include/atomic

// -*- C++ -*-
//===--------------------------- atomic -----------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_ATOMIC
#define _LIBCPP_ATOMIC

/*
    atomic synopsis

namespace std
{

// feature test macro [version.syn]

#define __cpp_lib_atomic_is_always_lock_free
#define __cpp_lib_atomic_flag_test
#define __cpp_lib_atomic_lock_free_type_aliases
#define __cpp_lib_atomic_wait

 // order and consistency

 enum memory_order: unspecified // enum class in C++20
 {
    relaxed,
    consume, // load-consume
    acquire, // load-acquire
    release, // store-release
    acq_rel, // store-release load-acquire
    seq_cst // store-release load-acquire
 };

 inline constexpr auto memory_order_relaxed = memory_order::relaxed;
 inline constexpr auto memory_order_consume = memory_order::consume;
 inline constexpr auto memory_order_acquire = memory_order::acquire;
 inline constexpr auto memory_order_release = memory_order::release;
 inline constexpr auto memory_order_acq_rel = memory_order::acq_rel;
 inline constexpr auto memory_order_seq_cst = memory_order::seq_cst;

template <class T> T kill_dependency(T y) noexcept;

// lock-free property

#define ATOMIC_BOOL_LOCK_FREE unspecified
#define ATOMIC_CHAR_LOCK_FREE unspecified
#define ATOMIC_CHAR8_T_LOCK_FREE unspecified // C++20
#define ATOMIC_CHAR16_T_LOCK_FREE unspecified
#define ATOMIC_CHAR32_T_LOCK_FREE unspecified
#define ATOMIC_WCHAR_T_LOCK_FREE unspecified
#define ATOMIC_SHORT_LOCK_FREE unspecified
#define ATOMIC_INT_LOCK_FREE unspecified
#define ATOMIC_LONG_LOCK_FREE unspecified
#define ATOMIC_LLONG_LOCK_FREE unspecified
#define ATOMIC_POINTER_LOCK_FREE unspecified

template <class T>
struct atomic
{
    using value_type = T;

    static constexpr bool is_always_lock_free;
    bool is_lock_free() const volatile noexcept;
    bool is_lock_free() const noexcept;

    atomic() noexcept = default; // until C++20
    constexpr atomic() noexcept(is_nothrow_default_constructible_v<T>); // since C++20
    constexpr atomic(T desr) noexcept;
    atomic(const atomic&) = delete;
    atomic& operator=(const atomic&) = delete;
    atomic& operator=(const atomic&) volatile = delete;

    T load(memory_order m = memory_order_seq_cst) const volatile noexcept;
    T load(memory_order m = memory_order_seq_cst) const noexcept;
    operator T() const volatile noexcept;
    operator T() const noexcept;
    void store(T desr, memory_order m = memory_order_seq_cst) volatile noexcept;
    void store(T desr, memory_order m = memory_order_seq_cst) noexcept;
    T operator=(T) volatile noexcept;
    T operator=(T) noexcept;

    T exchange(T desr, memory_order m = memory_order_seq_cst) volatile noexcept;
    T exchange(T desr, memory_order m = memory_order_seq_cst) noexcept;
    bool compare_exchange_weak(T& expc, T desr,
                               memory_order s, memory_order f) volatile noexcept;
    bool compare_exchange_weak(T& expc, T desr, memory_order s, memory_order f) noexcept;
    bool compare_exchange_strong(T& expc, T desr,
                                 memory_order s, memory_order f) volatile noexcept;
    bool compare_exchange_strong(T& expc, T desr,
                                 memory_order s, memory_order f) noexcept;
    bool compare_exchange_weak(T& expc, T desr,
                               memory_order m = memory_order_seq_cst) volatile noexcept;
    bool compare_exchange_weak(T& expc, T desr,
                               memory_order m = memory_order_seq_cst) noexcept;
    bool compare_exchange_strong(T& expc, T desr,
                                memory_order m = memory_order_seq_cst) volatile noexcept;
    bool compare_exchange_strong(T& expc, T desr,
                                 memory_order m = memory_order_seq_cst) noexcept;

    void wait(T, memory_order = memory_order::seq_cst) const volatile noexcept;
    void wait(T, memory_order = memory_order::seq_cst) const noexcept;
    void notify_one() volatile noexcept;
    void notify_one() noexcept;
    void notify_all() volatile noexcept;
    void notify_all() noexcept;
};

template <>
struct atomic<integral>
{
    using value_type = integral;
    using difference_type = value_type;

    static constexpr bool is_always_lock_free;
    bool is_lock_free() const volatile noexcept;
    bool is_lock_free() const noexcept;

    atomic() noexcept = default;
    constexpr atomic(integral desr) noexcept;
    atomic(const atomic&) = delete;
    atomic& operator=(const atomic&) = delete;
    atomic& operator=(const atomic&) volatile = delete;

    integral load(memory_order m = memory_order_seq_cst) const volatile noexcept;
    integral load(memory_order m = memory_order_seq_cst) const noexcept;
    operator integral() const volatile noexcept;
    operator integral() const noexcept;
    void store(integral desr, memory_order m = memory_order_seq_cst) volatile noexcept;
    void store(integral desr, memory_order m = memory_order_seq_cst) noexcept;
    integral operator=(integral desr) volatile noexcept;
    integral operator=(integral desr) noexcept;

    integral exchange(integral desr,
                      memory_order m = memory_order_seq_cst) volatile noexcept;
    integral exchange(integral desr, memory_order m = memory_order_seq_cst) noexcept;
    bool compare_exchange_weak(integral& expc, integral desr,
                               memory_order s, memory_order f) volatile noexcept;
    bool compare_exchange_weak(integral& expc, integral desr,
                               memory_order s, memory_order f) noexcept;
    bool compare_exchange_strong(integral& expc, integral desr,
                                 memory_order s, memory_order f) volatile noexcept;
    bool compare_exchange_strong(integral& expc, integral desr,
                                 memory_order s, memory_order f) noexcept;
    bool compare_exchange_weak(integral& expc, integral desr,
                               memory_order m = memory_order_seq_cst) volatile noexcept;
    bool compare_exchange_weak(integral& expc, integral desr,
                               memory_order m = memory_order_seq_cst) noexcept;
    bool compare_exchange_strong(integral& expc, integral desr,
                                memory_order m = memory_order_seq_cst) volatile noexcept;
    bool compare_exchange_strong(integral& expc, integral desr,
                                 memory_order m = memory_order_seq_cst) noexcept;

    integral fetch_add(integral op, memory_order m = memory_order_seq_cst) volatile noexcept;
    integral fetch_add(integral op, memory_order m = memory_order_seq_cst) noexcept;
    integral fetch_sub(integral op, memory_order m = memory_order_seq_cst) volatile noexcept;
    integral fetch_sub(integral op, memory_order m = memory_order_seq_cst) noexcept;
    integral fetch_and(integral op, memory_order m = memory_order_seq_cst) volatile noexcept;
    integral fetch_and(integral op, memory_order m = memory_order_seq_cst) noexcept;
    integral fetch_or(integral op, memory_order m = memory_order_seq_cst) volatile noexcept;
    integral fetch_or(integral op, memory_order m = memory_order_seq_cst) noexcept;
    integral fetch_xor(integral op, memory_order m = memory_order_seq_cst) volatile noexcept;
    integral fetch_xor(integral op, memory_order m = memory_order_seq_cst) noexcept;

    integral operator++(int) volatile noexcept;
    integral operator++(int) noexcept;
    integral operator--(int) volatile noexcept;
    integral operator--(int) noexcept;
    integral operator++() volatile noexcept;
    integral operator++() noexcept;
    integral operator--() volatile noexcept;
    integral operator--() noexcept;
    integral operator+=(integral op) volatile noexcept;
    integral operator+=(integral op) noexcept;
    integral operator-=(integral op) volatile noexcept;
    integral operator-=(integral op) noexcept;
    integral operator&=(integral op) volatile noexcept;
    integral operator&=(integral op) noexcept;
    integral operator|=(integral op) volatile noexcept;
    integral operator|=(integral op) noexcept;
    integral operator^=(integral op) volatile noexcept;
    integral operator^=(integral op) noexcept;

    void wait(integral, memory_order = memory_order::seq_cst) const volatile noexcept;
    void wait(integral, memory_order = memory_order::seq_cst) const noexcept;
    void notify_one() volatile noexcept;
    void notify_one() noexcept;
    void notify_all() volatile noexcept;
    void notify_all() noexcept;
};

template <class T>
struct atomic<T*>
{
    using value_type = T*;
    using difference_type = ptrdiff_t;

    static constexpr bool is_always_lock_free;
    bool is_lock_free() const volatile noexcept;
    bool is_lock_free() const noexcept;

    atomic() noexcept = default; // until C++20
    constexpr atomic() noexcept; // since C++20
    constexpr atomic(T* desr) noexcept;
    atomic(const atomic&) = delete;
    atomic& operator=(const atomic&) = delete;
    atomic& operator=(const atomic&) volatile = delete;

    T* load(memory_order m = memory_order_seq_cst) const volatile noexcept;
    T* load(memory_order m = memory_order_seq_cst) const noexcept;
    operator T*() const volatile noexcept;
    operator T*() const noexcept;
    void store(T* desr, memory_order m = memory_order_seq_cst) volatile noexcept;
    void store(T* desr, memory_order m = memory_order_seq_cst) noexcept;
    T* operator=(T*) volatile noexcept;
    T* operator=(T*) noexcept;

    T* exchange(T* desr, memory_order m = memory_order_seq_cst) volatile noexcept;
    T* exchange(T* desr, memory_order m = memory_order_seq_cst) noexcept;
    bool compare_exchange_weak(T*& expc, T* desr,
                               memory_order s, memory_order f) volatile noexcept;
    bool compare_exchange_weak(T*& expc, T* desr,
                               memory_order s, memory_order f) noexcept;
    bool compare_exchange_strong(T*& expc, T* desr,
                                 memory_order s, memory_order f) volatile noexcept;
    bool compare_exchange_strong(T*& expc, T* desr,
                                 memory_order s, memory_order f) noexcept;
    bool compare_exchange_weak(T*& expc, T* desr,
                               memory_order m = memory_order_seq_cst) volatile noexcept;
    bool compare_exchange_weak(T*& expc, T* desr,
                               memory_order m = memory_order_seq_cst) noexcept;
    bool compare_exchange_strong(T*& expc, T* desr,
                                memory_order m = memory_order_seq_cst) volatile noexcept;
    bool compare_exchange_strong(T*& expc, T* desr,
                                 memory_order m = memory_order_seq_cst) noexcept;
    T* fetch_add(ptrdiff_t op, memory_order m = memory_order_seq_cst) volatile noexcept;
    T* fetch_add(ptrdiff_t op, memory_order m = memory_order_seq_cst) noexcept;
    T* fetch_sub(ptrdiff_t op, memory_order m = memory_order_seq_cst) volatile noexcept;
    T* fetch_sub(ptrdiff_t op, memory_order m = memory_order_seq_cst) noexcept;

    T* operator++(int) volatile noexcept;
    T* operator++(int) noexcept;
    T* operator--(int) volatile noexcept;
    T* operator--(int) noexcept;
    T* operator++() volatile noexcept;
    T* operator++() noexcept;
    T* operator--() volatile noexcept;
    T* operator--() noexcept;
    T* operator+=(ptrdiff_t op) volatile noexcept;
    T* operator+=(ptrdiff_t op) noexcept;
    T* operator-=(ptrdiff_t op) volatile noexcept;
    T* operator-=(ptrdiff_t op) noexcept;

    void wait(T*, memory_order = memory_order::seq_cst) const volatile noexcept;
    void wait(T*, memory_order = memory_order::seq_cst) const noexcept;
    void notify_one() volatile noexcept;
    void notify_one() noexcept;
    void notify_all() volatile noexcept;
    void notify_all() noexcept;
};


template <class T>
  bool atomic_is_lock_free(const volatile atomic<T>* obj) noexcept;

template <class T>
  bool atomic_is_lock_free(const atomic<T>* obj) noexcept;

template <class T>
  void atomic_store(volatile atomic<T>* obj, T desr) noexcept;

template <class T>
  void atomic_store(atomic<T>* obj, T desr) noexcept;

template <class T>
  void atomic_store_explicit(volatile atomic<T>* obj, T desr, memory_order m) noexcept;

template <class T>
  void atomic_store_explicit(atomic<T>* obj, T desr, memory_order m) noexcept;

template <class T>
  T atomic_load(const volatile atomic<T>* obj) noexcept;

template <class T>
  T atomic_load(const atomic<T>* obj) noexcept;

template <class T>
  T atomic_load_explicit(const volatile atomic<T>* obj, memory_order m) noexcept;

template <class T>
  T atomic_load_explicit(const atomic<T>* obj, memory_order m) noexcept;

template <class T>
  T atomic_exchange(volatile atomic<T>* obj, T desr) noexcept;

template <class T>
  T atomic_exchange(atomic<T>* obj, T desr) noexcept;

template <class T>
  T atomic_exchange_explicit(volatile atomic<T>* obj, T desr, memory_order m) noexcept;

