object.h -Wcast-qual warning

[petere]

BPO	43412
Nosy	@terryjreedy, @vstinner, @leifwalsh, @petere
Superseder	bpo-44378: Py_IS_TYPE(): cast discards ‘const’ qualifier from pointer target type

^{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 2021-07-01.00:05:49.727>
created_at = <Date 2021-03-05.22:12:41.593>
labels = ['interpreter-core', '3.10']
title = 'object.h -Wcast-qual warning'
updated_at = <Date 2021-07-01.00:05:49.725>
user = 'https://github.com/petere'

bugs.python.org fields:

activity = <Date 2021-07-01.00:05:49.725>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2021-07-01.00:05:49.727>
closer = 'vstinner'
components = ['Interpreter Core']
creation = <Date 2021-03-05.22:12:41.593>
creator = 'petere'
dependencies = []
files = []
hgrepos = []
issue_num = 43412
keywords = []
message_count = 5.0
messages = ['388167', '388560', '388607', '396793', '396803']
nosy_count = 4.0
nosy_names = ['terry.reedy', 'vstinner', 'leif.walsh', 'petere']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '44378'
type = None
url = 'https://bugs.python.org/issue43412'
versions = ['Python 3.10']

[petere]

object.h contains an inline function that causes a -Wcast-qual warning from gcc. Since this file ends up visible in third-party code that includes Python.h, this makes it impossible to use -Wcast-qual in such code.

The problem is the change c5cb077, which replaced ob->ob_type by Py_TYPE(ob), which seems reasonable by itself, but Py_TYPE casts away the const, so it creates this problem.

This is a regression in Python 3.10.

[terryjreedy]

Victor, the apparent 3.10 regression is from your commit.

[vstinner]

object.h contains an inline function that causes a -Wcast-qual warning from gcc.

Which function? Can you please provide the warning?

Do you want to propose a fix?

[leifwalsh]

Duplicated by https://bugs.python.org/issue44378, which has a fix merged.

[vstinner]

Duplicated by https://bugs.python.org/issue44378, which has a fix merged.

Right. I close the issue as a duplicate.