Invalid use of mktime() in Ruby 1.8/1.9 results in incorrect Time objects

Hello,

I've found a bug in both Ruby 1.8 and 1.9, which occurs on systems  
that have Ruby compiled with HAVE_MKTIME. According to the man page:

The tm_year member must be for year 1901 or later. Calendar times  
before 20:45:52 UTC,  December 13, 1901 or after 03:14:07 UTC, January  
19, 2038 cannot be represented. Port-      able applications should  
not try to create dates before 00:00:00 UTC, January 1, 1970 or after  
00:00:00 UTC, January 1, 2038.

The warning issued here is exactly what happens in both 1.8 and 1.9.  
If Ruby is compiled with HAVE_MKTIME, the code eventually falls  
through to the following line in time.c (1.9 trunk):

  846 #if defined(HAVE_MKTIME)
  847         if ((t = mktime(&buf)) != -1)
  848             return t;
  849 #ifdef NEGATIVE_TIME_T
  850         if ((tmp = localtime(&t

If the Ruby call is for example Time.local(1900), the behavior of  
mktime apparently is to create a time object for 20:45:52 UTC,  
December 13, 1901 instead of returning -1. Whether or not this is  
correct behavior is not really an issue, because this behavior is not  
defined in the mktime() specification.

The expected behavior from Ruby's point of view is that is should  
raise an ArgumentError: time out of range.

The easiest solution is to simply remove the mktime() call and always  
use localtime() which exhibits the correct behavior. I've tested this,  
and this results in the correct behavior.

All this has been tested on a clean Debian Etch install with the  
latest Ruby compiled from trunk.

-- 
Regards,

Dirkjan Bussink