@encukou: I found this bug while enabling limited C API tests on Free Threading in test_cppext for PR gh-157493. IMO we should fix this issue in Python 3.15.0. Otherwise, developers may start writing extensions as PyABIInfo_VAR(abi_info) (without ;) which is currently accepted.

I checked the documentation: PyABIInfo_VAR is always used as PyABIInfo_VAR(abi_info); (with ;).

I agree. Thanks for the catch!

It's @hugovk's call though. For context:
With the fix, existing extension modules will work, but some existing ones might fail to compile until they get a small source fix.
All docs show the “correct” way to use PyABIInfo_VAR, but, projects that compile with strict C++03 compliance settings might have adjusted and will now need adjusting back.

IMO, for C-wielding early adopters, a NEWS entry is enough.

Yes, let's have this fixed for 3.15.0, please add the NEWS entry.

Should this go into main first?

Yes, let's have this fixed for 3.15.0, please add the NEWS entry.

I added a NEWS entry.

Should this go into main first?

I extracted the PyABIInfo_VAR macro fix from my larger PR gh-157493. The main change is under review. (I just fixed test_cppext when using clang.)

Should this go into main first?

IMO it should, to keep the change & NEWS together, and make it easier to revert if there's some unforeseen weirdness. I sent #157539.

(If you think keeping this in the bigger change is better I won't object, but then add the NEWS entry there.)

Thanks both, both merged!