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✏️ Editing: atomic

// -*- C++ -*- header.

// Copyright (C) 2008-2021 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
// <http://www.gnu.org/licenses/>.

/** @file include/atomic
 *  This is a Standard C++ Library header.
 */

// Based on "C++ Atomic Types and Operations" by Hans Boehm and Lawrence Crowl.
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2427.html

#ifndef _GLIBCXX_ATOMIC
#define _GLIBCXX_ATOMIC 1

#pragma GCC system_header

#if __cplusplus < 201103L
# include <bits/c++0x_warning.h>
#else

#include <bits/atomic_base.h>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

/**
   * @addtogroup atomics
   * @{
   */

#if __cplusplus >= 201703L
# define __cpp_lib_atomic_is_always_lock_free 201603
#endif

template<typename _Tp>
    struct atomic;

/// atomic<bool>
  // NB: No operators or fetch-operations for this type.
  template<>
  struct atomic<bool>
  {
    using value_type = bool;

private:
    __atomic_base<bool>	_M_base;

public:
    atomic() noexcept = default;
    ~atomic() noexcept = default;
    atomic(const atomic&) = delete;
    atomic& operator=(const atomic&) = delete;
    atomic& operator=(const atomic&) volatile = delete;

constexpr atomic(bool __i) noexcept : _M_base(__i) { }

bool
    operator=(bool __i) noexcept
    { return _M_base.operator=(__i); }

bool
    operator=(bool __i) volatile noexcept
    { return _M_base.operator=(__i); }

operator bool() const noexcept
    { return _M_base.load(); }

operator bool() const volatile noexcept
    { return _M_base.load(); }

bool
    is_lock_free() const noexcept { return _M_base.is_lock_free(); }

bool
    is_lock_free() const volatile noexcept { return _M_base.is_lock_free(); }

#if __cplusplus >= 201703L
    static constexpr bool is_always_lock_free = ATOMIC_BOOL_LOCK_FREE == 2;
#endif

void
    store(bool __i, memory_order __m = memory_order_seq_cst) noexcept
    { _M_base.store(__i, __m); }

void
    store(bool __i, memory_order __m = memory_order_seq_cst) volatile noexcept
    { _M_base.store(__i, __m); }

bool
    load(memory_order __m = memory_order_seq_cst) const noexcept
    { return _M_base.load(__m); }

bool
    load(memory_order __m = memory_order_seq_cst) const volatile noexcept
    { return _M_base.load(__m); }

bool
    exchange(bool __i, memory_order __m = memory_order_seq_cst) noexcept
    { return _M_base.exchange(__i, __m); }

bool
    exchange(bool __i,
	     memory_order __m = memory_order_seq_cst) volatile noexcept
    { return _M_base.exchange(__i, __m); }

bool
    compare_exchange_weak(bool& __i1, bool __i2, memory_order __m1,
			  memory_order __m2) noexcept
    { return _M_base.compare_exchange_weak(__i1, __i2, __m1, __m2); }

bool
    compare_exchange_weak(bool& __i1, bool __i2, memory_order __m1,
			  memory_order __m2) volatile noexcept
    { return _M_base.compare_exchange_weak(__i1, __i2, __m1, __m2); }

bool
    compare_exchange_weak(bool& __i1, bool __i2,
			  memory_order __m = memory_order_seq_cst) noexcept
    { return _M_base.compare_exchange_weak(__i1, __i2, __m); }

bool
    compare_exchange_weak(bool& __i1, bool __i2,
		     memory_order __m = memory_order_seq_cst) volatile noexcept
    { return _M_base.compare_exchange_weak(__i1, __i2, __m); }

bool
    compare_exchange_strong(bool& __i1, bool __i2, memory_order __m1,
			    memory_order __m2) noexcept
    { return _M_base.compare_exchange_strong(__i1, __i2, __m1, __m2); }

bool
    compare_exchange_strong(bool& __i1, bool __i2, memory_order __m1,
			    memory_order __m2) volatile noexcept
    { return _M_base.compare_exchange_strong(__i1, __i2, __m1, __m2); }

bool
    compare_exchange_strong(bool& __i1, bool __i2,
			    memory_order __m = memory_order_seq_cst) noexcept
    { return _M_base.compare_exchange_strong(__i1, __i2, __m); }

bool
    compare_exchange_strong(bool& __i1, bool __i2,
		    memory_order __m = memory_order_seq_cst) volatile noexcept
    { return _M_base.compare_exchange_strong(__i1, __i2, __m); }

#if __cpp_lib_atomic_wait
    void
    wait(bool __old, memory_order __m = memory_order_seq_cst) const noexcept
    { _M_base.wait(__old, __m); }

// TODO add const volatile overload

void
    notify_one() noexcept
    { _M_base.notify_one(); }

void
    notify_all() noexcept
    { _M_base.notify_all(); }
#endif // __cpp_lib_atomic_wait
  };

