Cyclic GC rules for subtyped objects with tp_dictoffset

[BChess]

Hi,

I'm writing a new PyTypeObject that is base type, supports cyclic GC,
and has a tp_dictoffset.  If my type is sub-typed by a python class,
what exactly are the rules for how I'm supposed to treat my PyDict
object with regards to cyclic GC?  Do I still visit it in my traverse
() function if I'm subtyped?  Do I decrement the refcount upon
dealloc?  By the documentation, I'm assuming I should always be using
_PyObject_GetDictPtr() to be accessing the dictionary, which I do.
But visiting the dictionary in traverse() in the case it's subtyped
results in a crash in weakrefobject.c.  I'm using Python 2.5.

Thanks for any help anyone has!
Ben