[issue40204] Docs build error with Sphinx 3.0 due to invalid C declaration

[Karthikeyan Singaravelan]

New submission from Karthikeyan Singaravelan <tir.karthi at gmail.com>:

The following error is caused in Docs build for a 3.8 backport since sphinx is ran with warnings. Sphinx released 3.0 on April 6. The last successful build on master uses Sphinx 2.2.0 [0]. My guess is sphinx new version possibly breaking the build on Python 3.8 where it's not pinned to use 2.2.0 pulling the latest version. The changelog for Sphinx has below note :

https://www.sphinx-doc.org/en/master/changes.html#release-3-0-0-released-apr-06-2020 

The C domain has been rewritten, with additional directives and roles. The existing ones are now more strict, resulting in new warnings.

Python 3.8 and Python 3.7 doesn't have Sphinx pinned to 2.2.0 while master does.

Python 3.8 Docs makefile : https://github.com/python/cpython/blob/f7b0259d0d243a71d79a3fda9ec7aad4306513eb/Doc/Makefile#L146

Failed build :

https://github.com/python/cpython/pull/19388/checks?check_run_id=563053793#step:7:46

Error :

Warning, treated as error:
/home/runner/work/cpython/cpython/Doc/c-api/buffer.rst:92:Error in declarator or parameters
Invalid C declaration: Expected identifier in nested name. [error at 5]
  void \*buf
  -----^
Makefile:49: recipe for target 'build' failed
make[1]: *** [build] Error 2


[0] https://github.com/python/cpython/runs/564123625#step:6:24

----------
assignee: docs at python
components: Documentation
messages: 365858
nosy: docs at python, eric.araujo, ezio.melotti, mdk, rhettinger, vstinner, willingc, xtreak
priority: normal
severity: normal
status: open
title: Docs build error with Sphinx 3.0 due to invalid C declaration
type: behavior
versions: Python 3.8

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<https://bugs.python.org/issue40204>
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