Date: Fri, 14 Aug 2015 11:39:54 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: strptime() lacks support for %z On Fri, Aug 14, 2015 at 05:08:23PM +0200, Szabolcs Nagy wrote: > > > > strftime uses tzset (timezone from TZ) but strptime cannot > > > > set TZ so it must put the timezone somewhere else. > > > > > > > > so strptime can't be consistent with strftime. > > > > with tz in struct tm, mktime/localtime no longer roundtrip. > > > > > > I don't follow. strftime uses the extended fields from struct tm. I > > > don't see anywhere it depends on tzset, nor reasons why strptime would > > > need tzset to be called. Am I missing something? > > > > > > > it seems %z does not use it in musl, %Z does > > > > __tm_to_tzname calls do_tzset() > > > > posix says > > "Local timezone information is used as though strftime() called tzset()" > > ah ok, the tz name and offset are independent > > i expected both of those would be used from TZ in > strftime, but musl already uses the tm struct offset. Because we support zoneinfo files, printing this information with strftime does not seem to be possible without using the data from the struct tm. There can be multiple different offsets and zone names depending on the date, and strftime does not seem to require a canonical-form struct tm, so trying to derive the zone/offset in effect from TZ and the standard struct tm members does not seem like it could be done reliably. Unfortunately this is all a bit of a mess because POSIX is in some sort of denial that zoneinfo is necessary... Rich
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