template <class T>
  T atomic_exchange_explicit(atomic<T>* obj, T desr, memory_order m) noexcept;

template <class T>
  bool atomic_compare_exchange_weak(volatile atomic<T>* obj, T* expc, T desr) noexcept;

template <class T>
  bool atomic_compare_exchange_weak(atomic<T>* obj, T* expc, T desr) noexcept;

template <class T>
  bool atomic_compare_exchange_strong(volatile atomic<T>* obj, T* expc, T desr) noexcept;

template <class T>
  bool atomic_compare_exchange_strong(atomic<T>* obj, T* expc, T desr) noexcept;

template <class T>
  bool atomic_compare_exchange_weak_explicit(volatile atomic<T>* obj, T* expc,
                                             T desr,
                                             memory_order s, memory_order f) noexcept;

template <class T>
  bool atomic_compare_exchange_weak_explicit(atomic<T>* obj, T* expc, T desr,
                                             memory_order s, memory_order f) noexcept;

template <class T>
  bool atomic_compare_exchange_strong_explicit(volatile atomic<T>* obj,
                                               T* expc, T desr,
                                               memory_order s, memory_order f) noexcept;

template <class T>
  bool atomic_compare_exchange_strong_explicit(atomic<T>* obj, T* expc,
                                               T desr,
                                               memory_order s, memory_order f) noexcept;

template <class T>
  void atomic_wait(const volatile atomic<T>* obj, T old) noexcept;

template <class T>
  void atomic_wait(const atomic<T>* obj, T old) noexcept;

template <class T>
  void atomic_wait_explicit(const volatile atomic<T>* obj, T old, memory_order m) noexcept;

template <class T>
  void atomic_wait_explicit(const atomic<T>* obj, T old, memory_order m) noexcept;

template <class T>
  void atomic_one(volatile atomic<T>* obj) noexcept;

template <class T>
  void atomic_one(atomic<T>* obj) noexcept;

template <class T>
  void atomic_all(volatile atomic<T>* obj) noexcept;

template <class T>
  void atomic_all(atomic<T>* obj) noexcept;

template <class Integral>
  Integral atomic_fetch_add(volatile atomic<Integral>* obj, Integral op) noexcept;

template <class Integral>
  Integral atomic_fetch_add(atomic<Integral>* obj, Integral op) noexcept;

template <class Integral>
  Integral atomic_fetch_add_explicit(volatile atomic<Integral>* obj, Integral op,
                              memory_order m) noexcept;
template <class Integral>
  Integral atomic_fetch_add_explicit(atomic<Integral>* obj, Integral op,
                              memory_order m) noexcept;
template <class Integral>
  Integral atomic_fetch_sub(volatile atomic<Integral>* obj, Integral op) noexcept;

template <class Integral>
  Integral atomic_fetch_sub(atomic<Integral>* obj, Integral op) noexcept;

template <class Integral>
  Integral atomic_fetch_sub_explicit(volatile atomic<Integral>* obj, Integral op,
                                     memory_order m) noexcept;

template <class Integral>
  Integral atomic_fetch_sub_explicit(atomic<Integral>* obj, Integral op,
                                     memory_order m) noexcept;

template <class Integral>
  Integral atomic_fetch_and(volatile atomic<Integral>* obj, Integral op) noexcept;

template <class Integral>
  Integral atomic_fetch_and(atomic<Integral>* obj, Integral op) noexcept;

template <class Integral>
  Integral atomic_fetch_and_explicit(volatile atomic<Integral>* obj, Integral op,
                                     memory_order m) noexcept;

template <class Integral>
  Integral atomic_fetch_and_explicit(atomic<Integral>* obj, Integral op,
                                     memory_order m) noexcept;

template <class Integral>
  Integral atomic_fetch_or(volatile atomic<Integral>* obj, Integral op) noexcept;

template <class Integral>
  Integral atomic_fetch_or(atomic<Integral>* obj, Integral op) noexcept;

template <class Integral>
  Integral atomic_fetch_or_explicit(volatile atomic<Integral>* obj, Integral op,
                             memory_order m) noexcept;

template <class Integral>
  Integral atomic_fetch_or_explicit(atomic<Integral>* obj, Integral op,
                             memory_order m) noexcept;

template <class Integral>
  Integral atomic_fetch_xor(volatile atomic<Integral>* obj, Integral op) noexcept;

template <class Integral>
  Integral atomic_fetch_xor(atomic<Integral>* obj, Integral op) noexcept;

template <class Integral>
  Integral atomic_fetch_xor_explicit(volatile atomic<Integral>* obj, Integral op,
                                     memory_order m) noexcept;

template <class Integral>
  Integral atomic_fetch_xor_explicit(atomic<Integral>* obj, Integral op,
                                     memory_order m) noexcept;

template <class T>
  T* atomic_fetch_add(volatile atomic<T*>* obj, ptrdiff_t op) noexcept;

template <class T>
  T* atomic_fetch_add(atomic<T*>* obj, ptrdiff_t op) noexcept;

template <class T>
  T* atomic_fetch_add_explicit(volatile atomic<T*>* obj, ptrdiff_t op,
                               memory_order m) noexcept;

template <class T>
  T* atomic_fetch_add_explicit(atomic<T*>* obj, ptrdiff_t op, memory_order m) noexcept;

template <class T>
  T* atomic_fetch_sub(volatile atomic<T*>* obj, ptrdiff_t op) noexcept;

template <class T>
  T* atomic_fetch_sub(atomic<T*>* obj, ptrdiff_t op) noexcept;

template <class T>
  T* atomic_fetch_sub_explicit(volatile atomic<T*>* obj, ptrdiff_t op,
                               memory_order m) noexcept;

template <class T>
  T* atomic_fetch_sub_explicit(atomic<T*>* obj, ptrdiff_t op, memory_order m) noexcept;

// Atomics for standard typedef types

typedef atomic<bool>               atomic_bool;
typedef atomic<char>               atomic_char;
typedef atomic<signed char>        atomic_schar;
typedef atomic<unsigned char>      atomic_uchar;
typedef atomic<short>              atomic_short;
typedef atomic<unsigned short>     atomic_ushort;
typedef atomic<int>                atomic_int;
typedef atomic<unsigned int>       atomic_uint;
typedef atomic<long>               atomic_long;
typedef atomic<unsigned long>      atomic_ulong;
typedef atomic<long long>          atomic_llong;
typedef atomic<unsigned long long> atomic_ullong;
typedef atomic<char8_t>            atomic_char8_t; // C++20
typedef atomic<char16_t>           atomic_char16_t;
typedef atomic<char32_t>           atomic_char32_t;
typedef atomic<wchar_t>            atomic_wchar_t;

typedef atomic<int_least8_t>   atomic_int_least8_t;
typedef atomic<uint_least8_t>  atomic_uint_least8_t;
typedef atomic<int_least16_t>  atomic_int_least16_t;
typedef atomic<uint_least16_t> atomic_uint_least16_t;
typedef atomic<int_least32_t>  atomic_int_least32_t;
typedef atomic<uint_least32_t> atomic_uint_least32_t;
typedef atomic<int_least64_t>  atomic_int_least64_t;
typedef atomic<uint_least64_t> atomic_uint_least64_t;

typedef atomic<int_fast8_t>   atomic_int_fast8_t;
typedef atomic<uint_fast8_t>  atomic_uint_fast8_t;
typedef atomic<int_fast16_t>  atomic_int_fast16_t;
typedef atomic<uint_fast16_t> atomic_uint_fast16_t;
typedef atomic<int_fast32_t>  atomic_int_fast32_t;
typedef atomic<uint_fast32_t> atomic_uint_fast32_t;
typedef atomic<int_fast64_t>  atomic_int_fast64_t;
typedef atomic<uint_fast64_t> atomic_uint_fast64_t;

typedef atomic<int8_t>   atomic_int8_t;
typedef atomic<uint8_t>  atomic_uint8_t;
typedef atomic<int16_t>  atomic_int16_t;
typedef atomic<uint16_t> atomic_uint16_t;
typedef atomic<int32_t>  atomic_int32_t;
typedef atomic<uint32_t> atomic_uint32_t;
typedef atomic<int64_t>  atomic_int64_t;
typedef atomic<uint64_t> atomic_uint64_t;

typedef atomic<intptr_t>  atomic_intptr_t;
typedef atomic<uintptr_t> atomic_uintptr_t;
typedef atomic<size_t>    atomic_size_t;
typedef atomic<ptrdiff_t> atomic_ptrdiff_t;
typedef atomic<intmax_t>  atomic_intmax_t;
typedef atomic<uintmax_t> atomic_uintmax_t;

// flag type and operations

typedef struct atomic_flag
{
    atomic_flag() noexcept = default; // until C++20
    constexpr atomic_flag() noexcept; // since C++20
    atomic_flag(const atomic_flag&) = delete;
    atomic_flag& operator=(const atomic_flag&) = delete;
    atomic_flag& operator=(const atomic_flag&) volatile = delete;

    bool test(memory_order m = memory_order_seq_cst) volatile noexcept;
    bool test(memory_order m = memory_order_seq_cst) noexcept;
    bool test_and_set(memory_order m = memory_order_seq_cst) volatile noexcept;
    bool test_and_set(memory_order m = memory_order_seq_cst) noexcept;
    void clear(memory_order m = memory_order_seq_cst) volatile noexcept;
    void clear(memory_order m = memory_order_seq_cst) noexcept;

    void wait(bool, memory_order = memory_order::seq_cst) const volatile noexcept;
    void wait(bool, memory_order = memory_order::seq_cst) const noexcept;
    void notify_one() volatile noexcept;
    void notify_one() noexcept;
    void notify_all() volatile noexcept;
    void notify_all() noexcept;
} atomic_flag;

bool atomic_flag_test(volatile atomic_flag* obj) noexcept;
bool atomic_flag_test(atomic_flag* obj) noexcept;
bool atomic_flag_test_explicit(volatile atomic_flag* obj,
                               memory_order m) noexcept;
bool atomic_flag_test_explicit(atomic_flag* obj, memory_order m) noexcept;
bool atomic_flag_test_and_set(volatile atomic_flag* obj) noexcept;
bool atomic_flag_test_and_set(atomic_flag* obj) noexcept;
bool atomic_flag_test_and_set_explicit(volatile atomic_flag* obj,
                                       memory_order m) noexcept;
bool atomic_flag_test_and_set_explicit(atomic_flag* obj, memory_order m) noexcept;
void atomic_flag_clear(volatile atomic_flag* obj) noexcept;
void atomic_flag_clear(atomic_flag* obj) noexcept;
void atomic_flag_clear_explicit(volatile atomic_flag* obj, memory_order m) noexcept;
void atomic_flag_clear_explicit(atomic_flag* obj, memory_order m) noexcept;

void atomic_wait(const volatile atomic_flag* obj, T old) noexcept;
void atomic_wait(const atomic_flag* obj, T old) noexcept;
void atomic_wait_explicit(const volatile atomic_flag* obj, T old, memory_order m) noexcept;
void atomic_wait_explicit(const atomic_flag* obj, T old, memory_order m) noexcept;
void atomic_one(volatile atomic_flag* obj) noexcept;
void atomic_one(atomic_flag* obj) noexcept;
void atomic_all(volatile atomic_flag* obj) noexcept;
void atomic_all(atomic_flag* obj) noexcept;

// fences

void atomic_thread_fence(memory_order m) noexcept;
void atomic_signal_fence(memory_order m) noexcept;

// deprecated

template <class T>
  void atomic_init(volatile atomic<T>* obj, typename atomic<T>::value_type desr) noexcept;

template <class T>
  void atomic_init(atomic<T>* obj, typename atomic<T>::value_type desr) noexcept;

#define ATOMIC_VAR_INIT(value) see below

#define ATOMIC_FLAG_INIT see below

}  // std

*/

#include <__availability>
#include <__config>
#include <__threading_support>
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <type_traits>
#include <version>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

#ifdef _LIBCPP_HAS_NO_THREADS
# error <atomic> is not supported on this single threaded system
#endif
#ifdef _LIBCPP_HAS_NO_ATOMIC_HEADER
# error <atomic> is not implemented
#endif
#ifdef kill_dependency
# error C++ standard library is incompatible with <stdatomic.h>
#endif

#define _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m) \
  _LIBCPP_DIAGNOSE_WARNING(__m == memory_order_consume || \
                           __m == memory_order_acquire || \
                           __m == memory_order_acq_rel,   \
                        "memory order argument to atomic operation is invalid")

#define _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m) \
  _LIBCPP_DIAGNOSE_WARNING(__m == memory_order_release || \
                           __m == memory_order_acq_rel,   \
                        "memory order argument to atomic operation is invalid")

#define _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__m, __f) \
  _LIBCPP_DIAGNOSE_WARNING(__f == memory_order_release || \
                           __f == memory_order_acq_rel,   \
                        "memory order argument to atomic operation is invalid")

_LIBCPP_BEGIN_NAMESPACE_STD

// Figure out what the underlying type for `memory_order` would be if it were
// declared as an unscoped enum (accounting for -fshort-enums). Use this result
// to pin the underlying type in C++20.
enum __legacy_memory_order {
    __mo_relaxed,
    __mo_consume,
    __mo_acquire,
    __mo_release,
    __mo_acq_rel,
    __mo_seq_cst
};

typedef underlying_type<__legacy_memory_order>::type __memory_order_underlying_t;

