[libvirt] [PATCHv2 1/4] util: new function virTimeLocalOffsetFromUTC

[Roman Bogorodskiy]

  Roman Bogorodskiy wrote:

>   Laine Stump wrote:
> 
> > Since there isn't a single libc API to get this value, this patch
> > supplies one which gets the value by grabbing current UTC, then
> > converting that into a struct tm with localtime_r(), then back to a
> > time_t using mktime; it again does the same operation, but using
> > gmtime_r() instead (for UTC). It then subtracts utc time from the
> > localtime, and finally adjusts if dst is set in the localtime timeinfo
> > (because for some reason mktime doesn't take that into account).
> > 
> > This function should be POSIX-compliant, and is threadsafe, but not
> > async signal safe. If it was ever necessary to know this value in a
> > child process, we could cache it with a one-time init function when
> > libvirtd starts, then just supply the cached value, but that
> > complexity isn't needed for current usage.
> 
> Appears it breaks virtimetest on FreeBSD:
> 
> TEST: virtimetest
> 20) Test localtime offset for "VIR-00:30"                             ... OK
> 21) Test localtime offset for "VIR-01:30"                             ... OK
> 22) Test localtime offset for "VIR-00:30VID,0/00:00:00,366/23:59:59"  ... FAILED
> 23) Test localtime offset for "VIR-02:30VID,0/00:00:00,366/23:59:59"  ... FAILED
> 24) Test localtime offset for "VIR-02:30VID-04:30,0/00:00:00,366/23:59:59" ... FAILED
> 25) Test localtime offset for "VIR-12:00VID-13:00,0/00:00:00,366/23:59:59" ... FAILED
> 26) Test localtime offset for "VIR02:45VID00:45,0/00:00:00,366/23:59:59" ... FAILED
> 27) Test localtime offset for "VIR05:00VID04:00,0/00:00:00,366/23:59:59" ... FAILED
> 28) Test localtime offset for "VIR11:00VID10:00,0/00:00:00,366/23:59:59" ... FAILED
> 
> My initial impression is that it's something wrong on the FreeBSD side,
> because date(1) doesn't respect TZs from failing tests, for example:
> 
> $ date
> Sat May 31 23:15:45 MSK 2014
> $ TZ=VIR-00:30 date                           
> Sat May 31 19:45:53 VIR 2014
> $ TZ=VIR-00:30VID,0/00:00:00,366/23:59:59 date
> Sat May 31 19:15:58 UTC 2014
> 
> So it looks like it's failing back to the UTC time.

After some more experiments I noticed that changing 366 to 365 makes it
work:

$ TZ=VIR-00:30VID,0/00:00:00,365/23:59:59 date
Sat May 31 21:34:25 VID 2014
$

And also changing that in the test makes it pass.

Looking at this document:

http://pubs.opengroup.org/onlinepubs/9699919799/

It describes TZ environment variable format and says about the days that
it should be:

0 <= n <= 365

I haven't yet found what should happen when the format given in TZ
environment variable doesn't follow the format.

Roman Bogorodskiy
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