in non-stop mode.
41459 @xref{interrupting remote targets}, for more info on the all-stop
41470 @item vFile:@var{operation}:@var{parameter}@dots{}
41471 @cindex @samp{vFile} packet
41472 Perform a file operation on the target system. For details,
41473 see @ref{Host I/O Packets}.
41475 @item vFlashErase:@var{addr},@var{length}
41476 @cindex @samp{vFlashErase} packet
41477 Direct the stub to erase @var{length} bytes of flash starting at
41478 @var{addr}. The region may enclose any number of flash blocks, but
41479 its start and end must fall on block boundaries, as indicated by the
41480 flash block size appearing in the memory map (@pxref{Memory Map
41481 Format}). @value{GDBN} groups flash memory programming operations
41482 together, and sends a @samp{vFlashDone} request after each group; the
41483 stub is allowed to delay erase operation until the @samp{vFlashDone}
41484 packet is received.
41494 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
41495 @cindex @samp{vFlashWrite} packet
41496 Direct the stub to write data to flash address @var{addr}. The data
41497 is passed in binary form using the same encoding as for the @samp{X}
41498 packet (@pxref{Binary Data}). The memory ranges specified by
41499 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
41500 not overlap, and must appear in order of increasing addresses
41501 (although @samp{vFlashErase} packets for higher addresses may already
41502 have been received; the ordering is guaranteed only between
41503 @samp{vFlashWrite} packets). If a packet writes to an address that was
41504 neither erased by a preceding @samp{vFlashErase} packet nor by some other
41505 target-specific method, the results are unpredictable.
41513 for vFlashWrite addressing non-flash memory
41519 @cindex @samp{vFlashDone} packet
41520 Indicate to the stub that flash programming operation is finished.
41521 The stub is permitted to delay or batch the effects of a group of
41522 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
41523 @samp{vFlashDone} packet is received. The contents of the affected
41524 regions of flash memory are unpredictable until the @samp{vFlashDone}
41525 request is completed.
41527 @item vKill;@var{pid}
41528 @cindex @samp{vKill} packet
41529 @anchor{vKill packet}
41530 Kill the process with the specified process ID @var{pid}, which is a
41531 hexadecimal integer identifying the process. This packet is used in
41532 preference to @samp{k} when multiprocess protocol extensions are
41533 supported; see @ref{multiprocess extensions}.
41543 @item vMustReplyEmpty
41544 @cindex @samp{vMustReplyEmpty} packet
41545 The correct reply to an unknown @samp{v} packet is to return the empty
41546 string, however, some older versions of @command{gdbserver} would
41547 incorrectly return @samp{OK} for unknown @samp{v} packets.
41549 The @samp{vMustReplyEmpty} is used as a feature test to check how
41550 @command{gdbserver} handles unknown packets, it is important that this
41551 packet be handled in the same way as other unknown @samp{v} packets.
41552 If this packet is handled differently to other unknown @samp{v}
41553 packets then it is possible that @value{GDBN} may run into problems in
41554 other areas, specifically around use of @samp{vFile:setfs:}.
41556 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
41557 @cindex @samp{vRun} packet
41558 Run the program @var{filename}, passing it each @var{argument} on its
41559 command line. The file and arguments are hex-encoded strings. If
41560 @var{filename} is an empty string, the stub may use a default program
41561 (e.g.@: the last program run). The program is created in the stopped
41564 @c FIXME: What about non-stop mode?
41566 This packet is only available in extended mode (@pxref{extended mode}).
41572 @item @r{Any stop packet}
41573 for success (@pxref{Stop Reply Packets})
41577 @cindex @samp{vStopped} packet
41578 @xref{Notification Packets}.
41580 @item X @var{addr},@var{length}:@var{XX@dots{}}
41582 @cindex @samp{X} packet
41583 Write data to memory, where the data is transmitted in binary.
41584 Memory is specified by its address @var{addr} and number of addressable memory
41585 units @var{length} (@pxref{addressable memory unit});
41586 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
41596 @item z @var{type},@var{addr},@var{kind}
41597 @itemx Z @var{type},@var{addr},@var{kind}
41598 @anchor{insert breakpoint or watchpoint packet}
41599 @cindex @samp{z} packet
41600 @cindex @samp{Z} packets
41601 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
41602 watchpoint starting at address @var{address} of kind @var{kind}.
41604 Each breakpoint and watchpoint packet @var{type} is documented
41607 @emph{Implementation notes: A remote target shall return an empty string
41608 for an unrecognized breakpoint or watchpoint packet @var{type}. A
41609 remote target shall support either both or neither of a given
41610 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
41611 avoid potential problems with duplicate packets, the operations should
41612 be implemented in an idempotent way.}
41614 @item z0,@var{addr},@var{kind}
41615 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41616 @cindex @samp{z0} packet
41617 @cindex @samp{Z0} packet
41618 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
41619 @var{addr} of type @var{kind}.
41621 A software breakpoint is implemented by replacing the instruction at
41622 @var{addr} with a software breakpoint or trap instruction. The
41623 @var{kind} is target-specific and typically indicates the size of the
41624 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
41625 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
41626 architectures have additional meanings for @var{kind}
41627 (@pxref{Architecture-Specific Protocol Details}); if no
41628 architecture-specific value is being used, it should be @samp{0}.
41629 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
41630 conditional expressions in bytecode form that should be evaluated on
41631 the target's side. These are the conditions that should be taken into
41632 consideration when deciding if the breakpoint trigger should be
41633 reported back to @value{GDBN}.
41635 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
41636 for how to best report a software breakpoint event to @value{GDBN}.
41638 The @var{cond_list} parameter is comprised of a series of expressions,
41639 concatenated without separators. Each expression has the following form:
41643 @item X @var{len},@var{expr}
41644 @var{len} is the length of the bytecode expression and @var{expr} is the
41645 actual conditional expression in bytecode form.
41649 The optional @var{cmd_list} parameter introduces commands that may be
41650 run on the target, rather than being reported back to @value{GDBN}.
41651 The parameter starts with a numeric flag @var{persist}; if the flag is
41652 nonzero, then the breakpoint may remain active and the commands
41653 continue to be run even when @value{GDBN} disconnects from the target.
41654 Following this flag is a series of expressions concatenated with no
41655 separators. Each expression has the following form:
41659 @item X @var{len},@var{expr}
41660 @var{len} is the length of the bytecode expression and @var{expr} is the
41661 actual commands expression in bytecode form.
41665 @emph{Implementation note: It is possible for a target to copy or move
41666 code that contains software breakpoints (e.g., when implementing
41667 overlays). The behavior of this packet, in the presence of such a
41668 target, is not defined.}
41680 @item z1,@var{addr},@var{kind}
41681 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41682 @cindex @samp{z1} packet
41683 @cindex @samp{Z1} packet
41684 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
41685 address @var{addr}.
41687 A hardware breakpoint is implemented using a mechanism that is not
41688 dependent on being able to modify the target's memory. The
41689 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
41690 same meaning as in @samp{Z0} packets.
41692 @emph{Implementation note: A hardware breakpoint is not affected by code
41705 @item z2,@var{addr},@var{kind}
41706 @itemx Z2,@var{addr},@var{kind}
41707 @cindex @samp{z2} packet
41708 @cindex @samp{Z2} packet
41709 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
41710 The number of bytes to watch is specified by @var{kind}.
41722 @item z3,@var{addr},@var{kind}
41723 @itemx Z3,@var{addr},@var{kind}
41724 @cindex @samp{z3} packet
41725 @cindex @samp{Z3} packet
41726 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
41727 The number of bytes to watch is specified by @var{kind}.
41739 @item z4,@var{addr},@var{kind}
41740 @itemx Z4,@var{addr},@var{kind}
41741 @cindex @samp{z4} packet
41742 @cindex @samp{Z4} packet
41743 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
41744 The number of bytes to watch is specified by @var{kind}.
41758 @node Stop Reply Packets
41759 @section Stop Reply Packets
41760 @cindex stop reply packets
41762 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
41763 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
41764 receive any of the below as a reply. Except for @samp{?}
41765 and @samp{vStopped}, that reply is only returned
41766 when the target halts. In the below the exact meaning of @dfn{signal
41767 number} is defined by the header @file{include/gdb/signals.h} in the
41768 @value{GDBN} source code.
41770 In non-stop mode, the server will simply reply @samp{OK} to commands
41771 such as @samp{vCont}; any stop will be the subject of a future
41772 notification. @xref{Remote Non-Stop}.
41774 As in the description of request packets, we include spaces in the
41775 reply templates for clarity; these are not part of the reply packet's
41776 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
41782 The program received signal number @var{AA} (a two-digit hexadecimal
41783 number). This is equivalent to a @samp{T} response with no
41784 @var{n}:@var{r} pairs.
41786 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
41787 @cindex @samp{T} packet reply
41788 The program received signal number @var{AA} (a two-digit hexadecimal
41789 number). This is equivalent to an @samp{S} response, except that the
41790 @samp{@var{n}:@var{r}} pairs can carry values of important registers
41791 and other information directly in the stop reply packet, reducing
41792 round-trip latency. Single-step and breakpoint traps are reported
41793 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
41797 If @var{n} is a hexadecimal number, it is a register number, and the
41798 corresponding @var{r} gives that register's value. The data @var{r} is a
41799 series of bytes in target byte order, with each byte given by a
41800 two-digit hex number.
41803 If @var{n} is @samp{thread}, then @var{r} is the thread ID of
41804 the stopped thread, as specified in @ref{thread-id syntax}.
41807 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
41808 the core on which the stop event was detected.
41811 If @var{n} is a recognized @dfn{stop reason}, it describes a more
41812 specific event that stopped the target. The currently defined stop
41813 reasons are listed below. The @var{aa} should be @samp{05}, the trap
41814 signal. At most one stop reason should be present.
41817 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
41818 and go on to the next; this allows us to extend the protocol in the
41822 The currently defined stop reasons are:
41828 The packet indicates a watchpoint hit, and @var{r} is the data address, in
41831 @item syscall_entry
41832 @itemx syscall_return
41833 The packet indicates a syscall entry or return, and @var{r} is the
41834 syscall number, in hex.
41836 @cindex shared library events, remote reply
41838 The packet indicates that the loaded libraries have changed.
41839 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
41840 list of loaded libraries. The @var{r} part is ignored.
41842 @cindex replay log events, remote reply
41844 The packet indicates that the target cannot continue replaying
41845 logged execution events, because it has reached the end (or the
41846 beginning when executing backward) of the log. The value of @var{r}
41847 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
41848 for more information.
41851 @anchor{swbreak stop reason}
41852 The packet indicates a software breakpoint instruction was executed,
41853 irrespective of whether it was @value{GDBN} that planted the
41854 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
41855 part must be left empty.
41857 On some architectures, such as x86, at the architecture level, when a
41858 breakpoint instruction executes the program counter points at the
41859 breakpoint address plus an offset. On such targets, the stub is
41860 responsible for adjusting the PC to point back at the breakpoint
41863 This packet should not be sent by default; older @value{GDBN} versions
41864 did not support it. @value{GDBN} requests it, by supplying an
41865 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41866 remote stub must also supply the appropriate @samp{qSupported} feature
41867 indicating support.
41869 This packet is required for correct non-stop mode operation.
41872 The packet indicates the target stopped for a hardware breakpoint.
41873 The @var{r} part must be left empty.
41875 The same remarks about @samp{qSupported} and non-stop mode above
41878 @cindex fork events, remote reply
41880 The packet indicates that @code{fork} was called, and @var{r} is the
41881 thread ID of the new child process, as specified in @ref{thread-id
41882 syntax}. This packet is only applicable to targets that support fork
41885 This packet should not be sent by default; older @value{GDBN} versions
41886 did not support it. @value{GDBN} requests it, by supplying an
41887 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41888 remote stub must also supply the appropriate @samp{qSupported} feature
41889 indicating support.
41891 @cindex vfork events, remote reply
41893 The packet indicates that @code{vfork} was called, and @var{r} is the
41894 thread ID of the new child process, as specified in @ref{thread-id
41895 syntax}. This packet is only applicable to targets that support vfork
41898 This packet should not be sent by default; older @value{GDBN} versions
41899 did not support it. @value{GDBN} requests it, by supplying an
41900 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41901 remote stub must also supply the appropriate @samp{qSupported} feature
41902 indicating support.
41904 @cindex vforkdone events, remote reply
41906 The packet indicates that a child process created by a vfork
41907 has either called @code{exec} or terminated, so that the
41908 address spaces of the parent and child process are no longer
41909 shared. The @var{r} part is ignored. This packet is only
41910 applicable to targets that support vforkdone events.
41912 This packet should not be sent by default; older @value{GDBN} versions
41913 did not support it. @value{GDBN} requests it, by supplying an
41914 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41915 remote stub must also supply the appropriate @samp{qSupported} feature
41916 indicating support.
41918 @cindex exec events, remote reply
41920 The packet indicates that @code{execve} was called, and @var{r}
41921 is the absolute pathname of the file that was executed, in hex.
41922 This packet is only applicable to targets that support exec events.
41924 This packet should not be sent by default; older @value{GDBN} versions
41925 did not support it. @value{GDBN} requests it, by supplying an
41926 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41927 remote stub must also supply the appropriate @samp{qSupported} feature
41928 indicating support.
41930 @cindex thread create event, remote reply
41931 @anchor{thread create event}
41933 The packet indicates that the thread was just created. The new thread
41934 is stopped until @value{GDBN} sets it running with a resumption packet
41935 (@pxref{vCont packet}). This packet should not be sent by default;
41936 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
41937 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
41938 @var{r} part is ignored.
41943 @itemx W @var{AA} ; process:@var{pid}
41944 The process exited, and @var{AA} is the exit status. This is only
41945 applicable to certain targets.
41947 The second form of the response, including the process ID of the
41948 exited process, can be used only when @value{GDBN} has reported
41949 support for multiprocess protocol extensions; see @ref{multiprocess
41950 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41954 @itemx X @var{AA} ; process:@var{pid}
41955 The process terminated with signal @var{AA}.
41957 The second form of the response, including the process ID of the
41958 terminated process, can be used only when @value{GDBN} has reported
41959 support for multiprocess protocol extensions; see @ref{multiprocess
41960 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41963 @anchor{thread exit event}
41964 @cindex thread exit event, remote reply
41965 @item w @var{AA} ; @var{tid}
41967 The thread exited, and @var{AA} is the exit status. This response
41968 should not be sent by default; @value{GDBN} requests it with the
41969 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
41970 @var{AA} is formatted as a big-endian hex string.
41973 There are no resumed threads left in the target. In other words, even
41974 though the process is alive, the last resumed thread has exited. For
41975 example, say the target process has two threads: thread 1 and thread
41976 2. The client leaves thread 1 stopped, and resumes thread 2, which
41977 subsequently exits. At this point, even though the process is still
41978 alive, and thus no @samp{W} stop reply is sent, no thread is actually
41979 executing either. The @samp{N} stop reply thus informs the client
41980 that it can stop waiting for stop replies. This packet should not be
41981 sent by default; older @value{GDBN} versions did not support it.
41982 @value{GDBN} requests it, by supplying an appropriate
41983 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
41984 also supply the appropriate @samp{qSupported} feature indicating
41987 @item O @var{XX}@dots{}
41988 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
41989 written as the program's console output. This can happen at any time
41990 while the program is running and the debugger should continue to wait
41991 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
41993 @item F @var{call-id},@var{parameter}@dots{}
41994 @var{call-id} is the identifier which says which host system call should
41995 be called. This is just the name of the function. Translation into the
41996 correct system call is only applicable as it's defined in @value{GDBN}.
41997 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
42000 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
42001 this very system call.
42003 The target replies with this packet when it expects @value{GDBN} to
42004 call a host system call on behalf of the target. @value{GDBN} replies
42005 with an appropriate @samp{F} packet and keeps up waiting for the next
42006 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
42007 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
42008 Protocol Extension}, for more details.
42012 @node General Query Packets
42013 @section General Query Packets
42014 @cindex remote query requests
42016 Packets starting with @samp{q} are @dfn{general query packets};
42017 packets starting with @samp{Q} are @dfn{general set packets}. General
42018 query and set packets are a semi-unified form for retrieving and
42019 sending information to and from the stub.
42021 The initial letter of a query or set packet is followed by a name
42022 indicating what sort of thing the packet applies to. For example,
42023 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
42024 definitions with the stub. These packet names follow some
42029 The name must not contain commas, colons or semicolons.
42031 Most @value{GDBN} query and set packets have a leading upper case
42034 The names of custom vendor packets should use a company prefix, in
42035 lower case, followed by a period. For example, packets designed at
42036 the Acme Corporation might begin with @samp{qacme.foo} (for querying
42037 foos) or @samp{Qacme.bar} (for setting bars).
42040 The name of a query or set packet should be separated from any
42041 parameters by a @samp{:}; the parameters themselves should be
42042 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
42043 full packet name, and check for a separator or the end of the packet,
42044 in case two packet names share a common prefix. New packets should not begin
42045 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
42046 packets predate these conventions, and have arguments without any terminator
42047 for the packet name; we suspect they are in widespread use in places that
42048 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
42049 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
42052 Like the descriptions of the other packets, each description here
42053 has a template showing the packet's overall syntax, followed by an
42054 explanation of the packet's meaning. We include spaces in some of the
42055 templates for clarity; these are not part of the packet's syntax. No
42056 @value{GDBN} packet uses spaces to separate its components.
42058 Here are the currently defined query and set packets:
42064 Turn on or off the agent as a helper to perform some debugging operations
42065 delegated from @value{GDBN} (@pxref{Control Agent}).
42067 @item QAllow:@var{op}:@var{val}@dots{}
42068 @cindex @samp{QAllow} packet
42069 Specify which operations @value{GDBN} expects to request of the
42070 target, as a semicolon-separated list of operation name and value
42071 pairs. Possible values for @var{op} include @samp{WriteReg},
42072 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
42073 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
42074 indicating that @value{GDBN} will not request the operation, or 1,
42075 indicating that it may. (The target can then use this to set up its
42076 own internals optimally, for instance if the debugger never expects to
42077 insert breakpoints, it may not need to install its own trap handler.)
42080 @cindex current thread, remote request
42081 @cindex @samp{qC} packet
42082 Return the current thread ID.
42086 @item QC @var{thread-id}
42087 Where @var{thread-id} is a thread ID as documented in
42088 @ref{thread-id syntax}.
42089 @item @r{(anything else)}
42090 Any other reply implies the old thread ID.
42093 @item qCRC:@var{addr},@var{length}
42094 @cindex CRC of memory block, remote request
42095 @cindex @samp{qCRC} packet
42096 @anchor{qCRC packet}
42097 Compute the CRC checksum of a block of memory using CRC-32 defined in
42098 IEEE 802.3. The CRC is computed byte at a time, taking the most
42099 significant bit of each byte first. The initial pattern code
42100 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
42102 @emph{Note:} This is the same CRC used in validating separate debug
42103 files (@pxref{Separate Debug Files, , Debugging Information in Separate
42104 Files}). However the algorithm is slightly different. When validating
42105 separate debug files, the CRC is computed taking the @emph{least}
42106 significant bit of each byte first, and the final result is inverted to
42107 detect trailing zeros.
42112 An error (such as memory fault)
42113 @item C @var{crc32}
42114 The specified memory region's checksum is @var{crc32}.
42117 @item QDisableRandomization:@var{value}
42118 @cindex disable address space randomization, remote request
42119 @cindex @samp{QDisableRandomization} packet
42120 Some target operating systems will randomize the virtual address space
42121 of the inferior process as a security feature, but provide a feature
42122 to disable such randomization, e.g.@: to allow for a more deterministic
42123 debugging experience. On such systems, this packet with a @var{value}
42124 of 1 directs the target to disable address space randomization for
42125 processes subsequently started via @samp{vRun} packets, while a packet
42126 with a @var{value} of 0 tells the target to enable address space
42129 This packet is only available in extended mode (@pxref{extended mode}).
42134 The request succeeded.
42137 An error occurred. The error number @var{nn} is given as hex digits.
42140 An empty reply indicates that @samp{QDisableRandomization} is not supported
42144 This packet is not probed by default; the remote stub must request it,
42145 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42146 This should only be done on targets that actually support disabling
42147 address space randomization.
42149 @item QStartupWithShell:@var{value}
42150 @cindex startup with shell, remote request
42151 @cindex @samp{QStartupWithShell} packet
42152 On UNIX-like targets, it is possible to start the inferior using a
42153 shell program. This is the default behavior on both @value{GDBN} and
42154 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
42155 used to inform @command{gdbserver} whether it should start the
42156 inferior using a shell or not.
42158 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
42159 to start the inferior. If @var{value} is @samp{1},
42160 @command{gdbserver} will use a shell to start the inferior. All other
42161 values are considered an error.
42163 This packet is only available in extended mode (@pxref{extended
42169 The request succeeded.
42172 An error occurred. The error number @var{nn} is given as hex digits.
42175 This packet is not probed by default; the remote stub must request it,
42176 by supplying an appropriate @samp{qSupported} response
42177 (@pxref{qSupported}). This should only be done on targets that
42178 actually support starting the inferior using a shell.
42180 Use of this packet is controlled by the @code{set startup-with-shell}
42181 command; @pxref{set startup-with-shell}.
42183 @item QEnvironmentHexEncoded:@var{hex-value}
42184 @anchor{QEnvironmentHexEncoded}
42185 @cindex set environment variable, remote request
42186 @cindex @samp{QEnvironmentHexEncoded} packet
42187 On UNIX-like targets, it is possible to set environment variables that
42188 will be passed to the inferior during the startup process. This
42189 packet is used to inform @command{gdbserver} of an environment
42190 variable that has been defined by the user on @value{GDBN} (@pxref{set
42193 The packet is composed by @var{hex-value}, an hex encoded
42194 representation of the @var{name=value} format representing an
42195 environment variable. The name of the environment variable is
42196 represented by @var{name}, and the value to be assigned to the
42197 environment variable is represented by @var{value}. If the variable
42198 has no value (i.e., the value is @code{null}), then @var{value} will
42201 This packet is only available in extended mode (@pxref{extended
42207 The request succeeded.
42210 This packet is not probed by default; the remote stub must request it,
42211 by supplying an appropriate @samp{qSupported} response
42212 (@pxref{qSupported}). This should only be done on targets that
42213 actually support passing environment variables to the starting
42216 This packet is related to the @code{set environment} command;
42217 @pxref{set environment}.
42219 @item QEnvironmentUnset:@var{hex-value}
42220 @anchor{QEnvironmentUnset}
42221 @cindex unset environment variable, remote request
42222 @cindex @samp{QEnvironmentUnset} packet
42223 On UNIX-like targets, it is possible to unset environment variables
42224 before starting the inferior in the remote target. This packet is
42225 used to inform @command{gdbserver} of an environment variable that has
42226 been unset by the user on @value{GDBN} (@pxref{unset environment}).
42228 The packet is composed by @var{hex-value}, an hex encoded
42229 representation of the name of the environment variable to be unset.
42231 This packet is only available in extended mode (@pxref{extended
42237 The request succeeded.
42240 This packet is not probed by default; the remote stub must request it,
42241 by supplying an appropriate @samp{qSupported} response
42242 (@pxref{qSupported}). This should only be done on targets that
42243 actually support passing environment variables to the starting
42246 This packet is related to the @code{unset environment} command;
42247 @pxref{unset environment}.
42249 @item QEnvironmentReset
42250 @anchor{QEnvironmentReset}
42251 @cindex reset environment, remote request
42252 @cindex @samp{QEnvironmentReset} packet
42253 On UNIX-like targets, this packet is used to reset the state of
42254 environment variables in the remote target before starting the
42255 inferior. In this context, reset means unsetting all environment
42256 variables that were previously set by the user (i.e., were not
42257 initially present in the environment). It is sent to
42258 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
42259 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
42260 (@pxref{QEnvironmentUnset}) packets.
42262 This packet is only available in extended mode (@pxref{extended
42268 The request succeeded.
42271 This packet is not probed by default; the remote stub must request it,
42272 by supplying an appropriate @samp{qSupported} response
42273 (@pxref{qSupported}). This should only be done on targets that
42274 actually support passing environment variables to the starting
42277 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
42278 @anchor{QSetWorkingDir packet}
42279 @cindex set working directory, remote request
42280 @cindex @samp{QSetWorkingDir} packet
42281 This packet is used to inform the remote server of the intended
42282 current working directory for programs that are going to be executed.
42284 The packet is composed by @var{directory}, an hex encoded
42285 representation of the directory that the remote inferior will use as
42286 its current working directory. If @var{directory} is an empty string,
42287 the remote server should reset the inferior's current working
42288 directory to its original, empty value.
42290 This packet is only available in extended mode (@pxref{extended
42296 The request succeeded.
42300 @itemx qsThreadInfo
42301 @cindex list active threads, remote request
42302 @cindex @samp{qfThreadInfo} packet
42303 @cindex @samp{qsThreadInfo} packet
42304 Obtain a list of all active thread IDs from the target (OS). Since there
42305 may be too many active threads to fit into one reply packet, this query
42306 works iteratively: it may require more than one query/reply sequence to
42307 obtain the entire list of threads. The first query of the sequence will
42308 be the @samp{qfThreadInfo} query; subsequent queries in the
42309 sequence will be the @samp{qsThreadInfo} query.
