3d7586b760
The C++ standard says it must, but some badly-configured toolchains seem to be lacking support. In particular, for some 32-bit platforms without native support for them, GCC implements 64-bit atomics via out-of-line functions in libatomic. If that library is missing... well, then std::atomic 64-bit doesn't work and we mustn't try to use it. This was found when trying to compile Qt 5.6 for MIPS 32-bit: Linking library libQt5Core.so.5.6.0 .obj/qsimd.o: In function `std::__atomic_base<unsigned long long>::load(std::memory_order) const': /opt/poky/1.7/sysroots/mips32r2-poky-linux/usr/include/c++/4.9.1/bits/atomic_base.h:500: undefined reference to `__atomic_load_8' .obj/qsimd.o: In function `std::__atomic_base<unsigned long long>::store(unsigned long long, std::memory_order)': /opt/poky/1.7/sysroots/mips32r2-poky-linux/usr/include/c++/4.9.1/bits/atomic_base.h:478: undefined reference to `__atomic_store_8' Yocto bug report: https://bugzilla.yoctoproject.org/show_bug.cgi?id=8274 Change-Id: I42e7ef1a481840699a8dffff140224d6614e5c36 Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com> Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com> Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
55 lines
2.1 KiB
C++
55 lines
2.1 KiB
C++
/****************************************************************************
|
|
**
|
|
** Copyright (C) 2015 Intel Corporation.
|
|
** Contact: http://www.qt.io/licensing/
|
|
**
|
|
** This file is part of the FOO module of the Qt Toolkit.
|
|
**
|
|
** $QT_BEGIN_LICENSE:LGPL21$
|
|
** Commercial License Usage
|
|
** Licensees holding valid commercial Qt licenses may use this file in
|
|
** accordance with the commercial license agreement provided with the
|
|
** Software or, alternatively, in accordance with the terms contained in
|
|
** a written agreement between you and The Qt Company. For licensing terms
|
|
** and conditions see http://www.qt.io/terms-conditions. For further
|
|
** information use the contact form at http://www.qt.io/contact-us.
|
|
**
|
|
** GNU Lesser General Public License Usage
|
|
** Alternatively, this file may be used under the terms of the GNU Lesser
|
|
** General Public License version 2.1 or version 3 as published by the Free
|
|
** Software Foundation and appearing in the file LICENSE.LGPLv21 and
|
|
** LICENSE.LGPLv3 included in the packaging of this file. Please review the
|
|
** following information to ensure the GNU Lesser General Public License
|
|
** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
|
|
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
|
|
**
|
|
** As a special exception, The Qt Company gives you certain additional
|
|
** rights. These rights are described in The Qt Company LGPL Exception
|
|
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
|
|
**
|
|
** $QT_END_LICENSE$
|
|
**
|
|
****************************************************************************/
|
|
|
|
#include <atomic>
|
|
#include <cstdint>
|
|
|
|
void test(volatile std::atomic<std::int64_t> &a)
|
|
{
|
|
std::int64_t v = a.load(std::memory_order_acquire);
|
|
while (!a.compare_exchange_strong(v, v + 1,
|
|
std::memory_order_acq_rel,
|
|
std::memory_order_acquire)) {
|
|
v = a.exchange(v - 1);
|
|
}
|
|
|
|
a.store(v + 1, std::memory_order_release);
|
|
}
|
|
|
|
int main(int, char **)
|
|
{
|
|
void *ptr = (void*)0xffffffc0; // any random pointer
|
|
test(*reinterpret_cast<std::atomic<std::int64_t> *>(ptr));
|
|
return 0;
|
|
}
|