warning   c4541:   dynamic_cast   used   on   polymorphic   type   'class   classname'   with   /gr-;   unpredictable   behavior   may   result  

你没有打开run-time   type   information   支持就使用dynamic_cast    
  菜单project－setting－c/c   -   c   language   -   enable   run-time   type   information   (rtti)