Enable move-only deleters

test/Jamfile

@@ -410,3 +410,4 @@ run owner_hash_test.cpp ;
 run sp_unordered_test.cpp ;
 
 run sp_unique_ptr_test2.cpp ;
+run sp_move_only_deleter.cpp ;

test/sp_move_only_deleter.cpp

@@ -0,0 +1,106 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/shared_ptr.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/config.hpp>
+#include <boost/config/pragma_message.hpp>
+#include <memory>
+#include <utility>
+
+#if defined( BOOST_NO_CXX11_RVALUE_REFERENCES )
+
+BOOST_PRAGMA_MESSAGE("Skipping test because BOOST_NO_CXX11_RVALUE_REFERENCES is defined")
+int main() {}
+
+#else
+
+struct Y
+{
+    static int instances;
+
+    bool deleted_;
+
+    Y(): deleted_( false )
+    {
+        ++instances;
+    }
+
+    ~Y()
+    {
+        BOOST_TEST( deleted_ );
+        --instances;
+    }
+
+private:
+
+    Y( Y const & );
+    Y & operator=( Y const & );
+};
+
+int Y::instances = 0;
+
+struct YD
+{
+    bool moved_;
+
+    YD(): moved_( false )
+    {
+    }
+
+    YD( YD&& r ): moved_( false )
+    {
+        r.moved_ = true;
+    }
+
+    void operator()( Y* p ) const
+    {
+        BOOST_TEST( !moved_ );
+
+        if( p )
+        {
+            p->deleted_ = true;
+            delete p;
+        }
+    }
+
+private:
+
+    YD( YD const & );
+    YD & operator=( YD const & );
+};
+
+int main()
+{
+    BOOST_TEST( Y::instances == 0 );
+
+    {
+        YD del;
+        boost::shared_ptr<Y> p( new Y, std::move( del ) );
+
+        BOOST_TEST( Y::instances == 1 );
+        BOOST_TEST( del.moved_ );
+
+        p.reset( new Y, YD() );
+
+        BOOST_TEST( Y::instances == 1 );
+
+        p = boost::shared_ptr<Y>( new Y, YD() );
+
+        BOOST_TEST( Y::instances == 1 );
+
+        YD del2;
+        p.reset( new Y, std::move( del2 ) );
+
+        BOOST_TEST( Y::instances == 1 );
+        BOOST_TEST( del2.moved_ );
+
+        p.reset();
+        BOOST_TEST( Y::instances == 0 );
+    }
+
+    return boost::report_errors();
+}
+
+#endif