The fix for 65168 didn't check c_inhibit_evaluation_warnings, which
means getting warnings about comparing the address of a reference to
NULL in places where we aren't actually interested in the value. This
patch corrects that, but this lead to some regressions because
cp_truthvalue_conversion was inappropriately setting that flag to
avoid -Wzero-as-null-pointer-constant warnings. So now we avoid those
warnings by comparing to nullptr rather than 0.
Tested x86_64-cp-linux-gnu, applying to trunk.
commit e274607c02db6d92af948b670cb90d4af452aa77
Author: Jason Merrill <ja...@redhat.com>
Date: Wed Jul 20 12:03:48 2016 -0400
PR c++/65168 - -Waddress in unevaluated context.
gcc/c-family/
* c-common.c (c_common_truthvalue_conversion): Check
c_inhibit_evaluation_warnings for warning about address of
reference.
gcc/cp/
* typeck.c (cp_truthvalue_conversion): Compare pointers to nullptr.
Don't set c_inhibit_evaluation_warnings.
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 936ddfb..9900e93 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -4551,6 +4551,7 @@ c_common_truthvalue_conversion (location_t location, tree
expr)
tree fromtype = TREE_TYPE (TREE_OPERAND (expr, 0));
if (POINTER_TYPE_P (totype)
+ && !c_inhibit_evaluation_warnings
&& TREE_CODE (fromtype) == REFERENCE_TYPE)
{
tree inner = expr;
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index f9e45ee..d4bfb11 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -5459,21 +5459,10 @@ tree
cp_truthvalue_conversion (tree expr)
{
tree type = TREE_TYPE (expr);
- if (TYPE_PTRDATAMEM_P (type)
+ if (TYPE_PTR_OR_PTRMEM_P (type)
/* Avoid ICE on invalid use of non-static member function. */
|| TREE_CODE (expr) == FUNCTION_DECL)
- return build_binary_op (EXPR_LOCATION (expr),
- NE_EXPR, expr, nullptr_node, 1);
- else if (TYPE_PTR_P (type) || TYPE_PTRMEMFUNC_P (type))
- {
- /* With -Wzero-as-null-pointer-constant do not warn for an
- 'if (p)' or a 'while (!p)', where p is a pointer. */
- tree ret;
- ++c_inhibit_evaluation_warnings;
- ret = c_common_truthvalue_conversion (input_location, expr);
- --c_inhibit_evaluation_warnings;
- return ret;
- }
+ return build_binary_op (input_location, NE_EXPR, expr, nullptr_node, 1);
else
return c_common_truthvalue_conversion (input_location, expr);
}
diff --git a/gcc/testsuite/g++.dg/warn/Waddress-3.C
b/gcc/testsuite/g++.dg/warn/Waddress-3.C
new file mode 100644
index 0000000..13d7cd2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Waddress-3.C
@@ -0,0 +1,14 @@
+// PR c++/65168
+// { dg-do compile { target c++11 } }
+// { dg-options -Waddress }
+// We shouldn't warn in unevaluated context about the address of a reference
+// always being true.
+
+template <class T, class U>
+auto f(U&& u) -> decltype(T(u)) { }
+
+int main()
+{
+ bool ar[4];
+ f<bool>(ar);
+}
diff --git a/gcc/testsuite/g++.dg/warn/Walways-true-1.C
b/gcc/testsuite/g++.dg/warn/Walways-true-1.C
index ae6f9dc..48b9f72 100644
--- a/gcc/testsuite/g++.dg/warn/Walways-true-1.C
+++ b/gcc/testsuite/g++.dg/warn/Walways-true-1.C
@@ -12,19 +12,19 @@ void
bar (int a)
{
lab:
- if (foo) // { dg-warning "always evaluate as" "correct warning" }
+ if (foo) // { dg-warning "always evaluate as|never be NULL" "correct
warning" }
foo (0);
if (foo (1))
;
- if (&i) // { dg-warning "always evaluate as" "correct warning" }
+ if (&i) // { dg-warning "always evaluate as|never be NULL" "correct
warning" }
foo (2);
if (i)
foo (3);
- if (&a) // { dg-warning "always evaluate as" "correct warning" }
+ if (&a) // { dg-warning "always evaluate as|never be NULL" "correct
warning" }
foo (4);
if (a)
foo (5);
- if (&&lab) // { dg-warning "always evaluate as" "correct warning" }
+ if (&&lab) // { dg-warning "always evaluate as|never be NULL" "correct
warning" }
foo (6);
if (foo == 0) // { dg-warning "never be NULL" "correct warning" }
foo (7);
diff --git a/gcc/testsuite/g++.dg/warn/Walways-true-2.C
b/gcc/testsuite/g++.dg/warn/Walways-true-2.C
index f157347..e4b5713 100644
--- a/gcc/testsuite/g++.dg/warn/Walways-true-2.C
+++ b/gcc/testsuite/g++.dg/warn/Walways-true-2.C
@@ -23,11 +23,11 @@ bar (int a)
foo (2);
if (i)
foo (3);
- if (&a) // { dg-warning "always evaluate as" "correct warning" }
+ if (&a) // { dg-warning "always evaluate as|never be NULL" "correct
warning" }
foo (4);
if (a)
foo (5);
- if (&&lab) // { dg-warning "always evaluate as" "correct warning" }
+ if (&&lab) // { dg-warning "always evaluate as|never be NULL" "correct
warning" }
foo (6);
if (foo == 0)
foo (7);
