systemd / systemd / 28630269468

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Committed by yuwata

Commit Message

test: ignore fails when the formatted timezone differs from the current one

When formatting a timestamp the C API takes into account historical data
from tzdata, so it returns a date strings with a historically-correct
timezone abbreviation. However, tzname[] doesn't do this and it returns
the most recent abbreviation for the given zone.

For example, according to tzdata America/Cancun switched from EST/EDT to
CST/CDT on 1998-08-02:

Zone America/Cancun     -5:47:04 -      LMT     1922 Jan  1  6:00u
                        -6:00   -       CST     1981 Dec 26  2:00
                        -5:00   -       EST     1983 Jan  4  0:00
                        -6:00   Mexico  C%sT    1997 Oct 26  2:00
                        -5:00   Mexico  E%sT    1998 Aug  2  2:00
                        -6:00   Mexico  C%sT    2015 Feb  1  2:00
                        -5:00   -       EST

So, formatting a timestamp from this time will yield a string with the
EDT timezone:

$ TZ=America/Cancun date -d "@902035565"
Sun Aug  2 01:26:05 EDT 1998

But using tzname[] (or strptime %z) shows the most recent data, where
America/Cancun uses EST (and doesn't use DST anymore, hence
tzname[1]=CDT that glibc remembers from the previous zone epoch):

$ TZ=America/Cancun ./tz
{EST, CDT}

This means that when we parse the formatted timestamp back we don't use
the historical timezone data, so we might end up with a different
offset:

TZ=America/Cancun, tzname[0]=EST, tzname[1]=CDT
@902035565603993 → Sun 1998-08-02 01:26:05 EDT → @902039165000000 → Sun 1998-08-02 01:26:05 CDT
src/test/test-time-util.c:452: Assertion failed: Expected "ignore" to be true
Aborted                    (core dumped) build-local/test-time-util

Instead of adding exceptions for every single timezone that switched
between different offsets in the past, let's address this a bit more
generally and skip the check if the parsed timezone doesn't match any of
the current timezones - this still keeps the check that the time... (continued)

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