gdb/expression.h

   1 /* Definitions for expressions stored in reversed prefix form, for GDB.
   2
   3    Copyright (C) 1986-2023 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #if !defined (EXPRESSION_H)
  21 #define EXPRESSION_H 1
  22
  23 #include "gdbtypes.h"
  24 #include "symtab.h"
  25
  26 /* While parsing expressions we need to track the innermost lexical block
  27    that we encounter.  In some situations we need to track the innermost
  28    block just for symbols, and in other situations we want to track the
  29    innermost block for symbols and registers.  These flags are used by the
  30    innermost block tracker to control which blocks we consider for the
  31    innermost block.  These flags can be combined together as needed.  */
  32
  33 enum innermost_block_tracker_type
  34 {
  35   /* Track the innermost block for symbols within an expression.  */
  36   INNERMOST_BLOCK_FOR_SYMBOLS = (1 << 0),
  37
  38   /* Track the innermost block for registers within an expression.  */
  39   INNERMOST_BLOCK_FOR_REGISTERS = (1 << 1)
  40 };
  41 DEF_ENUM_FLAGS_TYPE (enum innermost_block_tracker_type,
  42                      innermost_block_tracker_types);
  43
  44 enum exp_opcode : uint8_t
  45   {
  46 #define OP(name) name ,
  47
  48 #include "std-operator.def"
  49
  50 #undef OP
  51   };
  52
  53 /* Values of NOSIDE argument to eval_subexp.  */
  54
  55 enum noside
  56   {
  57     EVAL_NORMAL,
  58     EVAL_AVOID_SIDE_EFFECTS     /* Don't modify any variables or
  59                                    call any functions.  The value
  60                                    returned will have the correct
  61                                    type, and will have an
  62                                    approximately correct lvalue
  63                                    type (inaccuracy: anything that is
  64                                    listed as being in a register in
  65                                    the function in which it was
  66                                    declared will be lval_register).
  67                                    Ideally this would not even read
  68                                    target memory, but currently it
  69                                    does in many situations.  */
  70   };
  71
  72 struct expression;
  73 struct agent_expr;
  74 struct axs_value;
  75 struct type;
  76 struct ui_file;
  77
  78 namespace expr
  79 {
  80
  81 class operation;
  82 typedef std::unique_ptr<operation> operation_up;
  83
  84 /* Base class for an operation.  An operation is a single component of
  85    an expression.  */
  86
  87 class operation
  88 {
  89 protected:
  90
  91   operation () = default;
  92   DISABLE_COPY_AND_ASSIGN (operation);
  93
  94 public:
  95
  96   virtual ~operation () = default;
  97
  98   /* Evaluate this operation.  */
  99   virtual value *evaluate (struct type *expect_type,
 100                            struct expression *exp,
 101                            enum noside noside) = 0;
 102
 103   /* Evaluate this operation in a context where C-like coercion is
 104      needed.  */
 105   virtual value *evaluate_with_coercion (struct expression *exp,
 106                                          enum noside noside)
 107   {
 108     return evaluate (nullptr, exp, noside);
 109   }
 110
 111   /* Evaluate this expression in the context of a cast to
 112      EXPECT_TYPE.  */
 113   virtual value *evaluate_for_cast (struct type *expect_type,
 114                                     struct expression *exp,
 115                                     enum noside noside);
 116
 117   /* Evaluate this expression in the context of a sizeof
 118      operation.  */
 119   virtual value *evaluate_for_sizeof (struct expression *exp,
 120                                       enum noside noside);
 121
 122   /* Evaluate this expression in the context of an address-of
 123      operation.  Must return the address.  */
 124   virtual value *evaluate_for_address (struct expression *exp,
 125                                        enum noside noside);
 126
 127   /* Evaluate a function call, with this object as the callee.
 128      EXPECT_TYPE, EXP, and NOSIDE have the same meaning as in
 129      'evaluate'.  ARGS holds the operations that should be evaluated
 130      to get the arguments to the call.  */
 131   virtual value *evaluate_funcall (struct type *expect_type,
 132                                    struct expression *exp,
 133                                    enum noside noside,
 134                                    const std::vector<operation_up> &args)
 135   {
 136     /* Defer to the helper overload.  */
 137     return evaluate_funcall (expect_type, exp, noside, nullptr, args);
 138   }
 139
 140   /* True if this is a constant expression.  */
 141   virtual bool constant_p () const
 142   { return false; }
 143
 144   /* Return true if this operation uses OBJFILE (and will become
 145      dangling when OBJFILE is unloaded), otherwise return false.
