While it's still documented as "int", it seems that Python 3.0 changed the signature to Py_ssize_t for this one.

http://hg.python.org/cpython/file/4b3238923b01/Include/unicodeobject.h#l1650

Not sure what to make of it. Maybe it's just not important enough to worry. OTOH, changing it to Py_ssize_t in the Cython declarations won't really hurt, I think.