From 84a3423b97784ba86bcb37efb39fd528de3671cb Mon Sep 17 00:00:00 2001
From: Nathan Sidwell <nathan@acm.org>
Date: Sat, 23 May 2015 22:28:54 +0000
Subject: re PR c++/65936 (ICE: canonical types differ for identical types)

	cp/
	PR c++/65936
	* pt.c (lookup_template_class_1): Copy may_alias attribute too.

	testsuite/
	PR c++/65936
	* g++.dg/template/pr65936.C: New.

From-SVN: r223613
---
 gcc/cp/ChangeLog                        |  5 +++++
 gcc/cp/pt.c                             | 17 ++++++++++++-----
 gcc/testsuite/ChangeLog                 |  5 +++++
 gcc/testsuite/g++.dg/template/pr65936.C | 21 +++++++++++++++++++++
 4 files changed, 43 insertions(+), 5 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/pr65936.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 7c9b77e..35d5f34 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2015-05-23  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/65936
+	* pt.c (lookup_template_class_1): Copy may_alias attribute too.
+
 2015-05-22  Jim Wilson  <jim.wilson@linaro.org>
 
 	* Make-lang.in (check_g++_parallelize): Update comment.
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 407ef7d..a0c5d7c 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -7905,15 +7905,22 @@ lookup_template_class_1 (tree d1, tree arglist, tree in_decl, tree context,
       if (OVERLOAD_TYPE_P (t)
 	  && !DECL_ALIAS_TEMPLATE_P (gen_tmpl))
 	{
-	  if (tree attributes
-	      = lookup_attribute ("abi_tag", TYPE_ATTRIBUTES (template_type)))
+	  static const char *tags[] = {"abi_tag", "may_alias"};
+
+	  for (unsigned ix = 0; ix != 2; ix++)
 	    {
-	      if (!TREE_CHAIN (attributes))
+	      tree attributes
+		= lookup_attribute (tags[ix], TYPE_ATTRIBUTES (template_type));
+
+	      if (!attributes)
+		;
+	      else if (!TREE_CHAIN (attributes) && !TYPE_ATTRIBUTES (t))
 		TYPE_ATTRIBUTES (t) = attributes;
 	      else
 		TYPE_ATTRIBUTES (t)
-		  = build_tree_list (TREE_PURPOSE (attributes),
-				     TREE_VALUE (attributes));
+		  = tree_cons (TREE_PURPOSE (attributes),
+			       TREE_VALUE (attributes),
+			       TYPE_ATTRIBUTES (t));
 	    }
 	}
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index fe5d962..e302f01 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2015-05-23  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/65936
+	* g++.dg/template/pr65936.C: New.
+
 2015-05-22  Marc Glisse  <marc.glisse@inria.fr>
 
 	PR tree-optimization/63387
diff --git a/gcc/testsuite/g++.dg/template/pr65936.C b/gcc/testsuite/g++.dg/template/pr65936.C
new file mode 100644
index 0000000..afa2276
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/pr65936.C
@@ -0,0 +1,21 @@
+// checking ICE in canonical typing
+
+class A;
+
+template <typename> struct B
+{
+  typedef A type;
+};
+
+template <class T> class C
+  : public B<T>::type
+{
+} __attribute__ ((__may_alias__));
+
+class A
+{
+  operator const C<int> &()
+  {
+    return *static_cast<const C<int> *> (this);
+  }
+};
-- 
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