Date: Wed, 12 Aug 2020 14:57:08 +0200 From: Nikita Popov <nikita.ppv@...il.com> To: musl@...ts.openwall.com Subject: Re: strftime %Z behavior with manually populated struct tm > I haven't checked, but I believe most implementations just print the > zone name from the current timezone, using tm_isdst to decide whether > to print the standard or daylight version of the name. This is > insufficient with zoneinfo for zones where the name changed over time, > where it would print the wrong name for historical times. So instead > we support printing any one of the zone names from the current zone, > if the tm_zone member points to one of them, and blank otherwise. You are right. I was under the impression that glibc uses tm_zone, but double checking the implementation right now, it doesn't. So the behavioral discrepancy here comes from the fact that musl checks tm_zone at all, not the other way around. Sorry for looking in the completely wrong direction here. > I think you have the wrong commit link; that one does not look > related. If you have the real one I'd be interested in seeing what > they did. Indeed, I meant to link to https://github.com/python/cpython/commit/5633c4f342d957df2ef0d67b9bfb472a0d28a76b. What Python does is to retrieve musl's string for UTC using gmtime_r, as well as trying to match against the current tzname. > I think if applications want to use zones other than the actual > configured zone with strftime, they need to just do something like > expand the %Z themselves with the string they want before calling > strftime (note: this requires quoting any % in the name). With your explanation in mind, explicitly expanding %Z does seem like a good approach. I'll consider doing that. > I looked > hard for a better solution that wouldn't crash valid applications, and > couldn't find one at the time. Possibly it would make sense to fall back to using the current tzname if the pointer given in tm_zone is invalid, rather than an empty string? Regards, Nikita Content of type "text/html" skipped
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