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Thanks for your review, @encukou! I think I have addressed all of your comments and, as you anticipated, it simplifies things a great deal.

Would you mind taking another look?

Looks good now, thanks!
It does need a test. (Ideally comparing things to sys.maxsize and sysconfig.get_config_var, which should also serve as guide/validation for what the packaging tools will need to do for earlier Python versions.)

And, of course, it needs deciding on what should go here; but that's for the discussion thread.

Agreed about the tests and further discussion. I just wanted to stabilize the implementation sufficiently to be sure to write meaningful tests. Thanks again!

Tests are in place and easily extendable. Let's focus on the discussion and get this in 💪.