6591e42269
Adds __cpp_lib_atomic_wait feature test macro which was overlooked in the initial commit of this feature. Replaces uses of _GLIBCXX_HAVE_ATOMIC_WAIT. libstdc++-v3/ChangeLog: * include/bits/atomic_base.h: Replace usage of _GLIBCXX_HAVE_ATOMIC_WAIT with __cpp_lib_atomic_wait. * include/bits/atomic_timed_wait.h: Likewise. * include/bits/atomic_wait.h: Define __cpp_lib_atomic_wait feature test macro. * include/bits/semaphore_base.h: Replace usage of _GLIBCXX_HAVE_ATOMIC_WAIT with __cpp_lib_atomic_wait. * include/std/atomic: Likewise. * include/std/latch: Likewise. * include/std/semaphore: Likewise. * include/std/version: Define __cpp_lib_atomic wait feature test macro and replace usage of _GLIBCXX_HAVE_ATOMIC_WAIT. * testsuite/29_atomics/atomic/wait_notify/1.cc: New test. * testsuite/29_atomics/atomic/wait_notify/2.cc: Likewise.
94 lines
2.6 KiB
C++
94 lines
2.6 KiB
C++
// <latch> -*- C++ -*-
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// Copyright (C) 2020 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/** @file include/latch
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* This is a Standard C++ Library header.
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*/
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#ifndef _GLIBCXX_LATCH
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#define _GLIBCXX_LATCH 1
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#pragma GCC system_header
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#if __cplusplus > 201703L
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#include <bits/atomic_base.h>
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#include <ext/numeric_traits.h>
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#if __cpp_lib_atomic_wait
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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#define __cpp_lib_latch 201907L
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class latch
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{
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public:
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static constexpr ptrdiff_t
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max() noexcept
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{ return __gnu_cxx::__int_traits<ptrdiff_t>::__max; }
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constexpr explicit latch(ptrdiff_t __expected) noexcept
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: _M_a(__expected) { }
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~latch() = default;
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latch(const latch&) = delete;
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latch& operator=(const latch&) = delete;
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_GLIBCXX_ALWAYS_INLINE void
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count_down(ptrdiff_t __update = 1)
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{
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auto const __old = __atomic_impl::fetch_sub(&_M_a,
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__update, memory_order::release);
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if (__old == __update)
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__atomic_impl::notify_all(&_M_a);
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}
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_GLIBCXX_ALWAYS_INLINE bool
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try_wait() const noexcept
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{ return __atomic_impl::load(&_M_a, memory_order::acquire) == 0; }
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_GLIBCXX_ALWAYS_INLINE void
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wait() const noexcept
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{
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auto const __old = __atomic_impl::load(&_M_a, memory_order::acquire);
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std::__atomic_wait(&_M_a, __old, [this] { return this->try_wait(); });
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}
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_GLIBCXX_ALWAYS_INLINE void
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arrive_and_wait(ptrdiff_t __update = 1) noexcept
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{
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count_down(__update);
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wait();
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}
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private:
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alignas(__alignof__(ptrdiff_t)) ptrdiff_t _M_a;
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};
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace
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#endif // __cpp_lib_atomic_wait
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#endif // __cplusplus > 201703L
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#endif // _GLIBCXX_LATCH
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