[Bug libc/20745] New: localtime_r returns incorrect result.

["kosakagumi at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=20745

            Bug ID: 20745
           Summary: localtime_r returns incorrect result.
           Product: glibc
           Version: unspecified
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: kosakagumi at gmail dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

Hello.

I find a bug for localtime and localtime_r. The result is different by
gmtime_r and localtime_r

The result is the followings:

$ ./hoi 2015 6/30 493
In: 2015 6/30 Add:493 days
localtime_r:  2016 11/4
gmtime_r:     2016 11/4

In: 2015 6/30 Add:494 days
localtime_r:  2016 11/5
gmtime_r:     2016 11/5

In: 2015 6/30 Add:495 days
localtime_r:  2016 11/6
gmtime_r:     2016 11/6

In: 2015 6/30 Add:496 days
localtime_r:  2016 11/6
gmtime_r:     2016 11/7

In: 2015 6/30 Add:497 days
localtime_r:  2016 11/7
gmtime_r:     2016 11/8

When the program adds 496 days, the result is different between locatime_r and
gmtime_r. gmtime_r returns the correct value.

The program is the followings:

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

static int CalcEndDays(int Y,int M,int D,int AddDays)
{
  struct tm tm,ltime;
  time_t time,tt;

  tm.tm_sec = 0;
  tm.tm_min = 0;
  tm.tm_hour = 0;
  tm.tm_mday = D;
  tm.tm_mon = M - 1;
  tm.tm_year = Y - 1900;

  tt = (time_t)86400 * (time_t)(AddDays);

  time = mktime(&tm) + tt;

  localtime_r(&time,&ltime);
  fprintf(stderr,"localtime_r:  %d %d/%d\n",ltime.tm_year+1900, ltime.tm_mon+1,
ltime.tm_mday);

  gmtime_r(&time,&ltime);
  fprintf(stderr,"gmtime_r:     %d %d/%d\n",ltime.tm_year+1900, ltime.tm_mon+1,
ltime.tm_mday);

  fprintf(stderr,"\n");
}

int main(int argc,char **argv)
{
  int y, m, d,add,i;

  sscanf(argv[1], "%d", &y);
  sscanf(argv[2], "%d/%d",&m,&d);
  sscanf(argv[3], "%d",&add);

  for( i = 0 ; i < 5 ; i++ ) {
    fprintf(stderr,"In: %d %d/%d Add:%d days\n",y,m,d,add + i);
    CalcEndDays(y,m,d,add + i);
  }
}

Also the nm of the program is the followings:

         U fprintf@@GLIBC_2.0
         U fputc@@GLIBC_2.0
08048500 t frame_dummy
         U gmtime_r@@GLIBC_2.0
         U localtime_r@@GLIBC_2.0
08048620 T main
         U mktime@@GLIBC_2.0
0804a028 B stderr@@GLIBC_2.0

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