add boost on mac

macx64/include/boost/log/attributes/fallback_policy_fwd.hpp

@@ -0,0 +1,48 @@
+/*
+ *          Copyright Andrey Semashev 2007 - 2015.
+ * 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)
+ */
+/*!
+ * \file   fallback_policy_fwd.hpp
+ * \author Andrey Semashev
+ * \date   18.08.2012
+ *
+ * The header contains forward declaration of fallback policies when attribute value visitation or extraction fails.
+ */
+
+#ifndef BOOST_LOG_ATTRIBUTES_FALLBACK_POLICY_FWD_HPP_INCLUDED_
+#define BOOST_LOG_ATTRIBUTES_FALLBACK_POLICY_FWD_HPP_INCLUDED_
+
+#include <boost/log/detail/config.hpp>
+
+#ifdef BOOST_HAS_PRAGMA_ONCE
+#pragma once
+#endif
+
+namespace boost {
+
+BOOST_LOG_OPEN_NAMESPACE
+
+/*!
+ * The \c fallback_to_none policy results in returning an empty value reference if the attribute value cannot be extracted.
+ */
+struct fallback_to_none;
+
+/*!
+ * The \c fallback_to_throw policy results in throwing an exception if the attribute value cannot be extracted.
+ */
+struct fallback_to_throw;
+
+/*!
+ * The \c fallback_to_default policy results in a default value if the attribute value cannot be extracted.
+ */
+template< typename DefaultT >
+struct fallback_to_default;
+
+BOOST_LOG_CLOSE_NAMESPACE // namespace log
+
+} // namespace boost
+
+#endif // BOOST_LOG_ATTRIBUTES_FALLBACK_POLICY_FWD_HPP_INCLUDED_