[Bug time/30710] New: tzset doesn't fallback to UTC if TZ asked by the user is not installed

[Bug time/30710] New: tzset doesn't fallback to UTC if TZ asked by the user is not installed

[romain.naour at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30710

            Bug ID: 30710
           Summary: tzset doesn't fallback to UTC if TZ asked by the user
                    is not installed
           Product: glibc
           Version: 2.37
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: time
          Assignee: unassigned at sourceware dot org
          Reporter: romain.naour at gmail dot com
  Target Milestone: ---

Hello,

I recently switched from a uClibc-ng toolchain to a glibc toolchain with the
following test case:

Test1:
TZ=UTC date +%Z
UTC

OK

Test2:
# Default to UTC if TZ requested is missing.
TZ=America/Los_Angeles date +%Z
America

KO

"America" is returned while "UTC" is expected here (checked with uClibc-ng and
musl)

(On the tested rootfs TZDIR "/usr/share/zoneinfo" doesn't exist)

Test3:
TZ=plop date +%Z
plop

KO

Actually %Z return all or part of TZ content on any Linux OS using glibc.

Why glibc's tzset_internal() try to do something else than using UTC, when no
data file is found and the user set TZ with a random string (not even a POSIX
timezone specification in the form
stdoffset[dst[offset][,start[/time],end[/time]]) ?

https://sourceware.org/git/?p=glibc.git;a=blob;f=time/tzset.c;h=78c18f8147415c92dc6eb735be672fa7e0b8f76e;hb=78ca34d8c55eee6b0664f9c1d30fcca71077b843#l409

Reported by Buildroot gitlab-ci:
https://gitlab.com/buildroot.org/buildroot/-/jobs/4768561117

Best regards,
Romain

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[Bug time/30710] tzset doesn't fallback to UTC if TZ asked by the user is not installed

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30710

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sam at gentoo dot org

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[Bug time/30710] tzset doesn't fallback to UTC if TZ asked by the user is not installed

[romain.naour at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30710

--- Comment #1 from romain.naour at gmail dot com ---
It look like POSIX TZ-style string parsing doesn't specify the behaviour when
the parsing fail. 

"The interpretation of these fields is unspecified if either field is less than
three bytes (except for the case when dst is missing), more than {TZNAME_MAX}
bytes, or if they contain characters other than those specified."

https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03

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[Bug time/30710] tzset doesn't fallback to UTC if TZ asked by the user is not installed

[schwab@linux-m68k.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30710

Andreas Schwab <schwab@linux-m68k.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |NOTABUG

--- Comment #2 from Andreas Schwab <schwab@linux-m68k.org> ---
It _is_ using UTC, with the requested time zone name.

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