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. 25 enum __legacy_memory_order { 26 __mo_relaxed, 27 __mo_consume, 28 __mo_acquire, 29 __mo_release, 30 __mo_acq_rel, 31 __mo_seq_cst 32 }; 33 34 using __memory_order_underlying_t = underlying_type<__legacy_memory_order>::type; 35 36 #if _LIBCPP_STD_VER >= 20 37 38 enum class memory_order : __memory_order_underlying_t { 39 relaxed = __mo_relaxed, 40 consume = __mo_consume, 41 acquire = __mo_acquire, 42 release = __mo_release, 43 acq_rel = __mo_acq_rel, 44 seq_cst = __mo_seq_cst 45 }; 46 47 static_assert((is_same<underlying_type<memory_order>::type, __memory_order_underlying_t>::value), 48 "unexpected underlying type for std::memory_order"); 49 50 inline constexpr auto memory_order_relaxed = memory_order::relaxed; 51 inline constexpr auto memory_order_consume = memory_order::consume; 52 inline constexpr auto memory_order_acquire = memory_order::acquire; 53 inline constexpr auto memory_order_release = memory_order::release; 54 inline constexpr auto memory_order_acq_rel = memory_order::acq_rel; 55 inline constexpr auto memory_order_seq_cst = memory_order::seq_cst; 56 57 #else 58 59 enum memory_order { 60 memory_order_relaxed = __mo_relaxed, 61 memory_order_consume = __mo_consume, 62 memory_order_acquire = __mo_acquire, 63 memory_order_release = __mo_release, 64 memory_order_acq_rel = __mo_acq_rel, 65 memory_order_seq_cst = __mo_seq_cst, 66 }; 67 68 #endif // _LIBCPP_STD_VER >= 20 69 70 _LIBCPP_END_NAMESPACE_STD 71 72 #endif // _LIBCPP___ATOMIC_MEMORY_ORDER_H 73