PEP 703 and Packaging

[colesbury (Sam Gross)]

(Cross-posting here on @pf_moore’s suggestion. Please comment on the original post.)

I’ve posted a proposal to add a few functions to the stable ABI, which will allow cp313-abi3 stable ABI wheels to be supported by both the default 3.13+ CPython builds and the (experimental) --disable-gil builds.

Python ABIs and PEP 703

PEP 703 poses some issues regarding the stable ABI. I’ve described these issue below along with a short proposal. tl;dr The --disable-gil builds of CPython 3.13 will not be able to load existing wheels that target the stable ABI. However, we can make wheels that target the 3.13+ stable ABI work with both the default (with GIL) and --disable-gil builds going forward. Background CPython C API extensions can be compiled for either the stable ABI or version-specific ABI. Targeting the stable ABI a…

Here’s my packaging tools focused summary:

• cp313-abi3 wheels will work with CPython 3.13+ default and experimental --disable-gil builds.
• Older stable ABI wheels will continue to work with the default build, but not the experimental --disable-gil build.
• As is currently the case, cp313-abi3 wheels would not work with older (pre 3.13) versions of CPython.
• pypa/packaging would need to be updated to platform tags for --disable-gil builds.
• Toosl like pip, poetry, and hatch that use pypa/packaging would need to update their version of pypa/packaging to work correctly with the experimental --disable-gil build.
• A new field sys.implementation.abi_disable_gil to identify --disable-gil builds from the default (with GIL) build .

Here’s my summary for maintainers of extensions that use the stable ABI:

• Extensions maintainers that wish to support the experimental --disable-gil build will need to provide a wheel that targets the cp313-abi3 stable ABI (i.e., the Python 3.13 limited API). In practice, since they are likely to also support older versions of Python, this means building an extra wheel per platform. But the number of wheels would not further increase in 3.14 and later versions. (This is slightly improved compared to PEP 703). If they do not care to support the --disable-gil build, then no changes are necessary.

Here’s my summary for maintainers of extensions that do not use the stable ABI:

• Extensions maintainers that wish to support the experimental --disable-gil builds will need to build an extra wheels per platform (essentially unchanged from PEP 703). If they do not care to support the --disable-gil build, then no changes are necessary.