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Thanks @carljm for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖

GH-115140 is a backport of this pull request to the 3.12 branch.

There's a bunch of compiler warnings in Include/internal/pycore_symtable.h in the "files changed" tab of this PR -- were they caused by the PR?

I saw that but didn't comment because they looked obviously unrelated. I don't know what made them show up though; @carljm do you have any ideas?

No, the warnings look very odd to me (2 is not negative!), and I don't see how they could possibly be caused by this PR, either.

I thought they looked unrelated too, but they showed up on the 3.12 backport PR as well

Ok, after further exploration, this warning is related to the PR, and in fact reveals a bug in the PR. The expression ~DEF_FREE macro-expands to ~2<<4, and the precedence here is actually (~2)<<4 :(

It just happens that this doesn't cause any actual problem, because ~2<<4 is ...1010000 whereas ~(2<<4) is ...1011111 and those lower four bits correspond to DEF_GLOBAL, DEF_LOCAL, DEF_PARAM, and DEF_NONLOCAL, none of which would ever be set for a DEF_FREE __class__ anyway. So wrongly zeroing them out doesn't change anything.

This is a good reminder to always parenthesize your macro definitions! The best fix IMO would be to parenthesize all of those defines (e.g. #define DEF_FREE (2<<4)) rather than just parenthesizing my particular usage site.

The error is mostly confusing because it points to the wrong code location (the macro definition instead of usage site), but digging into the actual compiler logs, the warning points to both locations.

Thanks @AlexWaygood for pushing me to dig further into this!

I'll push a fix PR.