My Arch system does indeed have daylight saving set, but nmea.c forces the TZ to UTC where a positive value of tm_isdst does not make sense.
On Wed, Apr 21, 2021 at 1:51 PM Geva, Erez <erez.geva....@siemens.com> wrote: > Looks like the man page is not accurate. > Looking in > https://pubs.opengroup.org/onlinepubs/009695399/functions/mktime.html > > A positive or 0 value for tm_isdst shall cause mktime() to presume > initially that Daylight Savings Time, respectively, is or is not in effect > for the specified time. > A negative value for tm_isdst shall cause mktime() to attempt to determine > whether Daylight Savings Time is in effect for the specified time. > > My guess is that on Lars new system the daylight is NOT set, then the > mktime fail to determine the Daylight Savings and return error (-1). > > Erez > > -----Original Message----- > From: Richard Cochran <richardcoch...@gmail.com> > Sent: Tuesday, 20 April 2021 16:05 > To: Lars Munch <l...@segv.dk> > Cc: linuxptp-devel@lists.sourceforge.net > Subject: Re: [Linuxptp-devel] [PATCH] Fix uninitialized variable in > nmea_scan_rmc > > On Tue, Apr 20, 2021 at 11:44:06AM +0200, Lars Munch wrote: > > tm_isdst needs to be initialized to make sure mktime does not fail or > > calculates the wrong time. > > No, take a look at the mktime(3) man page. There you will read the > following. > > The mktime() function modifies the fields of the tm structure as > fol‐ > lows: tm_wday and tm_yday are set to values determined from the > con‐ > tents of the other fields; if structure members are outside > their > valid interval, they will be normalized (so that, for example, 40 > Oc‐ > tober is changed into 9 November); tm_isdst is set (regardless of > its > initial value) to a positive value or to 0, respectively, to > indicate > whether DST is or is not in effect at the specified time. > > Thanks, > Richard > > > _______________________________________________ > Linuxptp-devel mailing list > Linuxptp-devel@lists.sourceforge.net > > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.sourceforge.net%2Flists%2Flistinfo%2Flinuxptp-devel&data=04%7C01%7Cerez.geva.ext%40siemens.com%7C6b9d88bf27584b2d9eb508d9040556d6%7C38ae3bcd95794fd4addab42e1495d55a%7C1%7C0%7C637545243247255579%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=wHxP0yERXKP6unOP1ZPV%2F87BVduutafEUIOl8jH%2Bud4%3D&reserved=0 >
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