this_ptr question

In the extension that I'm working on, I have a few classes wrapping some library data and in the constructors of those classes I need to save the pointer (this_ptr) of the wrapper so that library can keep track of them.. What I found out, though is that this_ptr doesn't seem to be constant -- in the constructor it's one value, and then in the method call (same variable), it's a different value. Is there a way to do what I need? -Andrei "Try to spend the next 30 seconds not thinking about a blue-eyed polar bear." -Feodor Dostoevsky