abi3-abi3t-universal

This minimal extension demoes wide Stable ABI compatibility.

Four wheels to cover 3 CPython versions × 3 operating systems × 2 GIL/free-threading variants.

Note that up-to date tools -- ones that are aware of the abi3t wheel tag (for example, pip >= 26.1, packaging >= 26.1, uv >= 0.11.3).

CPython versions: 3.13, 3.14, and 3.15.0b1+.

OSs: Linux (64-bit x86), macOS (universal2), Windows (64-bit x86) (Covering other CPU architectures is possible but would mostly just complicate this demo.)

The shim

The file ft_compat.h contains the compatibility shim needed to make the new API necessary for abi3t (PEP 793 PyModExport & PEP 803 PySlot) work on older versions of Python. It's intended to be reusable, and includes a usage comment.

Note that the extension must be compiled with CPython 3.15+.

Installation

python -m pip install abi3-abi3t-universal

Usage

There's one trivial function that increments and returns a number, mostly to demo module state.

>>> import abi3_abi3t_universal
>>> abi3_abi3t_universal.increment_value()
0
>>> abi3_abi3t_universal.increment_value()
1
>>> abi3_abi3t_universal.increment_value()
2

Caveats

As abi3t is not widely supported in build tools at the time of writing, we use Setuptools, and reach into its internals to select the appropriate tags.

Windows

On Windows, until CPython 3.15.0b2, separate abi3 and abi3t wheels are required due to DLL linkage details. (This will not be fixed for 3.13 and 3.14.)

This project builds two wheels:

• abi3_abi3t_universal-0.2-cp313-abi3-win_amd64.whl
• abi3_abi3t_universal-0.2-cp313-abi3t-win_amd64.whl

For real libraries, it might be more practical to build 4 wheels, three of which can be dropped when 3.13 & 3.14 support is removed:

• abi3_abi3t_universal-0.2-cp313-cp313t-win_amd64.whl (for 3.13 FT)
• abi3_abi3t_universal-0.2-cp314-cp314t-win_amd64.whl (for 3.14 FT)
• abi3_abi3t_universal-0.2-cp313-abi3-win_amd64.whl (for 3.13 GIL & 3.14 GIL)
• abi3_abi3t_universal-0.2-cp315-abi3.abi3t-win_amd64.whl (3.15+)

(The first two can be merged into cp313.cp314-cp313t.cp314t but I'd be a bit worried about tool support for such a tag.)

Licence

All my contributions are marked CC0 1.0, see LICENCE.CC0.

The file ft_compat.h copies/adapts definitions from CPython headers, as necessary for compatibility. I'm pretty sure that's fair use, but I'm not a lawyer. Follow the PSF licence to be safe.