#if _LIBCPP_STD_VER > 17

enum class memory_order : __memory_order_underlying_t {
  relaxed = __mo_relaxed,
  consume = __mo_consume,
  acquire = __mo_acquire,
  release = __mo_release,
  acq_rel = __mo_acq_rel,
  seq_cst = __mo_seq_cst
};

inline constexpr auto memory_order_relaxed = memory_order::relaxed;
inline constexpr auto memory_order_consume = memory_order::consume;
inline constexpr auto memory_order_acquire = memory_order::acquire;
inline constexpr auto memory_order_release = memory_order::release;
inline constexpr auto memory_order_acq_rel = memory_order::acq_rel;
inline constexpr auto memory_order_seq_cst = memory_order::seq_cst;

#else

typedef enum memory_order {
  memory_order_relaxed = __mo_relaxed,
  memory_order_consume = __mo_consume,
  memory_order_acquire = __mo_acquire,
  memory_order_release = __mo_release,
  memory_order_acq_rel = __mo_acq_rel,
  memory_order_seq_cst = __mo_seq_cst,
} memory_order;

#endif // _LIBCPP_STD_VER > 17

template <typename _Tp> _LIBCPP_INLINE_VISIBILITY
bool __cxx_nonatomic_compare_equal(_Tp const& __lhs, _Tp const& __rhs) {
    return _VSTD::memcmp(&__lhs, &__rhs, sizeof(_Tp)) == 0;
}

static_assert((is_same<underlying_type<memory_order>::type, __memory_order_underlying_t>::value),
  "unexpected underlying type for std::memory_order");

#if defined(_LIBCPP_HAS_GCC_ATOMIC_IMP) || \
    defined(_LIBCPP_ATOMIC_ONLY_USE_BUILTINS)

// [atomics.types.generic]p1 guarantees _Tp is trivially copyable. Because
// the default operator= in an object is not volatile, a byte-by-byte copy
// is required.
template <typename _Tp, typename _Tv> _LIBCPP_INLINE_VISIBILITY
typename enable_if<is_assignable<_Tp&, _Tv>::value>::type
__cxx_atomic_assign_volatile(_Tp& __a_value, _Tv const& __val) {
  __a_value = __val;
}
template <typename _Tp, typename _Tv> _LIBCPP_INLINE_VISIBILITY
typename enable_if<is_assignable<_Tp&, _Tv>::value>::type
__cxx_atomic_assign_volatile(_Tp volatile& __a_value, _Tv volatile const& __val) {
  volatile char* __to = reinterpret_cast<volatile char*>(&__a_value);
  volatile char* __end = __to + sizeof(_Tp);
  volatile const char* __from = reinterpret_cast<volatile const char*>(&__val);
  while (__to != __end)
    *__to++ = *__from++;
}

#endif

#if defined(_LIBCPP_HAS_GCC_ATOMIC_IMP)

template <typename _Tp>
struct __cxx_atomic_base_impl {

  _LIBCPP_INLINE_VISIBILITY
#ifndef _LIBCPP_CXX03_LANG
    __cxx_atomic_base_impl() _NOEXCEPT = default;
#else
    __cxx_atomic_base_impl() _NOEXCEPT : __a_value() {}
#endif // _LIBCPP_CXX03_LANG
  _LIBCPP_CONSTEXPR explicit __cxx_atomic_base_impl(_Tp value) _NOEXCEPT
    : __a_value(value) {}
  _Tp __a_value;
};

_LIBCPP_INLINE_VISIBILITY inline _LIBCPP_CONSTEXPR int __to_gcc_order(memory_order __order) {
  // Avoid switch statement to make this a constexpr.
  return __order == memory_order_relaxed ? __ATOMIC_RELAXED:
         (__order == memory_order_acquire ? __ATOMIC_ACQUIRE:
          (__order == memory_order_release ? __ATOMIC_RELEASE:
           (__order == memory_order_seq_cst ? __ATOMIC_SEQ_CST:
            (__order == memory_order_acq_rel ? __ATOMIC_ACQ_REL:
              __ATOMIC_CONSUME))));
}

_LIBCPP_INLINE_VISIBILITY inline _LIBCPP_CONSTEXPR int __to_gcc_failure_order(memory_order __order) {
  // Avoid switch statement to make this a constexpr.
  return __order == memory_order_relaxed ? __ATOMIC_RELAXED:
         (__order == memory_order_acquire ? __ATOMIC_ACQUIRE:
          (__order == memory_order_release ? __ATOMIC_RELAXED:
           (__order == memory_order_seq_cst ? __ATOMIC_SEQ_CST:
            (__order == memory_order_acq_rel ? __ATOMIC_ACQUIRE:
              __ATOMIC_CONSUME))));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
void __cxx_atomic_init(volatile __cxx_atomic_base_impl<_Tp>* __a,  _Tp __val) {
  __cxx_atomic_assign_volatile(__a->__a_value, __val);
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
void __cxx_atomic_init(__cxx_atomic_base_impl<_Tp>* __a,  _Tp __val) {
  __a->__a_value = __val;
}

_LIBCPP_INLINE_VISIBILITY inline
void __cxx_atomic_thread_fence(memory_order __order) {
  __atomic_thread_fence(__to_gcc_order(__order));
}

_LIBCPP_INLINE_VISIBILITY inline
void __cxx_atomic_signal_fence(memory_order __order) {
  __atomic_signal_fence(__to_gcc_order(__order));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
void __cxx_atomic_store(volatile __cxx_atomic_base_impl<_Tp>* __a,  _Tp __val,
                        memory_order __order) {
  __atomic_store(&__a->__a_value, &__val,
                 __to_gcc_order(__order));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
void __cxx_atomic_store(__cxx_atomic_base_impl<_Tp>* __a,  _Tp __val,
                        memory_order __order) {
  __atomic_store(&__a->__a_value, &__val,
                 __to_gcc_order(__order));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_load(const volatile __cxx_atomic_base_impl<_Tp>* __a,
                      memory_order __order) {
  _Tp __ret;
  __atomic_load(&__a->__a_value, &__ret,
                __to_gcc_order(__order));
  return __ret;
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_load(const __cxx_atomic_base_impl<_Tp>* __a, memory_order __order) {
  _Tp __ret;
  __atomic_load(&__a->__a_value, &__ret,
                __to_gcc_order(__order));
  return __ret;
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_exchange(volatile __cxx_atomic_base_impl<_Tp>* __a,
                          _Tp __value, memory_order __order) {
  _Tp __ret;
  __atomic_exchange(&__a->__a_value, &__value, &__ret,
                    __to_gcc_order(__order));
  return __ret;
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_exchange(__cxx_atomic_base_impl<_Tp>* __a, _Tp __value,
                          memory_order __order) {
  _Tp __ret;
  __atomic_exchange(&__a->__a_value, &__value, &__ret,
                    __to_gcc_order(__order));
  return __ret;
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
bool __cxx_atomic_compare_exchange_strong(
    volatile __cxx_atomic_base_impl<_Tp>* __a, _Tp* __expected, _Tp __value,
    memory_order __success, memory_order __failure) {
  return __atomic_compare_exchange(&__a->__a_value, __expected, &__value,
                                   false,
                                   __to_gcc_order(__success),
                                   __to_gcc_failure_order(__failure));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
bool __cxx_atomic_compare_exchange_strong(
    __cxx_atomic_base_impl<_Tp>* __a, _Tp* __expected, _Tp __value, memory_order __success,
    memory_order __failure) {
  return __atomic_compare_exchange(&__a->__a_value, __expected, &__value,
                                   false,
                                   __to_gcc_order(__success),
                                   __to_gcc_failure_order(__failure));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
bool __cxx_atomic_compare_exchange_weak(
    volatile __cxx_atomic_base_impl<_Tp>* __a, _Tp* __expected, _Tp __value,
    memory_order __success, memory_order __failure) {
  return __atomic_compare_exchange(&__a->__a_value, __expected, &__value,
                                   true,
                                   __to_gcc_order(__success),
                                   __to_gcc_failure_order(__failure));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
bool __cxx_atomic_compare_exchange_weak(
    __cxx_atomic_base_impl<_Tp>* __a, _Tp* __expected, _Tp __value, memory_order __success,
    memory_order __failure) {
  return __atomic_compare_exchange(&__a->__a_value, __expected, &__value,
                                   true,
                                   __to_gcc_order(__success),
                                   __to_gcc_failure_order(__failure));
}

template <typename _Tp>
struct __skip_amt { enum {value = 1}; };

template <typename _Tp>
struct __skip_amt<_Tp*> { enum {value = sizeof(_Tp)}; };

// FIXME: Haven't figured out what the spec says about using arrays with
// atomic_fetch_add. Force a failure rather than creating bad behavior.
template <typename _Tp>
struct __skip_amt<_Tp[]> { };
template <typename _Tp, int n>
struct __skip_amt<_Tp[n]> { };

template <typename _Tp, typename _Td>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_add(volatile __cxx_atomic_base_impl<_Tp>* __a,
                           _Td __delta, memory_order __order) {
  return __atomic_fetch_add(&__a->__a_value, __delta * __skip_amt<_Tp>::value,
                            __to_gcc_order(__order));
}

template <typename _Tp, typename _Td>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_add(__cxx_atomic_base_impl<_Tp>* __a, _Td __delta,
                           memory_order __order) {
  return __atomic_fetch_add(&__a->__a_value, __delta * __skip_amt<_Tp>::value,
                            __to_gcc_order(__order));
}

template <typename _Tp, typename _Td>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_sub(volatile __cxx_atomic_base_impl<_Tp>* __a,
                           _Td __delta, memory_order __order) {
  return __atomic_fetch_sub(&__a->__a_value, __delta * __skip_amt<_Tp>::value,
                            __to_gcc_order(__order));
}

template <typename _Tp, typename _Td>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_sub(__cxx_atomic_base_impl<_Tp>* __a, _Td __delta,
                           memory_order __order) {
  return __atomic_fetch_sub(&__a->__a_value, __delta * __skip_amt<_Tp>::value,
                            __to_gcc_order(__order));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_and(volatile __cxx_atomic_base_impl<_Tp>* __a,
                           _Tp __pattern, memory_order __order) {
  return __atomic_fetch_and(&__a->__a_value, __pattern,
                            __to_gcc_order(__order));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_and(__cxx_atomic_base_impl<_Tp>* __a,
                           _Tp __pattern, memory_order __order) {
  return __atomic_fetch_and(&__a->__a_value, __pattern,
                            __to_gcc_order(__order));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_or(volatile __cxx_atomic_base_impl<_Tp>* __a,
                          _Tp __pattern, memory_order __order) {
  return __atomic_fetch_or(&__a->__a_value, __pattern,
                           __to_gcc_order(__order));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_or(__cxx_atomic_base_impl<_Tp>* __a, _Tp __pattern,
                          memory_order __order) {
  return __atomic_fetch_or(&__a->__a_value, __pattern,
                           __to_gcc_order(__order));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_xor(volatile __cxx_atomic_base_impl<_Tp>* __a,
                           _Tp __pattern, memory_order __order) {
  return __atomic_fetch_xor(&__a->__a_value, __pattern,
                            __to_gcc_order(__order));
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_xor(__cxx_atomic_base_impl<_Tp>* __a, _Tp __pattern,
                           memory_order __order) {
  return __atomic_fetch_xor(&__a->__a_value, __pattern,
                            __to_gcc_order(__order));
}

#define __cxx_atomic_is_lock_free(__s) __atomic_is_lock_free(__s, 0)

#elif defined(_LIBCPP_HAS_C_ATOMIC_IMP)

template <typename _Tp>
struct __cxx_atomic_base_impl {

  _LIBCPP_INLINE_VISIBILITY
#ifndef _LIBCPP_CXX03_LANG
    __cxx_atomic_base_impl() _NOEXCEPT = default;
#else
    __cxx_atomic_base_impl() _NOEXCEPT : __a_value() {}
#endif // _LIBCPP_CXX03_LANG
  _LIBCPP_CONSTEXPR explicit __cxx_atomic_base_impl(_Tp value) _NOEXCEPT
    : __a_value(value) {}
  _LIBCPP_DISABLE_EXTENSION_WARNING _Atomic(_Tp) __a_value;
};

#define __cxx_atomic_is_lock_free(__s) __c11_atomic_is_lock_free(__s)

_LIBCPP_INLINE_VISIBILITY inline
void __cxx_atomic_thread_fence(memory_order __order) _NOEXCEPT {
    __c11_atomic_thread_fence(static_cast<__memory_order_underlying_t>(__order));
}

