Added thirdparty: boost library

thirdparty/include/boost/contract/detail/exception.hpp

@@ -0,0 +1,31 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_EXCEPTION_HPP_
+#define BOOST_CONTRACT_DETAIL_EXCEPTION_HPP_
+
+// Copyright (C) 2008-2019 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+#include <boost/config.hpp>
+#include <exception>
+
+namespace boost { namespace contract { namespace detail {
+
+// Using this instead of std::uncaught_exception() because
+// std::uncaught_exception will be removed in C++20.
+inline bool uncaught_exception() BOOST_NOEXCEPT {
+    // Alternatively, this could just return `boost::core::uncaught_exceptions()
+    // > 0` but that emulates the exception count which is not needed by this
+    // lib (the implementation below is simpler and could be faster).
+    #ifdef __cpp_lib_uncaught_exceptions
+        return std::uncaught_exceptions() > 0;
+    #else
+        return std::uncaught_exception();
+    #endif
+}
+
+} } } // namespace
+
+#endif // #include guard
+