c++: Add -Wexceptions warning option [PR97675]

This PR asks that we add a warning option for an existing (very old)
warning, so that it can be disabled selectively.  clang++ uses
-Wexceptions for this, so I added this new option rather than using
e.g. -Wnoexcept.

gcc/c-family/ChangeLog:

	PR c++/97675
	* c.opt (Wexceptions): New option.

gcc/cp/ChangeLog:

	PR c++/97675
	* except.c (check_handlers_1): Use OPT_Wexceptions for the
	warning.  Use inform for the second part of the warning.

gcc/ChangeLog:

	PR c++/97675
	* doc/invoke.texi: Document -Wexceptions.

gcc/testsuite/ChangeLog:

	PR c++/97675
	* g++.old-deja/g++.eh/catch10.C: Adjust dg-warning.
	* g++.dg/warn/Wexceptions1.C: New test.
	* g++.dg/warn/Wexceptions2.C: New test.

diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 5bfe3a68f66b11bcc53d1c386142c53e6bba6490..ebd07cc805959d8fb80e04baaedadcceae9f95aa 100644 (file)
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -579,6 +579,10 @@ Werror-implicit-function-declaration
 C ObjC RejectNegative Warning Alias(Werror=, implicit-function-declaration)
 This switch is deprecated; use -Werror=implicit-function-declaration instead.
 
+Wexceptions
+C++ ObjC++ Var(warn_exceptions) Init(1)
+Warn when an exception handler is shadowed by another handler.
+
 Wextra
 C ObjC C++ ObjC++ Warning
 ; in common.opt

diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index cb1a4105dae16c81c0f2cb589b63d556ecabd6e1..985206f6a6496611cb863ba048f112720ceb2aa6 100644 (file)
--- a/gcc/cp/except.c
+++ b/gcc/cp/except.c
@@ -975,11 +975,10 @@ check_handlers_1 (tree master, tree_stmt_iterator i)
       tree handler = tsi_stmt (i);
       if (TREE_TYPE (handler) && can_convert_eh (type, TREE_TYPE (handler)))
        {
-         warning_at (EXPR_LOCATION (handler), 0,
-                     "exception of type %qT will be caught",
-                     TREE_TYPE (handler));
-         warning_at (EXPR_LOCATION (master), 0,
-                     "   by earlier handler for %qT", type);
+         if (warning_at (EXPR_LOCATION (handler), OPT_Wexceptions,
+                         "exception of type %qT will be caught by earlier "
+                         "handler", TREE_TYPE (handler)))
+           inform (EXPR_LOCATION (master), "for type %qT", type);
          break;
        }
     }

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 812fa46e906734f109d9434548f6b53e327d695e..32f90ef20229a1e0617e21fee89926f9cfff043e 100644 (file)
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -240,7 +240,7 @@ in the following sections.
 -Wctor-dtor-privacy  -Wno-delete-incomplete @gol
 -Wdelete-non-virtual-dtor  -Wdeprecated-copy  -Wdeprecated-copy-dtor @gol
 -Wno-deprecated-enum-enum-conversion -Wno-deprecated-enum-float-conversion @gol
--Weffc++  -Wextra-semi  -Wno-inaccessible-base @gol
+-Weffc++  -Wno-exceptions -Wextra-semi  -Wno-inaccessible-base @gol
 -Wno-inherited-variadic-ctor  -Wno-init-list-lifetime @gol
 -Wno-invalid-offsetof  -Wno-literal-suffix  -Wmismatched-tags @gol
 -Wmultiple-inheritance  -Wnamespaces  -Wnarrowing @gol
@@ -3739,6 +3739,12 @@ When selecting this option, be aware that the standard library
 headers do not obey all of these guidelines; use @samp{grep -v}
 to filter out those warnings.
 
+@item -Wno-exceptions @r{(C++ and Objective-C++ only)}
+@opindex Wexceptions
+@opindex Wno-exceptions
+Disable the warning about the case when an exception handler is shadowed by
+another handler, which can point out a wrong ordering of exception handlers.
+
 @item -Wstrict-null-sentinel @r{(C++ and Objective-C++ only)}
 @opindex Wstrict-null-sentinel
 @opindex Wno-strict-null-sentinel

diff --git a/gcc/testsuite/g++.dg/warn/Wexceptions1.C b/gcc/testsuite/g++.dg/warn/Wexceptions1.C
new file mode 100644 (file)
index 0000000..af140fd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wexceptions1.C
@@ -0,0 +1,9 @@
+// PR c++/97675
+
+struct Base { };
+struct Child : Base { };
+int main() {
+    try { throw Child(); }
+    catch (Base const&) { }
+    catch (Child const&) { } // { dg-warning "exception of type .Child. will be caught by earlier handler" }
+}

diff --git a/gcc/testsuite/g++.dg/warn/Wexceptions2.C b/gcc/testsuite/g++.dg/warn/Wexceptions2.C
new file mode 100644 (file)
index 0000000..07c5155
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wexceptions2.C
@@ -0,0 +1,10 @@
+// PR c++/97675
+// { dg-additional-options -Wno-exceptions }
+
+struct Base { };
+struct Child : Base { };
+int main() {
+    try { throw Child(); }
+    catch (Base const&) { }
+    catch (Child const&) { } // { dg-bogus "exception of type .Child. will be caught by earlier handler" }
+}

diff --git a/gcc/testsuite/g++.old-deja/g++.eh/catch10.C b/gcc/testsuite/g++.old-deja/g++.eh/catch10.C
index 2300a9461870d73b0c5d2ff1003473ce1adf6770..7cc609645a23099d73219b0bf403cd41b89c9526 100644 (file)
--- a/gcc/testsuite/g++.old-deja/g++.eh/catch10.C
+++ b/gcc/testsuite/g++.old-deja/g++.eh/catch10.C
@@ -13,8 +13,8 @@ void g()
   catch (A*) { }
 
   try { f(); }
-  catch (A*) { }               // { dg-warning "" } A* before B*
-  catch (B*) { }               // { dg-warning "" } A* before B*
+  catch (A*) { }               // { dg-message "for type" } A* before B*
+  catch (B*) { }               // { dg-warning "will be caught" } A* before B*
 
   try { f(); }
   catch (A*) { }