Regarding the crash,

From what I can see, the `tp_clear` method of bufferedrwpair is called during Py_Finalize() that leads to garbage collection. This NULLs `self->writer` for the rwpair object.

Later, in the same garbage collection routine, the `tp_clear` of textio (the wrapper) is called. This attempts to finalize its wrapped object by first calling the `closed` property of the wrapped object. This property read is propagated down to the wrapped bufferedrwpair, `bufferedrwpair_closed_get()`.

At this point, `self->writer` for the bufferedrwpair object is already NULL from the previous clear. Hence, the crash happens because a NULL pointer dereferencing is attempted.