Date: Sun, 25 Apr 2021 19:46:51 +0200 From: Sören Tempel <soeren@...ren-tempel.net> To: musl@...ts.openwall.com Subject: Handling of non-location specific TZ values Hi, While debugging a test failure of the calendar application calcurse on Alpine I noticed that musl does not support TZ values which don't include area/location information, e.g. TZ=CET . This is contrary to the documentation from the musl wiki which states the following : The zoneinfo file is interpreted as an absolute pathname if it begins with a slash, a relative pathname if it begins with a dot, and otherwise is searched in /usr/share/zoneinfo, /share/zoneinfo, and /etc/zoneinfo. Since commit 5c4f11d995cf178b3146cde0734d6988c145f243 musl only consults the zoneinfo database if the value of the TZ environment variable starts with a colon or contains a slash . As such, the zoneinfo database is not consulted for TZ=CET thereby causing musl to not determine DST etc. correctly for such TZ values. TZ values such as Europe/Kaliningrad are correctly looked up in the zoneinfo database though. The aforementioned commit claims that this strict check is necessary since "TZ=name is reserved for POSIX-form" which consists of a mandatory timezone name (std), an offset, and some more optional information . **If** TZ values adhering to the POSIX format should not be looked up in the zoneinfo database, it would be necessary to somehow determine if a given string adheres to the POSIX timezone format before performing the lookup. The glibc implementation seems to unconditionally consult the zoneinfo database and falls back to the POSIX format (__tzset_parse_tz) if no corresponding file was found in the database . Apart from glibc, the non-POSIX TZ format with TZ=<timezone> is also supported BSDs, e.g. OpenBSD . Any thoughts on how this could fixed in musl? Greetings, Sören : https://gitlab.alpinelinux.org/alpine/aports/-/merge_requests/19695 : https://wiki.musl-libc.org/environment-variables.html : https://git.musl-libc.org/cgit/musl/commit/?id=5c4f11d995cf178b3146cde0734d6988c145f243 : https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03 : https://sourceware.org/git/?p=glibc.git;a=blob;f=time/tzset.c;h=2fc51194b63bda8eeaff4f2ac111291ff43c28ad;hb=24f261f27fb8fd19ae294ff2a13bc5b7a0bafc91#l405 : https://github.com/openbsd/src/blob/2207c4325726fdc5c4bcd0011af0fdf7d3dab137/lib/libc/time/Theory
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