From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/10653 Path: news.gmane.org!.POSTED!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: musl's strptime does not support POSIX %U/%W Date: Fri, 21 Oct 2016 13:34:27 -0400 Message-ID: <20161021173427.GW19318@brightrain.aerifal.cx> References: <4bb408a9-76e3-f432-48d7-72b69181bbcc@cockroachlabs.com> <20161021161822.GV19318@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: blaine.gmane.org 1477071291 9407 195.159.176.226 (21 Oct 2016 17:34:51 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 21 Oct 2016 17:34:51 +0000 (UTC) User-Agent: Mutt/1.5.21 (2010-09-15) To: musl@lists.openwall.com Original-X-From: musl-return-10666-gllmg-musl=m.gmane.org@lists.openwall.com Fri Oct 21 19:34:47 2016 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.84_2) (envelope-from ) id 1bxdiL-0001Ml-8l for gllmg-musl@m.gmane.org; Fri, 21 Oct 2016 19:34:41 +0200 Original-Received: (qmail 9414 invoked by uid 550); 21 Oct 2016 17:34:41 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 9391 invoked from network); 21 Oct 2016 17:34:40 -0000 Content-Disposition: inline In-Reply-To: <20161021161822.GV19318@brightrain.aerifal.cx> Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:10653 Archived-At: On Fri, Oct 21, 2016 at 12:18:22PM -0400, Rich Felker wrote: > On Fri, Oct 21, 2016 at 11:00:35AM +0200, Raphael 'kena' Poss wrote: > > Hi all, > > > > we at CockroachDB would like to integrate strptime, but some of our > > users on Alpine Linux discovered that musl's strptime doesn't live up to > > expectations: > > > > conv_test.go:58: strptime("2018 10 4", "%Y %W %w"): got > > "2017-12-31T00:00:00Z", expected "2018-03-08T00:00:00Z" > > conv_test.go:58: strptime("2018 10 4", "%Y %U %w"): got > > "2017-12-31T00:00:00Z", expected "2018-03-15T00:00:00Z" > > > > Indeed there's a FIXME in there: > > https://git.musl-libc.org/cgit/musl/tree/src/time/strptime.c#n123 > > > > We've filed this internally as > > https://github.com/cockroachdb/cockroach/issues/10130 > > > > As of this day this is the only known limitation that prevents > > compatibility of CockroachDB with musl. If you have any suggestions / > > input we'd be glad to receive them! > > Indeed, somehow I thought this FIXME had been fixed a long time ago, > but it seems it hasn't. I'll see if we can get it added soon. Looking at this in more detail, I see why it wasn't done before: there's no clear spec for what output these should produce. struct tm does not contain a week-number field, so the result would have to be encoded in other fields -- but which ones? tm_yday? strptime is not specified to produce a full, consistent struct tm for all inputs, because many formats may be incomplete and other combinations of format and input may yield contradictory information. I'd be really interested in seeing some analysis of this situation by someone who's studied it and has a viable proposal other than just "reverse engineer glibc and do whatever it does". Rich