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
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