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.

1 files changed, 4 insertions, 5 deletions

diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index cb1a410..985206f 100644
--- 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;
 	}
     }