1/*
2 * Copyright Andrey Semashev 2007 - 2015.
3 * Distributed under the Boost Software License, Version 1.0.
4 * (See accompanying file LICENSE_1_0.txt or copy at
5 * http://www.boost.org/LICENSE_1_0.txt)
6 */
7/*!
8 * \file fallback_policy_fwd.hpp
9 * \author Andrey Semashev
10 * \date 18.08.2012
11 *
12 * The header contains forward declaration of fallback policies when attribute value visitation or extraction fails.
13 */
14
15#ifndef BOOST_LOG_ATTRIBUTES_FALLBACK_POLICY_FWD_HPP_INCLUDED_
16#define BOOST_LOG_ATTRIBUTES_FALLBACK_POLICY_FWD_HPP_INCLUDED_
17
18#include <boost/log/detail/config.hpp>
19
20#ifdef BOOST_HAS_PRAGMA_ONCE
21#pragma once
22#endif
23
24namespace boost {
25
26BOOST_LOG_OPEN_NAMESPACE
27
28/*!
29 * The \c fallback_to_none policy results in returning an empty value reference if the attribute value cannot be extracted.
30 */
31struct fallback_to_none;
32
33/*!
34 * The \c fallback_to_throw policy results in throwing an exception if the attribute value cannot be extracted.
35 */
36struct fallback_to_throw;
37
38/*!
39 * The \c fallback_to_default policy results in a default value if the attribute value cannot be extracted.
40 */
41template< typename DefaultT >
42struct fallback_to_default;
43
44BOOST_LOG_CLOSE_NAMESPACE // namespace log
45
46} // namespace boost
47
48#endif // BOOST_LOG_ATTRIBUTES_FALLBACK_POLICY_FWD_HPP_INCLUDED_
49

source code of boost/libs/log/include/boost/log/attributes/fallback_policy_fwd.hpp