[New-bugs-announce] [issue34672] '%Z' strftime specifier never works with musl

[Benjamin Peterson]

New submission from Benjamin Peterson <benjamin at python.org>:

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

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

----------
components: Library (Lib)
messages: 325319
nosy: benjamin.peterson
priority: normal
severity: normal
status: open
title: '%Z' strftime specifier never works with musl
versions: Python 2.7, Python 3.6, Python 3.7, Python 3.8

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue34672>
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