[patch] fix libstdc++/60658

[Jonathan Wakely]

This fixes a simple thinko in the atomic<T*> partial specialization
that uses sizeof(T) instead of sizeof(T*).

It's a regression since 4.6 so I'm committing it to trunk and the 4.7
and 4.8 branches.

Tested x86_64-linux.



commit cb68113312d9702bd17af760c775697d2d57f94a
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Tue Mar 25 19:23:37 2014 +0000

        PR libstdc++/60658
        * include/bits/atomic_base.h (__atomic_base<_PTp*>::is_lock_free()):
        Use sizeof pointer type not the element type.
        * testsuite/29_atomics/atomic/60658.cc: New.

diff --git a/libstdc++-v3/include/bits/atomic_base.h 
b/libstdc++-v3/include/bits/atomic_base.h
index 7d2ba75..242459a 100644
--- a/libstdc++-v3/include/bits/atomic_base.h
+++ b/libstdc++-v3/include/bits/atomic_base.h
@@ -768,11 +768,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       bool
       is_lock_free() const noexcept
-      { return __atomic_is_lock_free(_M_type_size(1), nullptr); }
+      { return __atomic_is_lock_free(sizeof(__pointer_type), nullptr); }
 
       bool
       is_lock_free() const volatile noexcept
-      { return __atomic_is_lock_free(_M_type_size(1), nullptr); }
+      { return __atomic_is_lock_free(sizeof(__pointer_type), nullptr); }
 
       _GLIBCXX_ALWAYS_INLINE void
       store(__pointer_type __p,
diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/60658.cc 
b/libstdc++-v3/testsuite/29_atomics/atomic/60658.cc
new file mode 100644
index 0000000..5634085
--- /dev/null
+++ b/libstdc++-v3/testsuite/29_atomics/atomic/60658.cc
@@ -0,0 +1,43 @@
+// { dg-require-atomic-builtins "" }
+// { dg-options "-std=gnu++11" }
+
+// 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>
+#include <testsuite_hooks.h>
+
+// libstdc++/60658
+
+struct Foo {
+  char buf[1];
+};
+
+struct Bar {
+  char buf[100];
+};
+
+int
+main ()
+{
+  bool test __attribute__((unused)) = true;
+
+  std::atomic<Foo*> a;
+  std::atomic<Bar*> b;
+
+  VERIFY (a.is_lock_free() == b.is_lock_free());
+}