[C/C++ PATCH] Fix a -Waddress regression (PR c/69768)

[Jakub Jelinek]

Hi!

On Thu, Feb 11, 2016 at 01:56:09PM -0500, Jason Merrill wrote:
> On 02/11/2016 11:25 AM, Jakub Jelinek wrote:
> >+	       && !integer_zerop (tree_strip_nop_conversions (op1)))
> 
> Maybe cp_fold rather than tree_strip_nop_conversions?

Is it safe to call cp_fully_fold (typeck.c only calls it by that name,
not cp_fold) on perhaps type or value dependent argument?
E.g. on
template <int N>
int
bar ()
{
  return "foo1" != (void *) N
	 && "foo2" != (const char *) ((void *) N)
	 && "foo3" != (const char *) ((void *) (N - N))
	 && "foo4" != (const char *) ((void *) (&e - &e))
	 && "foo5" != "foo6";
}
op1 is NON_DEPENDENT_EXPR.  If yes, here is an alternative (that has the same
behavior on the testcase as 5.x does).  The C FE didn't use to fold it, so
I'm preserving its behavior.

2016-02-11  Jakub Jelinek  <jakub@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): cp_fully_fold integer_zerop
	arguments for -Waddress warning.  Fix up formatting.

	* c-c++-common/Waddress-1.c: New test.

--- gcc/c/c-typeck.c.jj	2016-02-11 20:28:51.316491659 +0100
+++ gcc/c/c-typeck.c	2016-02-11 20:29:50.778672554 +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 20:28:51.196493312 +0100
+++ gcc/cp/typeck.c	2016-02-11 20:34:41.124672969 +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 (cp_fully_fold (op1)))
+	      || (TREE_CODE (orig_op1) == STRING_CST
+		  && !integer_zerop (cp_fully_fold (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 20:29:50.781672512 +0100
+++ gcc/testsuite/c-c++-common/Waddress-1.c	2016-02-11 20:35:40.299857817 +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-bogus "comparison with string literal results in unspecified behaviou?r" } */
+	 && "foo4" != (const char *) ((void *) (&e - &e))	/* { dg-warning "comparison with string literal results in unspecified behaviou?r" "" { target c } } */
+	 && "foo5" != "foo6";	/* { dg-warning "comparison with string literal results in unspecified behaviou?r" } */
+}


	Jakub