SystemError via chmod(symlink, ..., follow_symlinks=False)

[asottile]

BPO	32277
Nosy	@serhiy-storchaka, @asottile
PRs	bpo-32277: fix exception raised from chmod(..., follow_symlinks=False) #4797 [3.6] bpo-32277: Fix exception raised from chmod(..., follow_symlinks=False) (GH-4797) #4869

^{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 2017-12-14.17:31:17.099>
created_at = <Date 2017-12-11.17:45:53.458>
labels = ['extension-modules', 'type-bug', '3.7']
title = 'SystemError via chmod(symlink, ..., follow_symlinks=False)'
updated_at = <Date 2017-12-14.17:31:17.099>
user = 'https://github.com/asottile'

bugs.python.org fields:

activity = <Date 2017-12-14.17:31:17.099>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2017-12-14.17:31:17.099>
closer = 'serhiy.storchaka'
components = ['Extension Modules']
creation = <Date 2017-12-11.17:45:53.458>
creator = 'Anthony Sottile'
dependencies = []
files = []
hgrepos = []
issue_num = 32277
keywords = ['patch']
message_count = 6.0
messages = ['308062', '308070', '308072', '308319', '308320', '308324']
nosy_count = 2.0
nosy_names = ['serhiy.storchaka', 'Anthony Sottile']
pr_nums = ['4797', '4869']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue32277'
versions = ['Python 3.6', 'Python 3.7']

[asottile]

While investigating https://bugs.python.org/issue31940 I noticed the following is raised as SystemError instead of the expected NotImplementedError

(note: you need a platform with fchmodat but does not support nofollow)

touch foo
ln -s foo bar
python3.6 -c 'import os; os.chmod("bar", 0o666, follow_symlinks=False)

Expected: raised NotImplementedError
Actual: raised SystemError

[serhiy-storchaka]

Does any existing test failed on such platform?

[asottile]

I noticed it when I changed the test preconditions in #4783

I tried changing a test to trigger this (in this branch) but I found I was just implementing exactly the test in the skip condition which to me didn't feel like a very valuable test.

From what I can tell, the current testsuite passes on my machine before and after this change -- only with the small reproduction.

[serhiy-storchaka]

New changeset 233ef24 by Serhiy Storchaka (Anthony Sottile) in branch 'master':
bpo-32277: Fix exception raised from chmod(..., follow_symlinks=False) (bpo-4797)
233ef24

[serhiy-storchaka]

I was going to request a test, but the fix is obvious and writing a test for this case can be not easy. Thank you Anthony for your report and patch.

[serhiy-storchaka]

New changeset d1cb106 by Serhiy Storchaka (Miss Islington (bot)) in branch '3.6':
bpo-32277: Fix exception raised from chmod(..., follow_symlinks=False) (GH-4797) (bpo-4869)
d1cb106