_LIBCPP_INLINE_VISIBILITY inline
void __cxx_atomic_signal_fence(memory_order __order) _NOEXCEPT {
    __c11_atomic_signal_fence(static_cast<__memory_order_underlying_t>(__order));
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
void __cxx_atomic_init(__cxx_atomic_base_impl<_Tp> volatile* __a, _Tp __val) _NOEXCEPT {
    __c11_atomic_init(&__a->__a_value, __val);
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
void __cxx_atomic_init(__cxx_atomic_base_impl<_Tp> * __a, _Tp __val) _NOEXCEPT {
    __c11_atomic_init(&__a->__a_value, __val);
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
void __cxx_atomic_store(__cxx_atomic_base_impl<_Tp> volatile* __a, _Tp __val, memory_order __order) _NOEXCEPT {
    __c11_atomic_store(&__a->__a_value, __val, static_cast<__memory_order_underlying_t>(__order));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
void __cxx_atomic_store(__cxx_atomic_base_impl<_Tp> * __a, _Tp __val, memory_order __order) _NOEXCEPT {
    __c11_atomic_store(&__a->__a_value, __val, static_cast<__memory_order_underlying_t>(__order));
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_load(__cxx_atomic_base_impl<_Tp> const volatile* __a, memory_order __order) _NOEXCEPT {
    using __ptr_type = typename remove_const<decltype(__a->__a_value)>::type*;
    return __c11_atomic_load(const_cast<__ptr_type>(&__a->__a_value), static_cast<__memory_order_underlying_t>(__order));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_load(__cxx_atomic_base_impl<_Tp> const* __a, memory_order __order) _NOEXCEPT {
    using __ptr_type = typename remove_const<decltype(__a->__a_value)>::type*;
    return __c11_atomic_load(const_cast<__ptr_type>(&__a->__a_value), static_cast<__memory_order_underlying_t>(__order));
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_exchange(__cxx_atomic_base_impl<_Tp> volatile* __a, _Tp __value, memory_order __order) _NOEXCEPT {
    return __c11_atomic_exchange(&__a->__a_value, __value, static_cast<__memory_order_underlying_t>(__order));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_exchange(__cxx_atomic_base_impl<_Tp> * __a, _Tp __value, memory_order __order) _NOEXCEPT {
    return __c11_atomic_exchange(&__a->__a_value, __value, static_cast<__memory_order_underlying_t>(__order));
}

_LIBCPP_INLINE_VISIBILITY inline _LIBCPP_CONSTEXPR memory_order __to_failure_order(memory_order __order) {
  // Avoid switch statement to make this a constexpr.
  return __order == memory_order_release ? memory_order_relaxed:
         (__order == memory_order_acq_rel ? memory_order_acquire:
             __order);
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool __cxx_atomic_compare_exchange_strong(__cxx_atomic_base_impl<_Tp> volatile* __a, _Tp* __expected, _Tp __value, memory_order __success, memory_order __failure) _NOEXCEPT {
    return __c11_atomic_compare_exchange_strong(&__a->__a_value, __expected, __value, static_cast<__memory_order_underlying_t>(__success), static_cast<__memory_order_underlying_t>(__to_failure_order(__failure)));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool __cxx_atomic_compare_exchange_strong(__cxx_atomic_base_impl<_Tp> * __a, _Tp* __expected, _Tp __value, memory_order __success, memory_order __failure) _NOEXCEPT {
    return __c11_atomic_compare_exchange_strong(&__a->__a_value, __expected, __value, static_cast<__memory_order_underlying_t>(__success), static_cast<__memory_order_underlying_t>(__to_failure_order(__failure)));
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool __cxx_atomic_compare_exchange_weak(__cxx_atomic_base_impl<_Tp> volatile* __a, _Tp* __expected, _Tp __value, memory_order __success, memory_order __failure) _NOEXCEPT {
    return __c11_atomic_compare_exchange_weak(&__a->__a_value, __expected, __value, static_cast<__memory_order_underlying_t>(__success), static_cast<__memory_order_underlying_t>(__to_failure_order(__failure)));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool __cxx_atomic_compare_exchange_weak(__cxx_atomic_base_impl<_Tp> * __a, _Tp* __expected, _Tp __value, memory_order __success, memory_order __failure) _NOEXCEPT {
    return __c11_atomic_compare_exchange_weak(&__a->__a_value, __expected, __value,  static_cast<__memory_order_underlying_t>(__success), static_cast<__memory_order_underlying_t>(__to_failure_order(__failure)));
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_add(__cxx_atomic_base_impl<_Tp> volatile* __a, _Tp __delta, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_add(&__a->__a_value, __delta, static_cast<__memory_order_underlying_t>(__order));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_add(__cxx_atomic_base_impl<_Tp> * __a, _Tp __delta, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_add(&__a->__a_value, __delta, static_cast<__memory_order_underlying_t>(__order));
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp* __cxx_atomic_fetch_add(__cxx_atomic_base_impl<_Tp*> volatile* __a, ptrdiff_t __delta, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_add(&__a->__a_value, __delta, static_cast<__memory_order_underlying_t>(__order));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp* __cxx_atomic_fetch_add(__cxx_atomic_base_impl<_Tp*> * __a, ptrdiff_t __delta, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_add(&__a->__a_value, __delta, static_cast<__memory_order_underlying_t>(__order));
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_sub(__cxx_atomic_base_impl<_Tp> volatile* __a, _Tp __delta, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_sub(&__a->__a_value, __delta, static_cast<__memory_order_underlying_t>(__order));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_sub(__cxx_atomic_base_impl<_Tp> * __a, _Tp __delta, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_sub(&__a->__a_value, __delta, static_cast<__memory_order_underlying_t>(__order));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp* __cxx_atomic_fetch_sub(__cxx_atomic_base_impl<_Tp*> volatile* __a, ptrdiff_t __delta, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_sub(&__a->__a_value, __delta, static_cast<__memory_order_underlying_t>(__order));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp* __cxx_atomic_fetch_sub(__cxx_atomic_base_impl<_Tp*> * __a, ptrdiff_t __delta, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_sub(&__a->__a_value, __delta, static_cast<__memory_order_underlying_t>(__order));
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_and(__cxx_atomic_base_impl<_Tp> volatile* __a, _Tp __pattern, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_and(&__a->__a_value, __pattern, static_cast<__memory_order_underlying_t>(__order));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_and(__cxx_atomic_base_impl<_Tp> * __a, _Tp __pattern, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_and(&__a->__a_value, __pattern, static_cast<__memory_order_underlying_t>(__order));
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_or(__cxx_atomic_base_impl<_Tp> volatile* __a, _Tp __pattern, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_or(&__a->__a_value, __pattern, static_cast<__memory_order_underlying_t>(__order));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_or(__cxx_atomic_base_impl<_Tp> * __a, _Tp __pattern, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_or(&__a->__a_value, __pattern, static_cast<__memory_order_underlying_t>(__order));
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_xor(__cxx_atomic_base_impl<_Tp> volatile* __a, _Tp __pattern, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_xor(&__a->__a_value, __pattern, static_cast<__memory_order_underlying_t>(__order));
}
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_xor(__cxx_atomic_base_impl<_Tp> * __a, _Tp __pattern, memory_order __order) _NOEXCEPT {
    return __c11_atomic_fetch_xor(&__a->__a_value, __pattern, static_cast<__memory_order_underlying_t>(__order));
}

#endif // _LIBCPP_HAS_GCC_ATOMIC_IMP, _LIBCPP_HAS_C_ATOMIC_IMP

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp kill_dependency(_Tp __y) _NOEXCEPT
{
    return __y;
}

#if defined(__CLANG_ATOMIC_BOOL_LOCK_FREE)
# define ATOMIC_BOOL_LOCK_FREE      __CLANG_ATOMIC_BOOL_LOCK_FREE
# define ATOMIC_CHAR_LOCK_FREE      __CLANG_ATOMIC_CHAR_LOCK_FREE
#ifndef _LIBCPP_HAS_NO_CHAR8_T
# define ATOMIC_CHAR8_T_LOCK_FREE   __CLANG_ATOMIC_CHAR8_T_LOCK_FREE
#endif
# define ATOMIC_CHAR16_T_LOCK_FREE  __CLANG_ATOMIC_CHAR16_T_LOCK_FREE
# define ATOMIC_CHAR32_T_LOCK_FREE  __CLANG_ATOMIC_CHAR32_T_LOCK_FREE
# define ATOMIC_WCHAR_T_LOCK_FREE   __CLANG_ATOMIC_WCHAR_T_LOCK_FREE
# define ATOMIC_SHORT_LOCK_FREE     __CLANG_ATOMIC_SHORT_LOCK_FREE
# define ATOMIC_INT_LOCK_FREE       __CLANG_ATOMIC_INT_LOCK_FREE
# define ATOMIC_LONG_LOCK_FREE      __CLANG_ATOMIC_LONG_LOCK_FREE
# define ATOMIC_LLONG_LOCK_FREE     __CLANG_ATOMIC_LLONG_LOCK_FREE
# define ATOMIC_POINTER_LOCK_FREE   __CLANG_ATOMIC_POINTER_LOCK_FREE
#elif defined(__GCC_ATOMIC_BOOL_LOCK_FREE)
# define ATOMIC_BOOL_LOCK_FREE      __GCC_ATOMIC_BOOL_LOCK_FREE
# define ATOMIC_CHAR_LOCK_FREE      __GCC_ATOMIC_CHAR_LOCK_FREE
#ifndef _LIBCPP_HAS_NO_CHAR8_T
# define ATOMIC_CHAR8_T_LOCK_FREE   __GCC_ATOMIC_CHAR8_T_LOCK_FREE
#endif
# define ATOMIC_CHAR16_T_LOCK_FREE  __GCC_ATOMIC_CHAR16_T_LOCK_FREE
# define ATOMIC_CHAR32_T_LOCK_FREE  __GCC_ATOMIC_CHAR32_T_LOCK_FREE
# define ATOMIC_WCHAR_T_LOCK_FREE   __GCC_ATOMIC_WCHAR_T_LOCK_FREE
# define ATOMIC_SHORT_LOCK_FREE     __GCC_ATOMIC_SHORT_LOCK_FREE
# define ATOMIC_INT_LOCK_FREE       __GCC_ATOMIC_INT_LOCK_FREE
# define ATOMIC_LONG_LOCK_FREE      __GCC_ATOMIC_LONG_LOCK_FREE
# define ATOMIC_LLONG_LOCK_FREE     __GCC_ATOMIC_LLONG_LOCK_FREE
# define ATOMIC_POINTER_LOCK_FREE   __GCC_ATOMIC_POINTER_LOCK_FREE
#endif

#ifdef _LIBCPP_ATOMIC_ONLY_USE_BUILTINS

template<typename _Tp>
struct __cxx_atomic_lock_impl {

  _LIBCPP_INLINE_VISIBILITY
  __cxx_atomic_lock_impl() _NOEXCEPT
    : __a_value(), __a_lock(0) {}
  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR explicit
  __cxx_atomic_lock_impl(_Tp value) _NOEXCEPT
    : __a_value(value), __a_lock(0) {}

  _Tp __a_value;
  mutable __cxx_atomic_base_impl<_LIBCPP_ATOMIC_FLAG_TYPE> __a_lock;

  _LIBCPP_INLINE_VISIBILITY void __lock() const volatile {
    while(1 == __cxx_atomic_exchange(&__a_lock, _LIBCPP_ATOMIC_FLAG_TYPE(true), memory_order_acquire))
        /*spin*/;
  }
  _LIBCPP_INLINE_VISIBILITY void __lock() const {
    while(1 == __cxx_atomic_exchange(&__a_lock, _LIBCPP_ATOMIC_FLAG_TYPE(true), memory_order_acquire))
        /*spin*/;
  }
  _LIBCPP_INLINE_VISIBILITY void __unlock() const volatile {
    __cxx_atomic_store(&__a_lock, _LIBCPP_ATOMIC_FLAG_TYPE(false), memory_order_release);
  }
  _LIBCPP_INLINE_VISIBILITY void __unlock() const {
    __cxx_atomic_store(&__a_lock, _LIBCPP_ATOMIC_FLAG_TYPE(false), memory_order_release);
  }
  _LIBCPP_INLINE_VISIBILITY _Tp __read() const volatile {
    __lock();
    _Tp __old;
    __cxx_atomic_assign_volatile(__old, __a_value);
    __unlock();
    return __old;
  }
  _LIBCPP_INLINE_VISIBILITY _Tp __read() const {
    __lock();
    _Tp __old = __a_value;
    __unlock();
    return __old;
  }
};

