[Python-Dev] Usefulness of binary compatibility accross Python versions? (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Mon Dec 18 05:23:31 EST 2017

On Sun, 17 Dec 2017 21:07:02 -0500 Random832 <random832 at fastmail.com> wrote:

Is there any practical for of having the flag off for one slot and on for another slot that's been added later? Could this be replaced (that is, a slot for such a thing added before it's too late) with a simple counter that goes up with each version, and any "unused" slot should have NULL or some other sentinel value?

Any replacement here would break binary compatibility, which is what those flags are precisely meant to avoid.

If it really is important to have the flags themselves, just add another set of flags - PyTPFLAGSHAVEMOREFLAGS.

Yes, we could... but it's more complication again.

That said, if we decide to drop cross-version compatibility, we then are allowed to enlarge the tp_flags field to, say, 64 bits.

Regards

Antoine.

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