Easy way to convert a struct tm (expressed in UTC) to time_t type

Question

How do I do the above? There is mktime function but that treats the input as expressed in local time but how do i perform the conversion if my input tm variable happens to b

Answer 1

The following implementation of timegm(1) works swimmingly on Android, and probably works on other Unix variants as well:

time_t timegm( struct tm *tm ) {
  time_t t = mktime( tm );
  return t + localtime( &t )->tm_gmtoff;
}