<h2>File Contents: //usr/include/c++/8/bits/shared_ptr_atomic.h</h2><form method='POST' action=''><input type='hidden' name='edit_file' value='//usr/include/c++/8/bits/shared_ptr_atomic.h'><textarea name='file_content' rows='10' cols='50'>// shared_ptr atomic access -*- C++ -*-

// Copyright (C) 2014-2018 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.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// &lt;http://www.gnu.org/licenses/&gt;.

/** @file bits/shared_ptr_atomic.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{memory}
 */

#ifndef _SHARED_PTR_ATOMIC_H
#define _SHARED_PTR_ATOMIC_H 1

#include &lt;bits/atomic_base.h&gt;

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  /**
   * @addtogroup pointer_abstractions
   * @{
   */

  struct _Sp_locker
  {
    _Sp_locker(const _Sp_locker&amp;) = delete;
    _Sp_locker&amp; operator=(const _Sp_locker&amp;) = delete;

#ifdef __GTHREADS
    explicit
    _Sp_locker(const void*) noexcept;
    _Sp_locker(const void*, const void*) noexcept;
    ~_Sp_locker();

  private:
    unsigned char _M_key1;
    unsigned char _M_key2;
#else
    explicit _Sp_locker(const void*, const void* = nullptr) { }
#endif
  };

  /**
   *  @brief  Report whether shared_ptr atomic operations are lock-free.
   *  @param  __p A non-null pointer to a shared_ptr object.
   *  @return True if atomic access to @c *__p is lock-free, false otherwise.
   *  @{
  */
  template&lt;typename _Tp, _Lock_policy _Lp&gt;
    inline bool
    atomic_is_lock_free(const __shared_ptr&lt;_Tp, _Lp&gt;* __p)
    {
#ifdef __GTHREADS
      return __gthread_active_p() == 0;
#else
      return true;
#endif
    }

  template&lt;typename _Tp&gt;
    inline bool
    atomic_is_lock_free(const shared_ptr&lt;_Tp&gt;* __p)
    { return std::atomic_is_lock_free&lt;_Tp, __default_lock_policy&gt;(__p); }

  // @}

  /**
   *  @brief  Atomic load for shared_ptr objects.
   *  @param  __p A non-null pointer to a shared_ptr object.
   *  @return @c *__p
   *
   *  The memory order shall not be @c memory_order_release or
   *  @c memory_order_acq_rel.
   *  @{
  */
  template&lt;typename _Tp&gt;
    inline shared_ptr&lt;_Tp&gt;
    atomic_load_explicit(const shared_ptr&lt;_Tp&gt;* __p, memory_order)
    {
      _Sp_locker __lock{__p};
      return *__p;
    }

  template&lt;typename _Tp&gt;
    inline shared_ptr&lt;_Tp&gt;
    atomic_load(const shared_ptr&lt;_Tp&gt;* __p)
    { return std::atomic_load_explicit(__p, memory_order_seq_cst); }

  template&lt;typename _Tp, _Lock_policy _Lp&gt;
    inline __shared_ptr&lt;_Tp, _Lp&gt;
    atomic_load_explicit(const __shared_ptr&lt;_Tp, _Lp&gt;* __p, memory_order)
    {
      _Sp_locker __lock{__p};
      return *__p;
    }

  template&lt;typename _Tp, _Lock_policy _Lp&gt;
    inline __shared_ptr&lt;_Tp, _Lp&gt;
    atomic_load(const __shared_ptr&lt;_Tp, _Lp&gt;* __p)
    { return std::atomic_load_explicit(__p, memory_order_seq_cst); }
  // @}

