Implement support for the free-threaded build of CPython 3.13

[lysnikolaou]

What do these changes do?

• Change Cython dependency to 3.1.0+ for CPython 3.13 free-threading to support free-threading
• Test the free-threaded build on CI
• Compile Cython to C++ (instead of C) and change to a sequentially consistent atomic integer for frozen .

Are there changes in behavior for the user?

No.

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modifications, please add yourself to CONTRIBUTORS.txt
  • The format is <Name> <Surname>.
  • Please keep the list in alphabetical order, the file is sorted by name.
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> for example (588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the pr
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files."

[lysnikolaou]

If someone could hit Approve for the workflows to run, that'd be really helpful.

[bdraco]

CI Run.

If you need me to start it, feel free to reach out on discord or matrix as I likely won't see GitHub notifications as they tend to be overwhelming

[lysnikolaou]

I changed the approach here to use C++ atomics instead of critical sections. That should be faster / more scalable. If you can hit the green button again for the actions to run, that'd be great!

If you need me to start it, feel free to reach out on discord or matrix as I likely won't see GitHub notifications as they tend to be overwhelming

Not sure what Discord server you're talking about. I'd love an invitation if possible.

[bdraco]

I changed the approach here to use C++ atomics instead of critical sections. That should be faster / more scalable. If you can hit the green button again for the actions to run, that'd be great!

If you need me to start it, feel free to reach out on discord or matrix as I likely won't see GitHub notifications as they tend to be overwhelming

Not sure what Discord server you're talking about. I'd love an invitation if possible.

aio-libs uses Matrix https://matrix.to/#/#aio-libs:matrix.org

However I'm usually a lot easier to find on Home Assistant's Discord: https://discord.com/invite/home-assistant

[codecov]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 96.22%. Comparing base (c28f32d) to head (e54fe07).
Report is 36 commits behind head on master.

Files with missing lines	Patch %	Lines
packaging/pep517_backend/_backend.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #618      +/-   ##
==========================================
- Coverage   96.94%   96.22%   -0.73%     
==========================================
  Files          16       14       -2     
  Lines        1278     1139     -139     
  Branches       90       90              
==========================================
- Hits         1239     1096     -143     
- Misses         14       17       +3     
- Partials       25       26       +1     

Flag	Coverage Δ
CI-GHA	96.13% <83.33%> (-0.66%)	⬇️
MyPy	72.66% <83.33%> (-0.04%)	⬇️
OS-Linux	99.20% <ø> (-0.49%)	⬇️
OS-Windows	99.20% <ø> (-0.40%)	⬇️
OS-macOS	99.20% <ø> (ø)
Py-3.10.11	99.20% <ø> (-0.20%)	⬇️
Py-3.10.16	99.20% <ø> (-0.49%)	⬇️
Py-3.11.11	99.20% <ø> (-0.49%)	⬇️
Py-3.11.9	99.20% <ø> (-0.20%)	⬇️
Py-3.12.9	99.20% <ø> (-0.35%)	⬇️
Py-3.13.2	99.20% <ø> (-0.35%)	⬇️
Py-3.13.2t	99.20% <ø> (?)
Py-3.9.13	99.20% <ø> (-0.20%)	⬇️
Py-3.9.21	99.20% <ø> (-0.49%)	⬇️
Py-pypy7.3.16	98.41% <ø> (ø)
Py-pypy7.3.19	98.41% <ø> (ø)
VM-macos-latest	99.20% <ø> (ø)
VM-ubuntu-latest	99.20% <ø> (-0.49%)	⬇️
VM-windows-latest	99.20% <ø> (-0.40%)	⬇️
pytest	99.20% <ø> (-0.35%)	⬇️

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[lysnikolaou]

This is ready for another round of reviews, whenever anyone finds some spare cycles.

[bdraco]

LGTM. PR description needs to be updated to reflect the changes.

[webknjaz]

Just one thing that bothers me.

[bdraco]

Thanks @lysnikolaou