> (gdb) p *((PyWeakReference*)self)->wr_object
> $9 = {_ob_next = 0x0, _ob_prev = 0x0, ob_refcnt = 0, ob_type = 0x0}
> 
> If I am reading Py_TYPE right, Py_TYPE(self->wr_object) must be 0
> (=NULL).

Well, no, it should *always* be non-NULL (and it's a strong reference,
so it should be a pointer to a valid PyTypeObject).
There's nothing in the CPython source code which sets Py_TYPE(something)
(i.e. something->ob_type) to NULL.