Handling Error Conditions in Callbacks

I am working on my first XML project, therefore my first experience with
expat.  I had a question how other are dealing with error conditions
within their callback handlers.  Since the callbacks provide no return
value, I assume, one could use the UserData to store the error condition
and pop that up  the callback stack.  Just wanted to make sure I wasn't
missing any functionality within expat.

 

Thanks,

Jim