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bpo-43795: PEP 652 user documentation #25668

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merged 14 commits into from
May 11, 2021
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@encukou encukou commented Apr 27, 2021

  • Reformat the C API and ABI Versioning page (and extend/clarify a bit)
  • Rewrite the stable ABI docs into a general text on C API Compatibility
  • Add a list of Limited API contents, and notes for the individual items.
  • Replace Include/README.rst with a link to a devguide page with the same info

https://bugs.python.org/issue43795

Automerge-Triggered-By: GH:encukou

encukou added 2 commits April 27, 2021 21:16
Mark up all the version macros, adding them to the index and allowing
links to them.

Clarify that these are resolved at build time.

Add an example for Python 3.10. Some people might assume this is 0x10,
not 0xA, based on how well PY_VERSION_HEX "reads" in hex.

Link to the (upcoming) page on API and ABI stability.
encukou and others added 5 commits April 29, 2021 17:06
This replaces the existing :stableabi:, which wasn't really used.

Doc/data/stable_abi.dat is expanded to include all relevant
info (kind of the symbol and version it was added in), and the
c_annotations Sphinx extension reads this file and adds
notes similar to ones added by :stableabi: (which wasn't really
used).

Relevant prior work: python#23185
Co-authored-by: Will Ayd <william.ayd@icloud.com>
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encukou commented Apr 29, 2021

As per the PEP, I added a list of everything in the limited API, as well as notes in individual doc entries. A screenshot of the notes:

image

@encukou encukou marked this pull request as ready for review April 29, 2021 16:03
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encukou commented May 6, 2021

The docs notes will now show platform restrictions, based on #ifdef, like the “on Windows" here:

image

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This looks good to me. I had few nits to clarify.

Doc/c-api/apiabiversion.rst Show resolved Hide resolved
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Thank you @encukou. Nice work improving clarity here. I've made a few suggestions for consideration. Thanks again ☀️


Thus ``3.4.1a2`` is hexversion ``0x030401a2``.
CPython exposes its version number in the following macros.
Note that these correspond to the version code is built with,
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Perhaps bold part of this sentence re: build version vs run-time version.

version information can be found by treating it as a 32 bit number in
the following manner:

+-------+-------------------------+-------------------------+
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Nice table as an example 😄

(x>=2) on the particular :ref:`platform <stable-abi-platform>`.

Defining ``Py_LIMITED_API`` to a value of :c:data:`PY_VERSION_HEX` will
do the same, but allow additional API added up to specified version,
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Great improvements to this section. The wording in this item is slightly confusing. Does this mean: It will use the Limited API for this version and later versions. Earlier versions lose compatibility since additional API may exist prior to this version.

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Thanks for the note! It really helps to have a second set of eyes here.
I've shuffled the paragraph around; hopefully things are clearer with this order.


For example, while :c:func:`PyList_GetItem` is available, its “unsafe” macro
variant :c:func:`PyList_GET_ITEM` is not.
The macro can be faster because it can rely on version-specific implementation
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Good example.

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encukou commented May 7, 2021

Thank you for the thoughtful comments!

@miss-islington miss-islington merged commit b05955d into python:main May 11, 2021
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Sorry, I can't merge this PR. Reason: Base branch was modified. Review and try the merge again..

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Thanks @encukou for the PR 🌮🎉.. I'm working now to backport this PR to: 3.10.
🐍🍒⛏🤖

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GH-26034 is a backport of this pull request to the 3.10 branch.

@encukou encukou deleted the pep652-document branch May 11, 2021 14:04
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encukou commented May 11, 2021

This can be confusing; more and more often and I need a page to link to. So I merged this.
However, I'd be happy for more suggestions/improvements :)

willingc pushed a commit that referenced this pull request May 14, 2021
- Reformat the C API and ABI Versioning page (and extend/clarify a bit)
- Rewrite the stable ABI docs into a general text on C API Compatibility
- Add a list of Limited API contents, and notes for the individual items.
- Replace `Include/README.rst` with a link to a devguide page with the same info
(cherry picked from commit b05955d)

Co-authored-by: Petr Viktorin <encukou@gmail.com>

Co-authored-by: Petr Viktorin <encukou@gmail.com>
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6 participants