2 // detail/null_global.hpp
3 // ~~~~~~~~~~~~~~~~~~~~~~
5 // Copyright (c) 2003-2017 Christopher M. Kohlhoff (chris at kohlhoff dot com)
7 // Distributed under the Boost Software License, Version 1.0. (See accompanying
8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
11 #ifndef BOOST_ASIO_DETAIL_NULL_GLOBAL_HPP
12 #define BOOST_ASIO_DETAIL_NULL_GLOBAL_HPP
14 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
16 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
18 #include <boost/asio/detail/config.hpp>
20 #include <boost/asio/detail/push_options.hpp>
27 struct null_global_impl
34 // Destructor automatically cleans up the global.
40 static null_global_impl instance_;
45 null_global_impl<T> null_global_impl<T>::instance_;
50 if (null_global_impl<T>::instance_.ptr_ == 0)
51 null_global_impl<T>::instance_.ptr_ = new T;
52 return *null_global_impl<T>::instance_.ptr_;
59 #include <boost/asio/detail/pop_options.hpp>
61 #endif // BOOST_ASIO_DETAIL_NULL_GLOBAL_HPP