42311 NOTE: This packet replaces the @samp{qL} query (see below).
42315 @item m @var{thread-id}
42317 @item m @var{thread-id},@var{thread-id}@dots{}
42318 a comma-separated list of thread IDs
42320 (lower case letter @samp{L}) denotes end of list.
42323 In response to each query, the target will reply with a list of one or
42324 more thread IDs, separated by commas.
42325 @value{GDBN} will respond to each reply with a request for more thread
42326 ids (using the @samp{qs} form of the query), until the target responds
42327 with @samp{l} (lower-case ell, for @dfn{last}).
42328 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
42331 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
42332 initial connection with the remote target, and the very first thread ID
42333 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
42334 message. Therefore, the stub should ensure that the first thread ID in
42335 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
42337 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
42338 @cindex get thread-local storage address, remote request
42339 @cindex @samp{qGetTLSAddr} packet
42340 Fetch the address associated with thread local storage specified
42341 by @var{thread-id}, @var{offset}, and @var{lm}.
42343 @var{thread-id} is the thread ID associated with the
42344 thread for which to fetch the TLS address. @xref{thread-id syntax}.
42346 @var{offset} is the (big endian, hex encoded) offset associated with the
42347 thread local variable. (This offset is obtained from the debug
42348 information associated with the variable.)
42350 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
42351 load module associated with the thread local storage. For example,
42352 a @sc{gnu}/Linux system will pass the link map address of the shared
42353 object associated with the thread local storage under consideration.
42354 Other operating environments may choose to represent the load module
42355 differently, so the precise meaning of this parameter will vary.
42359 @item @var{XX}@dots{}
42360 Hex encoded (big endian) bytes representing the address of the thread
42361 local storage requested.
42364 An error occurred. The error number @var{nn} is given as hex digits.
42367 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
42370 @item qGetTIBAddr:@var{thread-id}
42371 @cindex get thread information block address
42372 @cindex @samp{qGetTIBAddr} packet
42373 Fetch address of the Windows OS specific Thread Information Block.
42375 @var{thread-id} is the thread ID associated with the thread.
42379 @item @var{XX}@dots{}
42380 Hex encoded (big endian) bytes representing the linear address of the
42381 thread information block.
42384 An error occured. This means that either the thread was not found, or the
42385 address could not be retrieved.
42388 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
42391 @item qL @var{startflag} @var{threadcount} @var{nextthread}
42392 Obtain thread information from RTOS. Where: @var{startflag} (one hex
42393 digit) is one to indicate the first query and zero to indicate a
42394 subsequent query; @var{threadcount} (two hex digits) is the maximum
42395 number of threads the response packet can contain; and @var{nextthread}
42396 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
42397 returned in the response as @var{argthread}.
42399 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
42403 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
42404 Where: @var{count} (two hex digits) is the number of threads being
42405 returned; @var{done} (one hex digit) is zero to indicate more threads
42406 and one indicates no further threads; @var{argthreadid} (eight hex
42407 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
42408 is a sequence of thread IDs, @var{threadid} (eight hex
42409 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
42412 @item qMemTags:@var{start address},@var{length}:@var{type}
42414 @cindex fetch memory tags
42415 @cindex @samp{qMemTags} packet
42416 Fetch memory tags of type @var{type} from the address range
42417 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
42418 target is responsible for calculating how many tags will be returned, as this
42419 is architecture-specific.
42421 @var{start address} is the starting address of the memory range.
42423 @var{length} is the length, in bytes, of the memory range.
42425 @var{type} is the type of tag the request wants to fetch. The type is a signed
42430 @item @var{mxx}@dots{}
42431 Hex encoded sequence of uninterpreted bytes, @var{xx}@dots{}, representing the
42432 tags found in the requested memory range.
42435 An error occured. This means that fetching of memory tags failed for some
42439 An empty reply indicates that @samp{qMemTags} is not supported by the stub,
42440 although this should not happen given @value{GDBN} will only send this packet
42441 if the stub has advertised support for memory tagging via @samp{qSupported}.
42444 @item QMemTags:@var{start address},@var{length}:@var{type}:@var{tag bytes}
42446 @cindex store memory tags
42447 @cindex @samp{QMemTags} packet
42448 Store memory tags of type @var{type} to the address range
42449 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
42450 target is responsible for interpreting the type, the tag bytes and modifying
42451 the memory tag granules accordingly, given this is architecture-specific.
42453 The interpretation of how many tags (@var{nt}) should be written to how many
42454 memory tag granules (@var{ng}) is also architecture-specific. The behavior is
42455 implementation-specific, but the following is suggested.
42457 If the number of memory tags, @var{nt}, is greater than or equal to the
42458 number of memory tag granules, @var{ng}, only @var{ng} tags will be
42461 If @var{nt} is less than @var{ng}, the behavior is that of a fill operation,
42462 and the tag bytes will be used as a pattern that will get repeated until
42463 @var{ng} tags are stored.
42465 @var{start address} is the starting address of the memory range. The address
42466 does not have any restriction on alignment or size.
42468 @var{length} is the length, in bytes, of the memory range.
42470 @var{type} is the type of tag the request wants to fetch. The type is a signed
42473 @var{tag bytes} is a sequence of hex encoded uninterpreted bytes which will be
42474 interpreted by the target. Each pair of hex digits is interpreted as a
42480 The request was successful and the memory tag granules were modified
42484 An error occured. This means that modifying the memory tag granules failed
42488 An empty reply indicates that @samp{QMemTags} is not supported by the stub,
42489 although this should not happen given @value{GDBN} will only send this packet
42490 if the stub has advertised support for memory tagging via @samp{qSupported}.
42494 @cindex section offsets, remote request
42495 @cindex @samp{qOffsets} packet
42496 Get section offsets that the target used when relocating the downloaded
42501 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
42502 Relocate the @code{Text} section by @var{xxx} from its original address.
42503 Relocate the @code{Data} section by @var{yyy} from its original address.
42504 If the object file format provides segment information (e.g.@: @sc{elf}
42505 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
42506 segments by the supplied offsets.
42508 @emph{Note: while a @code{Bss} offset may be included in the response,
42509 @value{GDBN} ignores this and instead applies the @code{Data} offset
42510 to the @code{Bss} section.}
42512 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
42513 Relocate the first segment of the object file, which conventionally
42514 contains program code, to a starting address of @var{xxx}. If
42515 @samp{DataSeg} is specified, relocate the second segment, which
42516 conventionally contains modifiable data, to a starting address of
42517 @var{yyy}. @value{GDBN} will report an error if the object file
42518 does not contain segment information, or does not contain at least
42519 as many segments as mentioned in the reply. Extra segments are
42520 kept at fixed offsets relative to the last relocated segment.
42523 @item qP @var{mode} @var{thread-id}
42524 @cindex thread information, remote request
42525 @cindex @samp{qP} packet
42526 Returns information on @var{thread-id}. Where: @var{mode} is a hex
42527 encoded 32 bit mode; @var{thread-id} is a thread ID
42528 (@pxref{thread-id syntax}).
42530 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
42533 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
42537 @cindex non-stop mode, remote request
42538 @cindex @samp{QNonStop} packet
42540 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
42541 @xref{Remote Non-Stop}, for more information.
42546 The request succeeded.
42549 An error occurred. The error number @var{nn} is given as hex digits.
42552 An empty reply indicates that @samp{QNonStop} is not supported by
42556 This packet is not probed by default; the remote stub must request it,
42557 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42558 Use of this packet is controlled by the @code{set non-stop} command;
42559 @pxref{Non-Stop Mode}.
42561 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
42562 @itemx QCatchSyscalls:0
42563 @cindex catch syscalls from inferior, remote request
42564 @cindex @samp{QCatchSyscalls} packet
42565 @anchor{QCatchSyscalls}
42566 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
42567 catching syscalls from the inferior process.
42569 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
42570 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
42571 is listed, every system call should be reported.
42573 Note that if a syscall not in the list is reported, @value{GDBN} will
42574 still filter the event according to its own list from all corresponding
42575 @code{catch syscall} commands. However, it is more efficient to only
42576 report the requested syscalls.
42578 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
42579 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
42581 If the inferior process execs, the state of @samp{QCatchSyscalls} is
42582 kept for the new process too. On targets where exec may affect syscall
42583 numbers, for example with exec between 32 and 64-bit processes, the
42584 client should send a new packet with the new syscall list.
42589 The request succeeded.
42592 An error occurred. @var{nn} are hex digits.
42595 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
42599 Use of this packet is controlled by the @code{set remote catch-syscalls}
42600 command (@pxref{Remote Configuration, set remote catch-syscalls}).
42601 This packet is not probed by default; the remote stub must request it,
42602 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42604 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42605 @cindex pass signals to inferior, remote request
42606 @cindex @samp{QPassSignals} packet
42607 @anchor{QPassSignals}
42608 Each listed @var{signal} should be passed directly to the inferior process.
42609 Signals are numbered identically to continue packets and stop replies
42610 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42611 strictly greater than the previous item. These signals do not need to stop
42612 the inferior, or be reported to @value{GDBN}. All other signals should be
42613 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
42614 combine; any earlier @samp{QPassSignals} list is completely replaced by the
42615 new list. This packet improves performance when using @samp{handle
42616 @var{signal} nostop noprint pass}.
42621 The request succeeded.
42624 An error occurred. The error number @var{nn} is given as hex digits.
42627 An empty reply indicates that @samp{QPassSignals} is not supported by
42631 Use of this packet is controlled by the @code{set remote pass-signals}
42632 command (@pxref{Remote Configuration, set remote pass-signals}).
42633 This packet is not probed by default; the remote stub must request it,
42634 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42636 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42637 @cindex signals the inferior may see, remote request
42638 @cindex @samp{QProgramSignals} packet
42639 @anchor{QProgramSignals}
42640 Each listed @var{signal} may be delivered to the inferior process.
42641 Others should be silently discarded.
42643 In some cases, the remote stub may need to decide whether to deliver a
42644 signal to the program or not without @value{GDBN} involvement. One
42645 example of that is while detaching --- the program's threads may have
42646 stopped for signals that haven't yet had a chance of being reported to
42647 @value{GDBN}, and so the remote stub can use the signal list specified
42648 by this packet to know whether to deliver or ignore those pending
42651 This does not influence whether to deliver a signal as requested by a
42652 resumption packet (@pxref{vCont packet}).
42654 Signals are numbered identically to continue packets and stop replies
42655 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42656 strictly greater than the previous item. Multiple
42657 @samp{QProgramSignals} packets do not combine; any earlier
42658 @samp{QProgramSignals} list is completely replaced by the new list.
42663 The request succeeded.
42666 An error occurred. The error number @var{nn} is given as hex digits.
42669 An empty reply indicates that @samp{QProgramSignals} is not supported
42673 Use of this packet is controlled by the @code{set remote program-signals}
42674 command (@pxref{Remote Configuration, set remote program-signals}).
42675 This packet is not probed by default; the remote stub must request it,
42676 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42678 @anchor{QThreadEvents}
42679 @item QThreadEvents:1
42680 @itemx QThreadEvents:0
42681 @cindex thread create/exit events, remote request
42682 @cindex @samp{QThreadEvents} packet
42684 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
42685 reporting of thread create and exit events. @xref{thread create
42686 event}, for the reply specifications. For example, this is used in
42687 non-stop mode when @value{GDBN} stops a set of threads and
42688 synchronously waits for the their corresponding stop replies. Without
42689 exit events, if one of the threads exits, @value{GDBN} would hang
42690 forever not knowing that it should no longer expect a stop for that
42691 same thread. @value{GDBN} does not enable this feature unless the
42692 stub reports that it supports it by including @samp{QThreadEvents+} in
42693 its @samp{qSupported} reply.
42698 The request succeeded.
42701 An error occurred. The error number @var{nn} is given as hex digits.
42704 An empty reply indicates that @samp{QThreadEvents} is not supported by
42708 Use of this packet is controlled by the @code{set remote thread-events}
42709 command (@pxref{Remote Configuration, set remote thread-events}).
42711 @item qRcmd,@var{command}
42712 @cindex execute remote command, remote request
42713 @cindex @samp{qRcmd} packet
42714 @var{command} (hex encoded) is passed to the local interpreter for
42715 execution. Invalid commands should be reported using the output
42716 string. Before the final result packet, the target may also respond
42717 with a number of intermediate @samp{O@var{output}} console output
42718 packets. @emph{Implementors should note that providing access to a
42719 stubs's interpreter may have security implications}.
42724 A command response with no output.
42726 A command response with the hex encoded output string @var{OUTPUT}.
42728 Indicate a badly formed request. The error number @var{NN} is given as
42731 An empty reply indicates that @samp{qRcmd} is not recognized.
42734 (Note that the @code{qRcmd} packet's name is separated from the
42735 command by a @samp{,}, not a @samp{:}, contrary to the naming
42736 conventions above. Please don't use this packet as a model for new
42739 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
42740 @cindex searching memory, in remote debugging
42742 @cindex @samp{qSearch:memory} packet
42744 @cindex @samp{qSearch memory} packet
42745 @anchor{qSearch memory}
42746 Search @var{length} bytes at @var{address} for @var{search-pattern}.
42747 Both @var{address} and @var{length} are encoded in hex;
42748 @var{search-pattern} is a sequence of bytes, also hex encoded.
42753 The pattern was not found.
42755 The pattern was found at @var{address}.
42757 A badly formed request or an error was encountered while searching memory.
42759 An empty reply indicates that @samp{qSearch:memory} is not recognized.
42762 @item QStartNoAckMode
42763 @cindex @samp{QStartNoAckMode} packet
42764 @anchor{QStartNoAckMode}
42765 Request that the remote stub disable the normal @samp{+}/@samp{-}
42766 protocol acknowledgments (@pxref{Packet Acknowledgment}).
42771 The stub has switched to no-acknowledgment mode.
42772 @value{GDBN} acknowledges this response,
42773 but neither the stub nor @value{GDBN} shall send or expect further
42774 @samp{+}/@samp{-} acknowledgments in the current connection.
42776 An empty reply indicates that the stub does not support no-acknowledgment mode.
42779 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
42780 @cindex supported packets, remote query
42781 @cindex features of the remote protocol
42782 @cindex @samp{qSupported} packet
42783 @anchor{qSupported}
42784 Tell the remote stub about features supported by @value{GDBN}, and
42785 query the stub for features it supports. This packet allows
42786 @value{GDBN} and the remote stub to take advantage of each others'
42787 features. @samp{qSupported} also consolidates multiple feature probes
42788 at startup, to improve @value{GDBN} performance---a single larger
42789 packet performs better than multiple smaller probe packets on
42790 high-latency links. Some features may enable behavior which must not
42791 be on by default, e.g.@: because it would confuse older clients or
42792 stubs. Other features may describe packets which could be
42793 automatically probed for, but are not. These features must be
42794 reported before @value{GDBN} will use them. This ``default
42795 unsupported'' behavior is not appropriate for all packets, but it
42796 helps to keep the initial connection time under control with new
42797 versions of @value{GDBN} which support increasing numbers of packets.
42801 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
42802 The stub supports or does not support each returned @var{stubfeature},
42803 depending on the form of each @var{stubfeature} (see below for the
42806 An empty reply indicates that @samp{qSupported} is not recognized,
42807 or that no features needed to be reported to @value{GDBN}.
42810 The allowed forms for each feature (either a @var{gdbfeature} in the
42811 @samp{qSupported} packet, or a @var{stubfeature} in the response)
42815 @item @var{name}=@var{value}
42816 The remote protocol feature @var{name} is supported, and associated
42817 with the specified @var{value}. The format of @var{value} depends
42818 on the feature, but it must not include a semicolon.
42820 The remote protocol feature @var{name} is supported, and does not
42821 need an associated value.
42823 The remote protocol feature @var{name} is not supported.
42825 The remote protocol feature @var{name} may be supported, and
42826 @value{GDBN} should auto-detect support in some other way when it is
42827 needed. This form will not be used for @var{gdbfeature} notifications,
42828 but may be used for @var{stubfeature} responses.
42831 Whenever the stub receives a @samp{qSupported} request, the
42832 supplied set of @value{GDBN} features should override any previous
42833 request. This allows @value{GDBN} to put the stub in a known
42834 state, even if the stub had previously been communicating with
42835 a different version of @value{GDBN}.
42837 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
42842 This feature indicates whether @value{GDBN} supports multiprocess
42843 extensions to the remote protocol. @value{GDBN} does not use such
42844 extensions unless the stub also reports that it supports them by
42845 including @samp{multiprocess+} in its @samp{qSupported} reply.
42846 @xref{multiprocess extensions}, for details.
42849 This feature indicates that @value{GDBN} supports the XML target
42850 description. If the stub sees @samp{xmlRegisters=} with target
42851 specific strings separated by a comma, it will report register
42855 This feature indicates whether @value{GDBN} supports the
42856 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
42857 instruction reply packet}).
42860 This feature indicates whether @value{GDBN} supports the swbreak stop
42861 reason in stop replies. @xref{swbreak stop reason}, for details.
42864 This feature indicates whether @value{GDBN} supports the hwbreak stop
42865 reason in stop replies. @xref{swbreak stop reason}, for details.
42868 This feature indicates whether @value{GDBN} supports fork event
42869 extensions to the remote protocol. @value{GDBN} does not use such
42870 extensions unless the stub also reports that it supports them by
42871 including @samp{fork-events+} in its @samp{qSupported} reply.
42874 This feature indicates whether @value{GDBN} supports vfork event
42875 extensions to the remote protocol. @value{GDBN} does not use such
42876 extensions unless the stub also reports that it supports them by
42877 including @samp{vfork-events+} in its @samp{qSupported} reply.
42880 This feature indicates whether @value{GDBN} supports exec event
42881 extensions to the remote protocol. @value{GDBN} does not use such
42882 extensions unless the stub also reports that it supports them by
42883 including @samp{exec-events+} in its @samp{qSupported} reply.
42885 @item vContSupported
42886 This feature indicates whether @value{GDBN} wants to know the
42887 supported actions in the reply to @samp{vCont?} packet.
42890 Stubs should ignore any unknown values for
42891 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
42892 packet supports receiving packets of unlimited length (earlier
42893 versions of @value{GDBN} may reject overly long responses). Additional values
42894 for @var{gdbfeature} may be defined in the future to let the stub take
42895 advantage of new features in @value{GDBN}, e.g.@: incompatible
42896 improvements in the remote protocol---the @samp{multiprocess} feature is
42897 an example of such a feature. The stub's reply should be independent
42898 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
42899 describes all the features it supports, and then the stub replies with
42900 all the features it supports.
42902 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
42903 responses, as long as each response uses one of the standard forms.
42905 Some features are flags. A stub which supports a flag feature
42906 should respond with a @samp{+} form response. Other features
42907 require values, and the stub should respond with an @samp{=}
42910 Each feature has a default value, which @value{GDBN} will use if
42911 @samp{qSupported} is not available or if the feature is not mentioned
42912 in the @samp{qSupported} response. The default values are fixed; a
42913 stub is free to omit any feature responses that match the defaults.
42915 Not all features can be probed, but for those which can, the probing
42916 mechanism is useful: in some cases, a stub's internal
42917 architecture may not allow the protocol layer to know some information
42918 about the underlying target in advance. This is especially common in
42919 stubs which may be configured for multiple targets.
42921 These are the currently defined stub features and their properties:
42923 @multitable @columnfractions 0.35 0.2 0.12 0.2
42924 @c NOTE: The first row should be @headitem, but we do not yet require
42925 @c a new enough version of Texinfo (4.7) to use @headitem.
42927 @tab Value Required
42931 @item @samp{PacketSize}
42936 @item @samp{qXfer:auxv:read}
42941 @item @samp{qXfer:btrace:read}
42946 @item @samp{qXfer:btrace-conf:read}
42951 @item @samp{qXfer:exec-file:read}
42956 @item @samp{qXfer:features:read}
42961 @item @samp{qXfer:libraries:read}
42966 @item @samp{qXfer:libraries-svr4:read}
42971 @item @samp{augmented-libraries-svr4-read}
42976 @item @samp{qXfer:memory-map:read}
42981 @item @samp{qXfer:sdata:read}
42986 @item @samp{qXfer:siginfo:read}
42991 @item @samp{qXfer:siginfo:write}
42996 @item @samp{qXfer:threads:read}
43001 @item @samp{qXfer:traceframe-info:read}
43006 @item @samp{qXfer:uib:read}
43011 @item @samp{qXfer:fdpic:read}
43016 @item @samp{Qbtrace:off}
43021 @item @samp{Qbtrace:bts}
43026 @item @samp{Qbtrace:pt}
43031 @item @samp{Qbtrace-conf:bts:size}
43036 @item @samp{Qbtrace-conf:pt:size}
43041 @item @samp{QNonStop}
43046 @item @samp{QCatchSyscalls}
43051 @item @samp{QPassSignals}
43056 @item @samp{QStartNoAckMode}
43061 @item @samp{multiprocess}
43066 @item @samp{ConditionalBreakpoints}
43071 @item @samp{ConditionalTracepoints}
43076 @item @samp{ReverseContinue}
43081 @item @samp{ReverseStep}
43086 @item @samp{TracepointSource}
43091 @item @samp{QAgent}
43096 @item @samp{QAllow}
43101 @item @samp{QDisableRandomization}
43106 @item @samp{EnableDisableTracepoints}
43111 @item @samp{QTBuffer:size}
43116 @item @samp{tracenz}
43121 @item @samp{BreakpointCommands}
43126 @item @samp{swbreak}
43131 @item @samp{hwbreak}
43136 @item @samp{fork-events}
43141 @item @samp{vfork-events}
43146 @item @samp{exec-events}
43151 @item @samp{QThreadEvents}
43156 @item @samp{no-resumed}
43161 @item @samp{memory-tagging}
43168 These are the currently defined stub features, in more detail:
43171 @cindex packet size, remote protocol
43172 @item PacketSize=@var{bytes}
43173 The remote stub can accept packets up to at least @var{bytes} in
43174 length. @value{GDBN} will send packets up to this size for bulk
43175 transfers, and will never send larger packets. This is a limit on the
43176 data characters in the packet, including the frame and checksum.
43177 There is no trailing NUL byte in a remote protocol packet; if the stub
43178 stores packets in a NUL-terminated format, it should allow an extra
43179 byte in its buffer for the NUL. If this stub feature is not supported,
43180 @value{GDBN} guesses based on the size of the @samp{g} packet response.
43182 @item qXfer:auxv:read
43183 The remote stub understands the @samp{qXfer:auxv:read} packet
43184 (@pxref{qXfer auxiliary vector read}).
43186 @item qXfer:btrace:read
43187 The remote stub understands the @samp{qXfer:btrace:read}
43188 packet (@pxref{qXfer btrace read}).
43190 @item qXfer:btrace-conf:read
43191 The remote stub understands the @samp{qXfer:btrace-conf:read}
43192 packet (@pxref{qXfer btrace-conf read}).
43194 @item qXfer:exec-file:read
43195 The remote stub understands the @samp{qXfer:exec-file:read} packet
43196 (@pxref{qXfer executable filename read}).
43198 @item qXfer:features:read
43199 The remote stub understands the @samp{qXfer:features:read} packet
43200 (@pxref{qXfer target description read}).
43202 @item qXfer:libraries:read
43203 The remote stub understands the @samp{qXfer:libraries:read} packet
43204 (@pxref{qXfer library list read}).
43206 @item qXfer:libraries-svr4:read
43207 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
43208 (@pxref{qXfer svr4 library list read}).
43210 @item augmented-libraries-svr4-read
43211 The remote stub understands the augmented form of the
43212 @samp{qXfer:libraries-svr4:read} packet
43213 (@pxref{qXfer svr4 library list read}).
43215 @item qXfer:memory-map:read
43216 The remote stub understands the @samp{qXfer:memory-map:read} packet
43217 (@pxref{qXfer memory map read}).
43219 @item qXfer:sdata:read
43220 The remote stub understands the @samp{qXfer:sdata:read} packet
43221 (@pxref{qXfer sdata read}).
43223 @item qXfer:siginfo:read
43224 The remote stub understands the @samp{qXfer:siginfo:read} packet
43225 (@pxref{qXfer siginfo read}).
43227 @item qXfer:siginfo:write
43228 The remote stub understands the @samp{qXfer:siginfo:write} packet
43229 (@pxref{qXfer siginfo write}).
43231 @item qXfer:threads:read
43232 The remote stub understands the @samp{qXfer:threads:read} packet
43233 (@pxref{qXfer threads read}).
43235 @item qXfer:traceframe-info:read
43236 The remote stub understands the @samp{qXfer:traceframe-info:read}
43237 packet (@pxref{qXfer traceframe info read}).
43239 @item qXfer:uib:read
43240 The remote stub understands the @samp{qXfer:uib:read}
43241 packet (@pxref{qXfer unwind info block}).
43243 @item qXfer:fdpic:read
43244 The remote stub understands the @samp{qXfer:fdpic:read}
43245 packet (@pxref{qXfer fdpic loadmap read}).
43248 The remote stub understands the @samp{QNonStop} packet
43249 (@pxref{QNonStop}).
