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re PR c/8083 (GCC does not warn for aliasing violations) 

PR c/8083
	* c-typeck.c (build_c_cast): Warn about type punning which breaks
	type based aliasing.
testsuite:
	* gcc.dg/alias-1.c: New test.

From-SVN: r57698
This commit is contained in:
Nathan Sidwell 2002-10-01 19:11:07 +00:00 committed by Nathan Sidwell
parent 0645ba8f0b
commit 73a7376815
4 changed files with 56 additions and 0 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,9 @@
2002-10-01 Nathan Sidwell <nathan@codesourcery.com>
PR c/8083
* c-typeck.c (build_c_cast): Warn about type punning which breaks
type based aliasing.
2002-10-01 Mark Mitchell <mark@codesourcery.com>
* stor-layout.c (update_alignment_for_field): New function.
@ -6,6 +12,7 @@
2002-10-01 Nathan Sidwell <nathan@codesourcery.com>
PR other/8077
* gcc.c (cc1_options): Add space on -auxbase-strip.
2002-10-01 Jim Wilson <wilson@redhat.com>

17
gcc/c-typeck.c
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@ -3759,6 +3759,23 @@ build_c_cast (type, expr)
&& !TREE_CONSTANT (value))
warning ("cast to pointer from integer of different size");
if (TREE_CODE (type) == POINTER_TYPE
&& TREE_CODE (otype) == POINTER_TYPE
&& TREE_CODE (expr) == ADDR_EXPR
&& DECL_P (TREE_OPERAND (expr, 0))
&& flag_strict_aliasing && extra_warnings
&& !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");
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");
}
ovalue = value;
value = convert (type, value);

4
gcc/testsuite/ChangeLog
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@ -1,3 +1,7 @@
2002-10-01 Nathan Sidwell <nathan@codesourcery.com>
* gcc.dg/alias-1.c: New test.
2002-10-01 Mark Mitchell <mark@codesourcery.com>
* gcc.dg/empty1.C: New test.

28
gcc/testsuite/gcc.dg/alias-1.c Normal file
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@ -0,0 +1,28 @@
// { dg-do compile }
// { dg-options "-W -fstrict-aliasing" }
// Copyright (C) 2002 Free Software Foundation, Inc.
// Contributed by Nathan Sidwell 29 Sep 2002 <nathan@codesourcery.com>
// 8083. warn about odd casts
typedef int YYSTYPE;
typedef struct tDefEntry
{
unsigned t;
} tDefEntry;
struct incomplete;
YYSTYPE
addSibMacro(
YYSTYPE list )
{
tDefEntry** ppT = (tDefEntry**)&list; // { dg-warning "type punning cast" "" }
struct incomplete *p = (struct incomplete *)&list; // { dg-warning "type punning to incomplete" "" }
return list;
}