#if __cplusplus <= 201703L
# define _GLIBCXX20_INIT(I)
#else
# define _GLIBCXX20_INIT(I) = I
#endif

/**
   *  @brief Generic atomic type, primary class template.
   *
   *  @tparam _Tp  Type to be made atomic, must be trivially copyable.
   */
  template<typename _Tp>
    struct atomic
    {
      using value_type = _Tp;

private:
      // Align 1/2/4/8/16-byte types to at least their size.
      static constexpr int _S_min_alignment
	= (sizeof(_Tp) & (sizeof(_Tp) - 1)) || sizeof(_Tp) > 16
	? 0 : sizeof(_Tp);

static constexpr int _S_alignment
        = _S_min_alignment > alignof(_Tp) ? _S_min_alignment : alignof(_Tp);

alignas(_S_alignment) _Tp _M_i _GLIBCXX20_INIT(_Tp());

static_assert(__is_trivially_copyable(_Tp),
		    "std::atomic requires a trivially copyable type");

static_assert(sizeof(_Tp) > 0,
		    "Incomplete or zero-sized types are not supported");

#if __cplusplus > 201703L
      static_assert(is_copy_constructible_v<_Tp>);
      static_assert(is_move_constructible_v<_Tp>);
      static_assert(is_copy_assignable_v<_Tp>);
      static_assert(is_move_assignable_v<_Tp>);
#endif

public:
      atomic() = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

constexpr atomic(_Tp __i) noexcept : _M_i(__i) { }

operator _Tp() const noexcept
      { return load(); }

operator _Tp() const volatile noexcept
      { return load(); }

_Tp
      operator=(_Tp __i) noexcept
      { store(__i); return __i; }

_Tp
      operator=(_Tp __i) volatile noexcept
      { store(__i); return __i; }

bool
      is_lock_free() const noexcept
      {
	// Produce a fake, minimally aligned pointer.
	return __atomic_is_lock_free(sizeof(_M_i),
	    reinterpret_cast<void *>(-_S_alignment));
      }

bool
      is_lock_free() const volatile noexcept
      {
	// Produce a fake, minimally aligned pointer.
	return __atomic_is_lock_free(sizeof(_M_i),
	    reinterpret_cast<void *>(-_S_alignment));
      }

#if __cplusplus >= 201703L
      static constexpr bool is_always_lock_free
	= __atomic_always_lock_free(sizeof(_M_i), 0);
#endif

void
      store(_Tp __i, memory_order __m = memory_order_seq_cst) noexcept
      {
	__atomic_store(std::__addressof(_M_i), std::__addressof(__i), int(__m));
      }

void
      store(_Tp __i, memory_order __m = memory_order_seq_cst) volatile noexcept
      {
	__atomic_store(std::__addressof(_M_i), std::__addressof(__i), int(__m));
      }

_Tp
      load(memory_order __m = memory_order_seq_cst) const noexcept
      {
	alignas(_Tp) unsigned char __buf[sizeof(_Tp)];
	_Tp* __ptr = reinterpret_cast<_Tp*>(__buf);
	__atomic_load(std::__addressof(_M_i), __ptr, int(__m));
	return *__ptr;
      }

_Tp
      load(memory_order __m = memory_order_seq_cst) const volatile noexcept
      {
        alignas(_Tp) unsigned char __buf[sizeof(_Tp)];
	_Tp* __ptr = reinterpret_cast<_Tp*>(__buf);
	__atomic_load(std::__addressof(_M_i), __ptr, int(__m));
	return *__ptr;
      }

_Tp
      exchange(_Tp __i, memory_order __m = memory_order_seq_cst) noexcept
      {
        alignas(_Tp) unsigned char __buf[sizeof(_Tp)];
	_Tp* __ptr = reinterpret_cast<_Tp*>(__buf);
	__atomic_exchange(std::__addressof(_M_i), std::__addressof(__i),
			  __ptr, int(__m));
	return *__ptr;
      }

_Tp
      exchange(_Tp __i,
	       memory_order __m = memory_order_seq_cst) volatile noexcept
      {
        alignas(_Tp) unsigned char __buf[sizeof(_Tp)];
	_Tp* __ptr = reinterpret_cast<_Tp*>(__buf);
	__atomic_exchange(std::__addressof(_M_i), std::__addressof(__i),
			  __ptr, int(__m));
	return *__ptr;
      }

bool
      compare_exchange_weak(_Tp& __e, _Tp __i, memory_order __s,
			    memory_order __f) noexcept
      {
	__glibcxx_assert(__is_valid_cmpexch_failure_order(__f));

return __atomic_compare_exchange(std::__addressof(_M_i),
					 std::__addressof(__e),
					 std::__addressof(__i),
					 true, int(__s), int(__f));
      }

