Use strnlen instead of strlen when the size i known.

[edge90]

BPO	41170
Nosy	@vstinner, @larryhastings, @ericvsmith, @edge90
PRs	bpo-41170: Use strnlen instead of strlen when the size i known. #21236

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

Show more details

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-06-30.14:44:52.513>
labels = ['expert-C-API', '3.10']
title = 'Use strnlen instead of strlen when the size i known.'
updated_at = <Date 2020-09-28.22:08:46.110>
user = 'https://proxy-ga.blitzz.co/proxy/123456/github.com/edge90'

bugs.python.org fields:

activity = <Date 2020-09-28.22:08:46.110>
actor = 'vstinner'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['C API']
creation = <Date 2020-06-30.14:44:52.513>
creator = 'Niclas Larsson'
dependencies = []
files = []
hgrepos = []
issue_num = 41170
keywords = ['patch']
message_count = 4.0
messages = ['372727', '372752', '377632', '377633']
nosy_count = 5.0
nosy_names = ['vstinner', 'larry', 'eric.smith', 'python-dev', 'Niclas Larsson']
pr_nums = ['21236']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://proxy-ga.blitzz.co/proxy/123456/bugs.python.org/issue41170'
versions = ['Python 3.10']

[ericvsmith]

Is strnlen() supported by all of the compilers we care about?

[larryhastings]

strnlen() isn't standard C, but an exciting new function strnlen_s() is, as of C11.

https://proxy-ga.blitzz.co/proxy/123456/en.cppreference.com/w/c/string/byte/strlen

(At this rate, we should be able to code CPython using that standard in about 2030.)

But! I found a 2005 thread on /. talking about strnlen in MSVC. So maybe it's there. Though Microsoft has this funny habit of putting an underscore in front of C library functions that aren't standard, so maybe it's _strnlen().

[vstinner]

PR 21236 was closed by his author, can this issue be closed?

[vstinner]

"Use strnlen instead of strlen when the size i known" rationale was "This PR changes strlen to strnlen so no buffer overruns are made when there's no null terminator", but strlen() was not called whne the string was not null terminated.

Serhiy wrote that strnlen() can be faster and that can be slower... If the goal is an optimization, a benchmark should prove it (on at least one platform).
#21236 (comment)

[furkanonder]

PR 21236 was closed by his author, can this issue be closed?

@serhiy-storchaka also says that he is inclined to close the issue and since author of the PR closed the PR I think issue can be close.