 146      OBJFILE must not be a separate debug info file.  */
 147   virtual bool uses_objfile (struct objfile *objfile) const
 148   { return false; }
 149
 150   /* Generate agent expression bytecodes for this operation.  */
 151   void generate_ax (struct expression *exp, struct agent_expr *ax,
 152                     struct axs_value *value,
 153                     struct type *cast_type = nullptr);
 154
 155   /* Return the opcode that is implemented by this operation.  */
 156   virtual enum exp_opcode opcode () const = 0;
 157
 158   /* Print this operation to STREAM.  */
 159   virtual void dump (struct ui_file *stream, int depth) const = 0;
 160
 161   /* Call to indicate that this is the outermost operation in the
 162      expression.  This should almost never be overridden.  */
 163   virtual void set_outermost () { }
 164
 165 protected:
 166
 167   /* A helper overload that wraps evaluate_subexp_do_call.  */
 168   value *evaluate_funcall (struct type *expect_type,
 169                            struct expression *exp,
 170                            enum noside noside,
 171                            const char *function_name,
 172                            const std::vector<operation_up> &args);
 173
 174   /* Called by generate_ax to do the work for this particular
 175      operation.  */
 176   virtual void do_generate_ax (struct expression *exp,
 177                                struct agent_expr *ax,
 178                                struct axs_value *value,
 179                                struct type *cast_type)
 180   {
 181     error (_("Cannot translate to agent expression"));
 182   }
 183 };
 184
 185 /* A helper function for creating an operation_up, given a type.  */
 186 template<typename T, typename... Arg>
 187 operation_up
 188 make_operation (Arg... args)
 189 {
 190   return operation_up (new T (std::forward<Arg> (args)...));
 191 }
 192
 193 }
 194
 195 struct expression
 196 {
 197   expression (const struct language_defn *lang, struct gdbarch *arch)
 198     : language_defn (lang),
 199       gdbarch (arch)
 200   {
 201   }
 202
 203   DISABLE_COPY_AND_ASSIGN (expression);
 204
 205   /* Return the opcode for the outermost sub-expression of this
 206      expression.  */
 207   enum exp_opcode first_opcode () const
 208   {
 209     return op->opcode ();
 210   }
 211
 212   /* Dump the expression to STREAM.  */
 213   void dump (struct ui_file *stream)
 214   {
 215     op->dump (stream, 0);
 216   }
 217
 218   /* Return true if this expression uses OBJFILE (and will become
 219      dangling when OBJFILE is unloaded), otherwise return false.
 220      OBJFILE must not be a separate debug info file.  */
 221   bool uses_objfile (struct objfile *objfile) const;
 222
 223   /* Evaluate the expression.  EXPECT_TYPE is the context type of the
 224      expression; normally this should be nullptr.  NOSIDE controls how
 225      evaluation is performed.  */
 226   struct value *evaluate (struct type *expect_type = nullptr,
 227                           enum noside noside = EVAL_NORMAL);
 228
 229   /* Evaluate an expression, avoiding all memory references
 230      and getting a value whose type alone is correct.  */
 231   struct value *evaluate_type ()
 232   { return evaluate (nullptr, EVAL_AVOID_SIDE_EFFECTS); }
 233
 234   /* Language it was entered in.  */
 235   const struct language_defn *language_defn;
 236   /* Architecture it was parsed in.  */
 237   struct gdbarch *gdbarch;
 238   expr::operation_up op;
 239 };
 240
 241 typedef std::unique_ptr<expression> expression_up;
 242
 243 /* When parsing expressions we track the innermost block that was
 244    referenced.  */
 245
 246 class innermost_block_tracker
 247 {
 248 public:
 249   innermost_block_tracker (innermost_block_tracker_types types
 250                            = INNERMOST_BLOCK_FOR_SYMBOLS)
 251     : m_types (types),
 252       m_innermost_block (NULL)
 253   { /* Nothing.  */ }
 254
 255   /* Update the stored innermost block if the new block B is more inner
 256      than the currently stored block, or if no block is stored yet.  The
 257      type T tells us whether the block B was for a symbol or for a
 258      register.  The stored innermost block is only updated if the type T is
 259      a type we are interested in, the types we are interested in are held
 260      in M_TYPES and set during RESET.  */
 261   void update (const struct block *b, innermost_block_tracker_types t);
 262
 263   /* Overload of main UPDATE method which extracts the block from BS.  */
 264   void update (const struct block_symbol &bs)
 265   {
 266     update (bs.block, INNERMOST_BLOCK_FOR_SYMBOLS);
 267   }
 268
 269   /* Return the stored innermost block.  Can be nullptr if no symbols or
 270      registers were found during an expression parse, and so no innermost
