Change add_newdocs to e.g. generate a header file at compile time with the docs (as is done in scipy.special), rather than patching them at runtime after PyType_Ready. Requires some hunting for the correct places to specify the docstrings. The current way tp_doc is hacked (after PyTypeReady) not only leaks the char* string yanked out of the PyStringObject, it does not work on PyPy.

gleaned from #10157, plagarized @pv 's hints