From 17de482e081eca52da08628b5fe276d419bc03a8 Mon Sep 17 00:00:00 2001
From: jason <jason@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Thu, 25 Feb 2016 14:09:18 +0000
Subject: [PATCH] 	PR c++/68049 	* tree.c (strip_typedefs): Use
 DECL_ORIGINAL_TYPE.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@233715 138bc75d-0d04-0410-961f-82ee72b054a4
---
 gcc/cp/ChangeLog                                 |  5 +++++
 gcc/cp/tree.c                                    | 10 +++++++++-
 gcc/testsuite/g++.dg/ext/attribute-may-alias-3.C | 22 ++++++++++++++++++++++
 3 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/ext/attribute-may-alias-3.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 3ae4daf..eb5cfe6 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2016-02-25  Jason Merrill  <jason@redhat.com>
+
+	PR c++/68049
+	* tree.c (strip_typedefs): Use DECL_ORIGINAL_TYPE.
+
 2016-02-25  Patrick Palka  <ppalka@gcc.gnu.org>
 
 	PR c++/69736
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 0f7287a..ac38ce3 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -1447,7 +1447,15 @@ strip_typedefs (tree t, bool *remove_attributes)
     }
 
   if (!result)
-      result = TYPE_MAIN_VARIANT (t);
+    {
+      if (typedef_variant_p (t))
+	/* Explicitly get the underlying type, as TYPE_MAIN_VARIANT doesn't
+	   strip typedefs with attributes.  */
+	result = TYPE_MAIN_VARIANT (DECL_ORIGINAL_TYPE (TYPE_NAME (t)));
+      else
+	result = TYPE_MAIN_VARIANT (t);
+    }
+  gcc_assert (!typedef_variant_p (result));
   if (TYPE_USER_ALIGN (t) != TYPE_USER_ALIGN (result)
       || TYPE_ALIGN (t) != TYPE_ALIGN (result))
     {
diff --git a/gcc/testsuite/g++.dg/ext/attribute-may-alias-3.C b/gcc/testsuite/g++.dg/ext/attribute-may-alias-3.C
new file mode 100644
index 0000000..ba6091b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/attribute-may-alias-3.C
@@ -0,0 +1,22 @@
+// PR c++/68049
+// { dg-do compile { target c++11 } }
+
+template <typename T> struct Bar
+{
+    using type = T;
+};
+template <typename T> struct Foo
+{
+    typedef typename Bar<T>::type alias_type [[gnu::may_alias]];
+
+    alias_type operator()() { return {}; }
+};
+
+template <typename T> void print(T) {}
+
+int main()
+{
+    print(Foo<int>()());
+    print(0);
+    return 0;
+}
-- 
2.7.4