Bug#998737: Problem found with possible fix suggestion

[ADA]

    Hi,

  I've found the problem, why the timestamp, which should be in ISO 8601 
format gets "corrupted". This problem exists in all current GNote 
packages, including the original source (GitLab GNote master).

  The problem is in datetime.cpp, function date_time_to_iso8601.

Link on GitLab:
   https://gitlab.gnome.org/GNOME/gnote/-/blob/master/src/sharp/datetime.cpp

Bug was introduced with this commit:
 
https://gitlab.gnome.org/GNOME/gnote/-/commit/b30cd91826d2ee3b953b2485683ba8011be0434d


  Short C program to demonstrate the problem, let's reuse portion of 
that function and dump the current timestamp to the console:


#include <stdio.h>
#include <string.h>

int main(void) {
     char buffer[36] = {0};

     sprintf(buffer, "%d-%02d-%02dT%02d:%02d:%02.6lfZ", 2021, 12, 9, 13, 
51, 3.01918745645);
     printf("%s\n", buffer);
}


This outputs:
2021-12-09T13:51:3.019187Z

There's no zero padding in the seconds part, due to how %02.6 is 
interpreted for floats. This is a possible fix:


#include <stdio.h>
#include <string.h>

int main(void) {
     char buffer[36] = {0};

     sprintf(buffer, "%d-%02d-%02dT%02d:%02d:%09.6lfZ", 2021, 12, 9, 13, 
51, 3.01918745645);
     printf("%s\n", buffer);
}


This outputs:
2021-12-09T13:51:03.019187Z


This is what we want to see. Just change %02.6lf to %09.6lf in the 
sprintf call.

   IMHO, this should be also communicated upstream. Thanks!

      Best regards,
           Zoltan Adasz