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

On Thu, May 22, 2014 at 02:07:27PM +0300, 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). man tzset: The second format is used when there is daylight saving time: std offset dst [offset],start[/time],end[/time]