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Subject: Re: Documentation: build failure with sphinx >= 3.0.0: exception:
 cannot import name 'c_funcptr_sig_re' from 'sphinx.domains.c'
To:     Salvatore Bonaccorso <carnil@debian.org>,
        linux-doc@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>
Cc:     Bhaskar Chowdhury <unixbhaskar@gmail.com>,
        LinuxKernel <linux-kernel@vger.kernel.org>,
        jforbes@fedoraproject.org
References: <20200408113705.GB1924@ArchLinux>
 <20200408132505.52e595bc@lwn.net> <20200408233450.GA14923@debian>
 <20200809132327.GA145573@eldamar.local>
 <20200812073059.GA509953@eldamar.local>
From:   Markus Heiser <markus.heiser@darmarit.de>
Message-ID: <579fbb36-515d-5af4-f7dc-c092d29fddd8@darmarit.de>
Date:   Wed, 12 Aug 2020 10:21:40 +0200
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Am 12.08.20 um 09:30 schrieb Salvatore Bonaccorso:
[..]
>> The problem is actually related to changes happening in Sphinx 3.0.0.
>> There is the followign issue filled upstream:
>>
>> https://github.com/sphinx-doc/sphinx/issues/7421
>>
>> 'c_funcptr_sig_re' was removed upstream in sphinx v3.0.0b1 and so the
>> kernel documentation build fails. This is reproducible with a recent
>> sphinx version (in attached case it is 3.2.0):
>>
>> $ make PYTHON=python3 xmldocs
>>    SPHINX  xmldocs --> file:///home/build/linux/Documentation/output/xml
>> make[2]: Nothing to be done for 'xml'.
>> Running Sphinx v3.2.0
>>
>> Extension error:
>> Could not import extension cdomain (exception: cannot import name 'c_funcptr_sig_re' from 'sphinx.domains.c' (/usr/lib/python3/dist-packages/sphinx/domains/c.py))
>> make[1]: *** [Documentation/Makefile:115: xmldocs] Error 2
>> make: *** [Makefile:1655: xmldocs] Error 2
>>
>> Distribution reports related to this issue:
>> https://bugs.debian.org/963636
>> https://bugs.archlinux.org/task/66178
>> https://bugs.archlinux.org/task/66156
> 
> As a workaround to make the documentation build again (but known that
> parts of the documentation will be broken), we could drop the cdomain
> extension.
> 
> Regards,
> Salvatore

@jon, do you have time to implement a patch?
.. sorry, I'am in a hurry :o

In the linked github issue you find also a patch that fixes a
cdomain.py.  I tested the patch (shee below) in the linux kernel.

   For me it works.

BTW: The patch of Documentation/sphinx/requirements.txt
was only nedded for a test.

   -- Markus --


---


diff --git a/Documentation/sphinx/cdomain.py b/Documentation/sphinx/cdomain.py
index cbac8e608dc4..65e15d48891e 100644
--- a/Documentation/sphinx/cdomain.py
+++ b/Documentation/sphinx/cdomain.py
@@ -31,16 +31,35 @@ u"""
         arguments types of function-like macros.

  """
+import re

  from docutils import nodes
  from docutils.parsers.rst import directives

  import sphinx
  from sphinx import addnodes
-from sphinx.domains.c import c_funcptr_sig_re, c_sig_re
  from sphinx.domains.c import CObject as Base_CObject
  from sphinx.domains.c import CDomain as Base_CDomain

+# C&P from commit https://github.com/return42/linuxdoc/commit/48f09de2
+# fixes 
https://github.com/sphinx-doc/sphinx/commit/0f49e30c51b5cc5055cda5b4b294c2dd9d1df573#r38750737
+
+# pylint: disable=invalid-name
+c_sig_re = re.compile(
+    r'''^([^(]*?)          # return type
+        ([\w:.]+)  \s*     # thing name (colon allowed for C++)
+        (?: \((.*)\) )?    # optionally arguments
+        (\s+const)? $      # const specifier
+    ''', re.VERBOSE)
+
+c_funcptr_sig_re = re.compile(
+    r'''^([^(]+?)          # return type
+        (\( [^()]+ \)) \s* # name in parentheses
+        \( (.*) \)         # arguments
+        (\s+const)? $      # const specifier
+    ''', re.VERBOSE)
+# pylint: enable=invalid-name
+
  __version__  = '1.0'

  # Get Sphinx version
diff --git a/Documentation/sphinx/requirements.txt 
b/Documentation/sphinx/requirements.txt
index 489f6626de67..f7486fd7ec85 100644
--- a/Documentation/sphinx/requirements.txt
+++ b/Documentation/sphinx/requirements.txt
@@ -1,3 +1,3 @@
  docutils
-Sphinx==2.4.4
+Sphinx==3.2.0
  sphinx_rtd_theme