Windows Stable ABI Support

• Pip version: 9.0.1
• Python version: Any py3
• Operating system: Windows

Description:

I’d like to be able to use the stable ABI to lessen the burden of distributing wheels. pip 9 supports this on macOS, but on Windows it does not. The stable ABI is a bit less useful on Windows due to CRT issues, but with the changes to CRT linking in Python 3.5 and above it seems like it should be possible to do a single stable ABI build that works with Python 3.5+? I am only a Windows Python user to the extent required by the build infrastructure for PyCA projects so hopefully someone more knowledgeable can help out here 😄

Assuming the stable ABI should be supported on Windows then we can start digging into the problem. It turns out that pep425tags.get_supported() doesn’t show abi3 as a supported tag on Windows. The implementation uses imp.get_suffixes() and on Windows this does not return anything with abi3 in it. Setuptools uses a function get_abi3_suffix that keys on pyd in Windows, but it’s unclear to me if this is the correct behavior. Is there a more correct way to detect support for stable ABI on Python 3 in Windows?

(Aside: It’d be nice if pep425tags had a canonical single repo that is then vendored by pip/wheel rather than being divergent modules)

[dstufft]

@zooba Ok so if #define Py_LIMITED_ABI is in the extension code, then it should already be linking against python3.dll?

[chrahunt]

The pip part of this was resolved for #7327 in #7367, essentially we now just use a plain “abi3” when installing for a supported version of CPython. I will close this now but if there’s still any pip-specific action indicated, please say so!