commit d0ccfb0523066c69f3d22d9cdd617a139c57f9e1
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Mar 30 14:28:01 2015 +0100

    	PR libstdc++/65147
    	* include/bits/atomic_base.h (__atomic_base): Align as underlying
    	type.
    	* include/std/atomic (atomic<T>): Hardcode alignment for 16-byte
    	types when __int128 is not available.
    	* testsuite/29_atomics/atomic/60695.cc: Adjust dg-error line number.
    	* testsuite/29_atomics/atomic/65147.cc: New.

diff --git a/libstdc++-v3/include/bits/atomic_base.h b/libstdc++-v3/include/bits/atomic_base.h
index 8104c98..48931ac 100644
--- a/libstdc++-v3/include/bits/atomic_base.h
+++ b/libstdc++-v3/include/bits/atomic_base.h
@@ -235,7 +235,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // 8 bytes, since that is what GCC built-in functions for atomic
   // memory access expect.
   template<typename _ITp>
-    struct __atomic_base
+    struct alignas(_ITp) __atomic_base
     {
     private:
       typedef _ITp 	__int_type;
@@ -559,7 +559,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   /// Partial specialization for pointer types.
   template<typename _PTp>
-    struct __atomic_base<_PTp*>
+    struct alignas(_PTp*) __atomic_base<_PTp*>
     {
     private:
       typedef _PTp* 	__pointer_type;
diff --git a/libstdc++-v3/include/std/atomic b/libstdc++-v3/include/std/atomic
index 88c8b17..2b09477 100644
--- a/libstdc++-v3/include/std/atomic
+++ b/libstdc++-v3/include/std/atomic
@@ -175,6 +175,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	: sizeof(_Tp) == sizeof(long long) ? alignof(long long)
 #ifdef _GLIBCXX_USE_INT128
 	: sizeof(_Tp) == sizeof(__int128)  ? alignof(__int128)
+#else
+	: sizeof(_Tp) == 16  ? 16
 #endif
 	: 0;
 
diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/60695.cc b/libstdc++-v3/testsuite/29_atomics/atomic/60695.cc
index 6f618a0..f755be0 100644
--- a/libstdc++-v3/testsuite/29_atomics/atomic/60695.cc
+++ b/libstdc++-v3/testsuite/29_atomics/atomic/60695.cc
@@ -27,4 +27,4 @@ struct X {
   char stuff[0]; // GNU extension, type has zero size
 };
 
-std::atomic<X> a;  // { dg-error "not supported" "" { target *-*-* } 189 }
+std::atomic<X> a;  // { dg-error "not supported" "" { target *-*-* } 191 }
diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/65147.cc b/libstdc++-v3/testsuite/29_atomics/atomic/65147.cc
new file mode 100644
index 0000000..bb92513
--- /dev/null
+++ b/libstdc++-v3/testsuite/29_atomics/atomic/65147.cc
@@ -0,0 +1,42 @@
+// Copyright (C) 2015 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++11" }
+// { dg-do compile }
+
+// PR libstdc++65147
+
+#include <atomic>
+
+static_assert( alignof(std::atomic<short>) == alignof(short),
+    "atomic short must be aligned like short" );
+
+static_assert( alignof(std::atomic<int>) == alignof(int),
+    "atomic int must be aligned like int" );
+
+static_assert( alignof(std::atomic<long>) == alignof(long),
+    "atomic long must be aligned like long" );
+
+static_assert( alignof(std::atomic<long long>) == alignof(long long),
+    "atomic long long must be aligned like long long" );
+
+struct S {
+  char s[16];
+};
+
+static_assert( alignof(std::atomic<S>) > 1,
+    "atomic 16-byte struct must not be aligned like char" );