1//===----------------------------------------------------------------------===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8 9#ifndef _LIBCPP___ATOMIC_MEMORY_ORDER_H 10#define _LIBCPP___ATOMIC_MEMORY_ORDER_H 11 12#include <__config> 13#include <__type_traits/is_same.h> 14#include <__type_traits/underlying_type.h> 15 16#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 17# pragma GCC system_header 18#endif 19 20_LIBCPP_BEGIN_NAMESPACE_STD 21 22// Figure out what the underlying type for `memory_order` would be if it were 23// declared as an unscoped enum (accounting for -fshort-enums). Use this result 24// to pin the underlying type in C++20. 25enum __legacy_memory_order { __mo_relaxed, __mo_consume, __mo_acquire, __mo_release, __mo_acq_rel, __mo_seq_cst }; 26 27using __memory_order_underlying_t = underlying_type<__legacy_memory_order>::type; 28 29#if _LIBCPP_STD_VER >= 20 30 31enum class memory_order : __memory_order_underlying_t { 32 relaxed = __mo_relaxed, 33 consume = __mo_consume, 34 acquire = __mo_acquire, 35 release = __mo_release, 36 acq_rel = __mo_acq_rel, 37 seq_cst = __mo_seq_cst 38}; 39 40static_assert((is_same<underlying_type<memory_order>::type, __memory_order_underlying_t>::value), 41 "unexpected underlying type for std::memory_order"); 42 43inline constexpr auto memory_order_relaxed = memory_order::relaxed; 44inline constexpr auto memory_order_consume = memory_order::consume; 45inline constexpr auto memory_order_acquire = memory_order::acquire; 46inline constexpr auto memory_order_release = memory_order::release; 47inline constexpr auto memory_order_acq_rel = memory_order::acq_rel; 48inline constexpr auto memory_order_seq_cst = memory_order::seq_cst; 49 50#else 51 52enum memory_order { 53 memory_order_relaxed = __mo_relaxed, 54 memory_order_consume = __mo_consume, 55 memory_order_acquire = __mo_acquire, 56 memory_order_release = __mo_release, 57 memory_order_acq_rel = __mo_acq_rel, 58 memory_order_seq_cst = __mo_seq_cst, 59}; 60 61#endif // _LIBCPP_STD_VER >= 20 62 63_LIBCPP_END_NAMESPACE_STD 64 65#endif // _LIBCPP___ATOMIC_MEMORY_ORDER_H 66