43251 @item QCatchSyscalls
43252 The remote stub understands the @samp{QCatchSyscalls} packet
43253 (@pxref{QCatchSyscalls}).
43256 The remote stub understands the @samp{QPassSignals} packet
43257 (@pxref{QPassSignals}).
43259 @item QStartNoAckMode
43260 The remote stub understands the @samp{QStartNoAckMode} packet and
43261 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
43264 @anchor{multiprocess extensions}
43265 @cindex multiprocess extensions, in remote protocol
43266 The remote stub understands the multiprocess extensions to the remote
43267 protocol syntax. The multiprocess extensions affect the syntax of
43268 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
43269 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
43270 replies. Note that reporting this feature indicates support for the
43271 syntactic extensions only, not that the stub necessarily supports
43272 debugging of more than one process at a time. The stub must not use
43273 multiprocess extensions in packet replies unless @value{GDBN} has also
43274 indicated it supports them in its @samp{qSupported} request.
43276 @item qXfer:osdata:read
43277 The remote stub understands the @samp{qXfer:osdata:read} packet
43278 ((@pxref{qXfer osdata read}).
43280 @item ConditionalBreakpoints
43281 The target accepts and implements evaluation of conditional expressions
43282 defined for breakpoints. The target will only report breakpoint triggers
43283 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
43285 @item ConditionalTracepoints
43286 The remote stub accepts and implements conditional expressions defined
43287 for tracepoints (@pxref{Tracepoint Conditions}).
43289 @item ReverseContinue
43290 The remote stub accepts and implements the reverse continue packet
43294 The remote stub accepts and implements the reverse step packet
43297 @item TracepointSource
43298 The remote stub understands the @samp{QTDPsrc} packet that supplies
43299 the source form of tracepoint definitions.
43302 The remote stub understands the @samp{QAgent} packet.
43305 The remote stub understands the @samp{QAllow} packet.
43307 @item QDisableRandomization
43308 The remote stub understands the @samp{QDisableRandomization} packet.
43310 @item StaticTracepoint
43311 @cindex static tracepoints, in remote protocol
43312 The remote stub supports static tracepoints.
43314 @item InstallInTrace
43315 @anchor{install tracepoint in tracing}
43316 The remote stub supports installing tracepoint in tracing.
43318 @item EnableDisableTracepoints
43319 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
43320 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
43321 to be enabled and disabled while a trace experiment is running.
43323 @item QTBuffer:size
43324 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
43325 packet that allows to change the size of the trace buffer.
43328 @cindex string tracing, in remote protocol
43329 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
43330 See @ref{Bytecode Descriptions} for details about the bytecode.
43332 @item BreakpointCommands
43333 @cindex breakpoint commands, in remote protocol
43334 The remote stub supports running a breakpoint's command list itself,
43335 rather than reporting the hit to @value{GDBN}.
43338 The remote stub understands the @samp{Qbtrace:off} packet.
43341 The remote stub understands the @samp{Qbtrace:bts} packet.
43344 The remote stub understands the @samp{Qbtrace:pt} packet.
43346 @item Qbtrace-conf:bts:size
43347 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
43349 @item Qbtrace-conf:pt:size
43350 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
43353 The remote stub reports the @samp{swbreak} stop reason for memory
43357 The remote stub reports the @samp{hwbreak} stop reason for hardware
43361 The remote stub reports the @samp{fork} stop reason for fork events.
43364 The remote stub reports the @samp{vfork} stop reason for vfork events
43365 and vforkdone events.
43368 The remote stub reports the @samp{exec} stop reason for exec events.
43370 @item vContSupported
43371 The remote stub reports the supported actions in the reply to
43372 @samp{vCont?} packet.
43374 @item QThreadEvents
43375 The remote stub understands the @samp{QThreadEvents} packet.
43378 The remote stub reports the @samp{N} stop reply.
43381 @item memory-tagging
43382 The remote stub supports and implements the required memory tagging
43383 functionality and understands the @samp{qMemTags} (@pxref{qMemTags}) and
43384 @samp{QMemTags} (@pxref{QMemTags}) packets.
43386 For AArch64 GNU/Linux systems, this feature also requires access to the
43387 @file{/proc/@var{pid}/smaps} file so memory mapping page flags can be inspected.
43388 This is done via the @samp{vFile} requests.
43393 @cindex symbol lookup, remote request
43394 @cindex @samp{qSymbol} packet
43395 Notify the target that @value{GDBN} is prepared to serve symbol lookup
43396 requests. Accept requests from the target for the values of symbols.
43401 The target does not need to look up any (more) symbols.
43402 @item qSymbol:@var{sym_name}
43403 The target requests the value of symbol @var{sym_name} (hex encoded).
43404 @value{GDBN} may provide the value by using the
43405 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
43409 @item qSymbol:@var{sym_value}:@var{sym_name}
43410 Set the value of @var{sym_name} to @var{sym_value}.
43412 @var{sym_name} (hex encoded) is the name of a symbol whose value the
43413 target has previously requested.
43415 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
43416 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
43422 The target does not need to look up any (more) symbols.
43423 @item qSymbol:@var{sym_name}
43424 The target requests the value of a new symbol @var{sym_name} (hex
43425 encoded). @value{GDBN} will continue to supply the values of symbols
43426 (if available), until the target ceases to request them.
43431 @itemx QTDisconnected
43438 @itemx qTMinFTPILen
43440 @xref{Tracepoint Packets}.
43442 @anchor{qThreadExtraInfo}
43443 @item qThreadExtraInfo,@var{thread-id}
43444 @cindex thread attributes info, remote request
43445 @cindex @samp{qThreadExtraInfo} packet
43446 Obtain from the target OS a printable string description of thread
43447 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
43448 for the forms of @var{thread-id}. This
43449 string may contain anything that the target OS thinks is interesting
43450 for @value{GDBN} to tell the user about the thread. The string is
43451 displayed in @value{GDBN}'s @code{info threads} display. Some
43452 examples of possible thread extra info strings are @samp{Runnable}, or
43453 @samp{Blocked on Mutex}.
43457 @item @var{XX}@dots{}
43458 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
43459 comprising the printable string containing the extra information about
43460 the thread's attributes.
43463 (Note that the @code{qThreadExtraInfo} packet's name is separated from
43464 the command by a @samp{,}, not a @samp{:}, contrary to the naming
43465 conventions above. Please don't use this packet as a model for new
43484 @xref{Tracepoint Packets}.
43486 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
43487 @cindex read special object, remote request
43488 @cindex @samp{qXfer} packet
43489 @anchor{qXfer read}
43490 Read uninterpreted bytes from the target's special data area
43491 identified by the keyword @var{object}. Request @var{length} bytes
43492 starting at @var{offset} bytes into the data. The content and
43493 encoding of @var{annex} is specific to @var{object}; it can supply
43494 additional details about what data to access.
43499 Data @var{data} (@pxref{Binary Data}) has been read from the
43500 target. There may be more data at a higher address (although
43501 it is permitted to return @samp{m} even for the last valid
43502 block of data, as long as at least one byte of data was read).
43503 It is possible for @var{data} to have fewer bytes than the @var{length} in the
43507 Data @var{data} (@pxref{Binary Data}) has been read from the target.
43508 There is no more data to be read. It is possible for @var{data} to
43509 have fewer bytes than the @var{length} in the request.
43512 The @var{offset} in the request is at the end of the data.
43513 There is no more data to be read.
43516 The request was malformed, or @var{annex} was invalid.
43519 The offset was invalid, or there was an error encountered reading the data.
43520 The @var{nn} part is a hex-encoded @code{errno} value.
43523 An empty reply indicates the @var{object} string was not recognized by
43524 the stub, or that the object does not support reading.
43527 Here are the specific requests of this form defined so far. All the
43528 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
43529 formats, listed above.
43532 @item qXfer:auxv:read::@var{offset},@var{length}
43533 @anchor{qXfer auxiliary vector read}
43534 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
43535 auxiliary vector}. Note @var{annex} must be empty.
43537 This packet is not probed by default; the remote stub must request it,
43538 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43540 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
43541 @anchor{qXfer btrace read}
43543 Return a description of the current branch trace.
43544 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
43545 packet may have one of the following values:
43549 Returns all available branch trace.
43552 Returns all available branch trace if the branch trace changed since
43553 the last read request.
43556 Returns the new branch trace since the last read request. Adds a new
43557 block to the end of the trace that begins at zero and ends at the source
43558 location of the first branch in the trace buffer. This extra block is
43559 used to stitch traces together.
43561 If the trace buffer overflowed, returns an error indicating the overflow.
43564 This packet is not probed by default; the remote stub must request it
43565 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43567 @item qXfer:btrace-conf:read::@var{offset},@var{length}
43568 @anchor{qXfer btrace-conf read}
43570 Return a description of the current branch trace configuration.
43571 @xref{Branch Trace Configuration Format}.
43573 This packet is not probed by default; the remote stub must request it
43574 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43576 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
43577 @anchor{qXfer executable filename read}
43578 Return the full absolute name of the file that was executed to create
43579 a process running on the remote system. The annex specifies the
43580 numeric process ID of the process to query, encoded as a hexadecimal
43581 number. If the annex part is empty the remote stub should return the
43582 filename corresponding to the currently executing process.
43584 This packet is not probed by default; the remote stub must request it,
43585 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43587 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
43588 @anchor{qXfer target description read}
43589 Access the @dfn{target description}. @xref{Target Descriptions}. The
43590 annex specifies which XML document to access. The main description is
43591 always loaded from the @samp{target.xml} annex.
43593 This packet is not probed by default; the remote stub must request it,
43594 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43596 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
43597 @anchor{qXfer library list read}
43598 Access the target's list of loaded libraries. @xref{Library List Format}.
43599 The annex part of the generic @samp{qXfer} packet must be empty
43600 (@pxref{qXfer read}).
43602 Targets which maintain a list of libraries in the program's memory do
43603 not need to implement this packet; it is designed for platforms where
43604 the operating system manages the list of loaded libraries.
43606 This packet is not probed by default; the remote stub must request it,
43607 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43609 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
43610 @anchor{qXfer svr4 library list read}
43611 Access the target's list of loaded libraries when the target is an SVR4
43612 platform. @xref{Library List Format for SVR4 Targets}. The annex part
43613 of the generic @samp{qXfer} packet must be empty unless the remote
43614 stub indicated it supports the augmented form of this packet
43615 by supplying an appropriate @samp{qSupported} response
43616 (@pxref{qXfer read}, @ref{qSupported}).
43618 This packet is optional for better performance on SVR4 targets.
43619 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
43621 This packet is not probed by default; the remote stub must request it,
43622 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43624 If the remote stub indicates it supports the augmented form of this
43625 packet then the annex part of the generic @samp{qXfer} packet may
43626 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
43627 arguments. The currently supported arguments are:
43630 @item start=@var{address}
43631 A hexadecimal number specifying the address of the @samp{struct
43632 link_map} to start reading the library list from. If unset or zero
43633 then the first @samp{struct link_map} in the library list will be
43634 chosen as the starting point.
43636 @item prev=@var{address}
43637 A hexadecimal number specifying the address of the @samp{struct
43638 link_map} immediately preceding the @samp{struct link_map}
43639 specified by the @samp{start} argument. If unset or zero then
43640 the remote stub will expect that no @samp{struct link_map}
43641 exists prior to the starting point.
43645 Arguments that are not understood by the remote stub will be silently
43648 @item qXfer:memory-map:read::@var{offset},@var{length}
43649 @anchor{qXfer memory map read}
43650 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
43651 annex part of the generic @samp{qXfer} packet must be empty
43652 (@pxref{qXfer read}).
43654 This packet is not probed by default; the remote stub must request it,
43655 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43657 @item qXfer:sdata:read::@var{offset},@var{length}
43658 @anchor{qXfer sdata read}
43660 Read contents of the extra collected static tracepoint marker
43661 information. The annex part of the generic @samp{qXfer} packet must
43662 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
43665 This packet is not probed by default; the remote stub must request it,
43666 by supplying an appropriate @samp{qSupported} response
43667 (@pxref{qSupported}).
43669 @item qXfer:siginfo:read::@var{offset},@var{length}
43670 @anchor{qXfer siginfo read}
43671 Read contents of the extra signal information on the target
43672 system. The annex part of the generic @samp{qXfer} packet must be
43673 empty (@pxref{qXfer read}).
43675 This packet is not probed by default; the remote stub must request it,
43676 by supplying an appropriate @samp{qSupported} response
43677 (@pxref{qSupported}).
43679 @item qXfer:threads:read::@var{offset},@var{length}
43680 @anchor{qXfer threads read}
43681 Access the list of threads on target. @xref{Thread List Format}. The
43682 annex part of the generic @samp{qXfer} packet must be empty
43683 (@pxref{qXfer read}).
43685 This packet is not probed by default; the remote stub must request it,
43686 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43688 @item qXfer:traceframe-info:read::@var{offset},@var{length}
43689 @anchor{qXfer traceframe info read}
43691 Return a description of the current traceframe's contents.
43692 @xref{Traceframe Info Format}. The annex part of the generic
43693 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
43695 This packet is not probed by default; the remote stub must request it,
43696 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43698 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
43699 @anchor{qXfer unwind info block}
43701 Return the unwind information block for @var{pc}. This packet is used
43702 on OpenVMS/ia64 to ask the kernel unwind information.
43704 This packet is not probed by default.
43706 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
43707 @anchor{qXfer fdpic loadmap read}
43708 Read contents of @code{loadmap}s on the target system. The
43709 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
43710 executable @code{loadmap} or interpreter @code{loadmap} to read.
43712 This packet is not probed by default; the remote stub must request it,
43713 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43715 @item qXfer:osdata:read::@var{offset},@var{length}
43716 @anchor{qXfer osdata read}
43717 Access the target's @dfn{operating system information}.
43718 @xref{Operating System Information}.
43722 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
43723 @cindex write data into object, remote request
43724 @anchor{qXfer write}
43725 Write uninterpreted bytes into the target's special data area
43726 identified by the keyword @var{object}, starting at @var{offset} bytes
43727 into the data. The binary-encoded data (@pxref{Binary Data}) to be
43728 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
43729 is specific to @var{object}; it can supply additional details about what data
43735 @var{nn} (hex encoded) is the number of bytes written.
43736 This may be fewer bytes than supplied in the request.
43739 The request was malformed, or @var{annex} was invalid.
43742 The offset was invalid, or there was an error encountered writing the data.
43743 The @var{nn} part is a hex-encoded @code{errno} value.
43746 An empty reply indicates the @var{object} string was not
43747 recognized by the stub, or that the object does not support writing.
43750 Here are the specific requests of this form defined so far. All the
43751 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
43752 formats, listed above.
43755 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
43756 @anchor{qXfer siginfo write}
43757 Write @var{data} to the extra signal information on the target system.
43758 The annex part of the generic @samp{qXfer} packet must be
43759 empty (@pxref{qXfer write}).
43761 This packet is not probed by default; the remote stub must request it,
43762 by supplying an appropriate @samp{qSupported} response
43763 (@pxref{qSupported}).
43766 @item qXfer:@var{object}:@var{operation}:@dots{}
43767 Requests of this form may be added in the future. When a stub does
43768 not recognize the @var{object} keyword, or its support for
43769 @var{object} does not recognize the @var{operation} keyword, the stub
43770 must respond with an empty packet.
43772 @item qAttached:@var{pid}
43773 @cindex query attached, remote request
43774 @cindex @samp{qAttached} packet
43775 Return an indication of whether the remote server attached to an
43776 existing process or created a new process. When the multiprocess
43777 protocol extensions are supported (@pxref{multiprocess extensions}),
43778 @var{pid} is an integer in hexadecimal format identifying the target
43779 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
43780 the query packet will be simplified as @samp{qAttached}.
43782 This query is used, for example, to know whether the remote process
43783 should be detached or killed when a @value{GDBN} session is ended with
43784 the @code{quit} command.
43789 The remote server attached to an existing process.
43791 The remote server created a new process.
43793 A badly formed request or an error was encountered.
43797 Enable branch tracing for the current thread using Branch Trace Store.
43802 Branch tracing has been enabled.
43804 A badly formed request or an error was encountered.
43808 Enable branch tracing for the current thread using Intel Processor Trace.
43813 Branch tracing has been enabled.
43815 A badly formed request or an error was encountered.
43819 Disable branch tracing for the current thread.
43824 Branch tracing has been disabled.
43826 A badly formed request or an error was encountered.
43829 @item Qbtrace-conf:bts:size=@var{value}
43830 Set the requested ring buffer size for new threads that use the
43831 btrace recording method in bts format.
43836 The ring buffer size has been set.
43838 A badly formed request or an error was encountered.
43841 @item Qbtrace-conf:pt:size=@var{value}
43842 Set the requested ring buffer size for new threads that use the
43843 btrace recording method in pt format.
43848 The ring buffer size has been set.
43850 A badly formed request or an error was encountered.
43855 @node Architecture-Specific Protocol Details
43856 @section Architecture-Specific Protocol Details
43858 This section describes how the remote protocol is applied to specific
43859 target architectures. Also see @ref{Standard Target Features}, for
43860 details of XML target descriptions for each architecture.
43863 * ARM-Specific Protocol Details::
43864 * MIPS-Specific Protocol Details::
43867 @node ARM-Specific Protocol Details
43868 @subsection @acronym{ARM}-specific Protocol Details
43871 * ARM Breakpoint Kinds::
43872 * ARM Memory Tag Types::
43875 @node ARM Breakpoint Kinds
43876 @subsubsection @acronym{ARM} Breakpoint Kinds
43877 @cindex breakpoint kinds, @acronym{ARM}
43879 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43884 16-bit Thumb mode breakpoint.
43887 32-bit Thumb mode (Thumb-2) breakpoint.
43890 32-bit @acronym{ARM} mode breakpoint.
43894 @node ARM Memory Tag Types
43895 @subsubsection @acronym{ARM} Memory Tag Types
43896 @cindex memory tag types, @acronym{ARM}
43898 These memory tag types are defined for the @samp{qMemTag} and @samp{QMemTag}
43911 @node MIPS-Specific Protocol Details
43912 @subsection @acronym{MIPS}-specific Protocol Details
43915 * MIPS Register packet Format::
43916 * MIPS Breakpoint Kinds::
43919 @node MIPS Register packet Format
43920 @subsubsection @acronym{MIPS} Register Packet Format
43921 @cindex register packet format, @acronym{MIPS}
43923 The following @code{g}/@code{G} packets have previously been defined.
43924 In the below, some thirty-two bit registers are transferred as
43925 sixty-four bits. Those registers should be zero/sign extended (which?)
43926 to fill the space allocated. Register bytes are transferred in target
43927 byte order. The two nibbles within a register byte are transferred
43928 most-significant -- least-significant.
43933 All registers are transferred as thirty-two bit quantities in the order:
43934 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
43935 registers; fsr; fir; fp.
43938 All registers are transferred as sixty-four bit quantities (including
43939 thirty-two bit registers such as @code{sr}). The ordering is the same
43944 @node MIPS Breakpoint Kinds
43945 @subsubsection @acronym{MIPS} Breakpoint Kinds
43946 @cindex breakpoint kinds, @acronym{MIPS}
43948 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43953 16-bit @acronym{MIPS16} mode breakpoint.
43956 16-bit @acronym{microMIPS} mode breakpoint.
43959 32-bit standard @acronym{MIPS} mode breakpoint.
43962 32-bit @acronym{microMIPS} mode breakpoint.
43966 @node Tracepoint Packets
43967 @section Tracepoint Packets
43968 @cindex tracepoint packets
43969 @cindex packets, tracepoint
43971 Here we describe the packets @value{GDBN} uses to implement
43972 tracepoints (@pxref{Tracepoints}).
43976 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
43977 @cindex @samp{QTDP} packet
43978 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
43979 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
43980 the tracepoint is disabled. The @var{step} gives the tracepoint's step
43981 count, and @var{pass} gives its pass count. If an @samp{F} is present,
43982 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
43983 the number of bytes that the target should copy elsewhere to make room
43984 for the tracepoint. If an @samp{X} is present, it introduces a
43985 tracepoint condition, which consists of a hexadecimal length, followed
43986 by a comma and hex-encoded bytes, in a manner similar to action
43987 encodings as described below. If the trailing @samp{-} is present,
43988 further @samp{QTDP} packets will follow to specify this tracepoint's
43994 The packet was understood and carried out.
43996 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43998 The packet was not recognized.
44001 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
44002 Define actions to be taken when a tracepoint is hit. The @var{n} and
44003 @var{addr} must be the same as in the initial @samp{QTDP} packet for
44004 this tracepoint. This packet may only be sent immediately after
44005 another @samp{QTDP} packet that ended with a @samp{-}. If the
44006 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
44007 specifying more actions for this tracepoint.
44009 In the series of action packets for a given tracepoint, at most one
44010 can have an @samp{S} before its first @var{action}. If such a packet
44011 is sent, it and the following packets define ``while-stepping''
44012 actions. Any prior packets define ordinary actions --- that is, those
44013 taken when the tracepoint is first hit. If no action packet has an
44014 @samp{S}, then all the packets in the series specify ordinary
44015 tracepoint actions.
44017 The @samp{@var{action}@dots{}} portion of the packet is a series of
44018 actions, concatenated without separators. Each action has one of the
44024 Collect the registers whose bits are set in @var{mask},
44025 a hexadecimal number whose @var{i}'th bit is set if register number
44026 @var{i} should be collected. (The least significant bit is numbered
44027 zero.) Note that @var{mask} may be any number of digits long; it may
44028 not fit in a 32-bit word.
44030 @item M @var{basereg},@var{offset},@var{len}
44031 Collect @var{len} bytes of memory starting at the address in register
44032 number @var{basereg}, plus @var{offset}. If @var{basereg} is
44033 @samp{-1}, then the range has a fixed address: @var{offset} is the
44034 address of the lowest byte to collect. The @var{basereg},
44035 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
44036 values (the @samp{-1} value for @var{basereg} is a special case).
44038 @item X @var{len},@var{expr}
44039 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
44040 it directs. The agent expression @var{expr} is as described in
44041 @ref{Agent Expressions}. Each byte of the expression is encoded as a
44042 two-digit hex number in the packet; @var{len} is the number of bytes
44043 in the expression (and thus one-half the number of hex digits in the
44048 Any number of actions may be packed together in a single @samp{QTDP}
44049 packet, as long as the packet does not exceed the maximum packet
44050 length (400 bytes, for many stubs). There may be only one @samp{R}
44051 action per tracepoint, and it must precede any @samp{M} or @samp{X}
44052 actions. Any registers referred to by @samp{M} and @samp{X} actions
44053 must be collected by a preceding @samp{R} action. (The
44054 ``while-stepping'' actions are treated as if they were attached to a
44055 separate tracepoint, as far as these restrictions are concerned.)
44060 The packet was understood and carried out.
44062 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
44064 The packet was not recognized.
44067 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
44068 @cindex @samp{QTDPsrc} packet
44069 Specify a source string of tracepoint @var{n} at address @var{addr}.
44070 This is useful to get accurate reproduction of the tracepoints
44071 originally downloaded at the beginning of the trace run. The @var{type}
44072 is the name of the tracepoint part, such as @samp{cond} for the
44073 tracepoint's conditional expression (see below for a list of types), while
44074 @var{bytes} is the string, encoded in hexadecimal.
44076 @var{start} is the offset of the @var{bytes} within the overall source
44077 string, while @var{slen} is the total length of the source string.
44078 This is intended for handling source strings that are longer than will
44079 fit in a single packet.
44080 @c Add detailed example when this info is moved into a dedicated
44081 @c tracepoint descriptions section.
44083 The available string types are @samp{at} for the location,
44084 @samp{cond} for the conditional, and @samp{cmd} for an action command.
44085 @value{GDBN} sends a separate packet for each command in the action
44086 list, in the same order in which the commands are stored in the list.
44088 The target does not need to do anything with source strings except
44089 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
44092 Although this packet is optional, and @value{GDBN} will only send it
44093 if the target replies with @samp{TracepointSource} @xref{General
44094 Query Packets}, it makes both disconnected tracing and trace files
44095 much easier to use. Otherwise the user must be careful that the
44096 tracepoints in effect while looking at trace frames are identical to
44097 the ones in effect during the trace run; even a small discrepancy
44098 could cause @samp{tdump} not to work, or a particular trace frame not
44101 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
44102 @cindex define trace state variable, remote request
44103 @cindex @samp{QTDV} packet
44104 Create a new trace state variable, number @var{n}, with an initial
44105 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
44106 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
44107 the option of not using this packet for initial values of zero; the
44108 target should simply create the trace state variables as they are
44109 mentioned in expressions. The value @var{builtin} should be 1 (one)
44110 if the trace state variable is builtin and 0 (zero) if it is not builtin.
44111 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
44112 @samp{qTsV} packet had it set. The contents of @var{name} is the
44113 hex-encoded name (without the leading @samp{$}) of the trace state
44116 @item QTFrame:@var{n}
44117 @cindex @samp{QTFrame} packet
44118 Select the @var{n}'th tracepoint frame from the buffer, and use the
44119 register and memory contents recorded there to answer subsequent
44120 request packets from @value{GDBN}.
