From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL autolearn=ham autolearn_force=no version=3.4.4 Received: from second.openwall.net (second.openwall.net [193.110.157.125]) by inbox.vuxu.org (Postfix) with SMTP id B9D8920DCC for ; Sun, 24 Mar 2024 18:04:30 +0100 (CET) Received: (qmail 5608 invoked by uid 550); 24 Mar 2024 16:59:47 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 5510 invoked from network); 24 Mar 2024 16:59:47 -0000 Date: Sun, 24 Mar 2024 13:04:36 -0400 From: Rich Felker To: Alexander Weps Cc: Daniel Gutson , musl@lists.openwall.com, Markus Wichmann Message-ID: <20240324170436.GV4163@brightrain.aerifal.cx> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] Broken mktime calculations when crossing DST boundary On Sun, Mar 24, 2024 at 01:36:42PM +0000, Alexander Weps wrote: > Also thanks for the Pacific/Apia example. Not only that it fails for that date: > Pattern: * * * * * * > Initial: 2011-12-29_23:59:59 > Expected: 2011-32-31_00:00:00 > Actual: 2011-12-29_00:00:00 > My cron tool again going back in time. > > It fails one other test. > > I have to run my tests on multiple timezones. > > And it works in glibc. > > And that's after I removed tm_isdst and rewrote half the code to accommodate. > > Can We agree on some simple premise that with no uncertain STD/DST > settings (tm_isdst = 0 or tm_isdst = 1), incrementing seconds by 1 > and calling mktime should never cause time to go back? > > Well, behold Pacific/Apia: > > I set 2011-12-29 23:59:59: > > tm_sec: 59 > tm_min: 59 > tm_hour: 23 > tm_mday: 29 > tm_mon: 11 > tm_year: 111 > tm_wday: 0 > tm_yday: 0 > tm_isdst: 1 > tm_gmtoff: 0 > tm_zone: (null) > > Calling mktime to see if everything is correct: > mktime(&tm); > > before: 2011-12-29 23:59:59 -10 > tm_sec: 59 > tm_min: 59 > tm_hour: 23 > tm_mday: 29 > tm_mon: 11 > tm_year: 111 > tm_wday: 4 > tm_yday: 362 > tm_isdst: 1 > tm_gmtoff: -36000 > tm_zone: -10 > > Incrementing seconds and calling mktime: > tm.tm_sec += 1; > mktime(&tm); > > after: 2011-12-29 00:00:00 -10 > tm_sec: 0 > tm_min: 0 > tm_hour: 0 > tm_mday: 29 > tm_mon: 11 > tm_year: 111 > tm_wday: 4 > tm_yday: 362 > tm_isdst: 1 > tm_gmtoff: -36000 > tm_zone: -10 > We went from: > 2011-12-29 23:59:59 -10 > To: > 2011-12-29 00:00:00 -10 > > By adding 1 second. The tm_isdst was not set to -1. > > This is totally unreliable. >From what I understand, you've set the input to a time that doesn't exist in the local timezone: 2011-12-30 00:00:00. This could be either 1 second after 2011-12-29 23:59:59, as you intended, or 1 day before 2011-12-31 00:00:00. The latter is how it was interpreted. However, it does not seem to have correctly set tm_gmtoff to reflect how it was interpreted. We should check this out because that's probably an actual bug. Rich