Add weak_from_this.

test/weak_from_this_test.cpp

@@ -0,0 +1,52 @@
+#include <boost/config.hpp>
+
+//
+//  weak_from_this_test.cpp
+//
+//  Copyright (c) 2002, 2003, 2015 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
+//
+
+
+#include <boost/enable_shared_from_this.hpp>
+#include <boost/shared_ptr.hpp>
+#include <boost/weak_ptr.hpp>
+#include <boost/detail/lightweight_test.hpp>
+
+class V: public boost::enable_shared_from_this<V>
+{
+};
+
+void test()
+{
+    boost::shared_ptr<V> p( new V );
+
+    boost::weak_ptr<V> q = p;
+    BOOST_TEST( !q.expired() );
+
+    boost::weak_ptr<V> q2 = p->weak_from_this();
+    BOOST_TEST( !q2.expired() );
+    BOOST_TEST( !(q < q2) && !(q2 < q) );
+
+    V v2( *p );
+
+    boost::weak_ptr<V> q3 = v2.weak_from_this();
+    BOOST_TEST( q3.expired() );
+
+    *p = V();
+
+    boost::weak_ptr<V> q4 = p->shared_from_this();
+    BOOST_TEST( !q4.expired() );
+    BOOST_TEST( !(q < q4) && !(q4 < q) );
+    BOOST_TEST( !(q2 < q4) && !(q4 < q2) );
+}
+
+int main()
+{
+    test();
+    return boost::report_errors();
+}