// boost/memory_order.hpp // // Defines enum boost::memory_order per the C++0x working draft // // Copyright (c) 2008, 2009 Peter Dimov // Copyright (c) 2018 Andrey Semashev // // Distributed under the Boost Software License, Version 1.0. // See accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) #ifndef BOOST_MEMORY_ORDER_HPP_INCLUDED #define BOOST_MEMORY_ORDER_HPP_INCLUDED #include #if defined(BOOST_HAS_PRAGMA_ONCE) # pragma once #endif namespace boost { // // Enum values are chosen so that code that needs to insert // a trailing fence for acquire semantics can use a single // test such as: // // if( mo & memory_order_acquire ) { ...fence... } // // For leading fences one can use: // // if( mo & memory_order_release ) { ...fence... } // // Architectures such as Alpha that need a fence on consume // can use: // // if( mo & ( memory_order_acquire | memory_order_consume ) ) { ...fence... } // // The values are also in the order of increasing "strength" // of the fences so that success/failure orders can be checked // efficiently in compare_exchange methods. // #if !defined(BOOST_NO_CXX11_SCOPED_ENUMS) enum class memory_order : unsigned int { relaxed = 0, consume = 1, acquire = 2, release = 4, acq_rel = 6, // acquire | release seq_cst = 14 // acq_rel | 8 }; BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST memory_order memory_order_relaxed = memory_order::relaxed; BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST memory_order memory_order_consume = memory_order::consume; BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST memory_order memory_order_acquire = memory_order::acquire; BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST memory_order memory_order_release = memory_order::release; BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST memory_order memory_order_acq_rel = memory_order::acq_rel; BOOST_INLINE_VARIABLE BOOST_CONSTEXPR_OR_CONST memory_order memory_order_seq_cst = memory_order::seq_cst; #undef BOOST_MEMORY_ORDER_INLINE_VARIABLE #else // !defined(BOOST_NO_CXX11_SCOPED_ENUMS) enum memory_order { memory_order_relaxed = 0, memory_order_consume = 1, memory_order_acquire = 2, memory_order_release = 4, memory_order_acq_rel = 6, // acquire | release memory_order_seq_cst = 14 // acq_rel | 8 }; #endif // !defined(BOOST_NO_CXX11_SCOPED_ENUMS) } // namespace boost #endif // #ifndef BOOST_MEMORY_ORDER_HPP_INCLUDED