44122 A successful reply from the stub indicates that the stub has found the
44123 requested frame. The response is a series of parts, concatenated
44124 without separators, describing the frame we selected. Each part has
44125 one of the following forms:
44129 The selected frame is number @var{n} in the trace frame buffer;
44130 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
44131 was no frame matching the criteria in the request packet.
44134 The selected trace frame records a hit of tracepoint number @var{t};
44135 @var{t} is a hexadecimal number.
44139 @item QTFrame:pc:@var{addr}
44140 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
44141 currently selected frame whose PC is @var{addr};
44142 @var{addr} is a hexadecimal number.
44144 @item QTFrame:tdp:@var{t}
44145 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
44146 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
44147 is a hexadecimal number.
44149 @item QTFrame:range:@var{start}:@var{end}
44150 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
44151 currently selected frame whose PC is between @var{start} (inclusive)
44152 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
44155 @item QTFrame:outside:@var{start}:@var{end}
44156 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
44157 frame @emph{outside} the given range of addresses (exclusive).
44160 @cindex @samp{qTMinFTPILen} packet
44161 This packet requests the minimum length of instruction at which a fast
44162 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
44163 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
44164 it depends on the target system being able to create trampolines in
44165 the first 64K of memory, which might or might not be possible for that
44166 system. So the reply to this packet will be 4 if it is able to
44173 The minimum instruction length is currently unknown.
44175 The minimum instruction length is @var{length}, where @var{length}
44176 is a hexadecimal number greater or equal to 1. A reply
44177 of 1 means that a fast tracepoint may be placed on any instruction
44178 regardless of size.
44180 An error has occurred.
44182 An empty reply indicates that the request is not supported by the stub.
44186 @cindex @samp{QTStart} packet
44187 Begin the tracepoint experiment. Begin collecting data from
44188 tracepoint hits in the trace frame buffer. This packet supports the
44189 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
44190 instruction reply packet}).
44193 @cindex @samp{QTStop} packet
44194 End the tracepoint experiment. Stop collecting trace frames.
44196 @item QTEnable:@var{n}:@var{addr}
44198 @cindex @samp{QTEnable} packet
44199 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
44200 experiment. If the tracepoint was previously disabled, then collection
44201 of data from it will resume.
44203 @item QTDisable:@var{n}:@var{addr}
44205 @cindex @samp{QTDisable} packet
44206 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
44207 experiment. No more data will be collected from the tracepoint unless
44208 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
44211 @cindex @samp{QTinit} packet
44212 Clear the table of tracepoints, and empty the trace frame buffer.
44214 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
44215 @cindex @samp{QTro} packet
44216 Establish the given ranges of memory as ``transparent''. The stub
44217 will answer requests for these ranges from memory's current contents,
44218 if they were not collected as part of the tracepoint hit.
44220 @value{GDBN} uses this to mark read-only regions of memory, like those
44221 containing program code. Since these areas never change, they should
44222 still have the same contents they did when the tracepoint was hit, so
44223 there's no reason for the stub to refuse to provide their contents.
44225 @item QTDisconnected:@var{value}
44226 @cindex @samp{QTDisconnected} packet
44227 Set the choice to what to do with the tracing run when @value{GDBN}
44228 disconnects from the target. A @var{value} of 1 directs the target to
44229 continue the tracing run, while 0 tells the target to stop tracing if
44230 @value{GDBN} is no longer in the picture.
44233 @cindex @samp{qTStatus} packet
44234 Ask the stub if there is a trace experiment running right now.
44236 The reply has the form:
44240 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
44241 @var{running} is a single digit @code{1} if the trace is presently
44242 running, or @code{0} if not. It is followed by semicolon-separated
44243 optional fields that an agent may use to report additional status.
44247 If the trace is not running, the agent may report any of several
44248 explanations as one of the optional fields:
44253 No trace has been run yet.
44255 @item tstop[:@var{text}]:0
44256 The trace was stopped by a user-originated stop command. The optional
44257 @var{text} field is a user-supplied string supplied as part of the
44258 stop command (for instance, an explanation of why the trace was
44259 stopped manually). It is hex-encoded.
44262 The trace stopped because the trace buffer filled up.
44264 @item tdisconnected:0
44265 The trace stopped because @value{GDBN} disconnected from the target.
44267 @item tpasscount:@var{tpnum}
44268 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
44270 @item terror:@var{text}:@var{tpnum}
44271 The trace stopped because tracepoint @var{tpnum} had an error. The
44272 string @var{text} is available to describe the nature of the error
44273 (for instance, a divide by zero in the condition expression); it
44277 The trace stopped for some other reason.
44281 Additional optional fields supply statistical and other information.
44282 Although not required, they are extremely useful for users monitoring
44283 the progress of a trace run. If a trace has stopped, and these
44284 numbers are reported, they must reflect the state of the just-stopped
44289 @item tframes:@var{n}
44290 The number of trace frames in the buffer.
44292 @item tcreated:@var{n}
44293 The total number of trace frames created during the run. This may
44294 be larger than the trace frame count, if the buffer is circular.
44296 @item tsize:@var{n}
44297 The total size of the trace buffer, in bytes.
44299 @item tfree:@var{n}
44300 The number of bytes still unused in the buffer.
44302 @item circular:@var{n}
44303 The value of the circular trace buffer flag. @code{1} means that the
44304 trace buffer is circular and old trace frames will be discarded if
44305 necessary to make room, @code{0} means that the trace buffer is linear
44308 @item disconn:@var{n}
44309 The value of the disconnected tracing flag. @code{1} means that
44310 tracing will continue after @value{GDBN} disconnects, @code{0} means
44311 that the trace run will stop.
44315 @item qTP:@var{tp}:@var{addr}
44316 @cindex tracepoint status, remote request
44317 @cindex @samp{qTP} packet
44318 Ask the stub for the current state of tracepoint number @var{tp} at
44319 address @var{addr}.
44323 @item V@var{hits}:@var{usage}
44324 The tracepoint has been hit @var{hits} times so far during the trace
44325 run, and accounts for @var{usage} in the trace buffer. Note that
44326 @code{while-stepping} steps are not counted as separate hits, but the
44327 steps' space consumption is added into the usage number.
44331 @item qTV:@var{var}
44332 @cindex trace state variable value, remote request
44333 @cindex @samp{qTV} packet
44334 Ask the stub for the value of the trace state variable number @var{var}.
44339 The value of the variable is @var{value}. This will be the current
44340 value of the variable if the user is examining a running target, or a
44341 saved value if the variable was collected in the trace frame that the
44342 user is looking at. Note that multiple requests may result in
44343 different reply values, such as when requesting values while the
44344 program is running.
44347 The value of the variable is unknown. This would occur, for example,
44348 if the user is examining a trace frame in which the requested variable
44353 @cindex @samp{qTfP} packet
44355 @cindex @samp{qTsP} packet
44356 These packets request data about tracepoints that are being used by
44357 the target. @value{GDBN} sends @code{qTfP} to get the first piece
44358 of data, and multiple @code{qTsP} to get additional pieces. Replies
44359 to these packets generally take the form of the @code{QTDP} packets
44360 that define tracepoints. (FIXME add detailed syntax)
44363 @cindex @samp{qTfV} packet
44365 @cindex @samp{qTsV} packet
44366 These packets request data about trace state variables that are on the
44367 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
44368 and multiple @code{qTsV} to get additional variables. Replies to
44369 these packets follow the syntax of the @code{QTDV} packets that define
44370 trace state variables.
44376 @cindex @samp{qTfSTM} packet
44377 @cindex @samp{qTsSTM} packet
44378 These packets request data about static tracepoint markers that exist
44379 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
44380 first piece of data, and multiple @code{qTsSTM} to get additional
44381 pieces. Replies to these packets take the following form:
44385 @item m @var{address}:@var{id}:@var{extra}
44387 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
44388 a comma-separated list of markers
44390 (lower case letter @samp{L}) denotes end of list.
44392 An error occurred. The error number @var{nn} is given as hex digits.
44394 An empty reply indicates that the request is not supported by the
44398 The @var{address} is encoded in hex;
44399 @var{id} and @var{extra} are strings encoded in hex.
44401 In response to each query, the target will reply with a list of one or
44402 more markers, separated by commas. @value{GDBN} will respond to each
44403 reply with a request for more markers (using the @samp{qs} form of the
44404 query), until the target responds with @samp{l} (lower-case ell, for
44407 @item qTSTMat:@var{address}
44409 @cindex @samp{qTSTMat} packet
44410 This packets requests data about static tracepoint markers in the
44411 target program at @var{address}. Replies to this packet follow the
44412 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
44413 tracepoint markers.
44415 @item QTSave:@var{filename}
44416 @cindex @samp{QTSave} packet
44417 This packet directs the target to save trace data to the file name
44418 @var{filename} in the target's filesystem. The @var{filename} is encoded
44419 as a hex string; the interpretation of the file name (relative vs
44420 absolute, wild cards, etc) is up to the target.
44422 @item qTBuffer:@var{offset},@var{len}
44423 @cindex @samp{qTBuffer} packet
44424 Return up to @var{len} bytes of the current contents of trace buffer,
44425 starting at @var{offset}. The trace buffer is treated as if it were
44426 a contiguous collection of traceframes, as per the trace file format.
44427 The reply consists as many hex-encoded bytes as the target can deliver
44428 in a packet; it is not an error to return fewer than were asked for.
44429 A reply consisting of just @code{l} indicates that no bytes are
44432 @item QTBuffer:circular:@var{value}
44433 This packet directs the target to use a circular trace buffer if
44434 @var{value} is 1, or a linear buffer if the value is 0.
44436 @item QTBuffer:size:@var{size}
44437 @anchor{QTBuffer-size}
44438 @cindex @samp{QTBuffer size} packet
44439 This packet directs the target to make the trace buffer be of size
44440 @var{size} if possible. A value of @code{-1} tells the target to
44441 use whatever size it prefers.
44443 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
44444 @cindex @samp{QTNotes} packet
44445 This packet adds optional textual notes to the trace run. Allowable
44446 types include @code{user}, @code{notes}, and @code{tstop}, the
44447 @var{text} fields are arbitrary strings, hex-encoded.
44451 @subsection Relocate instruction reply packet
44452 When installing fast tracepoints in memory, the target may need to
44453 relocate the instruction currently at the tracepoint address to a
44454 different address in memory. For most instructions, a simple copy is
44455 enough, but, for example, call instructions that implicitly push the
44456 return address on the stack, and relative branches or other
44457 PC-relative instructions require offset adjustment, so that the effect
44458 of executing the instruction at a different address is the same as if
44459 it had executed in the original location.
44461 In response to several of the tracepoint packets, the target may also
44462 respond with a number of intermediate @samp{qRelocInsn} request
44463 packets before the final result packet, to have @value{GDBN} handle
44464 this relocation operation. If a packet supports this mechanism, its
44465 documentation will explicitly say so. See for example the above
44466 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
44467 format of the request is:
44470 @item qRelocInsn:@var{from};@var{to}
44472 This requests @value{GDBN} to copy instruction at address @var{from}
44473 to address @var{to}, possibly adjusted so that executing the
44474 instruction at @var{to} has the same effect as executing it at
44475 @var{from}. @value{GDBN} writes the adjusted instruction to target
44476 memory starting at @var{to}.
44481 @item qRelocInsn:@var{adjusted_size}
44482 Informs the stub the relocation is complete. The @var{adjusted_size} is
44483 the length in bytes of resulting relocated instruction sequence.
44485 A badly formed request was detected, or an error was encountered while
44486 relocating the instruction.
44489 @node Host I/O Packets
44490 @section Host I/O Packets
44491 @cindex Host I/O, remote protocol
44492 @cindex file transfer, remote protocol
44494 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
44495 operations on the far side of a remote link. For example, Host I/O is
44496 used to upload and download files to a remote target with its own
44497 filesystem. Host I/O uses the same constant values and data structure
44498 layout as the target-initiated File-I/O protocol. However, the
44499 Host I/O packets are structured differently. The target-initiated
44500 protocol relies on target memory to store parameters and buffers.
44501 Host I/O requests are initiated by @value{GDBN}, and the
44502 target's memory is not involved. @xref{File-I/O Remote Protocol
44503 Extension}, for more details on the target-initiated protocol.
44505 The Host I/O request packets all encode a single operation along with
44506 its arguments. They have this format:
44510 @item vFile:@var{operation}: @var{parameter}@dots{}
44511 @var{operation} is the name of the particular request; the target
44512 should compare the entire packet name up to the second colon when checking
44513 for a supported operation. The format of @var{parameter} depends on
44514 the operation. Numbers are always passed in hexadecimal. Negative
44515 numbers have an explicit minus sign (i.e.@: two's complement is not
44516 used). Strings (e.g.@: filenames) are encoded as a series of
44517 hexadecimal bytes. The last argument to a system call may be a
44518 buffer of escaped binary data (@pxref{Binary Data}).
44522 The valid responses to Host I/O packets are:
44526 @item F @var{result} [, @var{errno}] [; @var{attachment}]
44527 @var{result} is the integer value returned by this operation, usually
44528 non-negative for success and -1 for errors. If an error has occured,
44529 @var{errno} will be included in the result specifying a
44530 value defined by the File-I/O protocol (@pxref{Errno Values}). For
44531 operations which return data, @var{attachment} supplies the data as a
44532 binary buffer. Binary buffers in response packets are escaped in the
44533 normal way (@pxref{Binary Data}). See the individual packet
44534 documentation for the interpretation of @var{result} and
44538 An empty response indicates that this operation is not recognized.
44542 These are the supported Host I/O operations:
44545 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
44546 Open a file at @var{filename} and return a file descriptor for it, or
44547 return -1 if an error occurs. The @var{filename} is a string,
44548 @var{flags} is an integer indicating a mask of open flags
44549 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
44550 of mode bits to use if the file is created (@pxref{mode_t Values}).
44551 @xref{open}, for details of the open flags and mode values.
44553 @item vFile:close: @var{fd}
44554 Close the open file corresponding to @var{fd} and return 0, or
44555 -1 if an error occurs.
44557 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
44558 Read data from the open file corresponding to @var{fd}. Up to
44559 @var{count} bytes will be read from the file, starting at @var{offset}
44560 relative to the start of the file. The target may read fewer bytes;
44561 common reasons include packet size limits and an end-of-file
44562 condition. The number of bytes read is returned. Zero should only be
44563 returned for a successful read at the end of the file, or if
44564 @var{count} was zero.
44566 The data read should be returned as a binary attachment on success.
44567 If zero bytes were read, the response should include an empty binary
44568 attachment (i.e.@: a trailing semicolon). The return value is the
44569 number of target bytes read; the binary attachment may be longer if
44570 some characters were escaped.
44572 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
44573 Write @var{data} (a binary buffer) to the open file corresponding
44574 to @var{fd}. Start the write at @var{offset} from the start of the
44575 file. Unlike many @code{write} system calls, there is no
44576 separate @var{count} argument; the length of @var{data} in the
44577 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
44578 which may be shorter than the length of @var{data}, or -1 if an
44581 @item vFile:fstat: @var{fd}
44582 Get information about the open file corresponding to @var{fd}.
44583 On success the information is returned as a binary attachment
44584 and the return value is the size of this attachment in bytes.
44585 If an error occurs the return value is -1. The format of the
44586 returned binary attachment is as described in @ref{struct stat}.
44588 @item vFile:unlink: @var{filename}
44589 Delete the file at @var{filename} on the target. Return 0,
44590 or -1 if an error occurs. The @var{filename} is a string.
44592 @item vFile:readlink: @var{filename}
44593 Read value of symbolic link @var{filename} on the target. Return
44594 the number of bytes read, or -1 if an error occurs.
44596 The data read should be returned as a binary attachment on success.
44597 If zero bytes were read, the response should include an empty binary
44598 attachment (i.e.@: a trailing semicolon). The return value is the
44599 number of target bytes read; the binary attachment may be longer if
44600 some characters were escaped.
44602 @item vFile:setfs: @var{pid}
44603 Select the filesystem on which @code{vFile} operations with
44604 @var{filename} arguments will operate. This is required for
44605 @value{GDBN} to be able to access files on remote targets where
44606 the remote stub does not share a common filesystem with the
44609 If @var{pid} is nonzero, select the filesystem as seen by process
44610 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
44611 the remote stub. Return 0 on success, or -1 if an error occurs.
44612 If @code{vFile:setfs:} indicates success, the selected filesystem
44613 remains selected until the next successful @code{vFile:setfs:}
44619 @section Interrupts
44620 @cindex interrupts (remote protocol)
44621 @anchor{interrupting remote targets}
44623 In all-stop mode, when a program on the remote target is running,
44624 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
44625 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
44626 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
44628 The precise meaning of @code{BREAK} is defined by the transport
44629 mechanism and may, in fact, be undefined. @value{GDBN} does not
44630 currently define a @code{BREAK} mechanism for any of the network
44631 interfaces except for TCP, in which case @value{GDBN} sends the
44632 @code{telnet} BREAK sequence.
44634 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
44635 transport mechanisms. It is represented by sending the single byte
44636 @code{0x03} without any of the usual packet overhead described in
44637 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
44638 transmitted as part of a packet, it is considered to be packet data
44639 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
44640 (@pxref{X packet}), used for binary downloads, may include an unescaped
44641 @code{0x03} as part of its packet.
44643 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
44644 When Linux kernel receives this sequence from serial port,
44645 it stops execution and connects to gdb.
44647 In non-stop mode, because packet resumptions are asynchronous
44648 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
44649 command to the remote stub, even when the target is running. For that
44650 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
44651 packet}) with the usual packet framing instead of the single byte
44654 Stubs are not required to recognize these interrupt mechanisms and the
44655 precise meaning associated with receipt of the interrupt is
44656 implementation defined. If the target supports debugging of multiple
44657 threads and/or processes, it should attempt to interrupt all
44658 currently-executing threads and processes.
44659 If the stub is successful at interrupting the
44660 running program, it should send one of the stop
44661 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
44662 of successfully stopping the program in all-stop mode, and a stop reply
44663 for each stopped thread in non-stop mode.
44664 Interrupts received while the
44665 program is stopped are queued and the program will be interrupted when
44666 it is resumed next time.
44668 @node Notification Packets
44669 @section Notification Packets
44670 @cindex notification packets
44671 @cindex packets, notification
44673 The @value{GDBN} remote serial protocol includes @dfn{notifications},
44674 packets that require no acknowledgment. Both the GDB and the stub
44675 may send notifications (although the only notifications defined at
44676 present are sent by the stub). Notifications carry information
44677 without incurring the round-trip latency of an acknowledgment, and so
44678 are useful for low-impact communications where occasional packet loss
44681 A notification packet has the form @samp{% @var{data} #
44682 @var{checksum}}, where @var{data} is the content of the notification,
44683 and @var{checksum} is a checksum of @var{data}, computed and formatted
44684 as for ordinary @value{GDBN} packets. A notification's @var{data}
44685 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
44686 receiving a notification, the recipient sends no @samp{+} or @samp{-}
44687 to acknowledge the notification's receipt or to report its corruption.
44689 Every notification's @var{data} begins with a name, which contains no
44690 colon characters, followed by a colon character.
44692 Recipients should silently ignore corrupted notifications and
44693 notifications they do not understand. Recipients should restart
44694 timeout periods on receipt of a well-formed notification, whether or
44695 not they understand it.
44697 Senders should only send the notifications described here when this
44698 protocol description specifies that they are permitted. In the
44699 future, we may extend the protocol to permit existing notifications in
44700 new contexts; this rule helps older senders avoid confusing newer
44703 (Older versions of @value{GDBN} ignore bytes received until they see
44704 the @samp{$} byte that begins an ordinary packet, so new stubs may
44705 transmit notifications without fear of confusing older clients. There
44706 are no notifications defined for @value{GDBN} to send at the moment, but we
44707 assume that most older stubs would ignore them, as well.)
44709 Each notification is comprised of three parts:
44711 @item @var{name}:@var{event}
44712 The notification packet is sent by the side that initiates the
44713 exchange (currently, only the stub does that), with @var{event}
44714 carrying the specific information about the notification, and
44715 @var{name} specifying the name of the notification.
44717 The acknowledge sent by the other side, usually @value{GDBN}, to
44718 acknowledge the exchange and request the event.
44721 The purpose of an asynchronous notification mechanism is to report to
44722 @value{GDBN} that something interesting happened in the remote stub.
44724 The remote stub may send notification @var{name}:@var{event}
44725 at any time, but @value{GDBN} acknowledges the notification when
44726 appropriate. The notification event is pending before @value{GDBN}
44727 acknowledges. Only one notification at a time may be pending; if
44728 additional events occur before @value{GDBN} has acknowledged the
44729 previous notification, they must be queued by the stub for later
44730 synchronous transmission in response to @var{ack} packets from
44731 @value{GDBN}. Because the notification mechanism is unreliable,
44732 the stub is permitted to resend a notification if it believes
44733 @value{GDBN} may not have received it.
44735 Specifically, notifications may appear when @value{GDBN} is not
44736 otherwise reading input from the stub, or when @value{GDBN} is
44737 expecting to read a normal synchronous response or a
44738 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
44739 Notification packets are distinct from any other communication from
44740 the stub so there is no ambiguity.
44742 After receiving a notification, @value{GDBN} shall acknowledge it by
44743 sending a @var{ack} packet as a regular, synchronous request to the
44744 stub. Such acknowledgment is not required to happen immediately, as
44745 @value{GDBN} is permitted to send other, unrelated packets to the
44746 stub first, which the stub should process normally.
44748 Upon receiving a @var{ack} packet, if the stub has other queued
44749 events to report to @value{GDBN}, it shall respond by sending a
44750 normal @var{event}. @value{GDBN} shall then send another @var{ack}
44751 packet to solicit further responses; again, it is permitted to send
44752 other, unrelated packets as well which the stub should process
44755 If the stub receives a @var{ack} packet and there are no additional
44756 @var{event} to report, the stub shall return an @samp{OK} response.
44757 At this point, @value{GDBN} has finished processing a notification
44758 and the stub has completed sending any queued events. @value{GDBN}
44759 won't accept any new notifications until the final @samp{OK} is
44760 received . If further notification events occur, the stub shall send
44761 a new notification, @value{GDBN} shall accept the notification, and
44762 the process shall be repeated.
44764 The process of asynchronous notification can be illustrated by the
44767 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
44770 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
44772 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
44777 The following notifications are defined:
44778 @multitable @columnfractions 0.12 0.12 0.38 0.38
44787 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
44788 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
44789 for information on how these notifications are acknowledged by
44791 @tab Report an asynchronous stop event in non-stop mode.
44795 @node Remote Non-Stop
44796 @section Remote Protocol Support for Non-Stop Mode
44798 @value{GDBN}'s remote protocol supports non-stop debugging of
44799 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
44800 supports non-stop mode, it should report that to @value{GDBN} by including
44801 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
44803 @value{GDBN} typically sends a @samp{QNonStop} packet only when
44804 establishing a new connection with the stub. Entering non-stop mode
44805 does not alter the state of any currently-running threads, but targets
44806 must stop all threads in any already-attached processes when entering
44807 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
44808 probe the target state after a mode change.
44810 In non-stop mode, when an attached process encounters an event that
44811 would otherwise be reported with a stop reply, it uses the
44812 asynchronous notification mechanism (@pxref{Notification Packets}) to
44813 inform @value{GDBN}. In contrast to all-stop mode, where all threads
44814 in all processes are stopped when a stop reply is sent, in non-stop
44815 mode only the thread reporting the stop event is stopped. That is,
44816 when reporting a @samp{S} or @samp{T} response to indicate completion
44817 of a step operation, hitting a breakpoint, or a fault, only the
44818 affected thread is stopped; any other still-running threads continue
44819 to run. When reporting a @samp{W} or @samp{X} response, all running
44820 threads belonging to other attached processes continue to run.
44822 In non-stop mode, the target shall respond to the @samp{?} packet as
44823 follows. First, any incomplete stop reply notification/@samp{vStopped}
44824 sequence in progress is abandoned. The target must begin a new
44825 sequence reporting stop events for all stopped threads, whether or not
44826 it has previously reported those events to @value{GDBN}. The first
44827 stop reply is sent as a synchronous reply to the @samp{?} packet, and
44828 subsequent stop replies are sent as responses to @samp{vStopped} packets
44829 using the mechanism described above. The target must not send
44830 asynchronous stop reply notifications until the sequence is complete.
44831 If all threads are running when the target receives the @samp{?} packet,
44832 or if the target is not attached to any process, it shall respond
44835 If the stub supports non-stop mode, it should also support the
44836 @samp{swbreak} stop reason if software breakpoints are supported, and
44837 the @samp{hwbreak} stop reason if hardware breakpoints are supported
44838 (@pxref{swbreak stop reason}). This is because given the asynchronous
44839 nature of non-stop mode, between the time a thread hits a breakpoint
44840 and the time the event is finally processed by @value{GDBN}, the
44841 breakpoint may have already been removed from the target. Due to
44842 this, @value{GDBN} needs to be able to tell whether a trap stop was
44843 caused by a delayed breakpoint event, which should be ignored, as
44844 opposed to a random trap signal, which should be reported to the user.