 271      block was defined.  */
 272   const struct block *block () const
 273   {
 274     return m_innermost_block;
 275   }
 276
 277 private:
 278   /* The type of innermost block being looked for.  */
 279   innermost_block_tracker_types m_types;
 280
 281   /* The currently stored innermost block found while parsing an
 282      expression.  */
 283   const struct block *m_innermost_block;
 284 };
 285
 286 /* Flags that can affect the parsers.  */
 287
 288 enum parser_flag
 289 {
 290   /* This flag is set if the expression is being evaluated in a
 291      context where a 'void' result type is expected.  Parsers are free
 292      to ignore this, or to use it to help with overload resolution
 293      decisions.  */
 294   PARSER_VOID_CONTEXT = (1 << 0),
 295
 296   /* This flag is set if a top-level comma terminates the
 297      expression.  */
 298   PARSER_COMMA_TERMINATES = (1 << 1),
 299
 300   /* This flag is set if the parser should print debugging output as
 301      it parses.  For yacc-based parsers, this translates to setting
 302      yydebug.  */
 303   PARSER_DEBUG = (1 << 2),
 304
 305   /* Normally the expression-parsing functions like parse_exp_1 will
 306      attempt to find a context block if one is not passed in.  If set,
 307      this flag suppresses this search and uses a null context for the
 308      parse.  */
 309   PARSER_LEAVE_BLOCK_ALONE = (1 << 3),
 310 };
 311 DEF_ENUM_FLAGS_TYPE (enum parser_flag, parser_flags);
 312
 313 /* From parse.c */
 314
 315 extern expression_up parse_expression (const char *,
 316                                        innermost_block_tracker * = nullptr,
 317                                        parser_flags flags = 0);
 318
 319 extern expression_up parse_expression_with_language (const char *string,
 320                                                      enum language lang);
 321
 322
 323 class completion_tracker;
 324
 325 /* Base class for expression completion.  An instance of this
 326    represents a completion request from the parser.  */
 327 struct expr_completion_base
 328 {
 329   /* Perform this object's completion.  EXP is the expression in which
 330      the completion occurs.  TRACKER is the tracker to update with the
 331      results.  Return true if completion was possible (even if no
 332      completions were found), false to fall back to ordinary
 333      expression completion (i.e., symbol names).  */
 334   virtual bool complete (struct expression *exp,
 335                          completion_tracker &tracker) = 0;
 336
 337   virtual ~expr_completion_base () = default;
 338 };
 339
 340 extern expression_up parse_expression_for_completion
 341      (const char *, std::unique_ptr<expr_completion_base> *completer);
 342
 343 extern expression_up parse_exp_1 (const char **, CORE_ADDR pc,
 344                                   const struct block *,
 345                                   parser_flags flags,
 346                                   innermost_block_tracker * = nullptr);
 347
 348 /* From eval.c */
 349
 350 /* Evaluate a function call.  The function to be called is in CALLEE and
 351    the arguments passed to the function are in ARGVEC.
 352    FUNCTION_NAME is the name of the function, if known.
 353    DEFAULT_RETURN_TYPE is used as the function's return type if the return
 354    type is unknown.  */
 355
 356 extern struct value *evaluate_subexp_do_call (expression *exp,
 357                                               enum noside noside,
 358                                               value *callee,
 359                                               gdb::array_view<value *> argvec,
 360                                               const char *function_name,
 361                                               type *default_return_type);
 362
 363 /* In an OP_RANGE expression, either bound could be empty, indicating
 364    that its value is by default that of the corresponding bound of the
 365    array or string.  Also, the upper end of the range can be exclusive
 366    or inclusive.  So we have six sorts of subrange.  This enumeration
 367    type is to identify this.  */
 368
 369 enum range_flag : unsigned
 370 {
 371   /* This is a standard range.  Both the lower and upper bounds are
 372      defined, and the bounds are inclusive.  */
 373   RANGE_STANDARD = 0,
 374
 375   /* The low bound was not given.  */
 376   RANGE_LOW_BOUND_DEFAULT = 1 << 0,
 377
 378   /* The high bound was not given.  */
 379   RANGE_HIGH_BOUND_DEFAULT = 1 << 1,
 380
 381   /* The high bound of this range is exclusive.  */
 382   RANGE_HIGH_BOUND_EXCLUSIVE = 1 << 2,
 383
 384   /* The range has a stride.  */
 385   RANGE_HAS_STRIDE = 1 << 3,
 386 };
 387
 388 DEF_ENUM_FLAGS_TYPE (enum range_flag, range_flags);
 389
 390 #endif /* !defined (EXPRESSION_H) */