Serhiy: PyDoc_VAR is used in the "two-pass" approach as a forward declaration for docstrings.  Imagine if, in winsound.c, sound_methods was defined above the "dump buffer" block.  The expansion of WINSOUND_PLAYSOUND_METHODDEF would include a reference to winsound_PlaySound__doc__, which hadn't been defined yet.

winsound.c is simple enough, it doesn't need the two-pass approach.  But two-pass would work well for _pickle.c, where there are four or five PyMethodDef structures in the middle of the file.  Part of this is just Zachary experimenting with two-pass.