[Bug 2030684] Re: tzname[1] empty after tzset() with env TZ="UTC"

[Benjamin Drung]

Change prepared in https://git.launchpad.net/~ubuntu-core-
dev/ubuntu/+source/tzdata/log/

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Title:
  tzname[1] empty after tzset() with env TZ="UTC"

Status in php8.2 package in Ubuntu:
  New
Status in postgresql-15 package in Ubuntu:
  New
Status in systemd package in Ubuntu:
  New
Status in tzdata package in Ubuntu:
  New
Status in tzdata package in Debian:
  Unknown

Bug description:
  The following program prints different output when run with tzdata
  2023c-7ubuntu1 from mantic, versus tzdata 2023c-8ubuntu1 from mantic-
  proposed:

  root at mantic:~# cat bug.c 
  #include <errno.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <time.h>

  int main(void) {
          int r;

          r = setenv("TZ", ":UTC", 1);
          if (r < 0) {
                  printf("Failed to set TZ env var: %s\n", strerror(errno));
                  return 1;
          }

          tzset();

          printf("timezone = %lu, daylight = %d\n", timezone, daylight);
          printf("tzname[0] = %s, tzname[1] = %s\n", tzname[0], tzname[1]);
  }

  root at mantic:~# gcc bug.c
  root at mantic:~# ./a.out 
  timezone = 0, daylight = 0
  tzname[0] = UTC, tzname[1] = UTC
  root at mantic:~# apt-cache policy tzdata
  tzdata:
    Installed: 2023c-7ubuntu1
    Candidate: 2023c-7ubuntu1
    Version table:
   *** 2023c-7ubuntu1 500
          500 http://archive.ubuntu.com/ubuntu mantic/main amd64 Packages
          100 /var/lib/dpkg/status

  If I install tzdata from mantic-proposed, I get different output:

  root at mantic:~# vi /etc/apt/sources.list
  root at mantic:~# apt update && apt install tzdata
  Hit:1 http://archive.ubuntu.com/ubuntu mantic InRelease
  Hit:2 http://security.ubuntu.com/ubuntu mantic-security InRelease
  Get:3 http://archive.ubuntu.com/ubuntu mantic-proposed InRelease [118 kB]
  Hit:4 http://archive.ubuntu.com/ubuntu mantic-updates InRelease
  Hit:5 http://archive.ubuntu.com/ubuntu mantic-backports InRelease
  Get:6 http://archive.ubuntu.com/ubuntu mantic-proposed/main amd64 Packages [35.9 kB]
  Get:7 http://archive.ubuntu.com/ubuntu mantic-proposed/main Translation-en [14.8 kB]
  Get:8 http://archive.ubuntu.com/ubuntu mantic-proposed/main amd64 DEP-11 Metadata [2376 B]
  Get:9 http://archive.ubuntu.com/ubuntu mantic-proposed/main amd64 c-n-f Metadata [1004 B]
  Get:10 http://archive.ubuntu.com/ubuntu mantic-proposed/restricted amd64 Packages [15.9 kB]
  Get:11 http://archive.ubuntu.com/ubuntu mantic-proposed/restricted Translation-en [3564 B]
  Get:12 http://archive.ubuntu.com/ubuntu mantic-proposed/restricted amd64 c-n-f Metadata [336 B]
  Fetched 192 kB in 1s (324 kB/s)                                     
  Reading package lists... Done
  Building dependency tree... Done
  Reading state information... Done
  72 packages can be upgraded. Run 'apt list --upgradable' to see them.
  root at mantic:~# apt install tzdata=2023c-8ubuntu1
  Reading package lists... Done
  Building dependency tree... Done
  Reading state information... Done
  The following packages were automatically installed and are no longer required:
    libefiboot1 libefivar1
  Use 'apt autoremove' to remove them.
  The following packages will be upgraded:
    tzdata
  1 upgraded, 0 newly installed, 0 to remove and 72 not upgraded.
  Need to get 269 kB of archives.
  After this operation, 142 kB disk space will be freed.
  Get:1 http://archive.ubuntu.com/ubuntu mantic-proposed/main amd64 tzdata all 2023c-8ubuntu1 [269 kB]
  Fetched 269 kB in 0s (867 kB/s)
  Preconfiguring packages ...
  (Reading database ... 39935 files and directories currently installed.)
  Preparing to unpack .../tzdata_2023c-8ubuntu1_all.deb ...
  Unpacking tzdata (2023c-8ubuntu1) over (2023c-7ubuntu1) ...
  Setting up tzdata (2023c-8ubuntu1) ...

  Current default time zone: 'Etc/UTC'
  Local time is now:      Mon Aug  7 21:18:35 UTC 2023.
  Universal Time is now:  Mon Aug  7 21:18:35 UTC 2023.
  Run 'dpkg-reconfigure tzdata' if you wish to change it.

  Scanning processes...                                                                                                                                                                                                                          
  Scanning candidates...                                                                                                                                                                                                                         

  Restarting services...
  Service restarts being deferred:
   systemctl restart systemd-logind.service
   systemctl restart unattended-upgrades.service

  No containers need to be restarted.

  No user sessions are running outdated binaries.

  No VM guests are running outdated hypervisor (qemu) binaries on this
  host.

  root at mantic:~# ./a.out 
  timezone = 0, daylight = 0
  tzname[0] = UTC, tzname[1] = 
  root at mantic:~# apt-cache policy tzdata-legacy
  tzdata-legacy:
    Installed: (none)
    Candidate: 2023c-7ubuntu1
    Version table:
       2023c-8ubuntu1 100
          100 http://archive.ubuntu.com/ubuntu mantic-proposed/main amd64 Packages
       2023c-7ubuntu1 500
          500 http://archive.ubuntu.com/ubuntu mantic/main amd64 Packages

  In particular, note that tzname[1] (the name of the daylight zone) is
  empty, whereas it previously printed "UTC".

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