Description

kmray

opened on Oct 30, 2025

Issue body actions

Bug report

Bug description:

Expected behavior:

• Path.chmod(stat.S_IWRITE | stat.S_IREAD) should clear the read-only attribute regardless of archive bit state
• Path.chmod(stat.S_IWRITE | stat.S_IREAD) should match os.chmod() behavior

Actual behavior:

• When archive bit is cleared, Path.chmod(stat.S_IWRITE | stat.S_IREAD) silently fails to clear read-only
• When archive bit is set, it works correctly
• Path.chmod(stat.S_IWRITE | stat.S_IREAD, follow_symlinks=False) always works

import os
import stat
import subprocess
from pathlib import Path


def is_read_only(file: str | os.PathLike) -> bool:
    return os.stat(file).st_file_attributes & stat.FILE_ATTRIBUTE_READONLY > 0


test_file = Path('test.txt')
test_file.touch()

subprocess.run(f'attrib -a +r {test_file}', check=True)
print(f'Initial (no archive): Read Only: {is_read_only(test_file)}')

test_file.chmod(stat.S_IWRITE | stat.S_IREAD)
print(f'After chmod(follow_symlinks=True): Read Only: {is_read_only(test_file)}')

test_file.chmod(stat.S_IWRITE | stat.S_IREAD, follow_symlinks=False)
print(f'After chmod(follow_symlinks=False): {is_read_only(test_file)}')

subprocess.run(f'attrib +a +r {test_file}', check=True)
print(f'Initial (archive): Read Only: {is_read_only(test_file)}')

test_file.chmod(stat.S_IWRITE | stat.S_IREAD)
print(f'After chmod(follow_symlinks=True): Read Only: {is_read_only(test_file)}')

test_file.chmod(stat.S_IWRITE | stat.S_IREAD, follow_symlinks=False)
print(f'After chmod(follow_symlinks=False): {is_read_only(test_file)}')

Output

Initial (no archive): Read Only: True
After chmod(follow_symlinks=True): Read Only: True
After chmod(follow_symlinks=False): False
Initial (archive): Read Only: True
After chmod(follow_symlinks=True): Read Only: False
After chmod(follow_symlinks=False): False

CPython versions tested on:

3.14

Operating systems tested on:

Windows

Linked PRs

• gh-140774: Fix pathlib.Path.chmod handling of Windows Archive bit #142018
• gh-140774: Fix clearing the read-only file attribute on Windows #154852

Activity

1. kmray

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Oct 30, 2025
2. cmaloney

   added

   OS-windows

   on Oct 30, 2025
3. StanFromIreland

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   topic-pathlib

   on Oct 30, 2025
4. pareshjoshij

   added 2 commits that reference this issue on Nov 27, 2025

   pythongh-140774: Fix pathlib.Path.chmod not handling the Archive bit …

   9cf6cd7

   Fix pythongh-140774: os.chmod fails to clear Read-Only if Archive bit…

   25cc0a2
5. yhay81

   added 2 commits that reference this issue on Nov 12, 2026

   Merge remote-tracking branch 'upstream/main' into pythongh-140774-hch…

   3b50d3d

   pythongh-140774: Set SetFileAttributesW argtypes and cover fd/Path.chmod

   80c74d0
6. yhay81 commented on Nov 12, 2026

   

   yhay81

   on Nov 12, 2026

   More actions

   Root-cause note for triage: although reported via Path.chmod(), the bug is in win32_hchmod() (Modules/posixmodule.c, introduced in GH-113049 / GH-113192), affecting os.chmod(..., follow_symlinks=True), os.chmod(fd, ...), os.fchmod(), and Path.chmod() alike (os.chmod() on Windows defaults to follow_symlinks=False, which goes through SetFileAttributesW() instead).

   Newly created files on NTFS carry FILE_ATTRIBUTE_ARCHIVE (0x20), so clearing FILE_ATTRIBUTE_READONLY (0x01) normally leaves info.FileAttributes != 0. When READONLY is the sole attribute (e.g. after attrib -a +r), info.FileAttributes &= ~FILE_ATTRIBUTE_READONLY yields 0, which FILE_BASIC_INFO documents as leaving attributes unchanged rather than clearing them; FILE_ATTRIBUTE_NORMAL must be passed instead. Fix and regression tests are in #154852.
7. yhay81

   added a commit that references this issue on Nov 12, 2026

   pythongh-140774: Remove redundant Path.chmod() test from Win32ChmodTests

   362a02a

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