From bug-octave-request at bevo dot che dot wisc dot edu  Tue Jan  4 10:48:14 2000
Subject: Still problems with time func since y2k (win95/gnuwin32)
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Rolf Fabian <fabian at tu-cottbus dot de>
Cc: "'bug-octave UWISC'" <bug-octave at bevo dot che dot wisc dot edu>
Date: Tue, 4 Jan 2000 10:48:35 -0600 (CST)

On  4-Jan-2000, Rolf Fabian <fabian at tu-cottbus dot de> wrote:

| yesterday, I've already reported problems with clock.m (returning
| year 1970 instead of 2000) on my win95/gnuwin32 installation since
| Jan. 1st 2000. I've got a reply from jwe, that it's highly unlikely
| to be an octave-bug because clock() simply calls ,localtime( time()
| )'.
| 
| Now I'm convinced, that the problem comes from ,time()' call, which
| should return the number of seconds since 1970 (UNIX epoch). The
| number returned by ,time()' is incorrect and by far too small !!
| 
| Please have a look at the following log
| 
| :> version
| ans=2.0.13	#win95/gnuwin32-b20
| :> system('date'); LT=localtime(TIME=time()), TIME, CLOCK=clock()
| Tue Jan  4 16:35:43  2000
| 
| LT =
| {
|   usec =  8.0900e+05
|   year = 70
|   mon = 0
|   mday = 25
|   sec = 22
|   min = 22
|   wday = 0
|   hour = 10
|   isdst = 0
|   yday = 24
| }
| 
| TIME =  2.1073e+06
| CLOCK =
|   1970.0000     1.0000    25.0000    10.0000    22.0000    22.8090
| 
| Because as a ,rule of thumb' an (average) year has about pi*1e7
| seconds , the output of TIME=time() octave built-in func. is
| obviously much too small and seems to be responsible for the
| problems observed.

Right, it looks like the system library's time function is returning
the wrong thing.  Octave's time function does just

  DEFUN_DLD (time, , ,
    "time ()\n\
  \n\
  Return current time.  On Unix systems, this is the number of\n\
  seconds since the epoch.")
  {
    time_t now;
    double fraction = 0.0;

  #if defined (HAVE_GETTIMEOFDAY)

    struct timeval tp;

  #if defined  (GETTIMEOFDAY_NO_TZ)
    gettimeofday (&tp);
  #else
    gettimeofday (&tp, 0);
  #endif

    now = tp.tv_sec;

    fraction = tp.tv_usec / 1e6;

  #else

    now = time (0);

  #endif

    return (double) now + fraction;
  }

Which I believe is the correct way to use these functions.  I suspect
that gettimeofday is returning something invalid on your system (you
have a nonzero microsecond field in your localtime struct, so it seems
likely that your binary was compiled with HAVE_GETTIMEOFDAY defined).
Probably the bug is either in the version of the cygwin library you
are using, or in the Windows system calls (if any, I haven't checked)
that it depends on to implement the gettimeofday function.

jwe






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