Yes, now that the custom allocator / tracing stuff is in place: 
otherwise there's no way for custom allocation or tracing to occur. 
Please go ahead and rework the patch when you have the time.

Also, since the setup of the reparse header is such an underdocumented 
nightmare, please add as much commentary as possible around the choice 
of allocations & offsets. I was reviewing your code with an eye on the 
various MSDN pages and examples and I still wasn't always able to follow 
your choices.

(BTW I'm not convinced that the PyMem change was the problem since the 
PyMem_Raw* functions simply hand off to malloc/free unless there's a 
custom allocator. Unless of course the missing memset-0 was significant 
here).