44845 Note the @samp{swbreak} feature implies that the target is responsible
44846 for adjusting the PC when a software breakpoint triggers, if
44847 necessary, such as on the x86 architecture.
44849 @node Packet Acknowledgment
44850 @section Packet Acknowledgment
44852 @cindex acknowledgment, for @value{GDBN} remote
44853 @cindex packet acknowledgment, for @value{GDBN} remote
44854 By default, when either the host or the target machine receives a packet,
44855 the first response expected is an acknowledgment: either @samp{+} (to indicate
44856 the package was received correctly) or @samp{-} (to request retransmission).
44857 This mechanism allows the @value{GDBN} remote protocol to operate over
44858 unreliable transport mechanisms, such as a serial line.
44860 In cases where the transport mechanism is itself reliable (such as a pipe or
44861 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
44862 It may be desirable to disable them in that case to reduce communication
44863 overhead, or for other reasons. This can be accomplished by means of the
44864 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
44866 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
44867 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
44868 and response format still includes the normal checksum, as described in
44869 @ref{Overview}, but the checksum may be ignored by the receiver.
44871 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
44872 no-acknowledgment mode, it should report that to @value{GDBN}
44873 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
44874 @pxref{qSupported}.
44875 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
44876 disabled via the @code{set remote noack-packet off} command
44877 (@pxref{Remote Configuration}),
44878 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
44879 Only then may the stub actually turn off packet acknowledgments.
44880 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
44881 response, which can be safely ignored by the stub.
44883 Note that @code{set remote noack-packet} command only affects negotiation
44884 between @value{GDBN} and the stub when subsequent connections are made;
44885 it does not affect the protocol acknowledgment state for any current
44887 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
44888 new connection is established,
44889 there is also no protocol request to re-enable the acknowledgments
44890 for the current connection, once disabled.
44895 Example sequence of a target being re-started. Notice how the restart
44896 does not get any direct output:
44901 @emph{target restarts}
44904 <- @code{T001:1234123412341234}
44908 Example sequence of a target being stepped by a single instruction:
44911 -> @code{G1445@dots{}}
44916 <- @code{T001:1234123412341234}
44920 <- @code{1455@dots{}}
44924 @node File-I/O Remote Protocol Extension
44925 @section File-I/O Remote Protocol Extension
44926 @cindex File-I/O remote protocol extension
44929 * File-I/O Overview::
44930 * Protocol Basics::
44931 * The F Request Packet::
44932 * The F Reply Packet::
44933 * The Ctrl-C Message::
44935 * List of Supported Calls::
44936 * Protocol-specific Representation of Datatypes::
44938 * File-I/O Examples::
44941 @node File-I/O Overview
44942 @subsection File-I/O Overview
44943 @cindex file-i/o overview
44945 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
44946 target to use the host's file system and console I/O to perform various
44947 system calls. System calls on the target system are translated into a
44948 remote protocol packet to the host system, which then performs the needed
44949 actions and returns a response packet to the target system.
44950 This simulates file system operations even on targets that lack file systems.
44952 The protocol is defined to be independent of both the host and target systems.
44953 It uses its own internal representation of datatypes and values. Both
44954 @value{GDBN} and the target's @value{GDBN} stub are responsible for
44955 translating the system-dependent value representations into the internal
44956 protocol representations when data is transmitted.
44958 The communication is synchronous. A system call is possible only when
44959 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
44960 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
44961 the target is stopped to allow deterministic access to the target's
44962 memory. Therefore File-I/O is not interruptible by target signals. On
44963 the other hand, it is possible to interrupt File-I/O by a user interrupt
44964 (@samp{Ctrl-C}) within @value{GDBN}.
44966 The target's request to perform a host system call does not finish
44967 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
44968 after finishing the system call, the target returns to continuing the
44969 previous activity (continue, step). No additional continue or step
44970 request from @value{GDBN} is required.
44973 (@value{GDBP}) continue
44974 <- target requests 'system call X'
44975 target is stopped, @value{GDBN} executes system call
44976 -> @value{GDBN} returns result
44977 ... target continues, @value{GDBN} returns to wait for the target
44978 <- target hits breakpoint and sends a Txx packet
44981 The protocol only supports I/O on the console and to regular files on
44982 the host file system. Character or block special devices, pipes,
44983 named pipes, sockets or any other communication method on the host
44984 system are not supported by this protocol.
44986 File I/O is not supported in non-stop mode.
44988 @node Protocol Basics
44989 @subsection Protocol Basics
44990 @cindex protocol basics, file-i/o
44992 The File-I/O protocol uses the @code{F} packet as the request as well
44993 as reply packet. Since a File-I/O system call can only occur when
44994 @value{GDBN} is waiting for a response from the continuing or stepping target,
44995 the File-I/O request is a reply that @value{GDBN} has to expect as a result
44996 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
44997 This @code{F} packet contains all information needed to allow @value{GDBN}
44998 to call the appropriate host system call:
45002 A unique identifier for the requested system call.
45005 All parameters to the system call. Pointers are given as addresses
45006 in the target memory address space. Pointers to strings are given as
45007 pointer/length pair. Numerical values are given as they are.
45008 Numerical control flags are given in a protocol-specific representation.
45012 At this point, @value{GDBN} has to perform the following actions.
45016 If the parameters include pointer values to data needed as input to a
45017 system call, @value{GDBN} requests this data from the target with a
45018 standard @code{m} packet request. This additional communication has to be
45019 expected by the target implementation and is handled as any other @code{m}
45023 @value{GDBN} translates all value from protocol representation to host
45024 representation as needed. Datatypes are coerced into the host types.
45027 @value{GDBN} calls the system call.
45030 It then coerces datatypes back to protocol representation.
45033 If the system call is expected to return data in buffer space specified
45034 by pointer parameters to the call, the data is transmitted to the
45035 target using a @code{M} or @code{X} packet. This packet has to be expected
45036 by the target implementation and is handled as any other @code{M} or @code{X}
45041 Eventually @value{GDBN} replies with another @code{F} packet which contains all
45042 necessary information for the target to continue. This at least contains
45049 @code{errno}, if has been changed by the system call.
45056 After having done the needed type and value coercion, the target continues
45057 the latest continue or step action.
45059 @node The F Request Packet
45060 @subsection The @code{F} Request Packet
45061 @cindex file-i/o request packet
45062 @cindex @code{F} request packet
45064 The @code{F} request packet has the following format:
45067 @item F@var{call-id},@var{parameter@dots{}}
45069 @var{call-id} is the identifier to indicate the host system call to be called.
45070 This is just the name of the function.
45072 @var{parameter@dots{}} are the parameters to the system call.
45073 Parameters are hexadecimal integer values, either the actual values in case
45074 of scalar datatypes, pointers to target buffer space in case of compound
45075 datatypes and unspecified memory areas, or pointer/length pairs in case
45076 of string parameters. These are appended to the @var{call-id} as a
45077 comma-delimited list. All values are transmitted in ASCII
45078 string representation, pointer/length pairs separated by a slash.
45084 @node The F Reply Packet
45085 @subsection The @code{F} Reply Packet
45086 @cindex file-i/o reply packet
45087 @cindex @code{F} reply packet
45089 The @code{F} reply packet has the following format:
45093 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
45095 @var{retcode} is the return code of the system call as hexadecimal value.
45097 @var{errno} is the @code{errno} set by the call, in protocol-specific
45099 This parameter can be omitted if the call was successful.
45101 @var{Ctrl-C flag} is only sent if the user requested a break. In this
45102 case, @var{errno} must be sent as well, even if the call was successful.
45103 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
45110 or, if the call was interrupted before the host call has been performed:
45117 assuming 4 is the protocol-specific representation of @code{EINTR}.
45122 @node The Ctrl-C Message
45123 @subsection The @samp{Ctrl-C} Message
45124 @cindex ctrl-c message, in file-i/o protocol
45126 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
45127 reply packet (@pxref{The F Reply Packet}),
45128 the target should behave as if it had
45129 gotten a break message. The meaning for the target is ``system call
45130 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
45131 (as with a break message) and return to @value{GDBN} with a @code{T02}
45134 It's important for the target to know in which
45135 state the system call was interrupted. There are two possible cases:
45139 The system call hasn't been performed on the host yet.
45142 The system call on the host has been finished.
45146 These two states can be distinguished by the target by the value of the
45147 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
45148 call hasn't been performed. This is equivalent to the @code{EINTR} handling
45149 on POSIX systems. In any other case, the target may presume that the
45150 system call has been finished --- successfully or not --- and should behave
45151 as if the break message arrived right after the system call.
45153 @value{GDBN} must behave reliably. If the system call has not been called
45154 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
45155 @code{errno} in the packet. If the system call on the host has been finished
45156 before the user requests a break, the full action must be finished by
45157 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
45158 The @code{F} packet may only be sent when either nothing has happened
45159 or the full action has been completed.
45162 @subsection Console I/O
45163 @cindex console i/o as part of file-i/o
45165 By default and if not explicitly closed by the target system, the file
45166 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
45167 on the @value{GDBN} console is handled as any other file output operation
45168 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
45169 by @value{GDBN} so that after the target read request from file descriptor
45170 0 all following typing is buffered until either one of the following
45175 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
45177 system call is treated as finished.
45180 The user presses @key{RET}. This is treated as end of input with a trailing
45184 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
45185 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
45189 If the user has typed more characters than fit in the buffer given to
45190 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
45191 either another @code{read(0, @dots{})} is requested by the target, or debugging
45192 is stopped at the user's request.
45195 @node List of Supported Calls
45196 @subsection List of Supported Calls
45197 @cindex list of supported file-i/o calls
45214 @unnumberedsubsubsec open
45215 @cindex open, file-i/o system call
45220 int open(const char *pathname, int flags);
45221 int open(const char *pathname, int flags, mode_t mode);
45225 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
45228 @var{flags} is the bitwise @code{OR} of the following values:
45232 If the file does not exist it will be created. The host
45233 rules apply as far as file ownership and time stamps
45237 When used with @code{O_CREAT}, if the file already exists it is
45238 an error and open() fails.
45241 If the file already exists and the open mode allows
45242 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
45243 truncated to zero length.
45246 The file is opened in append mode.
45249 The file is opened for reading only.
45252 The file is opened for writing only.
45255 The file is opened for reading and writing.
45259 Other bits are silently ignored.
45263 @var{mode} is the bitwise @code{OR} of the following values:
45267 User has read permission.
45270 User has write permission.
45273 Group has read permission.
45276 Group has write permission.
45279 Others have read permission.
45282 Others have write permission.
45286 Other bits are silently ignored.
45289 @item Return value:
45290 @code{open} returns the new file descriptor or -1 if an error
45297 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
45300 @var{pathname} refers to a directory.
45303 The requested access is not allowed.
45306 @var{pathname} was too long.
45309 A directory component in @var{pathname} does not exist.
45312 @var{pathname} refers to a device, pipe, named pipe or socket.
45315 @var{pathname} refers to a file on a read-only filesystem and
45316 write access was requested.
45319 @var{pathname} is an invalid pointer value.
45322 No space on device to create the file.
45325 The process already has the maximum number of files open.
45328 The limit on the total number of files open on the system
45332 The call was interrupted by the user.
45338 @unnumberedsubsubsec close
45339 @cindex close, file-i/o system call
45348 @samp{Fclose,@var{fd}}
45350 @item Return value:
45351 @code{close} returns zero on success, or -1 if an error occurred.
45357 @var{fd} isn't a valid open file descriptor.
45360 The call was interrupted by the user.
45366 @unnumberedsubsubsec read
45367 @cindex read, file-i/o system call
45372 int read(int fd, void *buf, unsigned int count);
45376 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
45378 @item Return value:
45379 On success, the number of bytes read is returned.
45380 Zero indicates end of file. If count is zero, read
45381 returns zero as well. On error, -1 is returned.
45387 @var{fd} is not a valid file descriptor or is not open for
45391 @var{bufptr} is an invalid pointer value.
45394 The call was interrupted by the user.
45400 @unnumberedsubsubsec write
45401 @cindex write, file-i/o system call
45406 int write(int fd, const void *buf, unsigned int count);
45410 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
45412 @item Return value:
45413 On success, the number of bytes written are returned.
45414 Zero indicates nothing was written. On error, -1
45421 @var{fd} is not a valid file descriptor or is not open for
45425 @var{bufptr} is an invalid pointer value.
45428 An attempt was made to write a file that exceeds the
45429 host-specific maximum file size allowed.
45432 No space on device to write the data.
45435 The call was interrupted by the user.
45441 @unnumberedsubsubsec lseek
45442 @cindex lseek, file-i/o system call
45447 long lseek (int fd, long offset, int flag);
45451 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
45453 @var{flag} is one of:
45457 The offset is set to @var{offset} bytes.
45460 The offset is set to its current location plus @var{offset}
45464 The offset is set to the size of the file plus @var{offset}
45468 @item Return value:
45469 On success, the resulting unsigned offset in bytes from
45470 the beginning of the file is returned. Otherwise, a
45471 value of -1 is returned.
45477 @var{fd} is not a valid open file descriptor.
45480 @var{fd} is associated with the @value{GDBN} console.
45483 @var{flag} is not a proper value.
45486 The call was interrupted by the user.
45492 @unnumberedsubsubsec rename
45493 @cindex rename, file-i/o system call
45498 int rename(const char *oldpath, const char *newpath);
45502 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
45504 @item Return value:
45505 On success, zero is returned. On error, -1 is returned.
45511 @var{newpath} is an existing directory, but @var{oldpath} is not a
45515 @var{newpath} is a non-empty directory.
45518 @var{oldpath} or @var{newpath} is a directory that is in use by some
45522 An attempt was made to make a directory a subdirectory
45526 A component used as a directory in @var{oldpath} or new
45527 path is not a directory. Or @var{oldpath} is a directory
45528 and @var{newpath} exists but is not a directory.
45531 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
45534 No access to the file or the path of the file.
45538 @var{oldpath} or @var{newpath} was too long.
45541 A directory component in @var{oldpath} or @var{newpath} does not exist.
45544 The file is on a read-only filesystem.
45547 The device containing the file has no room for the new
45551 The call was interrupted by the user.
45557 @unnumberedsubsubsec unlink
45558 @cindex unlink, file-i/o system call
45563 int unlink(const char *pathname);
45567 @samp{Funlink,@var{pathnameptr}/@var{len}}
45569 @item Return value:
45570 On success, zero is returned. On error, -1 is returned.
45576 No access to the file or the path of the file.
45579 The system does not allow unlinking of directories.
45582 The file @var{pathname} cannot be unlinked because it's
45583 being used by another process.
45586 @var{pathnameptr} is an invalid pointer value.
45589 @var{pathname} was too long.
45592 A directory component in @var{pathname} does not exist.
45595 A component of the path is not a directory.
45598 The file is on a read-only filesystem.
45601 The call was interrupted by the user.
45607 @unnumberedsubsubsec stat/fstat
45608 @cindex fstat, file-i/o system call
45609 @cindex stat, file-i/o system call
45614 int stat(const char *pathname, struct stat *buf);
45615 int fstat(int fd, struct stat *buf);
45619 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
45620 @samp{Ffstat,@var{fd},@var{bufptr}}
45622 @item Return value:
45623 On success, zero is returned. On error, -1 is returned.
45629 @var{fd} is not a valid open file.
45632 A directory component in @var{pathname} does not exist or the
45633 path is an empty string.
45636 A component of the path is not a directory.
45639 @var{pathnameptr} is an invalid pointer value.
45642 No access to the file or the path of the file.
45645 @var{pathname} was too long.
45648 The call was interrupted by the user.
45654 @unnumberedsubsubsec gettimeofday
45655 @cindex gettimeofday, file-i/o system call
45660 int gettimeofday(struct timeval *tv, void *tz);
45664 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
45666 @item Return value:
45667 On success, 0 is returned, -1 otherwise.
45673 @var{tz} is a non-NULL pointer.
45676 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
45682 @unnumberedsubsubsec isatty
45683 @cindex isatty, file-i/o system call
45688 int isatty(int fd);
45692 @samp{Fisatty,@var{fd}}
45694 @item Return value:
45695 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
45701 The call was interrupted by the user.
45706 Note that the @code{isatty} call is treated as a special case: it returns
45707 1 to the target if the file descriptor is attached
45708 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
45709 would require implementing @code{ioctl} and would be more complex than
45714 @unnumberedsubsubsec system
45715 @cindex system, file-i/o system call
45720 int system(const char *command);
45724 @samp{Fsystem,@var{commandptr}/@var{len}}
45726 @item Return value:
45727 If @var{len} is zero, the return value indicates whether a shell is
45728 available. A zero return value indicates a shell is not available.
45729 For non-zero @var{len}, the value returned is -1 on error and the
45730 return status of the command otherwise. Only the exit status of the
45731 command is returned, which is extracted from the host's @code{system}
45732 return value by calling @code{WEXITSTATUS(retval)}. In case
45733 @file{/bin/sh} could not be executed, 127 is returned.
45739 The call was interrupted by the user.
45744 @value{GDBN} takes over the full task of calling the necessary host calls
45745 to perform the @code{system} call. The return value of @code{system} on
45746 the host is simplified before it's returned
45747 to the target. Any termination signal information from the child process
45748 is discarded, and the return value consists
45749 entirely of the exit status of the called command.
45751 Due to security concerns, the @code{system} call is by default refused
45752 by @value{GDBN}. The user has to allow this call explicitly with the
45753 @code{set remote system-call-allowed 1} command.
45756 @item set remote system-call-allowed
45757 @kindex set remote system-call-allowed
45758 Control whether to allow the @code{system} calls in the File I/O
45759 protocol for the remote target. The default is zero (disabled).
45761 @item show remote system-call-allowed
45762 @kindex show remote system-call-allowed
45763 Show whether the @code{system} calls are allowed in the File I/O
45767 @node Protocol-specific Representation of Datatypes
45768 @subsection Protocol-specific Representation of Datatypes
45769 @cindex protocol-specific representation of datatypes, in file-i/o protocol
45772 * Integral Datatypes::
45774 * Memory Transfer::
45779 @node Integral Datatypes
45780 @unnumberedsubsubsec Integral Datatypes
45781 @cindex integral datatypes, in file-i/o protocol
45783 The integral datatypes used in the system calls are @code{int},
45784 @code{unsigned int}, @code{long}, @code{unsigned long},
45785 @code{mode_t}, and @code{time_t}.
45787 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
45788 implemented as 32 bit values in this protocol.
45790 @code{long} and @code{unsigned long} are implemented as 64 bit types.
45792 @xref{Limits}, for corresponding MIN and MAX values (similar to those
45793 in @file{limits.h}) to allow range checking on host and target.
45795 @code{time_t} datatypes are defined as seconds since the Epoch.
45797 All integral datatypes transferred as part of a memory read or write of a
45798 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
45801 @node Pointer Values
45802 @unnumberedsubsubsec Pointer Values
45803 @cindex pointer values, in file-i/o protocol
45805 Pointers to target data are transmitted as they are. An exception
45806 is made for pointers to buffers for which the length isn't
45807 transmitted as part of the function call, namely strings. Strings
45808 are transmitted as a pointer/length pair, both as hex values, e.g.@:
45815 which is a pointer to data of length 18 bytes at position 0x1aaf.
45816 The length is defined as the full string length in bytes, including
45817 the trailing null byte. For example, the string @code{"hello world"}
45818 at address 0x123456 is transmitted as
45824 @node Memory Transfer
45825 @unnumberedsubsubsec Memory Transfer
45826 @cindex memory transfer, in file-i/o protocol
45828 Structured data which is transferred using a memory read or write (for
45829 example, a @code{struct stat}) is expected to be in a protocol-specific format
45830 with all scalar multibyte datatypes being big endian. Translation to
45831 this representation needs to be done both by the target before the @code{F}
45832 packet is sent, and by @value{GDBN} before
45833 it transfers memory to the target. Transferred pointers to structured
45834 data should point to the already-coerced data at any time.
45838 @unnumberedsubsubsec struct stat
45839 @cindex struct stat, in file-i/o protocol
45841 The buffer of type @code{struct stat} used by the target and @value{GDBN}
45842 is defined as follows:
45846 unsigned int st_dev; /* device */
45847 unsigned int st_ino; /* inode */
45848 mode_t st_mode; /* protection */
45849 unsigned int st_nlink; /* number of hard links */
45850 unsigned int st_uid; /* user ID of owner */
45851 unsigned int st_gid; /* group ID of owner */
45852 unsigned int st_rdev; /* device type (if inode device) */
45853 unsigned long st_size; /* total size, in bytes */
45854 unsigned long st_blksize; /* blocksize for filesystem I/O */
45855 unsigned long st_blocks; /* number of blocks allocated */
45856 time_t st_atime; /* time of last access */
45857 time_t st_mtime; /* time of last modification */
45858 time_t st_ctime; /* time of last change */
45862 The integral datatypes conform to the definitions given in the
45863 appropriate section (see @ref{Integral Datatypes}, for details) so this
45864 structure is of size 64 bytes.
45866 The values of several fields have a restricted meaning and/or
45872 A value of 0 represents a file, 1 the console.
45875 No valid meaning for the target. Transmitted unchanged.
45878 Valid mode bits are described in @ref{Constants}. Any other
45879 bits have currently no meaning for the target.
45884 No valid meaning for the target. Transmitted unchanged.
45889 These values have a host and file system dependent
45890 accuracy. Especially on Windows hosts, the file system may not
45891 support exact timing values.
45894 The target gets a @code{struct stat} of the above representation and is
45895 responsible for coercing it to the target representation before
45898 Note that due to size differences between the host, target, and protocol
45899 representations of @code{struct stat} members, these members could eventually
45900 get truncated on the target.
45902 @node struct timeval
45903 @unnumberedsubsubsec struct timeval
45904 @cindex struct timeval, in file-i/o protocol
45906 The buffer of type @code{struct timeval} used by the File-I/O protocol
45907 is defined as follows:
45911 time_t tv_sec; /* second */
45912 long tv_usec; /* microsecond */
45916 The integral datatypes conform to the definitions given in the
45917 appropriate section (see @ref{Integral Datatypes}, for details) so this
45918 structure is of size 8 bytes.
45921 @subsection Constants
45922 @cindex constants, in file-i/o protocol
45924 The following values are used for the constants inside of the
45925 protocol. @value{GDBN} and target are responsible for translating these
45926 values before and after the call as needed.
45937 @unnumberedsubsubsec Open Flags
45938 @cindex open flags, in file-i/o protocol
45940 All values are given in hexadecimal representation.
45952 @node mode_t Values
45953 @unnumberedsubsubsec mode_t Values
45954 @cindex mode_t values, in file-i/o protocol
45956 All values are given in octal representation.
45973 @unnumberedsubsubsec Errno Values
45974 @cindex errno values, in file-i/o protocol
45976 All values are given in decimal representation.
46001 @code{EUNKNOWN} is used as a fallback error value if a host system returns
46002 any error value not in the list of supported error numbers.
46005 @unnumberedsubsubsec Lseek Flags
46006 @cindex lseek flags, in file-i/o protocol
46015 @unnumberedsubsubsec Limits
46016 @cindex limits, in file-i/o protocol
46018 All values are given in decimal representation.
46021 INT_MIN -2147483648
46023 UINT_MAX 4294967295
46024 LONG_MIN -9223372036854775808
46025 LONG_MAX 9223372036854775807
46026 ULONG_MAX 18446744073709551615
46029 @node File-I/O Examples
46030 @subsection File-I/O Examples
46031 @cindex file-i/o examples
46033 Example sequence of a write call, file descriptor 3, buffer is at target
46034 address 0x1234, 6 bytes should be written:
46037 <- @code{Fwrite,3,1234,6}
46038 @emph{request memory read from target}
46041 @emph{return "6 bytes written"}
46045 Example sequence of a read call, file descriptor 3, buffer is at target
46046 address 0x1234, 6 bytes should be read:
46049 <- @code{Fread,3,1234,6}
46050 @emph{request memory write to target}
46051 -> @code{X1234,6:XXXXXX}
46052 @emph{return "6 bytes read"}
46056 Example sequence of a read call, call fails on the host due to invalid
46057 file descriptor (@code{EBADF}):
46060 <- @code{Fread,3,1234,6}
46064 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
46068 <- @code{Fread,3,1234,6}
46073 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
46077 <- @code{Fread,3,1234,6}
46078 -> @code{X1234,6:XXXXXX}
46082 @node Library List Format
46083 @section Library List Format
46084 @cindex library list format, remote protocol
46086 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
46087 same process as your application to manage libraries. In this case,
46088 @value{GDBN} can use the loader's symbol table and normal memory
46089 operations to maintain a list of shared libraries. On other
46090 platforms, the operating system manages loaded libraries.
46091 @value{GDBN} can not retrieve the list of currently loaded libraries
46092 through memory operations, so it uses the @samp{qXfer:libraries:read}
46093 packet (@pxref{qXfer library list read}) instead. The remote stub
46094 queries the target's operating system and reports which libraries
46097 The @samp{qXfer:libraries:read} packet returns an XML document which
46098 lists loaded libraries and their offsets. Each library has an
46099 associated name and one or more segment or section base addresses,
46100 which report where the library was loaded in memory.