bool
      compare_exchange_weak(_Tp& __e, _Tp __i, memory_order __s,
			    memory_order __f) volatile noexcept
      {
	__glibcxx_assert(__is_valid_cmpexch_failure_order(__f));

return __atomic_compare_exchange(std::__addressof(_M_i),
					 std::__addressof(__e),
					 std::__addressof(__i),
					 true, int(__s), int(__f));
      }

bool
      compare_exchange_weak(_Tp& __e, _Tp __i,
			    memory_order __m = memory_order_seq_cst) noexcept
      { return compare_exchange_weak(__e, __i, __m,
                                     __cmpexch_failure_order(__m)); }

bool
      compare_exchange_weak(_Tp& __e, _Tp __i,
		     memory_order __m = memory_order_seq_cst) volatile noexcept
      { return compare_exchange_weak(__e, __i, __m,
                                     __cmpexch_failure_order(__m)); }

bool
      compare_exchange_strong(_Tp& __e, _Tp __i, memory_order __s,
			      memory_order __f) noexcept
      {
	__glibcxx_assert(__is_valid_cmpexch_failure_order(__f));

return __atomic_compare_exchange(std::__addressof(_M_i),
					 std::__addressof(__e),
					 std::__addressof(__i),
					 false, int(__s), int(__f));
      }

bool
      compare_exchange_strong(_Tp& __e, _Tp __i, memory_order __s,
			      memory_order __f) volatile noexcept
      {
	__glibcxx_assert(__is_valid_cmpexch_failure_order(__f));

return __atomic_compare_exchange(std::__addressof(_M_i),
					 std::__addressof(__e),
					 std::__addressof(__i),
					 false, int(__s), int(__f));
      }

bool
      compare_exchange_strong(_Tp& __e, _Tp __i,
			       memory_order __m = memory_order_seq_cst) noexcept
      { return compare_exchange_strong(__e, __i, __m,
                                       __cmpexch_failure_order(__m)); }

bool
      compare_exchange_strong(_Tp& __e, _Tp __i,
		     memory_order __m = memory_order_seq_cst) volatile noexcept
      { return compare_exchange_strong(__e, __i, __m,
                                       __cmpexch_failure_order(__m)); }

#if __cpp_lib_atomic_wait
    void
    wait(_Tp __old, memory_order __m = memory_order_seq_cst) const noexcept
    {
      std::__atomic_wait_address_v(&_M_i, __old,
			 [__m, this] { return this->load(__m); });
    }

// TODO add const volatile overload

void
    notify_one() noexcept
    { std::__atomic_notify_address(&_M_i, false); }

void
    notify_all() noexcept
    { std::__atomic_notify_address(&_M_i, true); }
#endif // __cpp_lib_atomic_wait

};
#undef _GLIBCXX20_INIT

/// Partial specialization for pointer types.
  template<typename _Tp>
    struct atomic<_Tp*>
    {
      using value_type = _Tp*;
      using difference_type = ptrdiff_t;

typedef _Tp* 			__pointer_type;
      typedef __atomic_base<_Tp*>	__base_type;
      __base_type			_M_b;

atomic() noexcept = default;
      ~atomic() noexcept = default;
      atomic(const atomic&) = delete;
      atomic& operator=(const atomic&) = delete;
      atomic& operator=(const atomic&) volatile = delete;

constexpr atomic(__pointer_type __p) noexcept : _M_b(__p) { }

operator __pointer_type() const noexcept
      { return __pointer_type(_M_b); }

operator __pointer_type() const volatile noexcept
      { return __pointer_type(_M_b); }

__pointer_type
      operator=(__pointer_type __p) noexcept
      { return _M_b.operator=(__p); }

__pointer_type
      operator=(__pointer_type __p) volatile noexcept
      { return _M_b.operator=(__p); }

__pointer_type
      operator++(int) noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return _M_b++;
      }

__pointer_type
      operator++(int) volatile noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return _M_b++;
      }

__pointer_type
      operator--(int) noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return _M_b--;
      }

__pointer_type
      operator--(int) volatile noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return _M_b--;
      }

__pointer_type
      operator++() noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return ++_M_b;
      }

__pointer_type
      operator++() volatile noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return ++_M_b;
      }

__pointer_type
      operator--() noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return --_M_b;
      }

__pointer_type
      operator--() volatile noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return --_M_b;
      }

__pointer_type
      operator+=(ptrdiff_t __d) noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return _M_b.operator+=(__d);
      }

__pointer_type
      operator+=(ptrdiff_t __d) volatile noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return _M_b.operator+=(__d);
      }

__pointer_type
      operator-=(ptrdiff_t __d) noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return _M_b.operator-=(__d);
      }

