Add boost/smart_ptr/enable_shared_from.hpp

include/boost/smart_ptr/enable_shared_from.hpp

@@ -0,0 +1,37 @@
+#ifndef BOOST_SMART_PTR_ENABLE_SHARED_FROM_HPP_INCLUDED
+#define BOOST_SMART_PTR_ENABLE_SHARED_FROM_HPP_INCLUDED
+
+//  enable_shared_from.hpp
+//
+//  Copyright 2019 Peter Dimov
+//
+//  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
+//
+//  See http://www.boost.org/libs/smart_ptr/ for documentation.
+
+#include <boost/smart_ptr/enable_shared_from_this.hpp>
+#include <boost/smart_ptr/detail/sp_noexcept.hpp>
+
+namespace boost
+{
+
+class enable_shared_from: public enable_shared_from_this<enable_shared_from>
+{
+};
+
+
+template<class T> shared_ptr<T> shared_from( T * p )
+{
+    return shared_ptr<T>( p->enable_shared_from::shared_from_this(), p );
+}
+
+template<class T> weak_ptr<T> weak_from( T * p ) BOOST_SP_NOEXCEPT
+{
+    return weak_ptr<T>( p->enable_shared_from::weak_from_this(), p );
+}
+
+} // namespace boost
+
+#endif  // #ifndef BOOST_SMART_PTR_ENABLE_SHARED_FROM_HPP_INCLUDED