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
void __cxx_atomic_init(volatile __cxx_atomic_lock_impl<_Tp>* __a,  _Tp __val) {
  __cxx_atomic_assign_volatile(__a->__a_value, __val);
}
template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
void __cxx_atomic_init(__cxx_atomic_lock_impl<_Tp>* __a,  _Tp __val) {
  __a->__a_value = __val;
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
void __cxx_atomic_store(volatile __cxx_atomic_lock_impl<_Tp>* __a,  _Tp __val, memory_order) {
  __a->__lock();
  __cxx_atomic_assign_volatile(__a->__a_value, __val);
  __a->__unlock();
}
template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
void __cxx_atomic_store(__cxx_atomic_lock_impl<_Tp>* __a,  _Tp __val, memory_order) {
  __a->__lock();
  __a->__a_value = __val;
  __a->__unlock();
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_load(const volatile __cxx_atomic_lock_impl<_Tp>* __a, memory_order) {
  return __a->__read();
}
template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_load(const __cxx_atomic_lock_impl<_Tp>* __a, memory_order) {
  return __a->__read();
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_exchange(volatile __cxx_atomic_lock_impl<_Tp>* __a, _Tp __value, memory_order) {
  __a->__lock();
  _Tp __old;
  __cxx_atomic_assign_volatile(__old, __a->__a_value);
  __cxx_atomic_assign_volatile(__a->__a_value, __value);
  __a->__unlock();
  return __old;
}
template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_exchange(__cxx_atomic_lock_impl<_Tp>* __a, _Tp __value, memory_order) {
  __a->__lock();
  _Tp __old = __a->__a_value;
  __a->__a_value = __value;
  __a->__unlock();
  return __old;
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
bool __cxx_atomic_compare_exchange_strong(volatile __cxx_atomic_lock_impl<_Tp>* __a,
                                          _Tp* __expected, _Tp __value, memory_order, memory_order) {
  _Tp __temp;
  __a->__lock();
  __cxx_atomic_assign_volatile(__temp, __a->__a_value);
  bool __ret = (_VSTD::memcmp(&__temp, __expected, sizeof(_Tp)) == 0);
  if(__ret)
    __cxx_atomic_assign_volatile(__a->__a_value, __value);
  else
    __cxx_atomic_assign_volatile(*__expected, __a->__a_value);
  __a->__unlock();
  return __ret;
}
template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
bool __cxx_atomic_compare_exchange_strong(__cxx_atomic_lock_impl<_Tp>* __a,
                                          _Tp* __expected, _Tp __value, memory_order, memory_order) {
  __a->__lock();
  bool __ret = (_VSTD::memcmp(&__a->__a_value, __expected, sizeof(_Tp)) == 0);
  if(__ret)
    _VSTD::memcpy(&__a->__a_value, &__value, sizeof(_Tp));
  else
    _VSTD::memcpy(__expected, &__a->__a_value, sizeof(_Tp));
  __a->__unlock();
  return __ret;
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
bool __cxx_atomic_compare_exchange_weak(volatile __cxx_atomic_lock_impl<_Tp>* __a,
                                        _Tp* __expected, _Tp __value, memory_order, memory_order) {
  _Tp __temp;
  __a->__lock();
  __cxx_atomic_assign_volatile(__temp, __a->__a_value);
  bool __ret = (_VSTD::memcmp(&__temp, __expected, sizeof(_Tp)) == 0);
  if(__ret)
    __cxx_atomic_assign_volatile(__a->__a_value, __value);
  else
    __cxx_atomic_assign_volatile(*__expected, __a->__a_value);
  __a->__unlock();
  return __ret;
}
template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
bool __cxx_atomic_compare_exchange_weak(__cxx_atomic_lock_impl<_Tp>* __a,
                                        _Tp* __expected, _Tp __value, memory_order, memory_order) {
  __a->__lock();
  bool __ret = (_VSTD::memcmp(&__a->__a_value, __expected, sizeof(_Tp)) == 0);
  if(__ret)
    _VSTD::memcpy(&__a->__a_value, &__value, sizeof(_Tp));
  else
    _VSTD::memcpy(__expected, &__a->__a_value, sizeof(_Tp));
  __a->__unlock();
  return __ret;
}

template <typename _Tp, typename _Td>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_add(volatile __cxx_atomic_lock_impl<_Tp>* __a,
                           _Td __delta, memory_order) {
  __a->__lock();
  _Tp __old;
  __cxx_atomic_assign_volatile(__old, __a->__a_value);
  __cxx_atomic_assign_volatile(__a->__a_value, _Tp(__old + __delta));
  __a->__unlock();
  return __old;
}
template <typename _Tp, typename _Td>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_add(__cxx_atomic_lock_impl<_Tp>* __a,
                           _Td __delta, memory_order) {
  __a->__lock();
  _Tp __old = __a->__a_value;
  __a->__a_value += __delta;
  __a->__unlock();
  return __old;
}

template <typename _Tp, typename _Td>
_LIBCPP_INLINE_VISIBILITY
_Tp* __cxx_atomic_fetch_add(volatile __cxx_atomic_lock_impl<_Tp*>* __a,
                           ptrdiff_t __delta, memory_order) {
  __a->__lock();
  _Tp* __old;
  __cxx_atomic_assign_volatile(__old, __a->__a_value);
  __cxx_atomic_assign_volatile(__a->__a_value, __old + __delta);
  __a->__unlock();
  return __old;
}
template <typename _Tp, typename _Td>
_LIBCPP_INLINE_VISIBILITY
_Tp* __cxx_atomic_fetch_add(__cxx_atomic_lock_impl<_Tp*>* __a,
                           ptrdiff_t __delta, memory_order) {
  __a->__lock();
  _Tp* __old = __a->__a_value;
  __a->__a_value += __delta;
  __a->__unlock();
  return __old;
}

template <typename _Tp, typename _Td>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_sub(volatile __cxx_atomic_lock_impl<_Tp>* __a,
                           _Td __delta, memory_order) {
  __a->__lock();
  _Tp __old;
  __cxx_atomic_assign_volatile(__old, __a->__a_value);
  __cxx_atomic_assign_volatile(__a->__a_value, _Tp(__old - __delta));
  __a->__unlock();
  return __old;
}
template <typename _Tp, typename _Td>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_sub(__cxx_atomic_lock_impl<_Tp>* __a,
                           _Td __delta, memory_order) {
  __a->__lock();
  _Tp __old = __a->__a_value;
  __a->__a_value -= __delta;
  __a->__unlock();
  return __old;
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_and(volatile __cxx_atomic_lock_impl<_Tp>* __a,
                           _Tp __pattern, memory_order) {
  __a->__lock();
  _Tp __old;
  __cxx_atomic_assign_volatile(__old, __a->__a_value);
  __cxx_atomic_assign_volatile(__a->__a_value, _Tp(__old & __pattern));
  __a->__unlock();
  return __old;
}
template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_and(__cxx_atomic_lock_impl<_Tp>* __a,
                           _Tp __pattern, memory_order) {
  __a->__lock();
  _Tp __old = __a->__a_value;
  __a->__a_value &= __pattern;
  __a->__unlock();
  return __old;
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_or(volatile __cxx_atomic_lock_impl<_Tp>* __a,
                          _Tp __pattern, memory_order) {
  __a->__lock();
  _Tp __old;
  __cxx_atomic_assign_volatile(__old, __a->__a_value);
  __cxx_atomic_assign_volatile(__a->__a_value, _Tp(__old | __pattern));
  __a->__unlock();
  return __old;
}
template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_or(__cxx_atomic_lock_impl<_Tp>* __a,
                          _Tp __pattern, memory_order) {
  __a->__lock();
  _Tp __old = __a->__a_value;
  __a->__a_value |= __pattern;
  __a->__unlock();
  return __old;
}

template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_xor(volatile __cxx_atomic_lock_impl<_Tp>* __a,
                           _Tp __pattern, memory_order) {
  __a->__lock();
  _Tp __old;
  __cxx_atomic_assign_volatile(__old, __a->__a_value);
  __cxx_atomic_assign_volatile(__a->__a_value, _Tp(__old ^ __pattern));
  __a->__unlock();
  return __old;
}
template <typename _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp __cxx_atomic_fetch_xor(__cxx_atomic_lock_impl<_Tp>* __a,
                           _Tp __pattern, memory_order) {
  __a->__lock();
  _Tp __old = __a->__a_value;
  __a->__a_value ^= __pattern;
  __a->__unlock();
  return __old;
}

#ifdef __cpp_lib_atomic_is_always_lock_free

template<typename _Tp> struct __cxx_is_always_lock_free {
    enum { __value = __atomic_always_lock_free(sizeof(_Tp), 0) }; };

#else

template<typename _Tp> struct __cxx_is_always_lock_free { enum { __value = false }; };
// Implementations must match the C ATOMIC_*_LOCK_FREE macro values.
template<> struct __cxx_is_always_lock_free<bool> { enum { __value = 2 == ATOMIC_BOOL_LOCK_FREE }; };
template<> struct __cxx_is_always_lock_free<char> { enum { __value = 2 == ATOMIC_CHAR_LOCK_FREE }; };
template<> struct __cxx_is_always_lock_free<signed char> { enum { __value = 2 == ATOMIC_CHAR_LOCK_FREE }; };
template<> struct __cxx_is_always_lock_free<unsigned char> { enum { __value = 2 == ATOMIC_CHAR_LOCK_FREE }; };
#ifndef _LIBCPP_HAS_NO_CHAR8_T
template<> struct __cxx_is_always_lock_free<char8_t> { enum { __value = 2 == ATOMIC_CHAR8_T_LOCK_FREE }; };
#endif
template<> struct __cxx_is_always_lock_free<char16_t> { enum { __value = 2 == ATOMIC_CHAR16_T_LOCK_FREE }; };
template<> struct __cxx_is_always_lock_free<char32_t> { enum { __value = 2 == ATOMIC_CHAR32_T_LOCK_FREE }; };
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
template<> struct __cxx_is_always_lock_free<wchar_t> { enum { __value = 2 == ATOMIC_WCHAR_T_LOCK_FREE }; };
#endif
template<> struct __cxx_is_always_lock_free<short> { enum { __value = 2 == ATOMIC_SHORT_LOCK_FREE }; };
template<> struct __cxx_is_always_lock_free<unsigned short> { enum { __value = 2 == ATOMIC_SHORT_LOCK_FREE }; };
template<> struct __cxx_is_always_lock_free<int> { enum { __value = 2 == ATOMIC_INT_LOCK_FREE }; };
template<> struct __cxx_is_always_lock_free<unsigned int> { enum { __value = 2 == ATOMIC_INT_LOCK_FREE }; };
template<> struct __cxx_is_always_lock_free<long> { enum { __value = 2 == ATOMIC_LONG_LOCK_FREE }; };
template<> struct __cxx_is_always_lock_free<unsigned long> { enum { __value = 2 == ATOMIC_LONG_LOCK_FREE }; };
template<> struct __cxx_is_always_lock_free<long long> { enum { __value = 2 == ATOMIC_LLONG_LOCK_FREE }; };
template<> struct __cxx_is_always_lock_free<unsigned long long> { enum { __value = 2 == ATOMIC_LLONG_LOCK_FREE }; };
template<typename _Tp> struct __cxx_is_always_lock_free<_Tp*> { enum { __value = 2 == ATOMIC_POINTER_LOCK_FREE }; };
template<> struct __cxx_is_always_lock_free<std::nullptr_t> { enum { __value = 2 == ATOMIC_POINTER_LOCK_FREE }; };

#endif //__cpp_lib_atomic_is_always_lock_free

template <typename _Tp,
          typename _Base = typename conditional<__cxx_is_always_lock_free<_Tp>::__value,
                                                __cxx_atomic_base_impl<_Tp>,
                                                __cxx_atomic_lock_impl<_Tp> >::type>
#else
template <typename _Tp,
          typename _Base = __cxx_atomic_base_impl<_Tp> >
#endif //_LIBCPP_ATOMIC_ONLY_USE_BUILTINS
struct __cxx_atomic_impl : public _Base {
    static_assert(is_trivially_copyable<_Tp>::value,
      "std::atomic<Tp> requires that 'Tp' be a trivially copyable type");

  _LIBCPP_INLINE_VISIBILITY __cxx_atomic_impl() _NOEXCEPT _LIBCPP_DEFAULT
  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR explicit __cxx_atomic_impl(_Tp value) _NOEXCEPT
    : _Base(value) {}
};

#ifdef __linux__
    using __cxx_contention_t = int32_t;
#else
    using __cxx_contention_t = int64_t;
#endif //__linux__

using __cxx_atomic_contention_t = __cxx_atomic_impl<__cxx_contention_t>;

#ifndef _LIBCPP_HAS_NO_PLATFORM_WAIT

_LIBCPP_AVAILABILITY_SYNC _LIBCPP_EXPORTED_FROM_ABI void __cxx_atomic_notify_one(void const volatile*);
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_EXPORTED_FROM_ABI void __cxx_atomic_notify_all(void const volatile*);
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_EXPORTED_FROM_ABI __cxx_contention_t __libcpp_atomic_monitor(void const volatile*);
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_EXPORTED_FROM_ABI void __libcpp_atomic_wait(void const volatile*, __cxx_contention_t);

