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337 lines
9.6 KiB
337 lines
9.6 KiB
// shared_ptr atomic access -*- C++ -*-
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// Copyright (C) 2014-2021 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 bits/shared_ptr_atomic.h
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* This is an internal header file, included by other library headers.
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* Do not attempt to use it directly. @headername{memory}
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*/
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#ifndef _SHARED_PTR_ATOMIC_H
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#define _SHARED_PTR_ATOMIC_H 1
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#include <bits/atomic_base.h>
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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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/**
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* @addtogroup pointer_abstractions
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* @{
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*/
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/// @relates shared_ptr @{
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/// @cond undocumented
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struct _Sp_locker
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{
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_Sp_locker(const _Sp_locker&) = delete;
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_Sp_locker& operator=(const _Sp_locker&) = delete;
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#ifdef __GTHREADS
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explicit
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_Sp_locker(const void*) noexcept;
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_Sp_locker(const void*, const void*) noexcept;
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~_Sp_locker();
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private:
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unsigned char _M_key1;
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unsigned char _M_key2;
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#else
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explicit _Sp_locker(const void*, const void* = nullptr) { }
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#endif
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};
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/// @endcond
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/**
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* @brief Report whether shared_ptr atomic operations are lock-free.
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* @param __p A non-null pointer to a shared_ptr object.
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* @return True if atomic access to @c *__p is lock-free, false otherwise.
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* @{
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*/
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template<typename _Tp, _Lock_policy _Lp>
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inline bool
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atomic_is_lock_free(const __shared_ptr<_Tp, _Lp>* __p)
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{
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#ifdef __GTHREADS
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return __gthread_active_p() == 0;
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#else
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return true;
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#endif
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}
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template<typename _Tp>
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inline bool
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atomic_is_lock_free(const shared_ptr<_Tp>* __p)
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{ return std::atomic_is_lock_free<_Tp, __default_lock_policy>(__p); }
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/// @}
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/**
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* @brief Atomic load for shared_ptr objects.
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* @param __p A non-null pointer to a shared_ptr object.
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* @return @c *__p
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*
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* The memory order shall not be @c memory_order_release or
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* @c memory_order_acq_rel.
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* @{
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*/
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template<typename _Tp>
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inline shared_ptr<_Tp>
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atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order)
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{
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_Sp_locker __lock{__p};
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return *__p;
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}
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template<typename _Tp>
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inline shared_ptr<_Tp>
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atomic_load(const shared_ptr<_Tp>* __p)
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{ return std::atomic_load_explicit(__p, memory_order_seq_cst); }
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template<typename _Tp, _Lock_policy _Lp>
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inline __shared_ptr<_Tp, _Lp>
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atomic_load_explicit(const __shared_ptr<_Tp, _Lp>* __p, memory_order)
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{
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_Sp_locker __lock{__p};
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return *__p;
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}
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template<typename _Tp, _Lock_policy _Lp>
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inline __shared_ptr<_Tp, _Lp>
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atomic_load(const __shared_ptr<_Tp, _Lp>* __p)
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{ return std::atomic_load_explicit(__p, memory_order_seq_cst); }
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/// @}
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/**
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* @brief Atomic store for shared_ptr objects.
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* @param __p A non-null pointer to a shared_ptr object.
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* @param __r The value to store.
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*
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* The memory order shall not be @c memory_order_acquire or
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* @c memory_order_acq_rel.
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* @{
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*/
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template<typename _Tp>
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inline void
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atomic_store_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r,
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memory_order)
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{
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_Sp_locker __lock{__p};
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__p->swap(__r); // use swap so that **__p not destroyed while lock held
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}
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template<typename _Tp>
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inline void
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atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
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{ std::atomic_store_explicit(__p, std::move(__r), memory_order_seq_cst); }
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template<typename _Tp, _Lock_policy _Lp>
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inline void
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atomic_store_explicit(__shared_ptr<_Tp, _Lp>* __p,
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__shared_ptr<_Tp, _Lp> __r,
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memory_order)
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{
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_Sp_locker __lock{__p};
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__p->swap(__r); // use swap so that **__p not destroyed while lock held
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}
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template<typename _Tp, _Lock_policy _Lp>
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inline void
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atomic_store(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp> __r)
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{ std::atomic_store_explicit(__p, std::move(__r), memory_order_seq_cst); }
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/// @}
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/**
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* @brief Atomic exchange for shared_ptr objects.
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* @param __p A non-null pointer to a shared_ptr object.
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* @param __r New value to store in @c *__p.
