Add section listing alternative approaches

[ericsnowcurrently]

There have been a number of informative discussions over the years (especially the last few years) about the future of the C-API. It would be worth taking advantage those discussions.

We can start by leaving links to those discussions here. Any of them that might warrant a deeper discussion could also get separate issues. (There's already some discussion about HPy.)

[ericsnowcurrently]

I'll start. @zooba wrote down what I think are some important design principles:

https://mail.python.org/archives/list/capi-sig@python.org/thread/B2VDVLABM4RQ4ATEJXFZYWEGTBZPUBKW/

I've opened #7 for a deeper discussion.

[encukou]

My notes: Draft: C API design strategy, Python C-API in non-C languages (and projects I asked to chime in)

[hodgestar]

Here is the high-level HPy API manifesto and the slightly longer explanation of each item:

• https://github.com/hpyproject/hpy/wiki/c-api-next-level-manifesto
• https://github.com/hpyproject/hpy/wiki/c-api-next-level-changes

And the HPy implementation https://github.com/hpyproject/hpy/ as prior art.

HPy can already run kiwisolver, matplotlib, and enough of numpy to run a simple Game of Life. The links are to the respective ports.

[ericsnowcurrently]

@vstinner has also made detailed proposals in the past and written extensively about it:

• (2019) https://pythoncapi.readthedocs.io/
• (2019) https://mail.python.org/archives/list/capi-sig@python.org/thread/RNI3UUI6XUPQQNECZT2DPZFMYIJ42KZ2/
• (2019) https://mail.python.org/archives/list/capi-sig@python.org/thread/HS7WDUYFTT2MCAHQQM55UHPJLAVNYCWX/
• (2018) https://mail.python.org/archives/list/capi-sig@python.org/thread/ENRZNKIFVKK5JUELQRZKGW4WL6FYCBZ3/
• (2018) https://mail.python.org/archives/list/capi-sig@python.org/thread/IUFDUHKM2M3HHXBJWVOA2ZJUW2AEMMQI/
• (2018) https://mail.python.org/archives/list/capi-sig@python.org/thread/STTM62RG57IZ2EYDTJ7SVW32S45I4FRO/
• (2017) https://vstinner.github.io/new-python-c-api.html
• https://vstinner.github.io/tag/c-api.html (other blog posts from Victor)

(Victor's personal Python notes at https://pythondev.readthedocs.io/ probably also have some related material.)

[ericsnowcurrently]

Here's a discussion I started about having an official cython-like tool:

https://mail.python.org/archives/list/capi-sig@python.org/thread/NSREULQDHSJ6SZTOY5YVSNX4U4AYJOI6/

[ericsnowcurrently]

A discussion started by @hodgestar about replacing the C-API with CFFI:

https://mail.python.org/archives/list/capi-sig@python.org/thread/ZV3IQWW7XL6MHZAJARHW62WNZDCX3A4M/

[ericsnowcurrently]

@vstinner also publishes a backward-compatibility shim header that relates here:

https://pythoncapi-compat.readthedocs.io/