_LIBCPP_AVAILABILITY_SYNC _LIBCPP_EXPORTED_FROM_ABI void __cxx_atomic_notify_one(__cxx_atomic_contention_t const volatile*);
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_EXPORTED_FROM_ABI void __cxx_atomic_notify_all(__cxx_atomic_contention_t const volatile*);
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_EXPORTED_FROM_ABI __cxx_contention_t __libcpp_atomic_monitor(__cxx_atomic_contention_t const volatile*);
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_EXPORTED_FROM_ABI void __libcpp_atomic_wait(__cxx_atomic_contention_t const volatile*, __cxx_contention_t);

template <class _Atp, class _Fn>
struct __libcpp_atomic_wait_backoff_impl {
    _Atp* __a;
    _Fn __test_fn;
    _LIBCPP_AVAILABILITY_SYNC
    _LIBCPP_INLINE_VISIBILITY bool operator()(chrono::nanoseconds __elapsed) const
    {
        if(__elapsed > chrono::microseconds(64))
        {
            auto const __monitor = __libcpp_atomic_monitor(__a);
            if(__test_fn())
                return true;
            __libcpp_atomic_wait(__a, __monitor);
        }
        else if(__elapsed > chrono::microseconds(4))
            __libcpp_thread_yield();
        else
            {} // poll
        return false;
    }
};

template <class _Atp, class _Fn>
_LIBCPP_AVAILABILITY_SYNC
_LIBCPP_INLINE_VISIBILITY bool __cxx_atomic_wait(_Atp* __a, _Fn && __test_fn)
{
    __libcpp_atomic_wait_backoff_impl<_Atp, typename decay<_Fn>::type> __backoff_fn = {__a, __test_fn};
    return __libcpp_thread_poll_with_backoff(__test_fn, __backoff_fn);
}

#else // _LIBCPP_HAS_NO_PLATFORM_WAIT

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY void __cxx_atomic_notify_all(__cxx_atomic_impl<_Tp> const volatile*) { }
template <class _Tp>
_LIBCPP_INLINE_VISIBILITY void __cxx_atomic_notify_one(__cxx_atomic_impl<_Tp> const volatile*) { }
template <class _Atp, class _Fn>
_LIBCPP_INLINE_VISIBILITY bool __cxx_atomic_wait(_Atp*, _Fn && __test_fn)
{
    return __libcpp_thread_poll_with_backoff(__test_fn, __libcpp_timed_backoff_policy());
}

#endif // _LIBCPP_HAS_NO_PLATFORM_WAIT

template <class _Atp, class _Tp>
struct __cxx_atomic_wait_test_fn_impl {
    _Atp* __a;
    _Tp __val;
    memory_order __order;
    _LIBCPP_INLINE_VISIBILITY bool operator()() const
    {
        return !__cxx_nonatomic_compare_equal(__cxx_atomic_load(__a, __order), __val);
    }
};

template <class _Atp, class _Tp>
_LIBCPP_AVAILABILITY_SYNC
_LIBCPP_INLINE_VISIBILITY bool __cxx_atomic_wait(_Atp* __a, _Tp const __val, memory_order __order)
{
    __cxx_atomic_wait_test_fn_impl<_Atp, _Tp> __test_fn = {__a, __val, __order};
    return __cxx_atomic_wait(__a, __test_fn);
}

// general atomic<T>

template <class _Tp, bool = is_integral<_Tp>::value && !is_same<_Tp, bool>::value>
struct __atomic_base  // false
{
    mutable __cxx_atomic_impl<_Tp> __a_;

#if defined(__cpp_lib_atomic_is_always_lock_free)
  static _LIBCPP_CONSTEXPR bool is_always_lock_free = __atomic_always_lock_free(sizeof(__a_), 0);
#endif

    _LIBCPP_INLINE_VISIBILITY
    bool is_lock_free() const volatile _NOEXCEPT
        {return __cxx_atomic_is_lock_free(sizeof(_Tp));}
    _LIBCPP_INLINE_VISIBILITY
    bool is_lock_free() const _NOEXCEPT
        {return static_cast<__atomic_base const volatile*>(this)->is_lock_free();}
    _LIBCPP_INLINE_VISIBILITY
    void store(_Tp __d, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
      _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m)
        {__cxx_atomic_store(&__a_, __d, __m);}
    _LIBCPP_INLINE_VISIBILITY
    void store(_Tp __d, memory_order __m = memory_order_seq_cst) _NOEXCEPT
      _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m)
        {__cxx_atomic_store(&__a_, __d, __m);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp load(memory_order __m = memory_order_seq_cst) const volatile _NOEXCEPT
      _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
        {return __cxx_atomic_load(&__a_, __m);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp load(memory_order __m = memory_order_seq_cst) const _NOEXCEPT
      _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
        {return __cxx_atomic_load(&__a_, __m);}
    _LIBCPP_INLINE_VISIBILITY
    operator _Tp() const volatile _NOEXCEPT {return load();}
    _LIBCPP_INLINE_VISIBILITY
    operator _Tp() const _NOEXCEPT          {return load();}
    _LIBCPP_INLINE_VISIBILITY
    _Tp exchange(_Tp __d, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
        {return __cxx_atomic_exchange(&__a_, __d, __m);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp exchange(_Tp __d, memory_order __m = memory_order_seq_cst) _NOEXCEPT
        {return __cxx_atomic_exchange(&__a_, __d, __m);}
    _LIBCPP_INLINE_VISIBILITY
    bool compare_exchange_weak(_Tp& __e, _Tp __d,
                               memory_order __s, memory_order __f) volatile _NOEXCEPT
      _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, __s, __f);}
    _LIBCPP_INLINE_VISIBILITY
    bool compare_exchange_weak(_Tp& __e, _Tp __d,
                               memory_order __s, memory_order __f) _NOEXCEPT
      _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, __s, __f);}
    _LIBCPP_INLINE_VISIBILITY
    bool compare_exchange_strong(_Tp& __e, _Tp __d,
                                 memory_order __s, memory_order __f) volatile _NOEXCEPT
      _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, __s, __f);}
    _LIBCPP_INLINE_VISIBILITY
    bool compare_exchange_strong(_Tp& __e, _Tp __d,
                                 memory_order __s, memory_order __f) _NOEXCEPT
      _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, __s, __f);}
    _LIBCPP_INLINE_VISIBILITY
    bool compare_exchange_weak(_Tp& __e, _Tp __d,
                              memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, __m, __m);}
    _LIBCPP_INLINE_VISIBILITY
    bool compare_exchange_weak(_Tp& __e, _Tp __d,
                               memory_order __m = memory_order_seq_cst) _NOEXCEPT
        {return __cxx_atomic_compare_exchange_weak(&__a_, &__e, __d, __m, __m);}
    _LIBCPP_INLINE_VISIBILITY
    bool compare_exchange_strong(_Tp& __e, _Tp __d,
                              memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, __m, __m);}
    _LIBCPP_INLINE_VISIBILITY
    bool compare_exchange_strong(_Tp& __e, _Tp __d,
                                 memory_order __m = memory_order_seq_cst) _NOEXCEPT
        {return __cxx_atomic_compare_exchange_strong(&__a_, &__e, __d, __m, __m);}

    _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY void wait(_Tp __v, memory_order __m = memory_order_seq_cst) const volatile _NOEXCEPT
        {__cxx_atomic_wait(&__a_, __v, __m);}
    _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY void wait(_Tp __v, memory_order __m = memory_order_seq_cst) const _NOEXCEPT
        {__cxx_atomic_wait(&__a_, __v, __m);}
    _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY void notify_one() volatile _NOEXCEPT
        {__cxx_atomic_notify_one(&__a_);}
    _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY void notify_one() _NOEXCEPT
        {__cxx_atomic_notify_one(&__a_);}
    _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY void notify_all() volatile _NOEXCEPT
        {__cxx_atomic_notify_all(&__a_);}
    _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY void notify_all() _NOEXCEPT
        {__cxx_atomic_notify_all(&__a_);}

#if _LIBCPP_STD_VER > 17
    _LIBCPP_INLINE_VISIBILITY constexpr
    __atomic_base() noexcept(is_nothrow_default_constructible_v<_Tp>) : __a_(_Tp()) {}
#else
    _LIBCPP_INLINE_VISIBILITY
    __atomic_base() _NOEXCEPT _LIBCPP_DEFAULT
#endif

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    __atomic_base(_Tp __d) _NOEXCEPT : __a_(__d) {}

#ifndef _LIBCPP_CXX03_LANG
    __atomic_base(const __atomic_base&) = delete;
#else
private:
    _LIBCPP_INLINE_VISIBILITY
    __atomic_base(const __atomic_base&);
#endif
};

#if defined(__cpp_lib_atomic_is_always_lock_free)
template <class _Tp, bool __b>
_LIBCPP_CONSTEXPR bool __atomic_base<_Tp, __b>::is_always_lock_free;
#endif

// atomic<Integral>

template <class _Tp>
struct __atomic_base<_Tp, true>
    : public __atomic_base<_Tp, false>
{
    typedef __atomic_base<_Tp, false> __base;

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    __atomic_base() _NOEXCEPT _LIBCPP_DEFAULT

    _LIBCPP_INLINE_VISIBILITY
    _LIBCPP_CONSTEXPR __atomic_base(_Tp __d) _NOEXCEPT : __base(__d) {}

    _LIBCPP_INLINE_VISIBILITY
    _Tp fetch_add(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
        {return __cxx_atomic_fetch_add(&this->__a_, __op, __m);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp fetch_add(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
        {return __cxx_atomic_fetch_add(&this->__a_, __op, __m);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp fetch_sub(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
        {return __cxx_atomic_fetch_sub(&this->__a_, __op, __m);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp fetch_sub(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
        {return __cxx_atomic_fetch_sub(&this->__a_, __op, __m);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp fetch_and(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
        {return __cxx_atomic_fetch_and(&this->__a_, __op, __m);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp fetch_and(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
        {return __cxx_atomic_fetch_and(&this->__a_, __op, __m);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp fetch_or(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
        {return __cxx_atomic_fetch_or(&this->__a_, __op, __m);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp fetch_or(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
        {return __cxx_atomic_fetch_or(&this->__a_, __op, __m);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp fetch_xor(_Tp __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
        {return __cxx_atomic_fetch_xor(&this->__a_, __op, __m);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp fetch_xor(_Tp __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT
        {return __cxx_atomic_fetch_xor(&this->__a_, __op, __m);}

    _LIBCPP_INLINE_VISIBILITY
    _Tp operator++(int) volatile _NOEXCEPT      {return fetch_add(_Tp(1));}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator++(int) _NOEXCEPT               {return fetch_add(_Tp(1));}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator--(int) volatile _NOEXCEPT      {return fetch_sub(_Tp(1));}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator--(int) _NOEXCEPT               {return fetch_sub(_Tp(1));}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator++() volatile _NOEXCEPT         {return fetch_add(_Tp(1)) + _Tp(1);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator++() _NOEXCEPT                  {return fetch_add(_Tp(1)) + _Tp(1);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator--() volatile _NOEXCEPT         {return fetch_sub(_Tp(1)) - _Tp(1);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator--() _NOEXCEPT                  {return fetch_sub(_Tp(1)) - _Tp(1);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator+=(_Tp __op) volatile _NOEXCEPT {return fetch_add(__op) + __op;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator+=(_Tp __op) _NOEXCEPT          {return fetch_add(__op) + __op;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator-=(_Tp __op) volatile _NOEXCEPT {return fetch_sub(__op) - __op;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator-=(_Tp __op) _NOEXCEPT          {return fetch_sub(__op) - __op;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator&=(_Tp __op) volatile _NOEXCEPT {return fetch_and(__op) & __op;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator&=(_Tp __op) _NOEXCEPT          {return fetch_and(__op) & __op;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator|=(_Tp __op) volatile _NOEXCEPT {return fetch_or(__op) | __op;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator|=(_Tp __op) _NOEXCEPT          {return fetch_or(__op) | __op;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator^=(_Tp __op) volatile _NOEXCEPT {return fetch_xor(__op) ^ __op;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator^=(_Tp __op) _NOEXCEPT          {return fetch_xor(__op) ^ __op;}
};

// atomic<T>

template <class _Tp>
struct atomic
    : public __atomic_base<_Tp>
{
    typedef __atomic_base<_Tp> __base;
    typedef _Tp value_type;
    typedef value_type difference_type;

#if _LIBCPP_STD_VER > 17
    _LIBCPP_INLINE_VISIBILITY
    atomic() = default;
#else
    _LIBCPP_INLINE_VISIBILITY
    atomic() _NOEXCEPT _LIBCPP_DEFAULT
#endif

    _LIBCPP_INLINE_VISIBILITY
    _LIBCPP_CONSTEXPR atomic(_Tp __d) _NOEXCEPT : __base(__d) {}

    _LIBCPP_INLINE_VISIBILITY
    _Tp operator=(_Tp __d) volatile _NOEXCEPT
        {__base::store(__d); return __d;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp operator=(_Tp __d) _NOEXCEPT
        {__base::store(__d); return __d;}

    atomic& operator=(const atomic&) = delete;
    atomic& operator=(const atomic&) volatile = delete;
};

// atomic<T*>

template <class _Tp>
struct atomic<_Tp*>
    : public __atomic_base<_Tp*>
{
    typedef __atomic_base<_Tp*> __base;
    typedef _Tp* value_type;
    typedef ptrdiff_t difference_type;

    _LIBCPP_INLINE_VISIBILITY
    atomic() _NOEXCEPT _LIBCPP_DEFAULT

    _LIBCPP_INLINE_VISIBILITY
    _LIBCPP_CONSTEXPR atomic(_Tp* __d) _NOEXCEPT : __base(__d) {}

    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator=(_Tp* __d) volatile _NOEXCEPT
        {__base::store(__d); return __d;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator=(_Tp* __d) _NOEXCEPT
        {__base::store(__d); return __d;}

