69 lines
2.0 KiB
C++
69 lines
2.0 KiB
C++
/*=============================================================================
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Copyright (c) 2015 Paul Fultz II
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static_const_var.h
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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==============================================================================*/
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#ifndef BOOST_HOF_GUARD_STATIC_CONST_H
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#define BOOST_HOF_GUARD_STATIC_CONST_H
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#include <boost/hof/detail/intrinsics.hpp>
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namespace boost { namespace hof { namespace detail {
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template<class T>
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struct static_const_storage
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{
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static constexpr T value = T();
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};
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template<class T>
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constexpr T static_const_storage<T>::value;
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struct static_const_var_factory
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{
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constexpr static_const_var_factory()
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{}
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template<class T>
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constexpr const T& operator=(const T&) const
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{
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static_assert(BOOST_HOF_IS_DEFAULT_CONSTRUCTIBLE(T), "Static const variable must be default constructible");
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return static_const_storage<T>::value;
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}
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};
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}
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template<class T>
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constexpr const T& static_const_var()
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{
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return detail::static_const_storage<T>::value;
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}
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}} // namespace boost::hof
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#if BOOST_HOF_HAS_RELAXED_CONSTEXPR || defined(_MSC_VER)
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#define BOOST_HOF_STATIC_CONSTEXPR const constexpr
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#else
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#define BOOST_HOF_STATIC_CONSTEXPR static constexpr
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#endif
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#if defined(__GNUC__) && !defined (__clang__) && __GNUC__ == 4 && __GNUC_MINOR__ < 7
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#define BOOST_HOF_STATIC_AUTO_REF extern __attribute__((weak)) constexpr auto
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#else
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#define BOOST_HOF_STATIC_AUTO_REF static constexpr auto&
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#endif
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// On gcc 4.6 use weak variables
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#if defined(__GNUC__) && !defined (__clang__) && __GNUC__ == 4 && __GNUC_MINOR__ < 7
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#define BOOST_HOF_STATIC_CONST_VAR(name) extern __attribute__((weak)) constexpr auto name
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#else
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#define BOOST_HOF_STATIC_CONST_VAR(name) static constexpr auto& name = boost::hof::detail::static_const_var_factory()
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#endif
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#define BOOST_HOF_DECLARE_STATIC_VAR(name, ...) BOOST_HOF_STATIC_CONST_VAR(name) = __VA_ARGS__{}
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#endif
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