Hi,
I suppose we can quickly resolve, one way or another, this rather old
issue. Considering:
extern void z();
void h() { if ( z != (void*)0 ); }
we -Waddress warn in C and we don't in C++, due to the rather subtle
differences between null_pointer_constant_p and null_ptr_cst_p. I
believe we could as well warn in C++ too, but then I'm afraid we have to
handle the case specially, like in the below. What do you think?
Thanks!
Paolo.
//////////////////////
Index: cp/typeck.c
===================================================================
--- cp/typeck.c (revision 213573)
+++ cp/typeck.c (working copy)
@@ -4353,12 +4353,11 @@ cp_build_binary_op (location_t location,
&& (code1 == INTEGER_TYPE || code1 == REAL_TYPE
|| code1 == COMPLEX_TYPE || code1 == ENUMERAL_TYPE))
short_compare = 1;
- else if ((code0 == POINTER_TYPE && code1 == POINTER_TYPE)
- || (TYPE_PTRDATAMEM_P (type0) && TYPE_PTRDATAMEM_P (type1)))
- result_type = composite_pointer_type (type0, type1, op0, op1,
- CPO_COMPARISON, complain);
else if ((code0 == POINTER_TYPE || TYPE_PTRDATAMEM_P (type0))
- && null_ptr_cst_p (op1))
+ && (null_ptr_cst_p (op1)
+ /* Handle (void*)0 too. */
+ || (TYPE_PTR_P (type1) && VOID_TYPE_P (TREE_TYPE (type1))
+ && integer_zerop (op1))))
{
if (TREE_CODE (op0) == ADDR_EXPR
&& decl_with_nonnull_addr_p (TREE_OPERAND (op0, 0)))
@@ -4371,7 +4370,10 @@ cp_build_binary_op (location_t location,
result_type = type0;
}
else if ((code1 == POINTER_TYPE || TYPE_PTRDATAMEM_P (type1))
- && null_ptr_cst_p (op0))
+ && (null_ptr_cst_p (op0)
+ /* Handle (void*)0 too. */
+ || (TYPE_PTR_P (type0) && VOID_TYPE_P (TREE_TYPE (type0))
+ && integer_zerop (op0))))
{
if (TREE_CODE (op1) == ADDR_EXPR
&& decl_with_nonnull_addr_p (TREE_OPERAND (op1, 0)))
@@ -4383,6 +4385,10 @@ cp_build_binary_op (location_t location,
}
result_type = type1;
}
+ else if ((code0 == POINTER_TYPE && code1 == POINTER_TYPE)
+ || (TYPE_PTRDATAMEM_P (type0) && TYPE_PTRDATAMEM_P (type1)))
+ result_type = composite_pointer_type (type0, type1, op0, op1,
+ CPO_COMPARISON, complain);
else if (null_ptr_cst_p (op0) && null_ptr_cst_p (op1))
/* One of the operands must be of nullptr_t type. */
result_type = TREE_TYPE (nullptr_node);
Index: testsuite/g++.dg/warn/Waddress-1.C
===================================================================
--- testsuite/g++.dg/warn/Waddress-1.C (revision 0)
+++ testsuite/g++.dg/warn/Waddress-1.C (working copy)
@@ -0,0 +1,7 @@
+// PR c++/43906
+// { dg-options "-Waddress" }
+
+extern void z();
+void f() { if ( z ) z(); } // { dg-warning "address" }
+void g() { if ( z != 0 ) z(); } // { dg-warning "address" }
+void h() { if ( z != (void*)0 ) z(); } // { dg-warning "address" }