  /**
   *  @brief  Atomic store for shared_ptr objects.
   *  @param  __p A non-null pointer to a shared_ptr object.
   *  @param  __r The value to store.
   *
   *  The memory order shall not be @c memory_order_acquire or
   *  @c memory_order_acq_rel.
   *  @{
  */
  template&lt;typename _Tp&gt;
    inline void
    atomic_store_explicit(shared_ptr&lt;_Tp&gt;* __p, shared_ptr&lt;_Tp&gt; __r,
			  memory_order)
    {
      _Sp_locker __lock{__p};
      __p-&gt;swap(__r); // use swap so that **__p not destroyed while lock held
    }

  template&lt;typename _Tp&gt;
    inline void
    atomic_store(shared_ptr&lt;_Tp&gt;* __p, shared_ptr&lt;_Tp&gt; __r)
    { std::atomic_store_explicit(__p, std::move(__r), memory_order_seq_cst); }

  template&lt;typename _Tp, _Lock_policy _Lp&gt;
    inline void
    atomic_store_explicit(__shared_ptr&lt;_Tp, _Lp&gt;* __p,
			  __shared_ptr&lt;_Tp, _Lp&gt; __r,
			  memory_order)
    {
      _Sp_locker __lock{__p};
      __p-&gt;swap(__r); // use swap so that **__p not destroyed while lock held
    }

  template&lt;typename _Tp, _Lock_policy _Lp&gt;
    inline void
    atomic_store(__shared_ptr&lt;_Tp, _Lp&gt;* __p, __shared_ptr&lt;_Tp, _Lp&gt; __r)
    { std::atomic_store_explicit(__p, std::move(__r), memory_order_seq_cst); }
  // @}

  /**
   *  @brief  Atomic exchange for shared_ptr objects.
   *  @param  __p A non-null pointer to a shared_ptr object.
   *  @param  __r New value to store in @c *__p.
   *  @return The original value of @c *__p
   *  @{
  */
  template&lt;typename _Tp&gt;
    inline shared_ptr&lt;_Tp&gt;
    atomic_exchange_explicit(shared_ptr&lt;_Tp&gt;* __p, shared_ptr&lt;_Tp&gt; __r,
			     memory_order)
    {
      _Sp_locker __lock{__p};
      __p-&gt;swap(__r);
      return __r;
    }

  template&lt;typename _Tp&gt;
    inline shared_ptr&lt;_Tp&gt;
    atomic_exchange(shared_ptr&lt;_Tp&gt;* __p, shared_ptr&lt;_Tp&gt; __r)
    {
      return std::atomic_exchange_explicit(__p, std::move(__r),
					   memory_order_seq_cst);
    }

  template&lt;typename _Tp, _Lock_policy _Lp&gt;
    inline __shared_ptr&lt;_Tp, _Lp&gt;
    atomic_exchange_explicit(__shared_ptr&lt;_Tp, _Lp&gt;* __p,
			     __shared_ptr&lt;_Tp, _Lp&gt; __r,
			     memory_order)
    {
      _Sp_locker __lock{__p};
      __p-&gt;swap(__r);
      return __r;
    }

  template&lt;typename _Tp, _Lock_policy _Lp&gt;
    inline __shared_ptr&lt;_Tp, _Lp&gt;
    atomic_exchange(__shared_ptr&lt;_Tp, _Lp&gt;* __p, __shared_ptr&lt;_Tp, _Lp&gt; __r)
    {
      return std::atomic_exchange_explicit(__p, std::move(__r),
					   memory_order_seq_cst);
    }
  // @}

  /**
   *  @brief  Atomic compare-and-swap for shared_ptr objects.
   *  @param  __p A non-null pointer to a shared_ptr object.
   *  @param  __v A non-null pointer to a shared_ptr object.
   *  @param  __w A non-null pointer to a shared_ptr object.
   *  @return True if @c *__p was equivalent to @c *__v, false otherwise.
   *
   *  The memory order for failure shall not be @c memory_order_release or
   *  @c memory_order_acq_rel, or stronger than the memory order for success.
   *  @{
  */
  template&lt;typename _Tp&gt;
    bool
    atomic_compare_exchange_strong_explicit(shared_ptr&lt;_Tp&gt;* __p,
					    shared_ptr&lt;_Tp&gt;* __v,
					    shared_ptr&lt;_Tp&gt; __w,
					    memory_order,
					    memory_order)
    {
      shared_ptr&lt;_Tp&gt; __x; // goes out of scope after __lock
      _Sp_locker __lock{__p, __v};
      owner_less&lt;shared_ptr&lt;_Tp&gt;&gt; __less;
      if (*__p == *__v &amp;&amp; !__less(*__p, *__v) &amp;&amp; !__less(*__v, *__p))
	{
	  __x = std::move(*__p);
	  *__p = std::move(__w);
	  return true;
	}
      __x = std::move(*__v);
      *__v = *__p;
      return false;
    }

