New option -Wstrict-aliasing=2.

	* alias.c (alias_sets_might_conflict_p): New.
	* c-typeck.c (build_c_cast): Call it if warn_strict_aliasing > 1.
	* common.opt (Wstrict-aliasing=): New.
	* flags.h (warn_strict_aliasing): Change type to int.
	* opts.c (warn_strict_aliasing): Change type to int.
	(common_handle_option): Handle OPT_Wstrict_aliasing_.
	* tree.h (alias_sets_might_conflict_p): Declare it.
	* doc/invoke.tex (-Wstrict-aliasing=2): Document it.

From-SVN: r79222

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e6a791c8c6ac0be81adf8fc733d368c852aa6a6f..6016aaaed542ab7f089f345d1fb1700738d12795 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,14 @@
+2004-03-09  James E Wilson  <wilson@specifixinc.com>
+
+       * alias.c (alias_sets_might_conflict_p): New.
+       * c-typeck.c (build_c_cast): Call it if warn_strict_aliasing > 1.
+       * common.opt (Wstrict-aliasing=): New.
+       * flags.h (warn_strict_aliasing): Change type to int.
+       * opts.c (warn_strict_aliasing): Change type to int.
+       (common_handle_option): Handle OPT_Wstrict_aliasing_.
+       * tree.h (alias_sets_might_conflict_p): Declare it.
+       * doc/invoke.tex (-Wstrict-aliasing=2): Document it.
+
 2004-03-10  Roman Zippel  <zippel@linux-m68k.org>
 
        PR bootstrap/12371

diff --git a/gcc/alias.c b/gcc/alias.c
index d670a7db19e9591a047742eb60ea58554409bae7..30013ec7d6a80ac624c40e04b933493543ae1603 100644 (file)
--- a/gcc/alias.c
+++ b/gcc/alias.c
@@ -290,6 +290,19 @@ alias_sets_conflict_p (HOST_WIDE_INT set1, HOST_WIDE_INT set2)
      child of the other.  Therefore, they cannot alias.  */
   return 0;
 }
+
+/* Return 1 if the two specified alias sets might conflict, or if any subtype
+   of these alias sets might conflict.  */
+
+int
+alias_sets_might_conflict_p (HOST_WIDE_INT set1, HOST_WIDE_INT set2)
+{
+  if (set1 == 0 || set2 == 0 || set1 == set2)
+    return 1;
+
+  return 0;
+}
+
 \f
 /* Return 1 if TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has
    has any readonly fields.  If any of the fields have types that

diff --git a/gcc/c-typeck.c b/gcc/c-typeck.c
index a49b5ea289883e816c98ca8fbd6aa570ab25bf62..f23fac78342e8f697e13b8e14f6822061fd78924 100644 (file)
--- a/gcc/c-typeck.c
+++ b/gcc/c-typeck.c
@@ -3027,10 +3027,17 @@ build_c_cast (tree type, tree expr)
             if the cast breaks type based aliasing.  */
          if (!COMPLETE_TYPE_P (TREE_TYPE (type)))
            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 ("dereferencing type-punned pointer will break strict-aliasing rules");
+         else
+           {
+             HOST_WIDE_INT set1 = get_alias_set (TREE_TYPE (TREE_OPERAND (expr, 0)));
+             HOST_WIDE_INT set2 = get_alias_set (TREE_TYPE (type));
+
+             if (!alias_sets_conflict_p (set1, set2))
+               warning ("dereferencing type-punned pointer will break strict-aliasing rules");
+             else if (warn_strict_aliasing > 1
+                      && !alias_sets_might_conflict_p (set1, set2))
+               warning ("dereferencing type-punned pointer might break strict-aliasing rules");
+           }
        }
 
       /* If pedantic, warn for conversions between function and object

diff --git a/gcc/common.opt b/gcc/common.opt
index d9faa60a8f5203f4f2eb4a065792a39691147a5b..f1a045316e4483bdb0fe74b3d87341a02e731e6b 100644 (file)
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -104,6 +104,10 @@ Wstrict-aliasing
 Common
 Warn about code which might break strict aliasing rules
 
+Wstrict-aliasing=
+Common Joined UInteger
+Warn about code which might break strict aliasing rules
+
 Wswitch
 Common
 Warn about enumerated switches, with no default, missing a case

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 8caed2b197875f93becc24a77527e86a418b0461..0c9f183387f3922d5d082c1ad6b96ddd73c92117 100644 (file)
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -226,7 +226,7 @@ in the following sections.
 -Wno-multichar  -Wnonnull  -Wpacked  -Wpadded @gol
 -Wparentheses  -Wpointer-arith  -Wredundant-decls @gol
 -Wreturn-type  -Wsequence-point  -Wshadow @gol
--Wsign-compare  -Wstrict-aliasing @gol
+-Wsign-compare  -Wstrict-aliasing -Wstrict-aliasing=2 @gol
 -Wswitch  -Wswitch-default  -Wswitch-enum @gol
 -Wsystem-headers  -Wtrigraphs  -Wundef  -Wuninitialized @gol
 -Wunknown-pragmas  -Wunreachable-code @gol
@@ -2449,6 +2449,13 @@ 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 -Wstrict-aliasing=2
+@opindex Wstrict-aliasing=2
+This option is only active when @option{-fstrict-aliasing} is active.
+It warns about all code which might break the strict aliasing rules that the
+compiler is using for optimization.  This warning catches all cases, but
+it will also give a warning for some ambiguous cases that are safe.
+
 @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 b088f6cb3ba6d0ee2b761ae953eda3f2d279f135..8a70fc31b781d3051a32a7ca3e1a7f9a112aa1ec 100644 (file)
--- a/gcc/flags.h
+++ b/gcc/flags.h
@@ -184,7 +184,7 @@ extern bool warn_deprecated_decl;
 /* Nonzero means warn about constructs which might not be strict
    aliasing safe.  */
 
-extern bool warn_strict_aliasing;
+extern int warn_strict_aliasing;
 
 /* Nonzero if generating code to do profiling.  */
 

diff --git a/gcc/opts.c b/gcc/opts.c
index fa1971cd651c9faa3c2c48d22eb095c0c8ef4526..99d576a3af8a656808819660f4eb4b56073088f5 100644 (file)
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -100,7 +100,7 @@ bool warn_shadow;
 
 /* Nonzero means warn about constructs which might not be
    strict-aliasing safe.  */
-bool warn_strict_aliasing;
+int warn_strict_aliasing;
 
 /* True to warn if a switch on an enum, that does not have a default
    case, fails to have a case for every enum value.  */
@@ -747,6 +747,7 @@ common_handle_option (size_t scode, const char *arg,
       break;
 
     case OPT_Wstrict_aliasing:
+    case OPT_Wstrict_aliasing_:
       warn_strict_aliasing = value;
       break;
 

diff --git a/gcc/tree.h b/gcc/tree.h
index 0a1e3fb0bd6ae80bb5faad76015658cf62770f59..6af6c662ff0516aaec55e130f5b4b07016c61a91 100644 (file)
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -2887,6 +2887,7 @@ extern tree strip_float_extensions (tree);
 extern void record_component_aliases (tree);
 extern HOST_WIDE_INT get_alias_set (tree);
 extern int alias_sets_conflict_p (HOST_WIDE_INT, HOST_WIDE_INT);
+extern int alias_sets_might_conflict_p (HOST_WIDE_INT, HOST_WIDE_INT);
 extern int readonly_fields_p (tree);
 extern int objects_must_conflict_p (tree, tree);