Thanks for the response!

> if a weakref W refers to object O, and W and O are _both_ in cyclic trash

I believe that in the examples W is not in cyclic trash, but remains referenced as a global in the frame. Only O is in cyclic trash (O references itself).

I would expect that W's callback would be invoked in this case, but only after O is guaranteed to be deleted. In some cases O can be resurrected in the finalizer.