Bug in strftime %z

[Christian Franke]

Corinna Vinschen wrote:
> On Jan  7 22:50, Corinna Vinschen wrote:
>> Hi Christian,
>>
>>
>> thanks for the testcase!
>>
>> On Dec 19 19:44, Christian Franke wrote:
>>> $ cat strftest.c
>>> #include <time.h>
>>> #include <stdio.h>
>>> #include <stdlib.h>
>>>
>>> int main(int argc, char **argv)
>>> {
>>>    time_t t = (argc > 1 ? atol(argv[1]) : time(NULL));
>>>    struct tm *tm = localtime(&t);
>>>    char buf[100];
>>>    strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S %z (%Z)", tm);
>>>    printf("%s\n", buf);
>>>    return 0;
>>> }
>>>
>>> $ gcc -o strftest strftest.c
>>>
>>> $ echo $TZ
>>> Europe/Berlin
>>>
>>> $ ./strftest 1419010000
>>> 2014-12-19 18:26:40 +0200 (CET)
>>>
>>> $ ./strftest 1436200000
>>> 2015-07-06 18:26:40 +0053 (CEST)
>> Surprisingly this is an old problem which exists in this form since 2011.
>> Weird that nobody noticed it so far.  Or I missed earlier bug reports :}
>> The underlying cause was that the info for std and dst offsets was taken
>> from the wrong spot in the file.  The weird 0053 offset is a result of
>> wrongly using the LMT offset for Europe/Berlin.
>>
>> While this fixes the problem for recent timestamps, it will probably
>> fail for older timestamps when other dst rules were active.
>>
>> The latest Cygwin versions come with an extended struct tm which adds
>> members tm_offset and tm_zone for newly built applications.  I'm working
>> on a patch so strftime utilizes these members if they are available.
>> I hope to get this finished tomorrow.
> I uploaded a snapshot containing the fixes in tzload and strftime to
> https://cygwin.com/snapshots/  Please give it a try.

%z now works as expected.

Thanks,
Christian


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