The TZ environment variable can validly contain a POSIX rule, rather
than an IANA ID, as described here:
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03
However, if TZ were set to such a value, leading to it being used as
systemTimeZoneId(), it would be passed to QTzTimeZonePrivate::init(),
which is a no-op unless it manages to open a zoneinfo/ file with the
given ianaId as name. When the environment variable doesn't name a
zoneinfo/ file, we would thus get an invalid time-zone. We can,
instead, check whether the ianaId looks like a valid POSIX rule and,
if it does, use it as m_posixRule, enabling us to correctly handle
this case.
Tweak parsing of POSIX rules so that a zone using name "UTC" or "GMT"
with an offset other than 0 will be rejected as invalid. This avoids
parsing a zone name such as "GMT+17" or "UTC+00:01" as a POSIX rule,
where it should be understood as an offset from UTC (and only certain
well-established offsets are supported).
Added two test-cases to tst_QTimeZone::tzTest() for validity of a
POSIX zone value - a simple one constructed during discussion of the
bug, the other taken from an example in:
http://leaf.sourceforge.net/doc/buci-tz3.html
Task-number: QTBUG-75565
Change-Id: Ia5cb1cc56b13b0f6b56258e48be98d04d909e32a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
ab2655c559