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* @return The original value of @c *__p
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* @{
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*/
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template<typename _Tp>
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inline shared_ptr<_Tp>
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atomic_exchange_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r,
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memory_order)
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{
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_Sp_locker __lock{__p};
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__p->swap(__r);
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return __r;
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}
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template<typename _Tp>
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inline shared_ptr<_Tp>
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atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
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{
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return std::atomic_exchange_explicit(__p, std::move(__r),
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memory_order_seq_cst);
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}
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template<typename _Tp, _Lock_policy _Lp>
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inline __shared_ptr<_Tp, _Lp>
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atomic_exchange_explicit(__shared_ptr<_Tp, _Lp>* __p,
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__shared_ptr<_Tp, _Lp> __r,
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memory_order)
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{
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_Sp_locker __lock{__p};
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__p->swap(__r);
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return __r;
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}
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template<typename _Tp, _Lock_policy _Lp>
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inline __shared_ptr<_Tp, _Lp>
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atomic_exchange(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp> __r)
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{
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return std::atomic_exchange_explicit(__p, std::move(__r),
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memory_order_seq_cst);
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}
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/// @}
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/**
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* @brief Atomic compare-and-swap for shared_ptr objects.
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* @param __p A non-null pointer to a shared_ptr object.
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* @param __v A non-null pointer to a shared_ptr object.
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* @param __w A non-null pointer to a shared_ptr object.
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* @return True if @c *__p was equivalent to @c *__v, false otherwise.
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*
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* The memory order for failure shall not be @c memory_order_release or
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* @c memory_order_acq_rel, or stronger than the memory order for success.
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* @{
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*/
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template<typename _Tp>
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bool
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atomic_compare_exchange_strong_explicit(shared_ptr<_Tp>* __p,
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shared_ptr<_Tp>* __v,
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shared_ptr<_Tp> __w,
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memory_order,
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memory_order)
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{
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shared_ptr<_Tp> __x; // goes out of scope after __lock
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_Sp_locker __lock{__p, __v};
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owner_less<shared_ptr<_Tp>> __less;
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if (*__p == *__v && !__less(*__p, *__v) && !__less(*__v, *__p))
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{
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__x = std::move(*__p);
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*__p = std::move(__w);
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return true;
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}
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__x = std::move(*__v);
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*__v = *__p;
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return false;
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}
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template<typename _Tp>
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inline bool
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atomic_compare_exchange_strong(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v,
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shared_ptr<_Tp> __w)
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{
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return std::atomic_compare_exchange_strong_explicit(__p, __v,
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std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
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}
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template<typename _Tp>
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inline bool
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atomic_compare_exchange_weak_explicit(shared_ptr<_Tp>* __p,
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shared_ptr<_Tp>* __v,
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shared_ptr<_Tp> __w,
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memory_order __success,
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memory_order __failure)
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{
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return std::atomic_compare_exchange_strong_explicit(__p, __v,
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std::move(__w), __success, __failure);
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}
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template<typename _Tp>
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inline bool
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atomic_compare_exchange_weak(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v,
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shared_ptr<_Tp> __w)
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{
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return std::atomic_compare_exchange_weak_explicit(__p, __v,
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std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
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}
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template<typename _Tp, _Lock_policy _Lp>
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bool
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atomic_compare_exchange_strong_explicit(__shared_ptr<_Tp, _Lp>* __p,
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__shared_ptr<_Tp, _Lp>* __v,
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__shared_ptr<_Tp, _Lp> __w,
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memory_order,
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memory_order)
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{
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__shared_ptr<_Tp, _Lp> __x; // goes out of scope after __lock
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_Sp_locker __lock{__p, __v};
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owner_less<__shared_ptr<_Tp, _Lp>> __less;
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if (*__p == *__v && !__less(*__p, *__v) && !__less(*__v, *__p))
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{
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__x = std::move(*__p);
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*__p = std::move(__w);
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return true;
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}
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__x = std::move(*__v);
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*__v = *__p;
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return false;
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}
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template<typename _Tp, _Lock_policy _Lp>
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inline bool
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atomic_compare_exchange_strong(__shared_ptr<_Tp, _Lp>* __p,
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__shared_ptr<_Tp, _Lp>* __v,
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__shared_ptr<_Tp, _Lp> __w)
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{
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return std::atomic_compare_exchange_strong_explicit(__p, __v,
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std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
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}
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template<typename _Tp, _Lock_policy _Lp>
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inline bool
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atomic_compare_exchange_weak_explicit(__shared_ptr<_Tp, _Lp>* __p,
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__shared_ptr<_Tp, _Lp>* __v,
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__shared_ptr<_Tp, _Lp> __w,
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memory_order __success,
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memory_order __failure)
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{
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return std::atomic_compare_exchange_strong_explicit(__p, __v,
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std::move(__w), __success, __failure);
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}
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template<typename _Tp, _Lock_policy _Lp>
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inline bool
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atomic_compare_exchange_weak(__shared_ptr<_Tp, _Lp>* __p,
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__shared_ptr<_Tp, _Lp>* __v,
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__shared_ptr<_Tp, _Lp> __w)
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{
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return std::atomic_compare_exchange_weak_explicit(__p, __v,
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std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
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}
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/// @}
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/// @} relates shared_ptr
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/// @} group pointer_abstractions
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace
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#endif // _SHARED_PTR_ATOMIC_H
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