46102 For the common case of libraries that are fully linked binaries, the
46103 library should have a list of segments. If the target supports
46104 dynamic linking of a relocatable object file, its library XML element
46105 should instead include a list of allocated sections. The segment or
46106 section bases are start addresses, not relocation offsets; they do not
46107 depend on the library's link-time base addresses.
46109 @value{GDBN} must be linked with the Expat library to support XML
46110 library lists. @xref{Expat}.
46112 A simple memory map, with one loaded library relocated by a single
46113 offset, looks like this:
46117 <library name="/lib/libc.so.6">
46118 <segment address="0x10000000"/>
46123 Another simple memory map, with one loaded library with three
46124 allocated sections (.text, .data, .bss), looks like this:
46128 <library name="sharedlib.o">
46129 <section address="0x10000000"/>
46130 <section address="0x20000000"/>
46131 <section address="0x30000000"/>
46136 The format of a library list is described by this DTD:
46139 <!-- library-list: Root element with versioning -->
46140 <!ELEMENT library-list (library)*>
46141 <!ATTLIST library-list version CDATA #FIXED "1.0">
46142 <!ELEMENT library (segment*, section*)>
46143 <!ATTLIST library name CDATA #REQUIRED>
46144 <!ELEMENT segment EMPTY>
46145 <!ATTLIST segment address CDATA #REQUIRED>
46146 <!ELEMENT section EMPTY>
46147 <!ATTLIST section address CDATA #REQUIRED>
46150 In addition, segments and section descriptors cannot be mixed within a
46151 single library element, and you must supply at least one segment or
46152 section for each library.
46154 @node Library List Format for SVR4 Targets
46155 @section Library List Format for SVR4 Targets
46156 @cindex library list format, remote protocol
46158 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
46159 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
46160 shared libraries. Still a special library list provided by this packet is
46161 more efficient for the @value{GDBN} remote protocol.
46163 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
46164 loaded libraries and their SVR4 linker parameters. For each library on SVR4
46165 target, the following parameters are reported:
46169 @code{name}, the absolute file name from the @code{l_name} field of
46170 @code{struct link_map}.
46172 @code{lm} with address of @code{struct link_map} used for TLS
46173 (Thread Local Storage) access.
46175 @code{l_addr}, the displacement as read from the field @code{l_addr} of
46176 @code{struct link_map}. For prelinked libraries this is not an absolute
46177 memory address. It is a displacement of absolute memory address against
46178 address the file was prelinked to during the library load.
46180 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
46183 Additionally the single @code{main-lm} attribute specifies address of
46184 @code{struct link_map} used for the main executable. This parameter is used
46185 for TLS access and its presence is optional.
46187 @value{GDBN} must be linked with the Expat library to support XML
46188 SVR4 library lists. @xref{Expat}.
46190 A simple memory map, with two loaded libraries (which do not use prelink),
46194 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
46195 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
46197 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
46199 </library-list-svr>
46202 The format of an SVR4 library list is described by this DTD:
46205 <!-- library-list-svr4: Root element with versioning -->
46206 <!ELEMENT library-list-svr4 (library)*>
46207 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
46208 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
46209 <!ELEMENT library EMPTY>
46210 <!ATTLIST library name CDATA #REQUIRED>
46211 <!ATTLIST library lm CDATA #REQUIRED>
46212 <!ATTLIST library l_addr CDATA #REQUIRED>
46213 <!ATTLIST library l_ld CDATA #REQUIRED>
46216 @node Memory Map Format
46217 @section Memory Map Format
46218 @cindex memory map format
46220 To be able to write into flash memory, @value{GDBN} needs to obtain a
46221 memory map from the target. This section describes the format of the
46224 The memory map is obtained using the @samp{qXfer:memory-map:read}
46225 (@pxref{qXfer memory map read}) packet and is an XML document that
46226 lists memory regions.
46228 @value{GDBN} must be linked with the Expat library to support XML
46229 memory maps. @xref{Expat}.
46231 The top-level structure of the document is shown below:
46234 <?xml version="1.0"?>
46235 <!DOCTYPE memory-map
46236 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
46237 "http://sourceware.org/gdb/gdb-memory-map.dtd">
46243 Each region can be either:
46248 A region of RAM starting at @var{addr} and extending for @var{length}
46252 <memory type="ram" start="@var{addr}" length="@var{length}"/>
46257 A region of read-only memory:
46260 <memory type="rom" start="@var{addr}" length="@var{length}"/>
46265 A region of flash memory, with erasure blocks @var{blocksize}
46269 <memory type="flash" start="@var{addr}" length="@var{length}">
46270 <property name="blocksize">@var{blocksize}</property>
46276 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
46277 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
46278 packets to write to addresses in such ranges.
46280 The formal DTD for memory map format is given below:
46283 <!-- ................................................... -->
46284 <!-- Memory Map XML DTD ................................ -->
46285 <!-- File: memory-map.dtd .............................. -->
46286 <!-- .................................... .............. -->
46287 <!-- memory-map.dtd -->
46288 <!-- memory-map: Root element with versioning -->
46289 <!ELEMENT memory-map (memory)*>
46290 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
46291 <!ELEMENT memory (property)*>
46292 <!-- memory: Specifies a memory region,
46293 and its type, or device. -->
46294 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
46295 start CDATA #REQUIRED
46296 length CDATA #REQUIRED>
46297 <!-- property: Generic attribute tag -->
46298 <!ELEMENT property (#PCDATA | property)*>
46299 <!ATTLIST property name (blocksize) #REQUIRED>
46302 @node Thread List Format
46303 @section Thread List Format
46304 @cindex thread list format
46306 To efficiently update the list of threads and their attributes,
46307 @value{GDBN} issues the @samp{qXfer:threads:read} packet
46308 (@pxref{qXfer threads read}) and obtains the XML document with
46309 the following structure:
46312 <?xml version="1.0"?>
46314 <thread id="id" core="0" name="name">
46315 ... description ...
46320 Each @samp{thread} element must have the @samp{id} attribute that
46321 identifies the thread (@pxref{thread-id syntax}). The
46322 @samp{core} attribute, if present, specifies which processor core
46323 the thread was last executing on. The @samp{name} attribute, if
46324 present, specifies the human-readable name of the thread. The content
46325 of the of @samp{thread} element is interpreted as human-readable
46326 auxiliary information. The @samp{handle} attribute, if present,
46327 is a hex encoded representation of the thread handle.
46330 @node Traceframe Info Format
46331 @section Traceframe Info Format
46332 @cindex traceframe info format
46334 To be able to know which objects in the inferior can be examined when
46335 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
46336 memory ranges, registers and trace state variables that have been
46337 collected in a traceframe.
46339 This list is obtained using the @samp{qXfer:traceframe-info:read}
46340 (@pxref{qXfer traceframe info read}) packet and is an XML document.
46342 @value{GDBN} must be linked with the Expat library to support XML
46343 traceframe info discovery. @xref{Expat}.
46345 The top-level structure of the document is shown below:
46348 <?xml version="1.0"?>
46349 <!DOCTYPE traceframe-info
46350 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
46351 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
46357 Each traceframe block can be either:
46362 A region of collected memory starting at @var{addr} and extending for
46363 @var{length} bytes from there:
46366 <memory start="@var{addr}" length="@var{length}"/>
46370 A block indicating trace state variable numbered @var{number} has been
46374 <tvar id="@var{number}"/>
46379 The formal DTD for the traceframe info format is given below:
46382 <!ELEMENT traceframe-info (memory | tvar)* >
46383 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
46385 <!ELEMENT memory EMPTY>
46386 <!ATTLIST memory start CDATA #REQUIRED
46387 length CDATA #REQUIRED>
46389 <!ATTLIST tvar id CDATA #REQUIRED>
46392 @node Branch Trace Format
46393 @section Branch Trace Format
46394 @cindex branch trace format
46396 In order to display the branch trace of an inferior thread,
46397 @value{GDBN} needs to obtain the list of branches. This list is
46398 represented as list of sequential code blocks that are connected via
46399 branches. The code in each block has been executed sequentially.
46401 This list is obtained using the @samp{qXfer:btrace:read}
46402 (@pxref{qXfer btrace read}) packet and is an XML document.
46404 @value{GDBN} must be linked with the Expat library to support XML
46405 traceframe info discovery. @xref{Expat}.
46407 The top-level structure of the document is shown below:
46410 <?xml version="1.0"?>
46412 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
46413 "http://sourceware.org/gdb/gdb-btrace.dtd">
46422 A block of sequentially executed instructions starting at @var{begin}
46423 and ending at @var{end}:
46426 <block begin="@var{begin}" end="@var{end}"/>
46431 The formal DTD for the branch trace format is given below:
46434 <!ELEMENT btrace (block* | pt) >
46435 <!ATTLIST btrace version CDATA #FIXED "1.0">
46437 <!ELEMENT block EMPTY>
46438 <!ATTLIST block begin CDATA #REQUIRED
46439 end CDATA #REQUIRED>
46441 <!ELEMENT pt (pt-config?, raw?)>
46443 <!ELEMENT pt-config (cpu?)>
46445 <!ELEMENT cpu EMPTY>
46446 <!ATTLIST cpu vendor CDATA #REQUIRED
46447 family CDATA #REQUIRED
46448 model CDATA #REQUIRED
46449 stepping CDATA #REQUIRED>
46451 <!ELEMENT raw (#PCDATA)>
46454 @node Branch Trace Configuration Format
46455 @section Branch Trace Configuration Format
46456 @cindex branch trace configuration format
46458 For each inferior thread, @value{GDBN} can obtain the branch trace
46459 configuration using the @samp{qXfer:btrace-conf:read}
46460 (@pxref{qXfer btrace-conf read}) packet.
46462 The configuration describes the branch trace format and configuration
46463 settings for that format. The following information is described:
46467 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
46470 The size of the @acronym{BTS} ring buffer in bytes.
46473 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
46477 The size of the @acronym{Intel PT} ring buffer in bytes.
46481 @value{GDBN} must be linked with the Expat library to support XML
46482 branch trace configuration discovery. @xref{Expat}.
46484 The formal DTD for the branch trace configuration format is given below:
46487 <!ELEMENT btrace-conf (bts?, pt?)>
46488 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
46490 <!ELEMENT bts EMPTY>
46491 <!ATTLIST bts size CDATA #IMPLIED>
46493 <!ELEMENT pt EMPTY>
46494 <!ATTLIST pt size CDATA #IMPLIED>
46497 @include agentexpr.texi
46499 @node Target Descriptions
46500 @appendix Target Descriptions
46501 @cindex target descriptions
46503 One of the challenges of using @value{GDBN} to debug embedded systems
46504 is that there are so many minor variants of each processor
46505 architecture in use. It is common practice for vendors to start with
46506 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
46507 and then make changes to adapt it to a particular market niche. Some
46508 architectures have hundreds of variants, available from dozens of
46509 vendors. This leads to a number of problems:
46513 With so many different customized processors, it is difficult for
46514 the @value{GDBN} maintainers to keep up with the changes.
46516 Since individual variants may have short lifetimes or limited
46517 audiences, it may not be worthwhile to carry information about every
46518 variant in the @value{GDBN} source tree.
46520 When @value{GDBN} does support the architecture of the embedded system
46521 at hand, the task of finding the correct architecture name to give the
46522 @command{set architecture} command can be error-prone.
46525 To address these problems, the @value{GDBN} remote protocol allows a
46526 target system to not only identify itself to @value{GDBN}, but to
46527 actually describe its own features. This lets @value{GDBN} support
46528 processor variants it has never seen before --- to the extent that the
46529 descriptions are accurate, and that @value{GDBN} understands them.
46531 @value{GDBN} must be linked with the Expat library to support XML
46532 target descriptions. @xref{Expat}.
46535 * Retrieving Descriptions:: How descriptions are fetched from a target.
46536 * Target Description Format:: The contents of a target description.
46537 * Predefined Target Types:: Standard types available for target
46539 * Enum Target Types:: How to define enum target types.
46540 * Standard Target Features:: Features @value{GDBN} knows about.
46543 @node Retrieving Descriptions
46544 @section Retrieving Descriptions
46546 Target descriptions can be read from the target automatically, or
46547 specified by the user manually. The default behavior is to read the
46548 description from the target. @value{GDBN} retrieves it via the remote
46549 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
46550 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
46551 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
46552 XML document, of the form described in @ref{Target Description
46555 Alternatively, you can specify a file to read for the target description.
46556 If a file is set, the target will not be queried. The commands to
46557 specify a file are:
46560 @cindex set tdesc filename
46561 @item set tdesc filename @var{path}
46562 Read the target description from @var{path}.
46564 @cindex unset tdesc filename
46565 @item unset tdesc filename
46566 Do not read the XML target description from a file. @value{GDBN}
46567 will use the description supplied by the current target.
46569 @cindex show tdesc filename
46570 @item show tdesc filename
46571 Show the filename to read for a target description, if any.
46575 @node Target Description Format
46576 @section Target Description Format
46577 @cindex target descriptions, XML format
46579 A target description annex is an @uref{http://www.w3.org/XML/, XML}
46580 document which complies with the Document Type Definition provided in
46581 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
46582 means you can use generally available tools like @command{xmllint} to
46583 check that your feature descriptions are well-formed and valid.
46584 However, to help people unfamiliar with XML write descriptions for
46585 their targets, we also describe the grammar here.
46587 Target descriptions can identify the architecture of the remote target
46588 and (for some architectures) provide information about custom register
46589 sets. They can also identify the OS ABI of the remote target.
46590 @value{GDBN} can use this information to autoconfigure for your
46591 target, or to warn you if you connect to an unsupported target.
46593 Here is a simple target description:
46596 <target version="1.0">
46597 <architecture>i386:x86-64</architecture>
46602 This minimal description only says that the target uses
46603 the x86-64 architecture.
46605 A target description has the following overall form, with [ ] marking
46606 optional elements and @dots{} marking repeatable elements. The elements
46607 are explained further below.
46610 <?xml version="1.0"?>
46611 <!DOCTYPE target SYSTEM "gdb-target.dtd">
46612 <target version="1.0">
46613 @r{[}@var{architecture}@r{]}
46614 @r{[}@var{osabi}@r{]}
46615 @r{[}@var{compatible}@r{]}
46616 @r{[}@var{feature}@dots{}@r{]}
46621 The description is generally insensitive to whitespace and line
46622 breaks, under the usual common-sense rules. The XML version
46623 declaration and document type declaration can generally be omitted
46624 (@value{GDBN} does not require them), but specifying them may be
46625 useful for XML validation tools. The @samp{version} attribute for
46626 @samp{<target>} may also be omitted, but we recommend
46627 including it; if future versions of @value{GDBN} use an incompatible
46628 revision of @file{gdb-target.dtd}, they will detect and report
46629 the version mismatch.
46631 @subsection Inclusion
46632 @cindex target descriptions, inclusion
46635 @cindex <xi:include>
46638 It can sometimes be valuable to split a target description up into
46639 several different annexes, either for organizational purposes, or to
46640 share files between different possible target descriptions. You can
46641 divide a description into multiple files by replacing any element of
46642 the target description with an inclusion directive of the form:
46645 <xi:include href="@var{document}"/>
46649 When @value{GDBN} encounters an element of this form, it will retrieve
46650 the named XML @var{document}, and replace the inclusion directive with
46651 the contents of that document. If the current description was read
46652 using @samp{qXfer}, then so will be the included document;
46653 @var{document} will be interpreted as the name of an annex. If the
46654 current description was read from a file, @value{GDBN} will look for
46655 @var{document} as a file in the same directory where it found the
46656 original description.
46658 @subsection Architecture
46659 @cindex <architecture>
46661 An @samp{<architecture>} element has this form:
46664 <architecture>@var{arch}</architecture>
46667 @var{arch} is one of the architectures from the set accepted by
46668 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46671 @cindex @code{<osabi>}
46673 This optional field was introduced in @value{GDBN} version 7.0.
46674 Previous versions of @value{GDBN} ignore it.
46676 An @samp{<osabi>} element has this form:
46679 <osabi>@var{abi-name}</osabi>
46682 @var{abi-name} is an OS ABI name from the same selection accepted by
46683 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
46685 @subsection Compatible Architecture
46686 @cindex @code{<compatible>}
46688 This optional field was introduced in @value{GDBN} version 7.0.
46689 Previous versions of @value{GDBN} ignore it.
46691 A @samp{<compatible>} element has this form:
46694 <compatible>@var{arch}</compatible>
46697 @var{arch} is one of the architectures from the set accepted by
46698 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46700 A @samp{<compatible>} element is used to specify that the target
46701 is able to run binaries in some other than the main target architecture
46702 given by the @samp{<architecture>} element. For example, on the
46703 Cell Broadband Engine, the main architecture is @code{powerpc:common}
46704 or @code{powerpc:common64}, but the system is able to run binaries
46705 in the @code{spu} architecture as well. The way to describe this
46706 capability with @samp{<compatible>} is as follows:
46709 <architecture>powerpc:common</architecture>
46710 <compatible>spu</compatible>
46713 @subsection Features
46716 Each @samp{<feature>} describes some logical portion of the target
46717 system. Features are currently used to describe available CPU
46718 registers and the types of their contents. A @samp{<feature>} element
46722 <feature name="@var{name}">
46723 @r{[}@var{type}@dots{}@r{]}
46729 Each feature's name should be unique within the description. The name
46730 of a feature does not matter unless @value{GDBN} has some special
46731 knowledge of the contents of that feature; if it does, the feature
46732 should have its standard name. @xref{Standard Target Features}.
46736 Any register's value is a collection of bits which @value{GDBN} must
46737 interpret. The default interpretation is a two's complement integer,
46738 but other types can be requested by name in the register description.
46739 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
46740 Target Types}), and the description can define additional composite
46743 Each type element must have an @samp{id} attribute, which gives
46744 a unique (within the containing @samp{<feature>}) name to the type.
46745 Types must be defined before they are used.
46748 Some targets offer vector registers, which can be treated as arrays
46749 of scalar elements. These types are written as @samp{<vector>} elements,
46750 specifying the array element type, @var{type}, and the number of elements,
46754 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
46758 If a register's value is usefully viewed in multiple ways, define it
46759 with a union type containing the useful representations. The
46760 @samp{<union>} element contains one or more @samp{<field>} elements,
46761 each of which has a @var{name} and a @var{type}:
46764 <union id="@var{id}">
46765 <field name="@var{name}" type="@var{type}"/>
46772 If a register's value is composed from several separate values, define
46773 it with either a structure type or a flags type.
46774 A flags type may only contain bitfields.
46775 A structure type may either contain only bitfields or contain no bitfields.
46776 If the value contains only bitfields, its total size in bytes must be
46779 Non-bitfield values have a @var{name} and @var{type}.
46782 <struct id="@var{id}">
46783 <field name="@var{name}" type="@var{type}"/>
46788 Both @var{name} and @var{type} values are required.
46789 No implicit padding is added.
46791 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
46794 <struct id="@var{id}" size="@var{size}">
46795 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
46801 <flags id="@var{id}" size="@var{size}">
46802 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
46807 The @var{name} value is required.
46808 Bitfield values may be named with the empty string, @samp{""},
46809 in which case the field is ``filler'' and its value is not printed.
46810 Not all bits need to be specified, so ``filler'' fields are optional.
46812 The @var{start} and @var{end} values are required, and @var{type}
46814 The field's @var{start} must be less than or equal to its @var{end},
46815 and zero represents the least significant bit.
46817 The default value of @var{type} is @code{bool} for single bit fields,
46818 and an unsigned integer otherwise.
46820 Which to choose? Structures or flags?
46822 Registers defined with @samp{flags} have these advantages over
46823 defining them with @samp{struct}:
46827 Arithmetic may be performed on them as if they were integers.
46829 They are printed in a more readable fashion.
46832 Registers defined with @samp{struct} have one advantage over
46833 defining them with @samp{flags}:
46837 One can fetch individual fields like in @samp{C}.
46840 (gdb) print $my_struct_reg.field3
46846 @subsection Registers
46849 Each register is represented as an element with this form:
46852 <reg name="@var{name}"
46853 bitsize="@var{size}"
46854 @r{[}regnum="@var{num}"@r{]}
46855 @r{[}save-restore="@var{save-restore}"@r{]}
46856 @r{[}type="@var{type}"@r{]}
46857 @r{[}group="@var{group}"@r{]}/>
46861 The components are as follows:
46866 The register's name; it must be unique within the target description.
46869 The register's size, in bits.
46872 The register's number. If omitted, a register's number is one greater
46873 than that of the previous register (either in the current feature or in
46874 a preceding feature); the first register in the target description
46875 defaults to zero. This register number is used to read or write
46876 the register; e.g.@: it is used in the remote @code{p} and @code{P}
46877 packets, and registers appear in the @code{g} and @code{G} packets
46878 in order of increasing register number.
46881 Whether the register should be preserved across inferior function
46882 calls; this must be either @code{yes} or @code{no}. The default is
46883 @code{yes}, which is appropriate for most registers except for
46884 some system control registers; this is not related to the target's
46888 The type of the register. It may be a predefined type, a type
46889 defined in the current feature, or one of the special types @code{int}
46890 and @code{float}. @code{int} is an integer type of the correct size
46891 for @var{bitsize}, and @code{float} is a floating point type (in the
46892 architecture's normal floating point format) of the correct size for
46893 @var{bitsize}. The default is @code{int}.
46896 The register group to which this register belongs. It can be one of the
46897 standard register groups @code{general}, @code{float}, @code{vector} or an
46898 arbitrary string. Group names should be limited to alphanumeric characters.
46899 If a group name is made up of multiple words the words may be separated by
46900 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
46901 @var{group} is specified, @value{GDBN} will not display the register in
46902 @code{info registers}.
46906 @node Predefined Target Types
46907 @section Predefined Target Types
46908 @cindex target descriptions, predefined types
46910 Type definitions in the self-description can build up composite types
46911 from basic building blocks, but can not define fundamental types. Instead,
46912 standard identifiers are provided by @value{GDBN} for the fundamental
46913 types. The currently supported types are:
46918 Boolean type, occupying a single bit.
46926 Signed integer types holding the specified number of bits.
46934 Unsigned integer types holding the specified number of bits.
46938 Pointers to unspecified code and data. The program counter and
46939 any dedicated return address register may be marked as code
46940 pointers; printing a code pointer converts it into a symbolic
46941 address. The stack pointer and any dedicated address registers
46942 may be marked as data pointers.
46945 Half precision IEEE floating point.
46948 Single precision IEEE floating point.
46951 Double precision IEEE floating point.
46954 The 16-bit @dfn{brain floating point} format used e.g.@: by x86 and ARM.
46957 The 12-byte extended precision format used by ARM FPA registers.
46960 The 10-byte extended precision format used by x87 registers.
46963 32bit @sc{eflags} register used by x86.
46966 32bit @sc{mxcsr} register used by x86.
46970 @node Enum Target Types
46971 @section Enum Target Types
46972 @cindex target descriptions, enum types
46974 Enum target types are useful in @samp{struct} and @samp{flags}
46975 register descriptions. @xref{Target Description Format}.
46977 Enum types have a name, size and a list of name/value pairs.
46980 <enum id="@var{id}" size="@var{size}">
46981 <evalue name="@var{name}" value="@var{value}"/>
46986 Enums must be defined before they are used.
46989 <enum id="levels_type" size="4">
46990 <evalue name="low" value="0"/>
46991 <evalue name="high" value="1"/>
46993 <flags id="flags_type" size="4">
46994 <field name="X" start="0"/>
46995 <field name="LEVEL" start="1" end="1" type="levels_type"/>
46997 <reg name="flags" bitsize="32" type="flags_type"/>
47000 Given that description, a value of 3 for the @samp{flags} register
47001 would be printed as:
47004 (gdb) info register flags
47005 flags 0x3 [ X LEVEL=high ]
47008 @node Standard Target Features
47009 @section Standard Target Features
47010 @cindex target descriptions, standard features
47012 A target description must contain either no registers or all the
47013 target's registers. If the description contains no registers, then
47014 @value{GDBN} will assume a default register layout, selected based on
47015 the architecture. If the description contains any registers, the
47016 default layout will not be used; the standard registers must be
47017 described in the target description, in such a way that @value{GDBN}
47018 can recognize them.
47020 This is accomplished by giving specific names to feature elements
47021 which contain standard registers. @value{GDBN} will look for features
47022 with those names and verify that they contain the expected registers;
47023 if any known feature is missing required registers, or if any required
47024 feature is missing, @value{GDBN} will reject the target
47025 description. You can add additional registers to any of the
47026 standard features --- @value{GDBN} will display them just as if
47027 they were added to an unrecognized feature.
47029 This section lists the known features and their expected contents.
47030 Sample XML documents for these features are included in the
47031 @value{GDBN} source tree, in the directory @file{gdb/features}.
47033 Names recognized by @value{GDBN} should include the name of the
47034 company or organization which selected the name, and the overall
47035 architecture to which the feature applies; so e.g.@: the feature
47036 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
47038 The names of registers are not case sensitive for the purpose
47039 of recognizing standard features, but @value{GDBN} will only display
47040 registers using the capitalization used in the description.
