Extension modules: :c:member:`~PyModuleDef.m_traverse`,
:c:member:`~PyModuleDef.m_clear` and :c:member:`~PyModuleDef.m_free` functions
of :c:type:`PyModuleDef` are no longer called if the module state was requested
but is not allocated yet. This is the case immediately after the module is
created and before the module is executed (:c:data:`Py_mod_exec` function). More
precisely, these functions are not called if :c:member:`~PyModuleDef.m_size` is
greater than 0 and the module state (as returned by
:c:func:`PyModule_GetState`) is ``NULL``.

Extension modules without module state (``m_size <= 0``) are not affected.
