This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
[C++ PATCH] Fix -Wnonnull-compare warning from dynamic_cast <...> (this) (PR c++/69850)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Jason Merrill <jason at redhat dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Thu, 18 Feb 2016 22:45:46 +0100
- Subject: [C++ PATCH] Fix -Wnonnull-compare warning from dynamic_cast <...> (this) (PR c++/69850)
- Authentication-results: sourceware.org; auth=none
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
And here is a fix for the dynamic_cast issue I've mentioned recently.
Alternatively, ifnonnull could build instead NE_EXPR with swapped last
two arguments on the COND_EXPR, and then I believe the cp_fold change would
not be needed.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Or do you prefer the NE_EXPR variant?
2016-02-18 Jakub Jelinek <jakub@redhat.com>
PR c++/69850
* rtti.c (ifnonnull): Set TREE_NO_WARNING on the EQ_EXPR
condition.
* cp-gimplify.c (cp_fold) <case COND_EXPR>: Preserve
TREE_NO_WARNING on comparison if folding swaps arguments.
* g++.dg/warn/Wnonnull-compare-4.C: New test.
--- gcc/cp/rtti.c.jj 2016-02-11 10:50:58.000000000 +0100
+++ gcc/cp/rtti.c 2016-02-18 18:04:24.611297291 +0100
@@ -507,10 +507,12 @@ get_typeid (tree type, tsubst_flags_t co
static tree
ifnonnull (tree test, tree result, tsubst_flags_t complain)
{
- return build3 (COND_EXPR, TREE_TYPE (result),
- build2 (EQ_EXPR, boolean_type_node, test,
- cp_convert (TREE_TYPE (test), nullptr_node,
- complain)),
+ tree cond = build2 (EQ_EXPR, boolean_type_node, test,
+ cp_convert (TREE_TYPE (test), nullptr_node, complain));
+ /* This is a compiler generated comparison, don't emit
+ e.g. -Wnonnull-compare warning for it. */
+ TREE_NO_WARNING (cond) = 1;
+ return build3 (COND_EXPR, TREE_TYPE (result), cond,
cp_convert (TREE_TYPE (result), nullptr_node, complain),
result);
}
--- gcc/cp/cp-gimplify.c.jj 2016-02-18 11:20:08.000000000 +0100
+++ gcc/cp/cp-gimplify.c 2016-02-18 18:14:26.213996843 +0100
@@ -2101,6 +2101,11 @@ cp_fold (tree x)
else
x = fold (x);
+ if (COMPARISON_CLASS_P (TREE_OPERAND (org_x, 0))
+ && TREE_NO_WARNING (TREE_OPERAND (org_x, 0))
+ && TREE_CODE (x) == TREE_CODE (org_x)
+ && COMPARISON_CLASS_P (TREE_OPERAND (x, 0)))
+ TREE_NO_WARNING (TREE_OPERAND (x, 0)) = 1;
break;
case CALL_EXPR:
--- gcc/testsuite/g++.dg/warn/Wnonnull-compare-4.C.jj 2016-02-18 18:03:04.777398778 +0100
+++ gcc/testsuite/g++.dg/warn/Wnonnull-compare-4.C 2016-02-18 18:02:46.414652133 +0100
@@ -0,0 +1,14 @@
+// PR c++/69850
+// { dg-do compile }
+// { dg-options "-Wnonnull-compare" }
+
+struct A { virtual ~A (); int foo (); };
+struct B { virtual ~B () { } };
+struct C : B, A { };
+
+int
+A::foo ()
+{
+ C *c = dynamic_cast<C *> (this); // { dg-bogus "nonnull argument" }
+ return !c;
+}
Jakub