On Thu, Feb 18, 2016 at 10:45:46PM +0100, Jakub Jelinek wrote:
> 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?
Here is the variant with NE_EXPR, it works on *nonnull* tests, haven't
tested it more yet, but will overnight.
Personally I think this is better, because folding wants to canonicalize
the COND_EXPR with EQ_EXPR and no code in the then branch to NE_EXPR
with no code in the else branch, so it means we waste some more GC memory.
2016-02-18 Jakub Jelinek <ja...@redhat.com>
PR c++/69850
* rtti.c (ifnonnull): Set TREE_NO_WARNING on the condition, use
NE_EXPR instead of EQ_EXPR and swap last two arguments on COND_EXPR.
* 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 22:47:04.023079812 +0100
@@ -507,12 +507,13 @@ 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)),
- cp_convert (TREE_TYPE (result), nullptr_node, complain),
- result);
+ tree cond = build2 (NE_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, result,
+ cp_convert (TREE_TYPE (result), nullptr_node, complain));
}
/* Execute a dynamic cast, as described in section 5.2.6 of the 9/93 working
--- 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
