[tz] tzcode-2014c breaks applications that use the binary tz files
eggert at cs.ucla.edu
Fri May 23 20:45:12 UTC 2014
On 05/23/2014 02:27 PM, Leonardo Chiquitto wrote:
> After updating to 2014c, we've received a couple of reports
> of applications that started to misbehave (show wrong times).
> One example is the clock applet from Gnome3
Thank you for the heads-up.
Do all the broken applications use Glib (the Gnome library)? If so,
thisappears to be Gnome bug 730332, which you can view here:
Starting with 2014c, zic generates a transition at the minimum time
value -2**63, to avoid ambiguities about what to do before then. The
interval_end function of Glib's gtimezone.c subtracts one from this, to
find the end time of the zeroth interval (i.e., the interval containing
all the "early" time stamps); in interval_end this subtraction overflows
and wraps around to 2**63 - 1, which causes Glib to go off the rails and
assume that *all* time stamps are "early". For example, Glib computes
Sao Paulo time stamps as if Brazil's circa-1913 rules were still in
effect, i.e., as if Sao Paulo were at UTC-3:06:28, which is incorrect by
6 minutes 28 seconds, which is the error you're observing.
This is a serious incompatibility. Distributions that use Glib should
not use tz 2014c's code to generate binary files. The 2014c data files
are fine; it's the 2014c zic.c that's causing the incompatibility.
This is clearly a bug in Glib, and I assume it'll be fixed soon, but
that's small consolation to the people affected by it. And one can't
help but wonder which other software packages have similar bugs.
A simple workaround is to back out the two zic.c changes you mentioned.
Another possibility would be for zic.c to generate a transition at time
-2**63 + 1 instead, so that the Glib code won't wrap around, but that
Yet another possibility might be to change zic.c to set the initial
transition to be -2**60 instead of -2**63; this would comfortably
predate the Big Bang so it's unlikely we'll see any real time stamps
I'll CC: this to Arthur David Olson to see whether he has a better idea.
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