gh-152563, test_math: Enable fma test on musl 1.2.6

[weixlu]

Proposal:

#131313 fix many tests on Alpine Linux (musl C library). About test_fma_zero_result, it says

    # gh-131032: musl is fixed but the fix is not yet released; when the fixed
    # version is known change this to:
    #   or support.linked_to_musl() < (1, <m>, <p>)

And now musl 1.2.6 is available, and I have verified that the test can pass. So let's enable it.

• docker image: alpine:edge
• musl version: 1.2.6-r2
• test result: pass

I also test the older version

• docker image: alpine:3.21
• musl version: 1.2.5-r11
• test result: skipped

• Issue: Enable fma test on Alpine Linux (musl C library) #152563

[vstinner]

image: alpine:edge
musl version: 1.2.6-r2
test result: pass

I just tested podman run --rm --interactive --tty alpine:edge: I still get musl 1.2.5.

~ # apk info musl
(...)
musl-1.2.5-r21 description:
the musl c library (libc) implementation

musl-1.2.5-r21 webpage:
https://musl.libc.org/

musl-1.2.5-r21 installed size:
650 KiB

I would prefer to wait until musl 1.2.6 final is released and available in Alpine Linux.

[weixlu]

@vstinner Thanks for the review. Yes, I just double-checked and alpine:edge still defaults to musl-1.2.5. I previously ran apk add --no-cache musl-dev, that's why I got 1.2.6-r2.

I would prefer to wait until musl 1.2.6 final is released and available in Alpine Linux.

No problem, let's wait until 1.2.6 is officially included in the default version.

[vstinner]

https://musl.libc.org/releases.html tells me that musl 1.2.6 was released in March 20, 2026.

No problem, let's wait until 1.2.6 is officially included in the default version.

@weixlu: Hi. Can you check if it's the case now?

[weixlu]

@vstinner Ah yes, thanks for reminder. I have verified that musl 1.2.6 is now officially included

$ docker run --rm alpine:edge apk info musl

musl-1.2.6-r2 description:
the musl c library (libc) implementation

musl-1.2.6-r2 webpage:
https://musl.libc.org/

musl-1.2.6-r2 installed size:
706 KiB

Also I've run test_math and it looks good. So I think this PR is ready to go

[vstinner]

I confirm that all FMA tests of test_math pass on the latest Alpine Linux with musl-1.2.6-r2.

~/cpython # apk info musl
musl-1.2.6-r2 description:
the musl c library (libc) implementation

musl-1.2.6-r2 webpage:
https://musl.libc.org/

musl-1.2.6-r2 installed size:
654 KiB

~/cpython # ./python
Python 3.16.0a0 (heads/main:fcfa919, Aug 11 2026, 13:30:35) [GCC 15.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from test import support
>>> support.linked_to_musl()
(1, 2, 6)

[vstinner]

cc @zware @bitdancer