[Inkscape-devel] Explicit destructor calls for libstdc++

Somebody knows why there are so many explicit destructor calls like :

sp_desktop_dispose (GObject *object) { SPDesktop *dt = SP_DESKTOP (object);

dt->sel_modified_connection.disconnect(); dt->sel_modified_connection.~connection();

dt->sel_changed_connection.disconnect(); dt->sel_changed_connection.~connection();

dt->_set_colorcomponent_signal.~signal();

Why not a simple delete (dt->sel_modified_connection); ?