src/time/mktime.c

   1 #include "time_impl.h"
   2 #include <errno.h>
   3
   4 time_t mktime(struct tm *tm)
   5 {
   6         struct tm new;
   7         long opp;
   8         long long t = __tm_to_secs(tm);
   9
  10         __secs_to_zone(t, 1, &new.tm_isdst, &new.__tm_gmtoff, &opp, &new.__tm_zone);
  11
  12         if (tm->tm_isdst>=0 && new.tm_isdst!=tm->tm_isdst)
  13                 t -= opp - new.__tm_gmtoff;
  14
  15         t -= new.__tm_gmtoff;
  16         if ((time_t)t != t) goto error;
  17
  18         __secs_to_zone(t, 0, &new.tm_isdst, &new.__tm_gmtoff, &opp, &new.__tm_zone);
  19
  20         if (__secs_to_tm(t + new.__tm_gmtoff, &new) < 0) goto error;
  21
  22         *tm = new;
  23         return t;
  24
  25 error:
  26         errno = EOVERFLOW;
  27         return -1;
  28 }