For future reference, the cdef problem should be fixed by cython/cython#5479

Re: module for cdef classes. A good fix looks really hard. The basic problem is that type defines its own property for __module__ which ignores whatever you set in the class dictionary for static types.

However. For heap types it works:

# distutils: extra_compile_args = -DCYTHON_USE_TYPE_SPECS=1

cdef class C:
    __module__ = "a"

print(C.__module__)  # prints "a"

Is that any use to Numpy?

(I'm also not sure that the issue that @mattip linked is a hugely great fix. It'd fix self.__module__ but not cls.__module__

Is that any use to Numpy?

Not sure I would enable it just for this sake, but I suspect heap-types are in our future anyway, so I don't mind doing it (unless someone has a clear downside).

FWIW, I don't think allowing to set __module__ and __name__/__qualname__ is very necessary/reasonable for non-heap types.
What I might allow (if it is easy) is exactly this:

cdef class myclass:
    __module__ = "something"

Which would set tp_name to f{__module__}.myclass rather than f{module.__name__}.myclass.