Module slot for checking ABI compatibility

[encukou (Petr Viktorin)]

@steve-s

Yes, but that passes PyObject* to the initial entry point, which invites for accessing its fields or passing it to some API calls, otherwise there would be no use for that parameter?

Yes, ideally you wouldn’t use it. I added it for hacks, hotfixes, and specialized loaders.
Also note that the slot I’m proposing isn’t meant to catch any ABI incompatibility – it’s meant to guard against common mistakes.

@steve-s

Eventually in the future CPython could support multiple ABIs, and the choice of the ABI must be done as the first thing. The module slots and whole module initialization contract is part of the ABI.

Sounds like we might need a new export hook in the future! Or a different filename tag at least.