我这里的MSDN上是这样说的:
Resources associated with a menu that is assigned to a window are freed automatically. If the menu is not assigned to a window, an application must free system resources associated with the menu before closing. An application frees menu resources by calling the DestroyMenu function.
也就是说,作为一个窗口的菜单,会自动释放。其它的菜单要人工释放。