Hi!
Until recently, integer_zerop would STRIP_NOPS, so that change regressed
some cases in the -Waddress warning that affect some real-world code.
The following patch re-adds stripping of nops for that case (but doesn't try
to fold it further).
With this patch, for C and C++98 we get the same behavior as in 5.x,
for C++11 and C++14 we warn even about the weirdo cases where (10 - 10)
or (&e - &e) is cast to a pointer (but, e.g. for C we have been and are
warning about the latter only). I'd say warning for such weird cases is
fine.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2016-02-11 Jakub Jelinek <ja...@redhat.com>
PR c/69768
* c-typeck.c (parser_build_binary_op): Strip nops from integer_zerop
arguments for -Waddress warning.
* typeck.c (cp_build_binary_op): Strip nops from integer_zerop
arguments for -Waddress warning. Fix up formatting.
* c-c++-common/Waddress-1.c: New test.
--- gcc/c/c-typeck.c.jj 2016-01-27 20:30:18.000000000 +0100
+++ gcc/c/c-typeck.c 2016-02-11 17:17:07.470222811 +0100
@@ -3597,8 +3597,10 @@ parser_build_binary_op (location_t locat
of testing for equality or inequality of a string literal with NULL. */
if (code == EQ_EXPR || code == NE_EXPR)
{
- if ((code1 == STRING_CST && !integer_zerop (arg2.value))
- || (code2 == STRING_CST && !integer_zerop (arg1.value)))
+ if ((code1 == STRING_CST
+ && !integer_zerop (tree_strip_nop_conversions (arg2.value)))
+ || (code2 == STRING_CST
+ && !integer_zerop (tree_strip_nop_conversions (arg1.value))))
warning_at (location, OPT_Waddress,
"comparison with string literal results in unspecified
behavior");
}
--- gcc/cp/typeck.c.jj 2016-02-11 10:50:58.000000000 +0100
+++ gcc/cp/typeck.c 2016-02-11 17:17:07.473222771 +0100
@@ -4487,9 +4487,12 @@ cp_build_binary_op (location_t location,
warning (OPT_Wfloat_equal,
"comparing floating point with == or != is unsafe");
if ((complain & tf_warning)
- && ((TREE_CODE (orig_op0) == STRING_CST && !integer_zerop (op1))
- || (TREE_CODE (orig_op1) == STRING_CST && !integer_zerop (op0))))
- warning (OPT_Waddress, "comparison with string literal results in
unspecified behaviour");
+ && ((TREE_CODE (orig_op0) == STRING_CST
+ && !integer_zerop (tree_strip_nop_conversions (op1)))
+ || (TREE_CODE (orig_op1) == STRING_CST
+ && !integer_zerop (tree_strip_nop_conversions (op0)))))
+ warning (OPT_Waddress, "comparison with string literal results "
+ "in unspecified behaviour");
build_type = boolean_type_node;
if ((code0 == INTEGER_TYPE || code0 == REAL_TYPE
--- gcc/testsuite/c-c++-common/Waddress-1.c.jj 2016-02-11 14:30:30.677090429
+0100
+++ gcc/testsuite/c-c++-common/Waddress-1.c 2016-02-11 17:18:13.970329341
+0100
@@ -0,0 +1,15 @@
+/* PR c/69768 */
+/* { dg-do compile } */
+/* { dg-options "-Waddress" } */
+
+static int e;
+
+int
+foo ()
+{
+ return "foo1" != (void *) 0 /* { dg-bogus "comparison with string literal
results in unspecified behaviou?r" } */
+ && "foo2" != (const char *) ((void *) 0) /* { dg-bogus
"comparison with string literal results in unspecified behaviou?r" } */
+ && "foo3" != (const char *) ((void *) (10 - 10)) /* { dg-warning
"comparison with string literal results in unspecified behaviou?r" "" { target
c++11 } } */
+ && "foo4" != (const char *) ((void *) (&e - &e)) /* { dg-warning
"comparison with string literal results in unspecified behaviou?r" "" { target
{ c || c++11 } } } */
+ && "foo5" != "foo6"; /* { dg-warning "comparison with string literal
results in unspecified behaviou?r" } */
+}
Jakub
