Undefinied _Py_Sigset_Converter function when HAVE_SIGSET_T not set

[RomanYurchak]

BPO	41498
Nosy	@brettcannon, @tiran, @serhiy-storchaka, @pablogsal, @miss-islington
PRs	bpo-41498: Fix build on platforms without sigset_t (GH-29770) #29770 [3.10] bpo-41498: Fix build on platforms without sigset_t (GH-29770) #29773 [3.9] bpo-41498: Fix build on platforms without sigset_t (GH-29770) (GH-29774) #29774

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-11-25.12:06:59.602>
created_at = <Date 2020-08-06.20:20:07.159>
labels = ['build', '3.8', '3.9']
title = 'Undefinied _Py_Sigset_Converter function when HAVE_SIGSET_T not set'
updated_at = <Date 2021-11-25.18:36:19.074>
user = 'https://bugs.python.org/RomanYurchak'

bugs.python.org fields:

activity = <Date 2021-11-25.18:36:19.074>
actor = 'brett.cannon'
assignee = 'none'
closed = True
closed_date = <Date 2021-11-25.12:06:59.602>
closer = 'christian.heimes'
components = []
creation = <Date 2020-08-06.20:20:07.159>
creator = 'Roman Yurchak'
dependencies = []
files = []
hgrepos = []
issue_num = 41498
keywords = ['patch']
message_count = 4.0
messages = ['374963', '406989', '406990', '406992']
nosy_count = 6.0
nosy_names = ['brett.cannon', 'christian.heimes', 'serhiy.storchaka', 'pablogsal', 'miss-islington', 'Roman Yurchak']
pr_nums = ['29770', '29773', '29774']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue41498'
versions = ['Python 3.8', 'Python 3.9']

[RomanYurchak]

The _Py_Sigset_Converter function is conditionally defined in

cpython/Modules/posixmodule.h

Line 27 in 777b611

PyAPI_FUNC(int) _Py_Sigset_Converter(PyObject *, void *);

if ifdef HAVE_SIGSET_T

However this function is called unconditionally in

cpython/Modules/clinic/signalmodule.c.h

Line 385 in 777b611

if (!_Py_Sigset_Converter(args[1], &mask)) {

(there are 4 such occurrences), which leads to a compilation error when HAVE_SIGSET_T is not set.

This is regression in 3.8+ as far as I can tell due to changes in #6720

I imagine the solution could be to always define this function but raise an exception if it is called when HAVE_SIGSET_T` is undefined, as done in the following patch: https://github.com/iodide-project/pyodide/blob/fc5495ffdb54a11fd588dc60ba6b8777f90c3724/cpython/patches/0006-fix-Py_Sigset_Converter.patch

Would this be acceptable, or is there a better way of handling it? Thanks!

[tiran]

New changeset dc19e86 by Christian Heimes in branch 'main':
bpo-41498: Fix build on platforms without sigset_t (GH-29770)
dc19e86

[miss-islington]

New changeset 632d589 by Miss Islington (bot) in branch '3.10':
[3.10] bpo-41498: Fix build on platforms without sigset_t (GH-29770) (GH-29773)
632d589

[tiran]

New changeset 71b4147 by Christian Heimes in branch '3.9':
[3.9] bpo-41498: Fix build on platforms without sigset_t (GH-29770) (GH-29774)
71b4147