From: Jonathan Wakely <jwakely@redhat.com>
Date: Tue, 14 Feb 2017 21:17:29 +0000 (+0000)
Subject: PR69301 don't assume atomic<T> can default construct T
X-Git-Tag: releases/gcc-5.5.0~521
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c990e075093b426e2aad975ee2591f1bb855e9f0;p=thirdparty%2Fgcc.git

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 83aa39b1d937..af2007343cdd 100644
--- 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 fdd07685541f..30f59d4f55e0 100644
--- 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 cdd1f0b992d4..8d848297fd94 100644
--- 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
index 000000000000..fb31a19af710
--- /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();
+}