gh-121249: Support _Complex types in the struct module

[skirpichev]

• Issue: Add support for C99 complex type (_Complex) to the struct module #121249

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📚 Documentation preview 📚: https://cpython-previews--121613.org.readthedocs.build/

[ZeroIntensity]

Nice PR! This looks like something that would have had to get approved on Discourse, though.

[ZeroIntensity]

Lets leave this to core devs.

This is why things get discussed on discourse first 😉

[ZeroIntensity]

This implementation LGTM.

Although, for core dev review, I'm not too sure about this behavior: if the compiler does not support C11 complex types, then the new format characters are disabled and raise an error with no further information.

I'm worried that this will lead to some bug reports later on wondering why E and C don't work on their system -- it would be ideal to raise a different error mentioning that the system doesn't support C11 (albeit, it would be more work to implement).

[picnixz]

Some minor comments but I also agree that having an error without info for an unknown format if complex are not supported is a bit weird.

[skirpichev]

Now on systems without _Complex type - a different error will be raised.

[picnixz]

On my side it's fine. I didn't check in details the functions bodies, but I assume that the tests should cover most of the cases. I think it remains to wait for Victor's and/or Serhiy's review.

[skirpichev]

As it's a follow up of #120894, CC @vstinner

[vstinner]

LGTM

[vstinner]

Merged, thanks.