Don’t call g_time_zone_new_offset() with offsets >24 hours

pwithnall commented 2 years ago

This is part of https://gitlab.gnome.org/GNOME/glib/-/issues/2620, which in turn came from Debian bug https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1007226.

Calling g_time_zone_new_offset() with a large offset (>24h) will cause an assertion failure in GLib <2.72.0. There’s a fix for GLib 2.72.0, but older versions of GLib will still have this (or a different) assertion failure.

g_time_zone_new_offset() isn’t an ideal API, in that it has no way of reporting errors, and not all timezone offsets are valid. Currently there is no direct replacement.

You have several options, depending on what makes the most sense for how GMime handles timezones internally:

Validate the offset before calling g_time_zone_new_offset(). The downside is that I can’t say for certain that offsets <24h will be valid, as the validity depends on what’s defined in the system tzdb
Check the return value of g_time_zone_new_offset() to see if it’s the UTC timezone. If it is, and that wasn’t expected (i.e. the offset wasn’t 0), then creating the timezone failed.
Call g_time_zone_new_identifier() instead, as g_time_zone_new_offset() does internally. It can report errors.