47043 * AArch64 Features::
47047 * LoongArch Features::
47048 * MicroBlaze Features::
47052 * Nios II Features::
47053 * OpenRISC 1000 Features::
47054 * PowerPC Features::
47055 * RISC-V Features::
47057 * S/390 and System z Features::
47063 @node AArch64 Features
47064 @subsection AArch64 Features
47065 @cindex target descriptions, AArch64 features
47067 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
47068 targets. It should contain registers @samp{x0} through @samp{x30},
47069 @samp{sp}, @samp{pc}, and @samp{cpsr}.
47071 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
47072 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
47075 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
47076 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
47077 through @samp{p15}, @samp{ffr} and @samp{vg}.
47079 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
47080 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
47083 @subsection ARC Features
47084 @cindex target descriptions, ARC Features
47086 ARC processors are so configurable that even core registers and their numbers
47087 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
47088 registers, which are important to @value{GDBN}, are not ``core'' registers in
47089 ARC. Therefore, there are two features that their presence is mandatory:
47090 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
47092 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
47097 @samp{r0} through @samp{r25} for normal register file targets.
47099 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
47100 register file targets.
47102 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
47103 @samp{blink}, @samp{lp_count}, @samp{pcl}.
47106 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
47107 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
47108 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
47109 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
47110 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
47111 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
47112 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
47113 because of their inaccessibility during user space debugging sessions.
47115 Extension core registers @samp{r32} through @samp{r59} are optional and their
47116 existence depends on the configuration. When debugging GNU/Linux applications,
47117 i.e.@: user space debugging, these core registers are not available.
47119 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
47120 is the list of registers pertinent to this feature:
47124 mandatory: @samp{pc} and @samp{status32}.
47126 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
47130 @subsection ARM Features
47131 @cindex target descriptions, ARM features
47133 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
47135 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
47136 @samp{lr}, @samp{pc}, and @samp{cpsr}.
47138 For M-profile targets (e.g.@: Cortex-M3), the @samp{org.gnu.gdb.arm.core}
47139 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
47140 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
47143 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
47144 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
47146 The @samp{org.gnu.gdb.arm.m-profile-mve} feature is optional. If present, it
47147 must contain register @samp{vpr}.
47149 If the @samp{org.gnu.gdb.arm.m-profile-mve} feature is available, @value{GDBN}
47150 will synthesize the @samp{p0} pseudo register from @samp{vpr} contents.
47152 If the @samp{org.gnu.gdb.arm.vfp} feature is available alongside the
47153 @samp{org.gnu.gdb.arm.m-profile-mve} feature, @value{GDBN} will
47154 synthesize the @samp{q} pseudo registers from @samp{d} register
47157 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
47158 it should contain at least registers @samp{wR0} through @samp{wR15} and
47159 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
47160 @samp{wCSSF}, and @samp{wCASF} registers are optional.
47162 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
47163 should contain at least registers @samp{d0} through @samp{d15}. If
47164 they are present, @samp{d16} through @samp{d31} should also be included.
47165 @value{GDBN} will synthesize the single-precision registers from
47166 halves of the double-precision registers.
47168 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
47169 need to contain registers; it instructs @value{GDBN} to display the
47170 VFP double-precision registers as vectors and to synthesize the
47171 quad-precision registers from pairs of double-precision registers.
47172 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
47173 be present and include 32 double-precision registers.
47175 The @samp{org.gnu.gdb.arm.m-profile-pacbti} feature is optional, and
47176 acknowledges support for the ARMv8.1-m PACBTI extensions. @value{GDBN}
47177 will track return address signing states and will decorate backtraces using
47178 the [PAC] marker, similar to AArch64's PAC extension.
47179 @xref{AArch64 PAC}.
47181 @node i386 Features
47182 @subsection i386 Features
47183 @cindex target descriptions, i386 features
47185 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
47186 targets. It should describe the following registers:
47190 @samp{eax} through @samp{edi} plus @samp{eip} for i386
47192 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
47194 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
47195 @samp{fs}, @samp{gs}
47197 @samp{st0} through @samp{st7}
47199 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
47200 @samp{foseg}, @samp{fooff} and @samp{fop}
47203 The register sets may be different, depending on the target.
47205 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
47206 describe registers:
47210 @samp{xmm0} through @samp{xmm7} for i386
47212 @samp{xmm0} through @samp{xmm15} for amd64
47217 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
47218 @samp{org.gnu.gdb.i386.sse} feature. It should
47219 describe the upper 128 bits of @sc{ymm} registers:
47223 @samp{ymm0h} through @samp{ymm7h} for i386
47225 @samp{ymm0h} through @samp{ymm15h} for amd64
47228 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
47229 Memory Protection Extension (MPX). It should describe the following registers:
47233 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
47235 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
47238 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
47239 describe a single register, @samp{orig_eax}.
47241 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
47242 describe two system registers: @samp{fs_base} and @samp{gs_base}.
47244 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
47245 @samp{org.gnu.gdb.i386.avx} feature. It should
47246 describe additional @sc{xmm} registers:
47250 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
47253 It should describe the upper 128 bits of additional @sc{ymm} registers:
47257 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
47261 describe the upper 256 bits of @sc{zmm} registers:
47265 @samp{zmm0h} through @samp{zmm7h} for i386.
47267 @samp{zmm0h} through @samp{zmm15h} for amd64.
47271 describe the additional @sc{zmm} registers:
47275 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
47278 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
47279 describe a single register, @samp{pkru}. It is a 32-bit register
47280 valid for i386 and amd64.
47282 @node LoongArch Features
47283 @subsection LoongArch Features
47284 @cindex target descriptions, LoongArch Features
47286 The @samp{org.gnu.gdb.loongarch.base} feature is required for LoongArch
47287 targets. It should contain the registers @samp{r0} through @samp{r31},
47288 @samp{pc}, and @samp{badv}. Either the architectural names (@samp{r0},
47289 @samp{r1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra}, etc).
47291 The @samp{org.gnu.gdb.loongarch.fpu} feature is optional. If present,
47292 it should contain registers @samp{f0} through @samp{f31}, @samp{fcc},
47295 @node MicroBlaze Features
47296 @subsection MicroBlaze Features
47297 @cindex target descriptions, MicroBlaze features
47299 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
47300 targets. It should contain registers @samp{r0} through @samp{r31},
47301 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
47302 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
47303 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
47305 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
47306 If present, it should contain registers @samp{rshr} and @samp{rslr}
47308 @node MIPS Features
47309 @subsection @acronym{MIPS} Features
47310 @cindex target descriptions, @acronym{MIPS} features
47312 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
47313 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
47314 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
47317 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
47318 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
47319 registers. They may be 32-bit or 64-bit depending on the target.
47321 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
47322 it may be optional in a future version of @value{GDBN}. It should
47323 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
47324 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
47326 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
47327 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
47328 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
47329 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
47331 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
47332 contain a single register, @samp{restart}, which is used by the
47333 Linux kernel to control restartable syscalls.
47335 @node M68K Features
47336 @subsection M68K Features
47337 @cindex target descriptions, M68K features
47340 @item @samp{org.gnu.gdb.m68k.core}
47341 @itemx @samp{org.gnu.gdb.coldfire.core}
47342 @itemx @samp{org.gnu.gdb.fido.core}
47343 One of those features must be always present.
47344 The feature that is present determines which flavor of m68k is
47345 used. The feature that is present should contain registers
47346 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
47347 @samp{sp}, @samp{ps} and @samp{pc}.
47349 @item @samp{org.gnu.gdb.coldfire.fp}
47350 This feature is optional. If present, it should contain registers
47351 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
47354 Note that, despite the fact that this feature's name says
47355 @samp{coldfire}, it is used to describe any floating point registers.
47356 The size of the registers must match the main m68k flavor; so, for
47357 example, if the primary feature is reported as @samp{coldfire}, then
47358 64-bit floating point registers are required.
47361 @node NDS32 Features
47362 @subsection NDS32 Features
47363 @cindex target descriptions, NDS32 features
47365 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
47366 targets. It should contain at least registers @samp{r0} through
47367 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
47370 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
47371 it should contain 64-bit double-precision floating-point registers
47372 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
47373 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
47375 @emph{Note:} The first sixteen 64-bit double-precision floating-point
47376 registers are overlapped with the thirty-two 32-bit single-precision
47377 floating-point registers. The 32-bit single-precision registers, if
47378 not being listed explicitly, will be synthesized from halves of the
47379 overlapping 64-bit double-precision registers. Listing 32-bit
47380 single-precision registers explicitly is deprecated, and the
47381 support to it could be totally removed some day.
47383 @node Nios II Features
47384 @subsection Nios II Features
47385 @cindex target descriptions, Nios II features
47387 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
47388 targets. It should contain the 32 core registers (@samp{zero},
47389 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
47390 @samp{pc}, and the 16 control registers (@samp{status} through
47393 @node OpenRISC 1000 Features
47394 @subsection Openrisc 1000 Features
47395 @cindex target descriptions, OpenRISC 1000 features
47397 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
47398 targets. It should contain the 32 general purpose registers (@samp{r0}
47399 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
47401 @node PowerPC Features
47402 @subsection PowerPC Features
47403 @cindex target descriptions, PowerPC features
47405 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
47406 targets. It should contain registers @samp{r0} through @samp{r31},
47407 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
47408 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
47410 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
47411 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
47413 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
47414 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
47415 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
47416 through @samp{v31} as aliases for the corresponding @samp{vrX}
47419 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
47420 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
47421 combine these registers with the floating point registers (@samp{f0}
47422 through @samp{f31}) and the altivec registers (@samp{vr0} through
47423 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
47424 @samp{vs63}, the set of vector-scalar registers for POWER7.
47425 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
47426 @samp{org.gnu.gdb.power.altivec}.
47428 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
47429 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
47430 @samp{spefscr}. SPE targets should provide 32-bit registers in
47431 @samp{org.gnu.gdb.power.core} and provide the upper halves in
47432 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
47433 these to present registers @samp{ev0} through @samp{ev31} to the
47436 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
47437 contain the 64-bit register @samp{ppr}.
47439 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
47440 contain the 64-bit register @samp{dscr}.
47442 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
47443 contain the 64-bit register @samp{tar}.
47445 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
47446 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
47449 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
47450 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
47451 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
47452 server PMU registers provided by @sc{gnu}/Linux.
47454 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
47455 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
47458 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
47459 contain the checkpointed general-purpose registers @samp{cr0} through
47460 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
47461 @samp{cctr}. These registers may all be either 32-bit or 64-bit
47462 depending on the target. It should also contain the checkpointed
47463 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
47466 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
47467 contain the checkpointed 64-bit floating-point registers @samp{cf0}
47468 through @samp{cf31}, as well as the checkpointed 64-bit register
47471 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
47472 should contain the checkpointed altivec registers @samp{cvr0} through
47473 @samp{cvr31}, all 128-bit wide. It should also contain the
47474 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
47477 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
47478 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
47479 will combine these registers with the checkpointed floating point
47480 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
47481 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
47482 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
47483 @samp{cvs63}. Therefore, this feature requires both
47484 @samp{org.gnu.gdb.power.htm.altivec} and
47485 @samp{org.gnu.gdb.power.htm.fpu}.
47487 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
47488 contain the 64-bit checkpointed register @samp{cppr}.
47490 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
47491 contain the 64-bit checkpointed register @samp{cdscr}.
47493 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
47494 contain the 64-bit checkpointed register @samp{ctar}.
47497 @node RISC-V Features
47498 @subsection RISC-V Features
47499 @cindex target descriptions, RISC-V Features
47501 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
47502 targets. It should contain the registers @samp{x0} through
47503 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
47504 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
47507 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
47508 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
47509 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
47510 architectural register names, or the ABI names can be used.
47512 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
47513 it should contain registers that are not backed by real registers on
47514 the target, but are instead virtual, where the register value is
47515 derived from other target state. In many ways these are like
47516 @value{GDBN}s pseudo-registers, except implemented by the target.
47517 Currently the only register expected in this set is the one byte
47518 @samp{priv} register that contains the target's privilege level in the
47519 least significant two bits.
47521 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
47522 should contain all of the target's standard CSRs. Standard CSRs are
47523 those defined in the RISC-V specification documents. There is some
47524 overlap between this feature and the fpu feature; the @samp{fflags},
47525 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
47526 expectation is that these registers will be in the fpu feature if the
47527 target has floating point hardware, but can be moved into the csr
47528 feature if the target has the floating point control registers, but no
47529 other floating point hardware.
47531 The @samp{org.gnu.gdb.riscv.vector} feature is optional. If present,
47532 it should contain registers @samp{v0} through @samp{v31}, all of which
47533 must be the same size. These requirements are based on the v0.10
47534 draft vector extension, as the vector extension is not yet final. In
47535 the event that the register set of the vector extension changes for
47536 the final specification, the requirements given here could change for
47537 future releases of @value{GDBN}.
47540 @subsection RX Features
47541 @cindex target descriptions, RX Features
47543 The @samp{org.gnu.gdb.rx.core} feature is required for RX
47544 targets. It should contain the registers @samp{r0} through
47545 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
47546 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
47548 @node S/390 and System z Features
47549 @subsection S/390 and System z Features
47550 @cindex target descriptions, S/390 features
47551 @cindex target descriptions, System z features
47553 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
47554 System z targets. It should contain the PSW and the 16 general
47555 registers. In particular, System z targets should provide the 64-bit
47556 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
47557 S/390 targets should provide the 32-bit versions of these registers.
47558 A System z target that runs in 31-bit addressing mode should provide
47559 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
47560 register's upper halves @samp{r0h} through @samp{r15h}, and their
47561 lower halves @samp{r0l} through @samp{r15l}.
47563 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
47564 contain the 64-bit registers @samp{f0} through @samp{f15}, and
47567 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
47568 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
47570 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
47571 contain the register @samp{orig_r2}, which is 64-bit wide on System z
47572 targets and 32-bit otherwise. In addition, the feature may contain
47573 the @samp{last_break} register, whose width depends on the addressing
47574 mode, as well as the @samp{system_call} register, which is always
47577 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
47578 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
47579 @samp{atia}, and @samp{tr0} through @samp{tr15}.
47581 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
47582 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
47583 combined by @value{GDBN} with the floating point registers @samp{f0}
47584 through @samp{f15} to present the 128-bit wide vector registers
47585 @samp{v0} through @samp{v15}. In addition, this feature should
47586 contain the 128-bit wide vector registers @samp{v16} through
47589 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
47590 the 64-bit wide guarded-storage-control registers @samp{gsd},
47591 @samp{gssm}, and @samp{gsepla}.
47593 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
47594 the 64-bit wide guarded-storage broadcast control registers
47595 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
47597 @node Sparc Features
47598 @subsection Sparc Features
47599 @cindex target descriptions, sparc32 features
47600 @cindex target descriptions, sparc64 features
47601 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
47602 targets. It should describe the following registers:
47606 @samp{g0} through @samp{g7}
47608 @samp{o0} through @samp{o7}
47610 @samp{l0} through @samp{l7}
47612 @samp{i0} through @samp{i7}
47615 They may be 32-bit or 64-bit depending on the target.
47617 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
47618 targets. It should describe the following registers:
47622 @samp{f0} through @samp{f31}
47624 @samp{f32} through @samp{f62} for sparc64
47627 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
47628 targets. It should describe the following registers:
47632 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
47633 @samp{fsr}, and @samp{csr} for sparc32
47635 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
47639 @node TIC6x Features
47640 @subsection TMS320C6x Features
47641 @cindex target descriptions, TIC6x features
47642 @cindex target descriptions, TMS320C6x features
47643 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
47644 targets. It should contain registers @samp{A0} through @samp{A15},
47645 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
47647 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
47648 contain registers @samp{A16} through @samp{A31} and @samp{B16}
47649 through @samp{B31}.
47651 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
47652 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
47654 @node Operating System Information
47655 @appendix Operating System Information
47656 @cindex operating system information
47658 Users of @value{GDBN} often wish to obtain information about the state of
47659 the operating system running on the target---for example the list of
47660 processes, or the list of open files. This section describes the
47661 mechanism that makes it possible. This mechanism is similar to the
47662 target features mechanism (@pxref{Target Descriptions}), but focuses
47663 on a different aspect of target.
47665 Operating system information is retrieved from the target via the
47666 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
47667 read}). The object name in the request should be @samp{osdata}, and
47668 the @var{annex} identifies the data to be fetched.
47675 @appendixsection Process list
47676 @cindex operating system information, process list
47678 When requesting the process list, the @var{annex} field in the
47679 @samp{qXfer} request should be @samp{processes}. The returned data is
47680 an XML document. The formal syntax of this document is defined in
47681 @file{gdb/features/osdata.dtd}.
47683 An example document is:
47686 <?xml version="1.0"?>
47687 <!DOCTYPE target SYSTEM "osdata.dtd">
47688 <osdata type="processes">
47690 <column name="pid">1</column>
47691 <column name="user">root</column>
47692 <column name="command">/sbin/init</column>
47693 <column name="cores">1,2,3</column>
47698 Each item should include a column whose name is @samp{pid}. The value
47699 of that column should identify the process on the target. The
47700 @samp{user} and @samp{command} columns are optional, and will be
47701 displayed by @value{GDBN}. The @samp{cores} column, if present,
47702 should contain a comma-separated list of cores that this process
47703 is running on. Target may provide additional columns,
47704 which @value{GDBN} currently ignores.
47706 @node Trace File Format
47707 @appendix Trace File Format
47708 @cindex trace file format
47710 The trace file comes in three parts: a header, a textual description
47711 section, and a trace frame section with binary data.
47713 The header has the form @code{\x7fTRACE0\n}. The first byte is
47714 @code{0x7f} so as to indicate that the file contains binary data,
47715 while the @code{0} is a version number that may have different values
47718 The description section consists of multiple lines of @sc{ascii} text
47719 separated by newline characters (@code{0xa}). The lines may include a
47720 variety of optional descriptive or context-setting information, such
47721 as tracepoint definitions or register set size. @value{GDBN} will
47722 ignore any line that it does not recognize. An empty line marks the end
47727 Specifies the size of a register block in bytes. This is equal to the
47728 size of a @code{g} packet payload in the remote protocol. @var{size}
47729 is an ascii decimal number. There should be only one such line in
47730 a single trace file.
47732 @item status @var{status}
47733 Trace status. @var{status} has the same format as a @code{qTStatus}
47734 remote packet reply. There should be only one such line in a single trace
47737 @item tp @var{payload}
47738 Tracepoint definition. The @var{payload} has the same format as
47739 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
47740 may take multiple lines of definition, corresponding to the multiple
47743 @item tsv @var{payload}
47744 Trace state variable definition. The @var{payload} has the same format as
47745 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
47746 may take multiple lines of definition, corresponding to the multiple
47749 @item tdesc @var{payload}
47750 Target description in XML format. The @var{payload} is a single line of
47751 the XML file. All such lines should be concatenated together to get
47752 the original XML file. This file is in the same format as @code{qXfer}
47753 @code{features} payload, and corresponds to the main @code{target.xml}
47754 file. Includes are not allowed.
47758 The trace frame section consists of a number of consecutive frames.
47759 Each frame begins with a two-byte tracepoint number, followed by a
47760 four-byte size giving the amount of data in the frame. The data in
47761 the frame consists of a number of blocks, each introduced by a
47762 character indicating its type (at least register, memory, and trace
47763 state variable). The data in this section is raw binary, not a
47764 hexadecimal or other encoding; its endianness matches the target's
47767 @c FIXME bi-arch may require endianness/arch info in description section
47770 @item R @var{bytes}
47771 Register block. The number and ordering of bytes matches that of a
47772 @code{g} packet in the remote protocol. Note that these are the
47773 actual bytes, in target order, not a hexadecimal encoding.
47775 @item M @var{address} @var{length} @var{bytes}...
47776 Memory block. This is a contiguous block of memory, at the 8-byte
47777 address @var{address}, with a 2-byte length @var{length}, followed by
47778 @var{length} bytes.
47780 @item V @var{number} @var{value}
47781 Trace state variable block. This records the 8-byte signed value
47782 @var{value} of trace state variable numbered @var{number}.
47786 Future enhancements of the trace file format may include additional types
47789 @node Index Section Format
47790 @appendix @code{.gdb_index} section format
47791 @cindex .gdb_index section format
47792 @cindex index section format
47794 This section documents the index section that is created by @code{save
47795 gdb-index} (@pxref{Index Files}). The index section is
47796 DWARF-specific; some knowledge of DWARF is assumed in this
47799 The mapped index file format is designed to be directly
47800 @code{mmap}able on any architecture. In most cases, a datum is
47801 represented using a little-endian 32-bit integer value, called an
47802 @code{offset_type}. Big endian machines must byte-swap the values
47803 before using them. Exceptions to this rule are noted. The data is
47804 laid out such that alignment is always respected.
47806 A mapped index consists of several areas, laid out in order.
47810 The file header. This is a sequence of values, of @code{offset_type}
47811 unless otherwise noted:
47815 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
47816 Version 4 uses a different hashing function from versions 5 and 6.
47817 Version 6 includes symbols for inlined functions, whereas versions 4
47818 and 5 do not. Version 7 adds attributes to the CU indices in the
47819 symbol table. Version 8 specifies that symbols from DWARF type units
47820 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
47821 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
47823 @value{GDBN} will only read version 4, 5, or 6 indices
47824 by specifying @code{set use-deprecated-index-sections on}.
47825 GDB has a workaround for potentially broken version 7 indices so it is
47826 currently not flagged as deprecated.
47829 The offset, from the start of the file, of the CU list.
47832 The offset, from the start of the file, of the types CU list. Note
47833 that this area can be empty, in which case this offset will be equal
47834 to the next offset.
47837 The offset, from the start of the file, of the address area.
47840 The offset, from the start of the file, of the symbol table.
47843 The offset, from the start of the file, of the constant pool.
47847 The CU list. This is a sequence of pairs of 64-bit little-endian
47848 values, sorted by the CU offset. The first element in each pair is
47849 the offset of a CU in the @code{.debug_info} section. The second
47850 element in each pair is the length of that CU. References to a CU
47851 elsewhere in the map are done using a CU index, which is just the
47852 0-based index into this table. Note that if there are type CUs, then
47853 conceptually CUs and type CUs form a single list for the purposes of
47857 The types CU list. This is a sequence of triplets of 64-bit
47858 little-endian values. In a triplet, the first value is the CU offset,
47859 the second value is the type offset in the CU, and the third value is
47860 the type signature. The types CU list is not sorted.
47863 The address area. The address area consists of a sequence of address
47864 entries. Each address entry has three elements:
47868 The low address. This is a 64-bit little-endian value.
47871 The high address. This is a 64-bit little-endian value. Like
47872 @code{DW_AT_high_pc}, the value is one byte beyond the end.
47875 The CU index. This is an @code{offset_type} value.
47879 The symbol table. This is an open-addressed hash table. The size of
47880 the hash table is always a power of 2.
47882 Each slot in the hash table consists of a pair of @code{offset_type}
47883 values. The first value is the offset of the symbol's name in the
47884 constant pool. The second value is the offset of the CU vector in the
47887 If both values are 0, then this slot in the hash table is empty. This
47888 is ok because while 0 is a valid constant pool index, it cannot be a
47889 valid index for both a string and a CU vector.
47891 The hash value for a table entry is computed by applying an
47892 iterative hash function to the symbol's name. Starting with an
47893 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
47894 the string is incorporated into the hash using the formula depending on the
47899 The formula is @code{r = r * 67 + c - 113}.
47901 @item Versions 5 to 7
47902 The formula is @code{r = r * 67 + tolower (c) - 113}.
47905 The terminating @samp{\0} is not incorporated into the hash.
47907 The step size used in the hash table is computed via
47908 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
47909 value, and @samp{size} is the size of the hash table. The step size
47910 is used to find the next candidate slot when handling a hash
47913 The names of C@t{++} symbols in the hash table are canonicalized. We
47914 don't currently have a simple description of the canonicalization
47915 algorithm; if you intend to create new index sections, you must read
47919 The constant pool. This is simply a bunch of bytes. It is organized
47920 so that alignment is correct: CU vectors are stored first, followed by
47923 A CU vector in the constant pool is a sequence of @code{offset_type}
47924 values. The first value is the number of CU indices in the vector.
47925 Each subsequent value is the index and symbol attributes of a CU in
47926 the CU list. This element in the hash table is used to indicate which
47927 CUs define the symbol and how the symbol is used.
47928 See below for the format of each CU index+attributes entry.
47930 A string in the constant pool is zero-terminated.
47933 Attributes were added to CU index values in @code{.gdb_index} version 7.
47934 If a symbol has multiple uses within a CU then there is one
47935 CU index+attributes value for each use.
47937 The format of each CU index+attributes entry is as follows
47943 This is the index of the CU in the CU list.
47945 These bits are reserved for future purposes and must be zero.
47947 The kind of the symbol in the CU.
47951 This value is reserved and should not be used.
47952 By reserving zero the full @code{offset_type} value is backwards compatible
47953 with previous versions of the index.
47955 The symbol is a type.
47957 The symbol is a variable or an enum value.
47959 The symbol is a function.
47961 Any other kind of symbol.
47963 These values are reserved.
47967 This bit is zero if the value is global and one if it is static.
47969 The determination of whether a symbol is global or static is complicated.
47970 The authorative reference is the file @file{dwarf2read.c} in
47971 @value{GDBN} sources.