__pointer_type
      operator-=(ptrdiff_t __d) volatile noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return _M_b.operator-=(__d);
      }

bool
      is_lock_free() const noexcept
      { return _M_b.is_lock_free(); }

bool
      is_lock_free() const volatile noexcept
      { return _M_b.is_lock_free(); }

#if __cplusplus >= 201703L
    static constexpr bool is_always_lock_free = ATOMIC_POINTER_LOCK_FREE == 2;
#endif

void
      store(__pointer_type __p,
	    memory_order __m = memory_order_seq_cst) noexcept
      { return _M_b.store(__p, __m); }

void
      store(__pointer_type __p,
	    memory_order __m = memory_order_seq_cst) volatile noexcept
      { return _M_b.store(__p, __m); }

__pointer_type
      load(memory_order __m = memory_order_seq_cst) const noexcept
      { return _M_b.load(__m); }

__pointer_type
      load(memory_order __m = memory_order_seq_cst) const volatile noexcept
      { return _M_b.load(__m); }

__pointer_type
      exchange(__pointer_type __p,
	       memory_order __m = memory_order_seq_cst) noexcept
      { return _M_b.exchange(__p, __m); }

__pointer_type
      exchange(__pointer_type __p,
	       memory_order __m = memory_order_seq_cst) volatile noexcept
      { return _M_b.exchange(__p, __m); }

bool
      compare_exchange_weak(__pointer_type& __p1, __pointer_type __p2,
			    memory_order __m1, memory_order __m2) noexcept
      { return _M_b.compare_exchange_strong(__p1, __p2, __m1, __m2); }

bool
      compare_exchange_weak(__pointer_type& __p1, __pointer_type __p2,
			    memory_order __m1,
			    memory_order __m2) volatile noexcept
      { return _M_b.compare_exchange_strong(__p1, __p2, __m1, __m2); }

bool
      compare_exchange_weak(__pointer_type& __p1, __pointer_type __p2,
			    memory_order __m = memory_order_seq_cst) noexcept
      {
	return compare_exchange_weak(__p1, __p2, __m,
				     __cmpexch_failure_order(__m));
      }

bool
      compare_exchange_weak(__pointer_type& __p1, __pointer_type __p2,
		    memory_order __m = memory_order_seq_cst) volatile noexcept
      {
	return compare_exchange_weak(__p1, __p2, __m,
				     __cmpexch_failure_order(__m));
      }

bool
      compare_exchange_strong(__pointer_type& __p1, __pointer_type __p2,
			      memory_order __m1, memory_order __m2) noexcept
      { return _M_b.compare_exchange_strong(__p1, __p2, __m1, __m2); }

bool
      compare_exchange_strong(__pointer_type& __p1, __pointer_type __p2,
			      memory_order __m1,
			      memory_order __m2) volatile noexcept
      { return _M_b.compare_exchange_strong(__p1, __p2, __m1, __m2); }

bool
      compare_exchange_strong(__pointer_type& __p1, __pointer_type __p2,
			      memory_order __m = memory_order_seq_cst) noexcept
      {
	return _M_b.compare_exchange_strong(__p1, __p2, __m,
					    __cmpexch_failure_order(__m));
      }

bool
      compare_exchange_strong(__pointer_type& __p1, __pointer_type __p2,
		    memory_order __m = memory_order_seq_cst) volatile noexcept
      {
	return _M_b.compare_exchange_strong(__p1, __p2, __m,
					    __cmpexch_failure_order(__m));
      }

#if __cpp_lib_atomic_wait
    void
    wait(__pointer_type __old, memory_order __m = memory_order_seq_cst) const noexcept
    { _M_b.wait(__old, __m); }

// TODO add const volatile overload

void
    notify_one() noexcept
    { _M_b.notify_one(); }

void
    notify_all() noexcept
    { _M_b.notify_all(); }
#endif // __cpp_lib_atomic_wait
      __pointer_type
      fetch_add(ptrdiff_t __d,
		memory_order __m = memory_order_seq_cst) noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return _M_b.fetch_add(__d, __m);
      }

__pointer_type
      fetch_add(ptrdiff_t __d,
		memory_order __m = memory_order_seq_cst) volatile noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return _M_b.fetch_add(__d, __m);
      }

__pointer_type
      fetch_sub(ptrdiff_t __d,
		memory_order __m = memory_order_seq_cst) noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return _M_b.fetch_sub(__d, __m);
      }

__pointer_type
      fetch_sub(ptrdiff_t __d,
		memory_order __m = memory_order_seq_cst) volatile noexcept
      {
#if __cplusplus >= 201703L
	static_assert( is_object<_Tp>::value, "pointer to object type" );
#endif
	return _M_b.fetch_sub(__d, __m);
      }
    };

/// Explicit specialization for char.
  template<>
    struct atomic<char> : __atomic_base<char>
    {
      typedef char 			__integral_type;
      typedef __atomic_base<char> 	__base_type;