timezone setting in the current year and for 100 years back, rather than
always examining years 1904-2004. The original coding would have problems
distinguishing zones whose behavior diverged only after 2004; which is a
situation we will surely face sometime, if it's not out there already.
In passing, also prevent selection of the dummy "Factory" timezone, even
if that's exactly what the system is using. Reporting time as GMT seems
better than that.
POSIX-style timezone specs that don't exactly match any database entry will
be treated as having correct USA DST rules. Also, document that this can
be changed if you want to use some other DST rules with a POSIX zone spec.
We could consider changing localtime.c's TZDEFRULESTRING, but since that
facility can only deal with one DST transition rule, it seems fairly useless
now; might as well just plan to override it using a "posixrules" entry.
Backpatch as far as 8.0. There isn't much we can do in 7.x ... either your
libc gets it right, or it doesn't.
the localtime timezone data) is not overwritten until we know the data
is good. tzload() is capable of failing after having begun modifying
the struct it's pointed at, and in such cases the static data was left
in a corrupt state. Bug does not exist pre-8.0 (since we didn't have
this code then) nor post-8.0 (since we already changed the code to
tzload into local variables initially). Per report from Nick Martens.
Also performed an initial run through of upgrading our Copyright date to
extend to 2005 ... first run here was very simple ... change everything
where: grep 1996-2004 && the word 'Copyright' ... scanned through the
generated list with 'less' first, and after, to make sure that I only
picked up the right entries ...
use it, as per my proposal of yesterday. This gives us a means of
determining the zone offset to impute to an unlabeled timestamp that
is both efficient and reliable, unlike all our previous tries involving
mktime() and localtime(). The behavior for invalid or ambiguous times
at a DST transition is fixed to be really and truly "assume standard
time", fixing a bug that has come and gone repeatedly but was back
again in 7.4. (There is some ongoing discussion about whether we should
raise an error instead, but for the moment I'll make it do what it was
previously intended to do.)
Windows.
Recap: When running on a localized windows version, the timezone name
returned is also localized, and therefor does not match our lookup
table.
Solution: The registry contains both the name of the timezone in english
and the localized name. The patch adds code to scan the registry for the
localized name and gets the english name from that, and then rescans the
table.
I have tested this on a Swedish WinXP, and it works without problems.
The registry layout is the same in Win2k, but I haven't specifically
tested it. It's also the same on different languages but again only
Swedish is tested.
Magnus Hagander
it with previous prototype to suppress complaints from picky compilers,
per report from Scott Bailey. Also, remove substitute strerror
definition --- not needed, since we link this with libpgport.
machines, break tie scores by preferring shorter zone names over longer;
for names of equal length, prefer the alphabetically first name. This
yields for example 'EST5EDT' not 'America/New_York' for US eastern time.
On Windows, abandon the whole concept of inspecting the detailed behavior
of the system TZ library, because it doesn't bear inspection :-(. Instead
use a hardwired mapping table to select our zone name based on the
result of strftime %Z output. Windows code from Magnus Hagander.
timezone database for the system behavior we find ourselves in. Scan
backwards from current time and choose the zone that matches furthest
back. As per discussion a week or so back.
accurate matching of our time zone to the system's zone. This method is
able to distinguish Antarctica/Casey from Australia/Perth, as in Chris
K-L's recent example; and it is not materially slower than before, because
the extra checks generally don't get done against very many time zones.
It seems possible that with this test we'd be able to correctly identify
Windows timezones without looking at the timezone name, but I do not
have the ability to try it.
place of time_t, as per prior discussion. The behavior does not change
on machines without a 64-bit-int type, but on machines with one, which
is most, we are rid of the bizarre boundary behavior at the edges of
the 32-bit-time_t range (1901 and 2038). The system will now treat
times over the full supported timestamp range as being in your local
time zone. It may seem a little bizarre to consider that times in
4000 BC are PST or EST, but this is surely at least as reasonable as
propagating Gregorian calendar rules back that far.
I did not modify the format of the zic timezone database files, which
means that for the moment the system will not know about daylight-savings
periods outside the range 1901-2038. Given the way the files are set up,
it's not a simple decision like 'widen to 64 bits'; we have to actually
think about the range of years that need to be supported. We should
probably inquire what the plans of the upstream zic people are before
making any decisions of our own.
database, not just ones that we cons up POSIX names for. This looks
grim but it seems to take less than a second even on a relatively slow
machine, and since it only happens once during postmaster startup, that
seems acceptable.
of correctly identifying the system's daylight-savings transition rules.
This still begs the question of how to look through the zic database to
find a matching zone definition, but at least now we'll have some chance
of recognizing the match when we find it.
