PATCH to disable the canonical types check in verify_type (PR c++/70029)

[Marek Polacek]

Looking at this PR again, seems we have reached conclusion that the way forward
for GCC 6 is to temporarily disable the check, so I'm posting a patch for that,
so as to finally resolve this PR.  The problem is that the C++ FE violates the
check when it sets FUNCTION_*_QUALIFIED flags.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2016-04-14  Marek Polacek  <polacek@redhat.com>
	    Jan Hubicka  <hubicka@ucw.cz>

	PR c++/70029
	* tree.c (verify_type): Disable the canonical type of main variant
	check.

	* g++.dg/torture/pr70029.C: New test.

diff --git gcc/testsuite/g++.dg/torture/pr70029.C gcc/testsuite/g++.dg/torture/pr70029.C
index e69de29..9592f0c 100644
--- gcc/testsuite/g++.dg/torture/pr70029.C
+++ gcc/testsuite/g++.dg/torture/pr70029.C
@@ -0,0 +1,12 @@
+// PR c++/70029
+// { dg-do compile }
+// { dg-options "-std=c++11 -g -flto" }
+// { dg-require-effective-target lto }
+
+struct A
+{
+  A();
+  int foo() && __attribute__ ((__warn_unused_result__)) { return 0; }
+};
+
+A a;
diff --git gcc/tree.c gcc/tree.c
index ed28429..c64d720 100644
--- gcc/tree.c
+++ gcc/tree.c
@@ -13584,7 +13584,9 @@ verify_type (const_tree t)
       debug_tree (ct);
       error_found = true;
     }
-  if (TYPE_MAIN_VARIANT (t) == t && ct && TYPE_MAIN_VARIANT (ct) != ct)
+  /* FIXME: this is violated by the C++ FE as discussed in PR70029, when
+     FUNCTION_*_QUALIFIED flags are set.  */
+  if (0 && TYPE_MAIN_VARIANT (t) == t && ct && TYPE_MAIN_VARIANT (ct) != ct)
    {
       error ("TYPE_CANONICAL of main variant is not main variant");
       debug_tree (ct);

	Marek