On 05/22/2014 05:07 AM, 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. > --- > > Change from V1: add test cases with TZ set to different values (if > someone knows how to force DST on/off, I would gladly add some test > cases for this as well). Re-reading POSIX: http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html I think you can do something like: VIR00:30VID where "VIR" is the normal time, and "VID" is the daylight-savings time 1 hour ahead. It was the absence of a second name that made POSIX treat the TZ value as not having daylight savings. I'll review the actual patch in another mail. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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