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'%Z' strftime specifier never works with musl #78853

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benjaminp opened this issue Sep 14, 2018 · 5 comments
Closed

'%Z' strftime specifier never works with musl #78853

benjaminp opened this issue Sep 14, 2018 · 5 comments
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3.7 (EOL) end of life 3.8 only security fixes stdlib Python modules in the Lib dir

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@benjaminp
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BPO 34672
Nosy @abalkin, @benjaminp, @zhangyangyu, @pganssle
PRs
  • bpo-34672: Try to pass the C library's own timezone strings back to it. #9288
  • bpo-34672: Don't pass NULL to gmtime_r. #9312
  • bpo-34672: fix a compiler warning in timemodule.c #10176
  • 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 2022-01-15.20:08:32.877>
    created_at = <Date 2018-09-14.04:01:29.001>
    labels = ['3.8', '3.7', 'library']
    title = "'%Z' strftime specifier never works with musl"
    updated_at = <Date 2022-01-15.20:08:32.876>
    user = 'https://github.com/benjaminp'

    bugs.python.org fields:

    activity = <Date 2022-01-15.20:08:32.876>
    actor = 'iritkatriel'
    assignee = 'none'
    closed = True
    closed_date = <Date 2022-01-15.20:08:32.877>
    closer = 'iritkatriel'
    components = ['Library (Lib)']
    creation = <Date 2018-09-14.04:01:29.001>
    creator = 'benjamin.peterson'
    dependencies = []
    files = []
    hgrepos = []
    issue_num = 34672
    keywords = ['patch']
    message_count = 5.0
    messages = ['325319', '325357', '325368', '328695', '328841']
    nosy_count = 4.0
    nosy_names = ['belopolsky', 'benjamin.peterson', 'xiang.zhang', 'p-ganssle']
    pr_nums = ['9288', '9312', '10176']
    priority = 'normal'
    resolution = 'fixed'
    stage = 'resolved'
    status = 'closed'
    superseder = None
    type = None
    url = 'https://bugs.python.org/issue34672'
    versions = ['Python 2.7', 'Python 3.6', 'Python 3.7', 'Python 3.8']

    @benjaminp
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    With the musl C library, one has failures like this:

    ======================================================================
    FAIL: test_strptime (test.test_time.TimeTestCase)
    ----------------------------------------------------------------------

    Traceback (most recent call last):
      File "/buildbot/buildarea/3.x.ware-alpine/build/Lib/test/test_time.py", line 273, in test_strptime
        time.strptime(strf_output, format)
    ValueError: time data '' does not match format '%Z'
    During handling of the above exception, another exception occurred:
    Traceback (most recent call last):
      File "/buildbot/buildarea/3.x.ware-alpine/build/Lib/test/test_time.py", line 276, in test_strptime
        (format, strf_output))
    AssertionError: conversion specifier '%Z' failed with '' input.

    The root problem is that time.strptime('%Z', time.gmtime()) won't work—it returns an empty string—even though time.gmtime() will probably have a valid tm_zone field. This is because musl has a safety mechanism where it refuses to process a tm_zone entry unless it produced the string. (See https://git.musl-libc.org/cgit/musl/commit/?id=d78be392e144c338f58ce6a51d82c859126c137d.)

    As a partial workaround, I propose we check whether an incoming time.struct_time instance has an tm_zone member equal to tzname[0] or tzname[1], and place one of those global strings into the C-level tm struct if they do match.

    @benjaminp benjaminp added 3.7 (EOL) end of life 3.8 only security fixes stdlib Python modules in the Lib dir labels Sep 14, 2018
    @benjaminp
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    New changeset 5633c4f by Benjamin Peterson in branch 'master':
    bpo-34672: Try to pass the C library's own timezone strings back to it. (GH-9288)
    5633c4f

    @benjaminp
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    New changeset b93062b by Benjamin Peterson in branch 'master':
    bpo-34672: Don't pass NULL to gmtime_r. (GH-9312)
    b93062b

    @zhangyangyu
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    New changeset 163eca3 by Xiang Zhang in branch 'master':
    bpo-34672: fix a compiler warning in timemodule.c (GH-10176)
    163eca3

    @abalkin
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    abalkin commented Oct 29, 2018

    It looks like this issue has been fixed by #53534. Can this be closed? Should we backport?

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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