Time t 1970 check

[joakim-hove]

1. All calls to util_make_date() -> ecl_util_make_date() in the libecl library.
2. Check if time_t/mktime() can accept values before 1970 during configuration.
3. If mktime() can not accept dates before 1970 : use hysterical heuristics to shift year into the interval [1970 - 2038).

[bska]

I don't understand. Isn't this slightly backwards? exit(0) from main() typically means "successful" while mktime() returns -1 if an error occurred.

Also, is there a reason you're using POSIX interfaces when the standard <time.h> also provides mktime()?

[joakim-hove]

Arggh: How to interleave answers in this interface?

I don't understand. Isn't this slightly backwards? exit(0) from main() typically means "successful" while mktime() returns -1 if an error occurred.

yes - it is backwards; I was waiting for that comment. Will fix before merging.

The POSIX thing was an oversight though. Will fix.

Thanks for the review.

[bska]

Just to follow up on the previous comment. The program below ought to print [something along the lines of]

Time = Mon Jan  1 00:00:00 1900

(and return successfully) on all platforms that support a basic C runtime system.

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

int main(void) {
  int       ret;
  struct tm ts = { 0 };

  ts.tm_mday   =   1  ;
  ts.tm_isdst  =  -1  ;

  {
    time_t t = mktime( &ts );
    if (t == -1)
      ret = EXIT_FAILURE;
    else {
      ret = EXIT_SUCCESS;
      printf("Time = %s", ctime(&t));
    }
  }

  return ret;
}

[joakim-hove]

Just to follow up on the previous comment. The program below ought to
print

Time = Mon Jan 1 00:00:00 1900

(and return successfully) on all platforms that support a basic C runtime
system.

You would have thought so - but no. The standard is unspecified as what to
do with times prior to Jan 1 00:00:00 1970, and the MS Visual Studio
runtime has decided to return -1 in that case.

http://stackoverflow.com/questions/471248/what-is-ultimately-a-time-t-typedef-to

Joakim

[bska]

@joakim-hove

You would have thought [that mktime() would be able to process times prior to 1970-01-01T00:00:00+0000] - but no.

I stand corrected. Thanks a lot for bringing that to my attention. Apparently I never paid enough attention to the fine details of the specification.