8 files changed, 45 insertions, 9 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 21fc42c..7196257 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,14 @@
+2002-10-08  Nathan Sidwell  <nathan@codesourcery.com>
+
+	* c-opts.c (c_common_decode_option): Add warn_strict_aliasing to
+	-Wall.
+	* c-typeck.c (build_c_cast): Use warn_strict_aliasing, tweak
+	message.
+	* flags.h (warn_strict_aliasing): Declare.
+	* toplev.c (warn_strict_aliasing): Define.
+	(lang_independent_options): Add it.
+	* doc/invoke.texi (-Wstrict-aliasing): Document it.
+
 2002-10-08  Zack Weinberg  <zack@codesourcery.com>
 
 	* system.h (GCCBUGURL): Delete.
diff --git a/gcc/c-opts.c b/gcc/c-opts.c
index ba86e45..d0e8b8e 100644
--- a/gcc/c-opts.c
+++ b/gcc/c-opts.c
@@ -702,7 +702,8 @@ c_common_decode_option (argc, argv)
       warn_sequence_point = on;	/* Was C only.  */
       warn_sign_compare = on;	/* Was C++ only.  */
       warn_switch = on;
-
+      warn_strict_aliasing = on;
+      
       /* Only warn about unknown pragmas that are not in system
 	 headers.  */                                        
       warn_unknown_pragmas = on;
diff --git a/gcc/c-typeck.c b/gcc/c-typeck.c
index 6fd14e5..b5bc210 100644
--- a/gcc/c-typeck.c
+++ b/gcc/c-typeck.c
@@ -3763,17 +3763,17 @@ build_c_cast (type, expr)
 	  && TREE_CODE (otype) == POINTER_TYPE
 	  && TREE_CODE (expr) == ADDR_EXPR
 	  && DECL_P (TREE_OPERAND (expr, 0))
-	  && flag_strict_aliasing && extra_warnings
+	  && flag_strict_aliasing && warn_strict_aliasing
 	  && !VOID_TYPE_P (TREE_TYPE (type)))
 	{
  	  /* Casting the address of a decl to non void pointer. Warn
 	     if the cast breaks type based aliasing.  */
 	  if (!COMPLETE_TYPE_P (TREE_TYPE (type)))
-	    warning ("type punning to incomplete type might not be type based aliasing safe");
+	    warning ("type-punning to incomplete type might break strict-aliasing rules");
 	  else if (!alias_sets_conflict_p
 		   (get_alias_set (TREE_TYPE (TREE_OPERAND (expr, 0))),
 		    get_alias_set (TREE_TYPE (type))))
-	    warning ("type punning cast is not type based aliasing safe");
+	    warning ("dereferencing type-punned pointer will break strict-aliasing rules");
 	}
       
       ovalue = value;
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index f112abe..51c6546 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -228,7 +228,7 @@ in the following sections.
 -Wno-import  -Wnonnull  -Wpacked  -Wpadded @gol
 -Wparentheses  -Wpointer-arith  -Wredundant-decls @gol
 -Wreturn-type  -Wsequence-point  -Wshadow @gol
--Wsign-compare  -Wswitch  -Wswitch-default -Wswitch-enum @gol
+-Wsign-compare  -Wstrict-aliasing -Wswitch  -Wswitch-default -Wswitch-enum @gol
 -Wsystem-headers -Wtrigraphs  -Wundef  -Wuninitialized @gol
 -Wunknown-pragmas  -Wunreachable-code @gol
 -Wunused  -Wunused-function  -Wunused-label  -Wunused-parameter @gol
@@ -2341,6 +2341,14 @@ GCC@.  If this command line option is used, warnings will even be issued
 for unknown pragmas in system header files.  This is not the case if
 the warnings were only enabled by the @option{-Wall} command line option.
 
+@item -Wstrict-aliasing
+@opindex Wstrict-aliasing
+This option is only active when @option{-fstrict-aliasing} is active.
+It warns about code which might break the strict aliasing rules that the
+compiler is using for optimization. The warning does not catch all
+cases, but does attempt to catch the more common pitfalls. It is
+included in @option{-Wall}.
+
 @item -Wall
 @opindex Wall
 All of the above @samp{-W} options combined.  This enables all the
diff --git a/gcc/flags.h b/gcc/flags.h
index e0e7b09a..c549275 100644
--- a/gcc/flags.h
+++ b/gcc/flags.h
@@ -184,6 +184,11 @@ extern int warn_disabled_optimization;
 
 extern int warn_deprecated_decl;
 
+/* Nonzero means warn about constructs which might not be strict
+   aliasing safe.  */
+
+extern int warn_strict_aliasing;
+
 /* Nonzero if generating code to do profiling.  */
 
 extern int profile_flag;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e8e298b..7370005 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2002-10-08  Nathan Sidwell  <nathan@codesourcery.com>
+
+	* gcc.dg/alias-1.c: Tweak expected warning.
+
 2002-10-06  D.Venkatasubramanian <dvenkat@noida.hcltech.com>
 
 	* gcc.dg/20020411-1.c: Disable for 16-bit "int".
diff --git a/gcc/testsuite/gcc.dg/alias-1.c b/gcc/testsuite/gcc.dg/alias-1.c
index 71056e9..a723083 100644
--- a/gcc/testsuite/gcc.dg/alias-1.c
+++ b/gcc/testsuite/gcc.dg/alias-1.c
@@ -1,5 +1,5 @@
 // { dg-do compile }
-// { dg-options "-W -fstrict-aliasing" }
+// { dg-options "-Wstrict-aliasing -fstrict-aliasing" }
 
 // Copyright (C) 2002 Free Software Foundation, Inc.
 // Contributed by Nathan Sidwell 29 Sep 2002 <nathan@codesourcery.com>
@@ -19,9 +19,9 @@ YYSTYPE
  addSibMacro(
          YYSTYPE  list )
  {
-     tDefEntry** ppT   = (tDefEntry**)&list; // { dg-warning "type punning cast" "" }
+     tDefEntry** ppT   = (tDefEntry**)&list; // { dg-warning "type-punned pointer" "" }
  
-     struct incomplete *p = (struct incomplete *)&list; // { dg-warning "type punning to incomplete" "" }
+     struct incomplete *p = (struct incomplete *)&list; // { dg-warning "type-punning to incomplete" "" }
      
      return list;
  }
diff --git a/gcc/toplev.c b/gcc/toplev.c
index 1ef00cd..81035b0 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -1511,6 +1511,11 @@ int warn_missing_noreturn;
 
 int warn_deprecated_decl = 1;
 
+/* Nonzero means warn about constructs which might not be
+   strict-aliasing safe.  */
+
+int warn_strict_aliasing;
+
 /* Likewise for -W.  */
 
 static const lang_independent_options W_options[] =
@@ -1556,7 +1561,9 @@ static const lang_independent_options W_options[] =
   {"deprecated-declarations", &warn_deprecated_decl, 1,
    N_("Warn about uses of __attribute__((deprecated)) declarations") },
   {"missing-noreturn", &warn_missing_noreturn, 1,
-   N_("Warn about functions which might be candidates for attribute noreturn") }
+   N_("Warn about functions which might be candidates for attribute noreturn") },
+  {"strict-aliasing", &warn_strict_aliasing, 1,
+   N_ ("Warn about code which might break the strict aliasing rules") }
 };
 
 void