re PR libstdc++/60695 (std::atomic<X> doesn't work when X is of zero size)

	PR libstdc++/60695
	* include/std/atomic (atomic<_Tp>): Add static assertion.
	* testsuite/29_atomics/atomic/60695.cc: New.

From-SVN: r209418

libstdc++-v3/ChangeLog

@@ -3,6 +3,10 @@
 	PR libstdc++/60734
 	* include/bits/stl_tree.h (_Rb_tree::_M_end): Fix invalid cast.
 
+	PR libstdc++/60695
+	* include/std/atomic (atomic<_Tp>): Add static assertion.
+	* testsuite/29_atomics/atomic/60695.cc: New.
+
 2014-04-14  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/bits/stl_vector.h (_Vector_base::_Vector_impl,

libstdc++-v3/include/std/atomic

@@ -163,6 +163,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     private:
       _Tp _M_i;
 
+      // TODO: static_assert(is_trivially_copyable<_Tp>::value, "");
+
+      static_assert(sizeof(_Tp) > 0,
+		    "Incomplete or zero-sized types are not supported");
+
     public:
       atomic() noexcept = default;
       ~atomic() noexcept = default;

libstdc++-v3/testsuite/29_atomics/atomic/60695.cc

+// { dg-require-atomic-builtins "" }
+// { dg-options "-std=gnu++11" }
+// { dg-do compile }
+
+// Copyright (C) 2014 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/>.
+
+#include <atomic>
+
+// libstdc++/60695
+
+struct X {
+  char stuff[0]; // GNU extension, type has zero size
+};
+
+std::atomic<X> a;  // { dg-error "not supported" "" { target *-*-* } 168 }