Imported Upstream version 1.67.0upstream/1.67.0

1 files changed, 68 insertions, 0 deletions

diff --git a/boost/hof/detail/static_const_var.hpp b/boost/hof/detail/static_const_var.hpp
new file mode 100644
index 0000000000..553bd23294
--- /dev/null
+++ b/boost/hof/detail/static_const_var.hpp
@@ -0,0 +1,68 @@
+/*=============================================================================
+    Copyright (c) 2015 Paul Fultz II
+    static_const_var.h
+    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_HOF_GUARD_STATIC_CONST_H
+#define BOOST_HOF_GUARD_STATIC_CONST_H
+
+#include <boost/hof/detail/intrinsics.hpp>
+
+namespace boost { namespace hof { namespace detail {
+
+template<class T>
+struct static_const_storage
+{
+    static constexpr T value = T();
+};
+
+template<class T>
+constexpr T static_const_storage<T>::value;
+
+struct static_const_var_factory
+{
+    constexpr static_const_var_factory()
+    {}
+
+    template<class T>
+    constexpr const T& operator=(const T&) const
+    {
+        static_assert(BOOST_HOF_IS_DEFAULT_CONSTRUCTIBLE(T), "Static const variable must be default constructible");
+        return static_const_storage<T>::value;
+    }
+};
+}
+
+template<class T>
+constexpr const T& static_const_var()
+{
+    return detail::static_const_storage<T>::value;
+}
+
+
+}} // namespace boost::hof
+
+#if BOOST_HOF_HAS_RELAXED_CONSTEXPR || defined(_MSC_VER)
+#define BOOST_HOF_STATIC_CONSTEXPR const constexpr
+#else
+#define BOOST_HOF_STATIC_CONSTEXPR static constexpr
+#endif
+
+#if defined(__GNUC__) && !defined (__clang__) && __GNUC__ == 4 && __GNUC_MINOR__ < 7
+#define BOOST_HOF_STATIC_AUTO_REF extern __attribute__((weak)) constexpr auto
+#else
+#define BOOST_HOF_STATIC_AUTO_REF static constexpr auto&
+#endif
+
+// On gcc 4.6 use weak variables
+#if defined(__GNUC__) && !defined (__clang__) && __GNUC__ == 4 && __GNUC_MINOR__ < 7
+#define BOOST_HOF_STATIC_CONST_VAR(name) extern __attribute__((weak)) constexpr auto name
+#else
+#define BOOST_HOF_STATIC_CONST_VAR(name) static constexpr auto& name = boost::hof::detail::static_const_var_factory()
+#endif
+
+#define BOOST_HOF_DECLARE_STATIC_VAR(name, ...) BOOST_HOF_STATIC_CONST_VAR(name) = __VA_ARGS__{}
+
+#endif