PR69301 don't assume atomic<T> can default construct T

Backport from mainline
2017-01-18  Jonathan Wakely  <jwakely@redhat.com>

	PR libstdc++/69301
	* include/std/atomic (atomic<T>::load, atomic<T>::exchange): Use
	aligned buffer instead of default-initialized variable.
	* testsuite/29_atomics/atomic/69301.cc: New test.
	* include/ext/pointer.h (_Pointer_adapter::operator++(int))
	(_Pointer_adapter::operator--(int)): Likewise.

From-SVN: r245457

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 83aa39b1d93738bcea41719596508765a4cf832b..af2007343cdd4fa0a42ed896069089cb1f67c319 100644 (file)
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,15 @@
 2017-02-14  Jonathan Wakely  <jwakely@redhat.com>
 
+       Backport from mainline
+       2017-01-18  Jonathan Wakely  <jwakely@redhat.com>
+
+       PR libstdc++/69301
+       * include/std/atomic (atomic<T>::load, atomic<T>::exchange): Use
+       aligned buffer instead of default-initialized variable.
+       * testsuite/29_atomics/atomic/69301.cc: New test.
+       * include/ext/pointer.h (_Pointer_adapter::operator++(int))
+       (_Pointer_adapter::operator--(int)): Likewise.
+
        Backport from mainline
        2017-01-16  Jonathan Wakely  <jwakely@redhat.com>
 

diff --git a/libstdc++-v3/include/ext/pointer.h b/libstdc++-v3/include/ext/pointer.h
index fdd07685541fb8dc5d921fec09dee022519b4031..30f59d4f55e0da04feda0f7125a8a1cb57b1f8ec 100644 (file)
--- a/libstdc++-v3/include/ext/pointer.h
+++ b/libstdc++-v3/include/ext/pointer.h
@@ -449,9 +449,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       inline _Pointer_adapter 
       operator++(int)
       {
-        _Pointer_adapter tmp(*this);
+        _Pointer_adapter __tmp(*this);
         _Storage_policy::set(_Storage_policy::get() + 1);
-        return tmp;
+        return __tmp;
       }
   
       inline _Pointer_adapter& 
@@ -464,9 +464,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       inline _Pointer_adapter
       operator--(int) 
       {
-        _Pointer_adapter tmp(*this);
+        _Pointer_adapter __tmp(*this);
         _Storage_policy::set(_Storage_policy::get() - 1);
-        return tmp;
+        return __tmp;
       }
   
     }; // class _Pointer_adapter

diff --git a/libstdc++-v3/include/std/atomic b/libstdc++-v3/include/std/atomic
index cdd1f0b992d436efcb09386ebf6689852802e6ba..8d848297fd94c689af8f67c78fe18541ccc28f1f 100644 (file)
--- a/libstdc++-v3/include/std/atomic
+++ b/libstdc++-v3/include/std/atomic
@@ -230,35 +230,39 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       _Tp
       load(memory_order __m = memory_order_seq_cst) const noexcept
-      { 
-        _Tp tmp;
-       __atomic_load(&_M_i, &tmp, __m);
-       return tmp;
+      {
+       alignas(_Tp) unsigned char __buf[sizeof(_Tp)];
+       _Tp* __ptr = reinterpret_cast<_Tp*>(__buf);
+       __atomic_load(&_M_i, __ptr, __m);
+       return *__ptr;
       }
 
       _Tp
       load(memory_order __m = memory_order_seq_cst) const volatile noexcept
-      { 
-        _Tp tmp;
-       __atomic_load(&_M_i, &tmp, __m);
-       return tmp;
+      {
+        alignas(_Tp) unsigned char __buf[sizeof(_Tp)];
+       _Tp* __ptr = reinterpret_cast<_Tp*>(__buf);
+       __atomic_load(&_M_i, __ptr, __m);
+       return *__ptr;
       }
 
       _Tp
       exchange(_Tp __i, memory_order __m = memory_order_seq_cst) noexcept
-      { 
-        _Tp tmp;
-       __atomic_exchange(&_M_i, &__i, &tmp, __m);
-       return tmp;
+      {
+        alignas(_Tp) unsigned char __buf[sizeof(_Tp)];
+       _Tp* __ptr = reinterpret_cast<_Tp*>(__buf);
+       __atomic_exchange(&_M_i, &__i, __ptr, __m);
+       return *__ptr;
       }
 
       _Tp
       exchange(_Tp __i, 
               memory_order __m = memory_order_seq_cst) volatile noexcept
-      { 
-        _Tp tmp;
-       __atomic_exchange(&_M_i, &__i, &tmp, __m);
-       return tmp;
+      {
+        alignas(_Tp) unsigned char __buf[sizeof(_Tp)];
+       _Tp* __ptr = reinterpret_cast<_Tp*>(__buf);
+       __atomic_exchange(&_M_i, &__i, __ptr, __m);
+       return *__ptr;
       }
 
       bool

diff --git a/libstdc++-v3/testsuite/29_atomics/atomic/69301.cc b/libstdc++-v3/testsuite/29_atomics/atomic/69301.cc
new file mode 100644 (file)
index 0000000..fb31a19
--- /dev/null
+++ b/libstdc++-v3/testsuite/29_atomics/atomic/69301.cc
@@ -0,0 +1,57 @@
+// Copyright (C) 2017 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-require-atomic-builtins "" }
+
+#include <atomic>
+#include <testsuite_hooks.h>
+
+struct NonDefaultConstructible
+{
+  NonDefaultConstructible(int i) : val(i) { }
+  int val;
+};
+
+template class std::atomic<NonDefaultConstructible>;
+
+void
+test01()
+{
+  std::atomic<NonDefaultConstructible> a(1);
+  const auto n1 = a.exchange(2);
+  VERIFY( n1.val == 1 );
+  const auto n2 = a.load();
+  VERIFY( n2.val == 2 );
+}
+
+void
+test02()
+{
+  volatile std::atomic<NonDefaultConstructible> a(1);
+  const auto n1 = a.exchange(2);
+  VERIFY( n1.val == 1 );
+  const auto n2 = a.load();
+  VERIFY( n2.val == 2 );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+}