Indeed, any positive random number in tm.tm_isdst will set DST in effect it
seems.
On my stripped down ARM system with no timezone information, it will simply
return -1.
On Tue, Apr 20, 2021 at 4:26 PM Michael Galassi <mich...@galassi.us> wrote:
> Somewhere lies a bug. The following code snippet:
> #include <stdio.h>
> #include <time.h>
> int main()
> {
> struct tm t;
> time_t now = time((void*)0);
> localtime_r(&now, &t);
> t.tm_isdst = 1;
> printf("%ld\n", mktime(&t));
> t.tm_isdst = 0;
> printf("%ld\n", mktime(&t));
> t.tm_isdst = -1;
> printf("%ld\n", mktime(&t));
> }
> Yields:
> 1618928503
> 1618932103
> 1618932103
> This is true on FreeBSD 13 and Ubuntu 18.04, both fully patched.
>
> -michael
>
> On Tue, Apr 20, 2021 at 7:04 AM Richard Cochran <richardcoch...@gmail.com>
> wrote:
>
>> 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://lists.sourceforge.net/lists/listinfo/linuxptp-devel
>>
>
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