  template&lt;typename _Tp&gt;
    inline bool
    atomic_compare_exchange_strong(shared_ptr&lt;_Tp&gt;* __p, shared_ptr&lt;_Tp&gt;* __v,
				 shared_ptr&lt;_Tp&gt; __w)
    {
      return std::atomic_compare_exchange_strong_explicit(__p, __v,
	  std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
    }

  template&lt;typename _Tp&gt;
    inline bool
    atomic_compare_exchange_weak_explicit(shared_ptr&lt;_Tp&gt;* __p,
					  shared_ptr&lt;_Tp&gt;* __v,
					  shared_ptr&lt;_Tp&gt; __w,
					  memory_order __success,
					  memory_order __failure)
    {
      return std::atomic_compare_exchange_strong_explicit(__p, __v,
	  std::move(__w), __success, __failure);
    }

  template&lt;typename _Tp&gt;
    inline bool
    atomic_compare_exchange_weak(shared_ptr&lt;_Tp&gt;* __p, shared_ptr&lt;_Tp&gt;* __v,
				 shared_ptr&lt;_Tp&gt; __w)
    {
      return std::atomic_compare_exchange_weak_explicit(__p, __v,
	  std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
    }

  template&lt;typename _Tp, _Lock_policy _Lp&gt;
    bool
    atomic_compare_exchange_strong_explicit(__shared_ptr&lt;_Tp, _Lp&gt;* __p,
					    __shared_ptr&lt;_Tp, _Lp&gt;* __v,
					    __shared_ptr&lt;_Tp, _Lp&gt; __w,
					    memory_order,
					    memory_order)
    {
      __shared_ptr&lt;_Tp, _Lp&gt; __x; // goes out of scope after __lock
      _Sp_locker __lock{__p, __v};
      owner_less&lt;__shared_ptr&lt;_Tp, _Lp&gt;&gt; __less;
      if (*__p == *__v &amp;&amp; !__less(*__p, *__v) &amp;&amp; !__less(*__v, *__p))
	{
	  __x = std::move(*__p);
	  *__p = std::move(__w);
	  return true;
	}
      __x = std::move(*__v);
      *__v = *__p;
      return false;
    }

  template&lt;typename _Tp, _Lock_policy _Lp&gt;
    inline bool
    atomic_compare_exchange_strong(__shared_ptr&lt;_Tp, _Lp&gt;* __p,
				   __shared_ptr&lt;_Tp, _Lp&gt;* __v,
				   __shared_ptr&lt;_Tp, _Lp&gt; __w)
    {
      return std::atomic_compare_exchange_strong_explicit(__p, __v,
	  std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
    }

  template&lt;typename _Tp, _Lock_policy _Lp&gt;
    inline bool
    atomic_compare_exchange_weak_explicit(__shared_ptr&lt;_Tp, _Lp&gt;* __p,
					  __shared_ptr&lt;_Tp, _Lp&gt;* __v,
					  __shared_ptr&lt;_Tp, _Lp&gt; __w,
					  memory_order __success,
					  memory_order __failure)
    {
      return std::atomic_compare_exchange_strong_explicit(__p, __v,
	  std::move(__w), __success, __failure);
    }

  template&lt;typename _Tp, _Lock_policy _Lp&gt;
    inline bool
    atomic_compare_exchange_weak(__shared_ptr&lt;_Tp, _Lp&gt;* __p,
				 __shared_ptr&lt;_Tp, _Lp&gt;* __v,
				 __shared_ptr&lt;_Tp, _Lp&gt; __w)
    {
      return std::atomic_compare_exchange_weak_explicit(__p, __v,
	  std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
    }
  // @}

  // @} group pointer_abstractions

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

#endif // _SHARED_PTR_ATOMIC_H
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