47975 This pseudo-code describes the computation of a symbol's kind and
47976 global/static attributes in the index.
47979 is_external = get_attribute (die, DW_AT_external);
47980 language = get_attribute (cu_die, DW_AT_language);
47983 case DW_TAG_typedef:
47984 case DW_TAG_base_type:
47985 case DW_TAG_subrange_type:
47989 case DW_TAG_enumerator:
47991 is_static = language != CPLUS;
47993 case DW_TAG_subprogram:
47995 is_static = ! (is_external || language == ADA);
47997 case DW_TAG_constant:
47999 is_static = ! is_external;
48001 case DW_TAG_variable:
48003 is_static = ! is_external;
48005 case DW_TAG_namespace:
48009 case DW_TAG_class_type:
48010 case DW_TAG_interface_type:
48011 case DW_TAG_structure_type:
48012 case DW_TAG_union_type:
48013 case DW_TAG_enumeration_type:
48015 is_static = language != CPLUS;
48023 @appendix Download debugging resources with Debuginfod
48026 @code{debuginfod} is an HTTP server for distributing ELF, DWARF and source
48029 With the @code{debuginfod} client library, @file{libdebuginfod}, @value{GDBN}
48030 can query servers using the build IDs associated with missing debug info,
48031 executables and source files in order to download them on demand.
48033 For instructions on building @value{GDBN} with @file{libdebuginfod},
48034 @pxref{Configure Options,,--with-debuginfod}. @code{debuginfod} is packaged
48035 with @code{elfutils}, starting with version 0.178. See
48036 @uref{https://sourceware.org/elfutils/Debuginfod.html} for more information
48037 regarding @code{debuginfod}.
48040 * Debuginfod Settings:: Configuring debuginfod with @value{GDBN}
48043 @node Debuginfod Settings
48044 @section Debuginfod Settings
48046 @value{GDBN} provides the following commands for configuring @code{debuginfod}.
48049 @kindex set debuginfod enabled
48050 @anchor{set debuginfod enabled}
48051 @item set debuginfod enabled
48052 @itemx set debuginfod enabled on
48053 @cindex enable debuginfod
48054 @value{GDBN} will attempt to query @code{debuginfod} servers when missing debug
48055 info or source files.
48057 @item set debuginfod enabled off
48058 @value{GDBN} will not attempt to query @code{debuginfod} servers when missing
48059 debug info or source files. By default, @code{debuginfod enabled} is set to
48060 @code{off} for non-interactive sessions.
48062 @item set debuginfod enabled ask
48063 @value{GDBN} will prompt the user to enable or disable @code{debuginfod} before
48064 attempting to perform the next query. By default, @code{debuginfod enabled}
48065 is set to @code{ask} for interactive sessions.
48067 @kindex show debuginfod enabled
48068 @item show debuginfod enabled
48069 Display whether @code{debuginfod enabled} is set to @code{on}, @code{off} or
48072 @kindex set debuginfod urls
48073 @cindex configure debuginfod URLs
48074 @item set debuginfod urls
48075 @itemx set debuginfod urls @var{urls}
48076 Set the space-separated list of URLs that @code{debuginfod} will attempt to
48077 query. Only @code{http://}, @code{https://} and @code{file://} protocols
48078 should be used. The default value of @code{debuginfod urls} is copied from
48079 the @var{DEBUGINFOD_URLS} environment variable.
48081 @kindex show debuginfod urls
48082 @item show debuginfod urls
48083 Display the list of URLs that @code{debuginfod} will attempt to query.
48085 @kindex set debuginfod verbose
48086 @cindex debuginfod verbosity
48087 @item set debuginfod verbose
48088 @itemx set debuginfod verbose @var{n}
48089 Enable or disable @code{debuginfod}-related output. Use a non-zero value
48090 to enable and @code{0} to disable. @code{debuginfod} output is shown by
48093 @kindex show debuginfod verbose
48094 @item show debuginfod verbose
48095 Show the current verbosity setting.
48100 @appendix Manual pages
48104 * gdb man:: The GNU Debugger man page
48105 * gdbserver man:: Remote Server for the GNU Debugger man page
48106 * gcore man:: Generate a core file of a running program
48107 * gdbinit man:: gdbinit scripts
48108 * gdb-add-index man:: Add index files to speed up GDB
48114 @c man title gdb The GNU Debugger
48116 @c man begin SYNOPSIS gdb
48117 gdb [OPTIONS] [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
48120 @c man begin DESCRIPTION gdb
48121 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
48122 going on ``inside'' another program while it executes -- or what another
48123 program was doing at the moment it crashed.
48125 @value{GDBN} can do four main kinds of things (plus other things in support of
48126 these) to help you catch bugs in the act:
48130 Start your program, specifying anything that might affect its behavior.
48133 Make your program stop on specified conditions.
48136 Examine what has happened, when your program has stopped.
48139 Change things in your program, so you can experiment with correcting the
48140 effects of one bug and go on to learn about another.
48143 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
48146 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
48147 commands from the terminal until you tell it to exit with the @value{GDBN}
48148 command @code{quit} or @code{exit}. You can get online help from @value{GDBN} itself
48149 by using the command @code{help}.
48151 You can run @code{gdb} with no arguments or options; but the most
48152 usual way to start @value{GDBN} is with one argument or two, specifying an
48153 executable program as the argument:
48159 You can also start with both an executable program and a core file specified:
48165 You can, instead, specify a process ID as a second argument or use option
48166 @code{-p}, if you want to debug a running process:
48174 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
48175 can omit the @var{program} filename.
48177 Here are some of the most frequently needed @value{GDBN} commands:
48179 @c pod2man highlights the right hand side of the @item lines.
48181 @item break [@var{file}:][@var{function}|@var{line}]
48182 Set a breakpoint at @var{function} or @var{line} (in @var{file}).
48184 @item run [@var{arglist}]
48185 Start your program (with @var{arglist}, if specified).
48188 Backtrace: display the program stack.
48190 @item print @var{expr}
48191 Display the value of an expression.
48194 Continue running your program (after stopping, e.g.@: at a breakpoint).
48197 Execute next program line (after stopping); step @emph{over} any
48198 function calls in the line.
48200 @item edit [@var{file}:]@var{function}
48201 look at the program line where it is presently stopped.
48203 @item list [@var{file}:]@var{function}
48204 type the text of the program in the vicinity of where it is presently stopped.
48207 Execute next program line (after stopping); step @emph{into} any
48208 function calls in the line.
48210 @item help [@var{name}]
48211 Show information about @value{GDBN} command @var{name}, or general information
48212 about using @value{GDBN}.
48216 Exit from @value{GDBN}.
48220 For full details on @value{GDBN},
48221 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48222 by Richard M. Stallman and Roland H. Pesch. The same text is available online
48223 as the @code{gdb} entry in the @code{info} program.
48227 @c man begin OPTIONS gdb
48228 Any arguments other than options specify an executable
48229 file and core file (or process ID); that is, the first argument
48230 encountered with no
48231 associated option flag is equivalent to a @option{--se} option, and the second,
48232 if any, is equivalent to a @option{-c} option if it's the name of a file.
48234 both long and abbreviated forms; both are shown here. The long forms are also
48235 recognized if you truncate them, so long as enough of the option is
48236 present to be unambiguous.
48238 The abbreviated forms are shown here with @samp{-} and long forms are shown
48239 with @samp{--} to reflect how they are shown in @option{--help}. However,
48240 @value{GDBN} recognizes all of the following conventions for most options:
48243 @item --option=@var{value}
48244 @item --option @var{value}
48245 @item -option=@var{value}
48246 @item -option @var{value}
48247 @item --o=@var{value}
48248 @item --o @var{value}
48249 @item -o=@var{value}
48250 @item -o @var{value}
48253 All the options and command line arguments you give are processed
48254 in sequential order. The order makes a difference when the @option{-x}
48260 List all options, with brief explanations.
48262 @item --symbols=@var{file}
48263 @itemx -s @var{file}
48264 Read symbol table from @var{file}.
48267 Enable writing into executable and core files.
48269 @item --exec=@var{file}
48270 @itemx -e @var{file}
48271 Use @var{file} as the executable file to execute when
48272 appropriate, and for examining pure data in conjunction with a core
48275 @item --se=@var{file}
48276 Read symbol table from @var{file} and use it as the executable
48279 @item --core=@var{file}
48280 @itemx -c @var{file}
48281 Use @var{file} as a core dump to examine.
48283 @item --command=@var{file}
48284 @itemx -x @var{file}
48285 Execute @value{GDBN} commands from @var{file}.
48287 @item --eval-command=@var{command}
48288 @item -ex @var{command}
48289 Execute given @value{GDBN} @var{command}.
48291 @item --init-eval-command=@var{command}
48293 Execute @value{GDBN} @var{command} before loading the inferior.
48295 @item --directory=@var{directory}
48296 @itemx -d @var{directory}
48297 Add @var{directory} to the path to search for source files.
48300 Do not execute commands from @file{~/.config/gdb/gdbinit},
48301 @file{~/.gdbinit}, @file{~/.config/gdb/gdbearlyinit}, or
48302 @file{~/.gdbearlyinit}
48306 Do not execute commands from any @file{.gdbinit} or
48307 @file{.gdbearlyinit} initialization files.
48312 ``Quiet''. Do not print the introductory and copyright messages. These
48313 messages are also suppressed in batch mode.
48316 Run in batch mode. Exit with status @code{0} after processing all the command
48317 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
48318 Exit with nonzero status if an error occurs in executing the @value{GDBN}
48319 commands in the command files.
48321 Batch mode may be useful for running @value{GDBN} as a filter, for example to
48322 download and run a program on another computer; in order to make this
48323 more useful, the message
48326 Program exited normally.
48330 (which is ordinarily issued whenever a program running under @value{GDBN} control
48331 terminates) is not issued when running in batch mode.
48333 @item --batch-silent
48334 Run in batch mode, just like @option{--batch}, but totally silent. All @value{GDBN}
48335 output is supressed (stderr is unaffected). This is much quieter than
48336 @option{--silent} and would be useless for an interactive session.
48338 This is particularly useful when using targets that give @samp{Loading section}
48339 messages, for example.
48341 Note that targets that give their output via @value{GDBN}, as opposed to writing
48342 directly to @code{stdout}, will also be made silent.
48344 @item --args @var{prog} [@var{arglist}]
48345 Change interpretation of command line so that arguments following this
48346 option are passed as arguments to the inferior. As an example, take
48347 the following command:
48354 It would start @value{GDBN} with @option{-q}, not printing the introductory message. On
48355 the other hand, using:
48358 gdb --args ./a.out -q
48362 starts @value{GDBN} with the introductory message, and passes the option to the inferior.
48364 @item --pid=@var{pid}
48365 Attach @value{GDBN} to an already running program, with the PID @var{pid}.
48368 Open the terminal user interface.
48371 Read all symbols from the given symfile on the first access.
48374 Do not read symbol files.
48376 @item --return-child-result
48377 @value{GDBN}'s exit code will be the same as the child's exit code.
48379 @item --configuration
48380 Print details about GDB configuration and then exit.
48383 Print version information and then exit.
48385 @item --cd=@var{directory}
48386 Run @value{GDBN} using @var{directory} as its working directory,
48387 instead of the current directory.
48389 @item --data-directory=@var{directory}
48391 Run @value{GDBN} using @var{directory} as its data directory. The data
48392 directory is where @value{GDBN} searches for its auxiliary files.
48396 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
48397 @value{GDBN} to output the full file name and line number in a standard,
48398 recognizable fashion each time a stack frame is displayed (which
48399 includes each time the program stops). This recognizable format looks
48400 like two @samp{\032} characters, followed by the file name, line number
48401 and character position separated by colons, and a newline. The
48402 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
48403 characters as a signal to display the source code for the frame.
48405 @item -b @var{baudrate}
48406 Set the line speed (baud rate or bits per second) of any serial
48407 interface used by @value{GDBN} for remote debugging.
48409 @item -l @var{timeout}
48410 Set timeout, in seconds, for remote debugging.
48412 @item --tty=@var{device}
48413 Run using @var{device} for your program's standard input and output.
48417 @c man begin SEEALSO gdb
48419 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48420 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48421 documentation are properly installed at your site, the command
48428 should give you access to the complete manual.
48430 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48431 Richard M. Stallman and Roland H. Pesch, July 1991.
48435 @node gdbserver man
48436 @heading gdbserver man
48438 @c man title gdbserver Remote Server for the GNU Debugger
48440 @c man begin SYNOPSIS gdbserver
48441 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
48443 gdbserver --attach @var{comm} @var{pid}
48445 gdbserver --multi @var{comm}
48449 @c man begin DESCRIPTION gdbserver
48450 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
48451 than the one which is running the program being debugged.
48454 @subheading Usage (server (target) side)
48457 Usage (server (target) side):
48460 First, you need to have a copy of the program you want to debug put onto
48461 the target system. The program can be stripped to save space if needed, as
48462 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
48463 the @value{GDBN} running on the host system.
48465 To use the server, you log on to the target system, and run the @command{gdbserver}
48466 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
48467 your program, and (c) its arguments. The general syntax is:
48470 target> gdbserver @var{comm} @var{program} [@var{args} ...]
48473 For example, using a serial port, you might say:
48477 @c @file would wrap it as F</dev/com1>.
48478 target> gdbserver /dev/com1 emacs foo.txt
48481 target> gdbserver @file{/dev/com1} emacs foo.txt
48485 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
48486 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
48487 waits patiently for the host @value{GDBN} to communicate with it.
48489 To use a TCP connection, you could say:
48492 target> gdbserver host:2345 emacs foo.txt
48495 This says pretty much the same thing as the last example, except that we are
48496 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
48497 that we are expecting to see a TCP connection from @code{host} to local TCP port
48498 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
48499 want for the port number as long as it does not conflict with any existing TCP
48500 ports on the target system. This same port number must be used in the host
48501 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
48502 you chose a port number that conflicts with another service, @command{gdbserver} will
48503 print an error message and exit.
48505 @command{gdbserver} can also attach to running programs.
48506 This is accomplished via the @option{--attach} argument. The syntax is:
48509 target> gdbserver --attach @var{comm} @var{pid}
48512 @var{pid} is the process ID of a currently running process. It isn't
48513 necessary to point @command{gdbserver} at a binary for the running process.
48515 To start @code{gdbserver} without supplying an initial command to run
48516 or process ID to attach, use the @option{--multi} command line option.
48517 In such case you should connect using @kbd{target extended-remote} to start
48518 the program you want to debug.
48521 target> gdbserver --multi @var{comm}
48525 @subheading Usage (host side)
48531 You need an unstripped copy of the target program on your host system, since
48532 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
48533 would, with the target program as the first argument. (You may need to use the
48534 @option{--baud} option if the serial line is running at anything except 9600 baud.)
48535 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
48536 new command you need to know about is @code{target remote}
48537 (or @code{target extended-remote}). Its argument is either
48538 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
48539 descriptor. For example:
48543 @c @file would wrap it as F</dev/ttyb>.
48544 (gdb) target remote /dev/ttyb
48547 (gdb) target remote @file{/dev/ttyb}
48552 communicates with the server via serial line @file{/dev/ttyb}, and:
48555 (gdb) target remote the-target:2345
48559 communicates via a TCP connection to port 2345 on host `the-target', where
48560 you previously started up @command{gdbserver} with the same port number. Note that for
48561 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
48562 command, otherwise you may get an error that looks something like
48563 `Connection refused'.
48565 @command{gdbserver} can also debug multiple inferiors at once,
48568 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
48569 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
48572 @ref{Inferiors Connections and Programs}.
48574 In such case use the @code{extended-remote} @value{GDBN} command variant:
48577 (gdb) target extended-remote the-target:2345
48580 The @command{gdbserver} option @option{--multi} may or may not be used in such
48584 @c man begin OPTIONS gdbserver
48585 There are three different modes for invoking @command{gdbserver}:
48590 Debug a specific program specified by its program name:
48593 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
48596 The @var{comm} parameter specifies how should the server communicate
48597 with @value{GDBN}; it is either a device name (to use a serial line),
48598 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
48599 stdin/stdout of @code{gdbserver}. Specify the name of the program to
48600 debug in @var{prog}. Any remaining arguments will be passed to the
48601 program verbatim. When the program exits, @value{GDBN} will close the
48602 connection, and @code{gdbserver} will exit.
48605 Debug a specific program by specifying the process ID of a running
48609 gdbserver --attach @var{comm} @var{pid}
48612 The @var{comm} parameter is as described above. Supply the process ID
48613 of a running program in @var{pid}; @value{GDBN} will do everything
48614 else. Like with the previous mode, when the process @var{pid} exits,
48615 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
48618 Multi-process mode -- debug more than one program/process:
48621 gdbserver --multi @var{comm}
48624 In this mode, @value{GDBN} can instruct @command{gdbserver} which
48625 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
48626 close the connection when a process being debugged exits, so you can
48627 debug several processes in the same session.
48630 In each of the modes you may specify these options:
48635 List all options, with brief explanations.
48638 This option causes @command{gdbserver} to print its version number and exit.
48641 @command{gdbserver} will attach to a running program. The syntax is:
48644 target> gdbserver --attach @var{comm} @var{pid}
48647 @var{pid} is the process ID of a currently running process. It isn't
48648 necessary to point @command{gdbserver} at a binary for the running process.
48651 To start @code{gdbserver} without supplying an initial command to run
48652 or process ID to attach, use this command line option.
48653 Then you can connect using @kbd{target extended-remote} and start
48654 the program you want to debug. The syntax is:
48657 target> gdbserver --multi @var{comm}
48661 Instruct @code{gdbserver} to display extra status information about the debugging
48663 This option is intended for @code{gdbserver} development and for bug reports to
48666 @item --remote-debug
48667 Instruct @code{gdbserver} to display remote protocol debug output.
48668 This option is intended for @code{gdbserver} development and for bug reports to
48671 @item --debug-file=@var{filename}
48672 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
48673 This option is intended for @code{gdbserver} development and for bug reports to
48676 @item --debug-format=option1@r{[},option2,...@r{]}
48677 Instruct @code{gdbserver} to include extra information in each line
48678 of debugging output.
48679 @xref{Other Command-Line Arguments for gdbserver}.
48682 Specify a wrapper to launch programs
48683 for debugging. The option should be followed by the name of the
48684 wrapper, then any command-line arguments to pass to the wrapper, then
48685 @kbd{--} indicating the end of the wrapper arguments.
48688 By default, @command{gdbserver} keeps the listening TCP port open, so that
48689 additional connections are possible. However, if you start @code{gdbserver}
48690 with the @option{--once} option, it will stop listening for any further
48691 connection attempts after connecting to the first @value{GDBN} session.
48693 @c --disable-packet is not documented for users.
48695 @c --disable-randomization and --no-disable-randomization are superseded by
48696 @c QDisableRandomization.
48701 @c man begin SEEALSO gdbserver
48703 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48704 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48705 documentation are properly installed at your site, the command
48711 should give you access to the complete manual.
48713 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48714 Richard M. Stallman and Roland H. Pesch, July 1991.
48721 @c man title gcore Generate a core file of a running program
48724 @c man begin SYNOPSIS gcore
48725 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
48729 @c man begin DESCRIPTION gcore
48730 Generate core dumps of one or more running programs with process IDs
48731 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
48732 is equivalent to one produced by the kernel when the process crashes
48733 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
48734 limit). However, unlike after a crash, after @command{gcore} finishes
48735 its job the program remains running without any change.
48738 @c man begin OPTIONS gcore
48741 Dump all memory mappings. The actual effect of this option depends on
48742 the Operating System. On @sc{gnu}/Linux, it will disable
48743 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
48744 enable @code{dump-excluded-mappings} (@pxref{set
48745 dump-excluded-mappings}).
48747 @item -o @var{prefix}
48748 The optional argument @var{prefix} specifies the prefix to be used
48749 when composing the file names of the core dumps. The file name is
48750 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
48751 process ID of the running program being analyzed by @command{gcore}.
48752 If not specified, @var{prefix} defaults to @var{gcore}.
48756 @c man begin SEEALSO gcore
48758 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48759 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48760 documentation are properly installed at your site, the command
48767 should give you access to the complete manual.
48769 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48770 Richard M. Stallman and Roland H. Pesch, July 1991.
48777 @c man title gdbinit GDB initialization scripts
48780 @c man begin SYNOPSIS gdbinit
48781 @ifset SYSTEM_GDBINIT
48782 @value{SYSTEM_GDBINIT}
48785 @ifset SYSTEM_GDBINIT_DIR
48786 @value{SYSTEM_GDBINIT_DIR}/*
48789 ~/.config/gdb/gdbinit
48797 @c man begin DESCRIPTION gdbinit
48798 These files contain @value{GDBN} commands to automatically execute during
48799 @value{GDBN} startup. The lines of contents are canned sequences of commands,
48802 the @value{GDBN} manual in node @code{Sequences}
48803 -- shell command @code{info -f gdb -n Sequences}.
48809 Please read more in
48811 the @value{GDBN} manual in node @code{Startup}
48812 -- shell command @code{info -f gdb -n Startup}.
48819 @ifset SYSTEM_GDBINIT
48820 @item @value{SYSTEM_GDBINIT}
48822 @ifclear SYSTEM_GDBINIT
48823 @item (not enabled with @code{--with-system-gdbinit} during compilation)
48825 System-wide initialization file. It is executed unless user specified
48826 @value{GDBN} option @code{-nx} or @code{-n}.
48829 the @value{GDBN} manual in node @code{System-wide configuration}
48830 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
48832 @ifset SYSTEM_GDBINIT_DIR
48833 @item @value{SYSTEM_GDBINIT_DIR}
48835 @ifclear SYSTEM_GDBINIT_DIR
48836 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
48838 System-wide initialization directory. All files in this directory are
48839 executed on startup unless user specified @value{GDBN} option @code{-nx} or
48840 @code{-n}, as long as they have a recognized file extension.
48843 the @value{GDBN} manual in node @code{System-wide configuration}
48844 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
48847 @ref{System-wide configuration}.
48850 @item @file{~/.config/gdb/gdbinit} or @file{~/.gdbinit}
48851 User initialization file. It is executed unless user specified
48852 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
48854 @item @file{.gdbinit}
48855 Initialization file for current directory. It may need to be enabled with
48856 @value{GDBN} security command @code{set auto-load local-gdbinit}.
48859 the @value{GDBN} manual in node @code{Init File in the Current Directory}
48860 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
48863 @ref{Init File in the Current Directory}.
48868 @c man begin SEEALSO gdbinit
48870 gdb(1), @code{info -f gdb -n Startup}
48872 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48873 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48874 documentation are properly installed at your site, the command
48880 should give you access to the complete manual.
48882 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48883 Richard M. Stallman and Roland H. Pesch, July 1991.
48887 @node gdb-add-index man
48888 @heading gdb-add-index
48889 @pindex gdb-add-index
48890 @anchor{gdb-add-index}
48892 @c man title gdb-add-index Add index files to speed up GDB
48894 @c man begin SYNOPSIS gdb-add-index
48895 gdb-add-index @var{filename}
48898 @c man begin DESCRIPTION gdb-add-index
48899 When @value{GDBN} finds a symbol file, it scans the symbols in the
48900 file in order to construct an internal symbol table. This lets most
48901 @value{GDBN} operations work quickly--at the cost of a delay early on.
48902 For large programs, this delay can be quite lengthy, so @value{GDBN}
48903 provides a way to build an index, which speeds up startup.
48905 To determine whether a file contains such an index, use the command
48906 @kbd{readelf -S filename}: the index is stored in a section named
48907 @code{.gdb_index}. The index file can only be produced on systems
48908 which use ELF binaries and DWARF debug information (i.e., sections
48909 named @code{.debug_*}).
48911 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
48912 in the @env{PATH} environment variable. If you want to use different
48913 versions of these programs, you can specify them through the
48914 @env{GDB} and @env{OBJDUMP} environment variables.
48918 the @value{GDBN} manual in node @code{Index Files}
48919 -- shell command @kbd{info -f gdb -n "Index Files"}.
48926 @c man begin SEEALSO gdb-add-index
48928 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48929 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48930 documentation are properly installed at your site, the command
48936 should give you access to the complete manual.
48938 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48939 Richard M. Stallman and Roland H. Pesch, July 1991.
48945 @node GNU Free Documentation License
48946 @appendix GNU Free Documentation License
48949 @node Concept Index
48950 @unnumbered Concept Index
48954 @node Command and Variable Index
48955 @unnumbered Command, Variable, and Function Index
48960 % I think something like @@colophon should be in texinfo. In the
48962 \long\def\colophon{\hbox to0pt{}\vfill
48963 \centerline{The body of this manual is set in}
48964 \centerline{\fontname\tenrm,}
48965 \centerline{with headings in {\bf\fontname\tenbf}}
48966 \centerline{and examples in {\tt\fontname\tentt}.}
48967 \centerline{{\it\fontname\tenit\/},}
48968 \centerline{{\bf\fontname\tenbf}, and}
48969 \centerline{{\sl\fontname\tensl\/}}
48970 \centerline{are used for emphasis.}\vfill}
48972 % Blame: doc@@cygnus.com, 1991.