    _LIBCPP_INLINE_VISIBILITY
    _Tp* fetch_add(ptrdiff_t __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT {
        // __atomic_fetch_add accepts function pointers, guard against them.
        static_assert(!is_function<typename remove_pointer<_Tp>::type>::value, "Pointer to function isn't allowed");
        return __cxx_atomic_fetch_add(&this->__a_, __op, __m);
    }

    _LIBCPP_INLINE_VISIBILITY
    _Tp* fetch_add(ptrdiff_t __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT {
        // __atomic_fetch_add accepts function pointers, guard against them.
        static_assert(!is_function<typename remove_pointer<_Tp>::type>::value, "Pointer to function isn't allowed");
        return __cxx_atomic_fetch_add(&this->__a_, __op, __m);
    }

    _LIBCPP_INLINE_VISIBILITY
    _Tp* fetch_sub(ptrdiff_t __op, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT {
        // __atomic_fetch_add accepts function pointers, guard against them.
        static_assert(!is_function<typename remove_pointer<_Tp>::type>::value, "Pointer to function isn't allowed");
        return __cxx_atomic_fetch_sub(&this->__a_, __op, __m);
    }

    _LIBCPP_INLINE_VISIBILITY
    _Tp* fetch_sub(ptrdiff_t __op, memory_order __m = memory_order_seq_cst) _NOEXCEPT {
        // __atomic_fetch_add accepts function pointers, guard against them.
        static_assert(!is_function<typename remove_pointer<_Tp>::type>::value, "Pointer to function isn't allowed");
        return __cxx_atomic_fetch_sub(&this->__a_, __op, __m);
    }

    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator++(int) volatile _NOEXCEPT            {return fetch_add(1);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator++(int) _NOEXCEPT                     {return fetch_add(1);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator--(int) volatile _NOEXCEPT            {return fetch_sub(1);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator--(int) _NOEXCEPT                     {return fetch_sub(1);}
    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator++() volatile _NOEXCEPT               {return fetch_add(1) + 1;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator++() _NOEXCEPT                        {return fetch_add(1) + 1;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator--() volatile _NOEXCEPT               {return fetch_sub(1) - 1;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator--() _NOEXCEPT                        {return fetch_sub(1) - 1;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator+=(ptrdiff_t __op) volatile _NOEXCEPT {return fetch_add(__op) + __op;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator+=(ptrdiff_t __op) _NOEXCEPT          {return fetch_add(__op) + __op;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator-=(ptrdiff_t __op) volatile _NOEXCEPT {return fetch_sub(__op) - __op;}
    _LIBCPP_INLINE_VISIBILITY
    _Tp* operator-=(ptrdiff_t __op) _NOEXCEPT          {return fetch_sub(__op) - __op;}

    atomic& operator=(const atomic&) = delete;
    atomic& operator=(const atomic&) volatile = delete;
};

// atomic_is_lock_free

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool
atomic_is_lock_free(const volatile atomic<_Tp>* __o) _NOEXCEPT
{
    return __o->is_lock_free();
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool
atomic_is_lock_free(const atomic<_Tp>* __o) _NOEXCEPT
{
    return __o->is_lock_free();
}

// atomic_init

template <class _Tp>
_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_INLINE_VISIBILITY
void
atomic_init(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type __d) _NOEXCEPT
{
    __cxx_atomic_init(&__o->__a_, __d);
}

template <class _Tp>
_LIBCPP_DEPRECATED_IN_CXX20 _LIBCPP_INLINE_VISIBILITY
void
atomic_init(atomic<_Tp>* __o, typename atomic<_Tp>::value_type __d) _NOEXCEPT
{
    __cxx_atomic_init(&__o->__a_, __d);
}

// atomic_store

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
void
atomic_store(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type __d) _NOEXCEPT
{
    __o->store(__d);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
void
atomic_store(atomic<_Tp>* __o, typename atomic<_Tp>::value_type __d) _NOEXCEPT
{
    __o->store(__d);
}

// atomic_store_explicit

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
void
atomic_store_explicit(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type __d, memory_order __m) _NOEXCEPT
  _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m)
{
    __o->store(__d, __m);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
void
atomic_store_explicit(atomic<_Tp>* __o, typename atomic<_Tp>::value_type __d, memory_order __m) _NOEXCEPT
  _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m)
{
    __o->store(__d, __m);
}

// atomic_load

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp
atomic_load(const volatile atomic<_Tp>* __o) _NOEXCEPT
{
    return __o->load();
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp
atomic_load(const atomic<_Tp>* __o) _NOEXCEPT
{
    return __o->load();
}

// atomic_load_explicit

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp
atomic_load_explicit(const volatile atomic<_Tp>* __o, memory_order __m) _NOEXCEPT
  _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
{
    return __o->load(__m);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp
atomic_load_explicit(const atomic<_Tp>* __o, memory_order __m) _NOEXCEPT
  _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
{
    return __o->load(__m);
}

// atomic_exchange

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp
atomic_exchange(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type __d) _NOEXCEPT
{
    return __o->exchange(__d);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp
atomic_exchange(atomic<_Tp>* __o, typename atomic<_Tp>::value_type __d) _NOEXCEPT
{
    return __o->exchange(__d);
}

// atomic_exchange_explicit

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp
atomic_exchange_explicit(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type __d, memory_order __m) _NOEXCEPT
{
    return __o->exchange(__d, __m);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp
atomic_exchange_explicit(atomic<_Tp>* __o, typename atomic<_Tp>::value_type __d, memory_order __m) _NOEXCEPT
{
    return __o->exchange(__d, __m);
}

// atomic_compare_exchange_weak

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool
atomic_compare_exchange_weak(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type* __e, typename atomic<_Tp>::value_type __d) _NOEXCEPT
{
    return __o->compare_exchange_weak(*__e, __d);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool
atomic_compare_exchange_weak(atomic<_Tp>* __o, typename atomic<_Tp>::value_type* __e, typename atomic<_Tp>::value_type __d) _NOEXCEPT
{
    return __o->compare_exchange_weak(*__e, __d);
}

// atomic_compare_exchange_strong

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool
atomic_compare_exchange_strong(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type* __e, typename atomic<_Tp>::value_type __d) _NOEXCEPT
{
    return __o->compare_exchange_strong(*__e, __d);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool
atomic_compare_exchange_strong(atomic<_Tp>* __o, typename atomic<_Tp>::value_type* __e, typename atomic<_Tp>::value_type __d) _NOEXCEPT
{
    return __o->compare_exchange_strong(*__e, __d);
}

// atomic_compare_exchange_weak_explicit

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool
atomic_compare_exchange_weak_explicit(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type* __e,
                                      typename atomic<_Tp>::value_type __d,
                                      memory_order __s, memory_order __f) _NOEXCEPT
  _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
{
    return __o->compare_exchange_weak(*__e, __d, __s, __f);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool
atomic_compare_exchange_weak_explicit(atomic<_Tp>* __o, typename atomic<_Tp>::value_type* __e, typename atomic<_Tp>::value_type __d,
                                      memory_order __s, memory_order __f) _NOEXCEPT
  _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
{
    return __o->compare_exchange_weak(*__e, __d, __s, __f);
}

// atomic_compare_exchange_strong_explicit

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool
atomic_compare_exchange_strong_explicit(volatile atomic<_Tp>* __o,
                                        typename atomic<_Tp>::value_type* __e, typename atomic<_Tp>::value_type __d,
                                        memory_order __s, memory_order __f) _NOEXCEPT
  _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
{
    return __o->compare_exchange_strong(*__e, __d, __s, __f);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
bool
atomic_compare_exchange_strong_explicit(atomic<_Tp>* __o, typename atomic<_Tp>::value_type* __e,
                                        typename atomic<_Tp>::value_type __d,
                                        memory_order __s, memory_order __f) _NOEXCEPT
  _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
{
    return __o->compare_exchange_strong(*__e, __d, __s, __f);
}

// atomic_wait

template <class _Tp>
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
void atomic_wait(const volatile atomic<_Tp>* __o,
                 typename atomic<_Tp>::value_type __v) _NOEXCEPT
{
    return __o->wait(__v);
}

template <class _Tp>
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
void atomic_wait(const atomic<_Tp>* __o,
                 typename atomic<_Tp>::value_type __v) _NOEXCEPT
{
    return __o->wait(__v);
}

// atomic_wait_explicit

template <class _Tp>
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
void atomic_wait_explicit(const volatile atomic<_Tp>* __o,
                          typename atomic<_Tp>::value_type __v,
                          memory_order __m) _NOEXCEPT
  _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
{
    return __o->wait(__v, __m);
}

template <class _Tp>
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
void atomic_wait_explicit(const atomic<_Tp>* __o,
                          typename atomic<_Tp>::value_type __v,
                          memory_order __m) _NOEXCEPT
  _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
{
    return __o->wait(__v, __m);
}

// atomic_notify_one

template <class _Tp>
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
void atomic_notify_one(volatile atomic<_Tp>* __o) _NOEXCEPT
{
    __o->notify_one();
}
template <class _Tp>
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
void atomic_notify_one(atomic<_Tp>* __o) _NOEXCEPT
{
    __o->notify_one();
}

// atomic_notify_one

template <class _Tp>
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
void atomic_notify_all(volatile atomic<_Tp>* __o) _NOEXCEPT
{
    __o->notify_all();
}
template <class _Tp>
_LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
void atomic_notify_all(atomic<_Tp>* __o) _NOEXCEPT
{
    __o->notify_all();
}

// atomic_fetch_add

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp
atomic_fetch_add(volatile atomic<_Tp>* __o, typename atomic<_Tp>::difference_type __op) _NOEXCEPT
{
    return __o->fetch_add(__op);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp
atomic_fetch_add(atomic<_Tp>* __o, typename atomic<_Tp>::difference_type __op) _NOEXCEPT
{
    return __o->fetch_add(__op);
}

// atomic_fetch_add_explicit

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp atomic_fetch_add_explicit(volatile atomic<_Tp>* __o, typename atomic<_Tp>::difference_type __op, memory_order __m) _NOEXCEPT
{
    return __o->fetch_add(__op, __m);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp atomic_fetch_add_explicit(atomic<_Tp>* __o, typename atomic<_Tp>::difference_type __op, memory_order __m) _NOEXCEPT
{
    return __o->fetch_add(__op, __m);
}

// atomic_fetch_sub

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp atomic_fetch_sub(volatile atomic<_Tp>* __o, typename atomic<_Tp>::difference_type __op) _NOEXCEPT
{
    return __o->fetch_sub(__op);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp atomic_fetch_sub(atomic<_Tp>* __o, typename atomic<_Tp>::difference_type __op) _NOEXCEPT
{
    return __o->fetch_sub(__op);
}

// atomic_fetch_sub_explicit

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp atomic_fetch_sub_explicit(volatile atomic<_Tp>* __o, typename atomic<_Tp>::difference_type __op, memory_order __m) _NOEXCEPT
{
    return __o->fetch_sub(__op, __m);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
_Tp atomic_fetch_sub_explicit(atomic<_Tp>* __o, typename atomic<_Tp>::difference_type __op, memory_order __m) _NOEXCEPT
{
    return __o->fetch_sub(__op, __m);
}

// atomic_fetch_and

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_integral<_Tp>::value && !is_same<_Tp, bool>::value,
    _Tp
>::type
atomic_fetch_and(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type __op) _NOEXCEPT
{
    return __o->fetch_and(__op);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_integral<_Tp>::value && !is_same<_Tp, bool>::value,
    _Tp
>::type
atomic_fetch_and(atomic<_Tp>* __o, typename atomic<_Tp>::value_type __op) _NOEXCEPT
{
    return __o->fetch_and(__op);
}

// atomic_fetch_and_explicit

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_integral<_Tp>::value && !is_same<_Tp, bool>::value,
    _Tp
>::type
atomic_fetch_and_explicit(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type __op, memory_order __m) _NOEXCEPT
{
    return __o->fetch_and(__op, __m);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_integral<_Tp>::value && !is_same<_Tp, bool>::value,
    _Tp
>::type
atomic_fetch_and_explicit(atomic<_Tp>* __o, typename atomic<_Tp>::value_type __op, memory_order __m) _NOEXCEPT
{
    return __o->fetch_and(__op, __m);
}

// atomic_fetch_or

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_integral<_Tp>::value && !is_same<_Tp, bool>::value,
    _Tp
>::type
atomic_fetch_or(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type __op) _NOEXCEPT
{
    return __o->fetch_or(__op);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_integral<_Tp>::value && !is_same<_Tp, bool>::value,
    _Tp
>::type
atomic_fetch_or(atomic<_Tp>* __o, typename atomic<_Tp>::value_type __op) _NOEXCEPT
{
    return __o->fetch_or(__op);
}

// atomic_fetch_or_explicit

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_integral<_Tp>::value && !is_same<_Tp, bool>::value,
    _Tp
>::type
atomic_fetch_or_explicit(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type __op, memory_order __m) _NOEXCEPT
{
    return __o->fetch_or(__op, __m);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_integral<_Tp>::value && !is_same<_Tp, bool>::value,
    _Tp
>::type
atomic_fetch_or_explicit(atomic<_Tp>* __o, typename atomic<_Tp>::value_type __op, memory_order __m) _NOEXCEPT
{
    return __o->fetch_or(__op, __m);
}

