Use clear Stack

· To push objects into the cleanup stack, you can
-Use cleanupstack: pushl (PTR) for pointers ---- the memory will be deleted when an exception exits.
-Use cleanupclosepushl (handle) for the handle ---- the handle is closed when an exception exits.

· To clear the stack from the pop-up object, you can
-Use cleanupstack: Pop (pointer) to pop up the top object of the stack.
-Use cleanupstack: popanddestroy (pointer) to pop up and delete/close objects.

· Features of objects that need to be pushed into the cleanup Stack
-This object is referenced by a local pointer.
-During the lifetime of the object, a function that may exit abnormally is called.

· Do not push member variables of the class into the cleanup Stack