// atomic_fetch_xor

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_integral<_Tp>::value && !is_same<_Tp, bool>::value,
    _Tp
>::type
atomic_fetch_xor(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type __op) _NOEXCEPT
{
    return __o->fetch_xor(__op);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_integral<_Tp>::value && !is_same<_Tp, bool>::value,
    _Tp
>::type
atomic_fetch_xor(atomic<_Tp>* __o, typename atomic<_Tp>::value_type __op) _NOEXCEPT
{
    return __o->fetch_xor(__op);
}

// atomic_fetch_xor_explicit

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_integral<_Tp>::value && !is_same<_Tp, bool>::value,
    _Tp
>::type
atomic_fetch_xor_explicit(volatile atomic<_Tp>* __o, typename atomic<_Tp>::value_type __op, memory_order __m) _NOEXCEPT
{
    return __o->fetch_xor(__op, __m);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_integral<_Tp>::value && !is_same<_Tp, bool>::value,
    _Tp
>::type
atomic_fetch_xor_explicit(atomic<_Tp>* __o, typename atomic<_Tp>::value_type __op, memory_order __m) _NOEXCEPT
{
    return __o->fetch_xor(__op, __m);
}

// flag type and operations

typedef struct atomic_flag
{
    __cxx_atomic_impl<_LIBCPP_ATOMIC_FLAG_TYPE> __a_;

    _LIBCPP_INLINE_VISIBILITY
    bool test(memory_order __m = memory_order_seq_cst) const volatile _NOEXCEPT
        {return _LIBCPP_ATOMIC_FLAG_TYPE(true) == __cxx_atomic_load(&__a_, __m);}
    _LIBCPP_INLINE_VISIBILITY
    bool test(memory_order __m = memory_order_seq_cst) const _NOEXCEPT
        {return _LIBCPP_ATOMIC_FLAG_TYPE(true) == __cxx_atomic_load(&__a_, __m);}

    _LIBCPP_INLINE_VISIBILITY
    bool test_and_set(memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
        {return __cxx_atomic_exchange(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(true), __m);}
    _LIBCPP_INLINE_VISIBILITY
    bool test_and_set(memory_order __m = memory_order_seq_cst) _NOEXCEPT
        {return __cxx_atomic_exchange(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(true), __m);}
    _LIBCPP_INLINE_VISIBILITY
    void clear(memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
        {__cxx_atomic_store(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(false), __m);}
    _LIBCPP_INLINE_VISIBILITY
    void clear(memory_order __m = memory_order_seq_cst) _NOEXCEPT
        {__cxx_atomic_store(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(false), __m);}

    _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
    void wait(bool __v, memory_order __m = memory_order_seq_cst) const volatile _NOEXCEPT
        {__cxx_atomic_wait(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(__v), __m);}
    _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
    void wait(bool __v, memory_order __m = memory_order_seq_cst) const _NOEXCEPT
        {__cxx_atomic_wait(&__a_, _LIBCPP_ATOMIC_FLAG_TYPE(__v), __m);}
    _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
    void notify_one() volatile _NOEXCEPT
        {__cxx_atomic_notify_one(&__a_);}
    _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
    void notify_one() _NOEXCEPT
        {__cxx_atomic_notify_one(&__a_);}
    _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
    void notify_all() volatile _NOEXCEPT
        {__cxx_atomic_notify_all(&__a_);}
    _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY
    void notify_all() _NOEXCEPT
        {__cxx_atomic_notify_all(&__a_);}

#if _LIBCPP_STD_VER > 17
    _LIBCPP_INLINE_VISIBILITY constexpr
    atomic_flag() _NOEXCEPT : __a_(false) {}
#else
    _LIBCPP_INLINE_VISIBILITY
    atomic_flag() _NOEXCEPT _LIBCPP_DEFAULT
#endif

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    atomic_flag(bool __b) _NOEXCEPT : __a_(__b) {} // EXTENSION

#ifndef _LIBCPP_CXX03_LANG
    atomic_flag(const atomic_flag&) = delete;
    atomic_flag& operator=(const atomic_flag&) = delete;
    atomic_flag& operator=(const atomic_flag&) volatile = delete;
#else
private:
    _LIBCPP_INLINE_VISIBILITY
    atomic_flag(const atomic_flag&);
    _LIBCPP_INLINE_VISIBILITY
    atomic_flag& operator=(const atomic_flag&);
    _LIBCPP_INLINE_VISIBILITY
    atomic_flag& operator=(const atomic_flag&) volatile;
#endif
} atomic_flag;


inline _LIBCPP_INLINE_VISIBILITY
bool
atomic_flag_test(const volatile atomic_flag* __o) _NOEXCEPT
{
    return __o->test();
}

inline _LIBCPP_INLINE_VISIBILITY
bool
atomic_flag_test(const atomic_flag* __o) _NOEXCEPT
{
    return __o->test();
}

inline _LIBCPP_INLINE_VISIBILITY
bool
atomic_flag_test_explicit(const volatile atomic_flag* __o, memory_order __m) _NOEXCEPT
{
    return __o->test(__m);
}

inline _LIBCPP_INLINE_VISIBILITY
bool
atomic_flag_test_explicit(const atomic_flag* __o, memory_order __m) _NOEXCEPT
{
    return __o->test(__m);
}

inline _LIBCPP_INLINE_VISIBILITY
bool
atomic_flag_test_and_set(volatile atomic_flag* __o) _NOEXCEPT
{
    return __o->test_and_set();
}

inline _LIBCPP_INLINE_VISIBILITY
bool
atomic_flag_test_and_set(atomic_flag* __o) _NOEXCEPT
{
    return __o->test_and_set();
}

inline _LIBCPP_INLINE_VISIBILITY
bool
atomic_flag_test_and_set_explicit(volatile atomic_flag* __o, memory_order __m) _NOEXCEPT
{
    return __o->test_and_set(__m);
}

inline _LIBCPP_INLINE_VISIBILITY
bool
atomic_flag_test_and_set_explicit(atomic_flag* __o, memory_order __m) _NOEXCEPT
{
    return __o->test_and_set(__m);
}

inline _LIBCPP_INLINE_VISIBILITY
void
atomic_flag_clear(volatile atomic_flag* __o) _NOEXCEPT
{
    __o->clear();
}

inline _LIBCPP_INLINE_VISIBILITY
void
atomic_flag_clear(atomic_flag* __o) _NOEXCEPT
{
    __o->clear();
}

inline _LIBCPP_INLINE_VISIBILITY
void
atomic_flag_clear_explicit(volatile atomic_flag* __o, memory_order __m) _NOEXCEPT
{
    __o->clear(__m);
}

inline _LIBCPP_INLINE_VISIBILITY
void
atomic_flag_clear_explicit(atomic_flag* __o, memory_order __m) _NOEXCEPT
{
    __o->clear(__m);
}

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_SYNC
void
atomic_flag_wait(const volatile atomic_flag* __o, bool __v) _NOEXCEPT
{
    __o->wait(__v);
}

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_SYNC
void
atomic_flag_wait(const atomic_flag* __o, bool __v) _NOEXCEPT
{
    __o->wait(__v);
}

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_SYNC
void
atomic_flag_wait_explicit(const volatile atomic_flag* __o,
                          bool __v, memory_order __m) _NOEXCEPT
{
    __o->wait(__v, __m);
}

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_SYNC
void
atomic_flag_wait_explicit(const atomic_flag* __o,
                          bool __v, memory_order __m) _NOEXCEPT
{
    __o->wait(__v, __m);
}

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_SYNC
void
atomic_flag_notify_one(volatile atomic_flag* __o) _NOEXCEPT
{
    __o->notify_one();
}

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_SYNC
void
atomic_flag_notify_one(atomic_flag* __o) _NOEXCEPT
{
    __o->notify_one();
}

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_SYNC
void
atomic_flag_notify_all(volatile atomic_flag* __o) _NOEXCEPT
{
    __o->notify_all();
}

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_SYNC
void
atomic_flag_notify_all(atomic_flag* __o) _NOEXCEPT
{
    __o->notify_all();
}

// fences

inline _LIBCPP_INLINE_VISIBILITY
void
atomic_thread_fence(memory_order __m) _NOEXCEPT
{
    __cxx_atomic_thread_fence(__m);
}

inline _LIBCPP_INLINE_VISIBILITY
void
atomic_signal_fence(memory_order __m) _NOEXCEPT
{
    __cxx_atomic_signal_fence(__m);
}

// Atomics for standard typedef types

typedef atomic<bool>               atomic_bool;
typedef atomic<char>               atomic_char;
typedef atomic<signed char>        atomic_schar;
typedef atomic<unsigned char>      atomic_uchar;
typedef atomic<short>              atomic_short;
typedef atomic<unsigned short>     atomic_ushort;
typedef atomic<int>                atomic_int;
typedef atomic<unsigned int>       atomic_uint;
typedef atomic<long>               atomic_long;
typedef atomic<unsigned long>      atomic_ulong;
typedef atomic<long long>          atomic_llong;
typedef atomic<unsigned long long> atomic_ullong;
#ifndef _LIBCPP_HAS_NO_CHAR8_T
typedef atomic<char8_t>            atomic_char8_t;
#endif
typedef atomic<char16_t>           atomic_char16_t;
typedef atomic<char32_t>           atomic_char32_t;
#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
typedef atomic<wchar_t>            atomic_wchar_t;
#endif

typedef atomic<int_least8_t>   atomic_int_least8_t;
typedef atomic<uint_least8_t>  atomic_uint_least8_t;
typedef atomic<int_least16_t>  atomic_int_least16_t;
typedef atomic<uint_least16_t> atomic_uint_least16_t;
typedef atomic<int_least32_t>  atomic_int_least32_t;
typedef atomic<uint_least32_t> atomic_uint_least32_t;
typedef atomic<int_least64_t>  atomic_int_least64_t;
typedef atomic<uint_least64_t> atomic_uint_least64_t;

typedef atomic<int_fast8_t>   atomic_int_fast8_t;
typedef atomic<uint_fast8_t>  atomic_uint_fast8_t;
typedef atomic<int_fast16_t>  atomic_int_fast16_t;
typedef atomic<uint_fast16_t> atomic_uint_fast16_t;
typedef atomic<int_fast32_t>  atomic_int_fast32_t;
typedef atomic<uint_fast32_t> atomic_uint_fast32_t;
typedef atomic<int_fast64_t>  atomic_int_fast64_t;
typedef atomic<uint_fast64_t> atomic_uint_fast64_t;

typedef atomic< int8_t>  atomic_int8_t;
typedef atomic<uint8_t>  atomic_uint8_t;
typedef atomic< int16_t> atomic_int16_t;
typedef atomic<uint16_t> atomic_uint16_t;
typedef atomic< int32_t> atomic_int32_t;
typedef atomic<uint32_t> atomic_uint32_t;
typedef atomic< int64_t> atomic_int64_t;
typedef atomic<uint64_t> atomic_uint64_t;

typedef atomic<intptr_t>  atomic_intptr_t;
typedef atomic<uintptr_t> atomic_uintptr_t;
typedef atomic<size_t>    atomic_size_t;
typedef atomic<ptrdiff_t> atomic_ptrdiff_t;
typedef atomic<intmax_t>  atomic_intmax_t;
typedef atomic<uintmax_t> atomic_uintmax_t;

// atomic_*_lock_free : prefer the contention type most highly, then the largest lock-free type

#ifdef __cpp_lib_atomic_is_always_lock_free
# define _LIBCPP_CONTENTION_LOCK_FREE __atomic_always_lock_free(sizeof(__cxx_contention_t), 0)
#else
# define _LIBCPP_CONTENTION_LOCK_FREE false
#endif

#if ATOMIC_LLONG_LOCK_FREE == 2
typedef conditional<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, long long>::type          __libcpp_signed_lock_free;
typedef conditional<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, unsigned long long>::type __libcpp_unsigned_lock_free;
#elif ATOMIC_INT_LOCK_FREE == 2
typedef conditional<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, int>::type                __libcpp_signed_lock_free;
typedef conditional<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, unsigned int>::type       __libcpp_unsigned_lock_free;
#elif ATOMIC_SHORT_LOCK_FREE == 2
typedef conditional<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, short>::type              __libcpp_signed_lock_free;
typedef conditional<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, unsigned short>::type     __libcpp_unsigned_lock_free;
#elif ATOMIC_CHAR_LOCK_FREE == 2
typedef conditional<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, char>::type               __libcpp_signed_lock_free;
typedef conditional<_LIBCPP_CONTENTION_LOCK_FREE, __cxx_contention_t, unsigned char>::type      __libcpp_unsigned_lock_free;
#else
    // No signed/unsigned lock-free types
#endif

typedef atomic<__libcpp_signed_lock_free> atomic_signed_lock_free;
typedef atomic<__libcpp_unsigned_lock_free> atomic_unsigned_lock_free;

#define ATOMIC_FLAG_INIT {false}
#define ATOMIC_VAR_INIT(__v) {__v}

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP_ATOMIC