From: tdu AT enter DOT net (Tim Updegrove)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: uclock erratic
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Date: Thu, 04 May 2000 02:07:45 GMT
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To: djgpp AT delorie DOT com
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Now that I've checked the archives once my lovely wife was off the
phone, I see uclock() has a problem in the 1st 55ms.  The 281 version
is probably the compiler version and not the DJGPP version.  Okay, I
found it.  I have DJGPP version 2.02.  Is this problem fixed in a
later version?  Thank-you for your help again (and your patience)..

On Thu, 04 May 2000 01:30:38 GMT, tdu AT enter DOT net (Tim Updegrove) wrote:

>The uclock() function appears to be returning crazy values sometimes.
>The returned value seems to have wrapped but the program only runs
>less than one minute.  The very 1st call to uclock() returns 0 and
>subsequent calls return higher values as expected.  If uclock() is
>being called in a tight loop, the difference between two calls is
>about 0xa00.  The problem is that sometimes a value like 0xffff0e87
>will be returned when the preceding returned value was something like
>0x00000be7 (I've made up the lower 16 bits because I don't recall
>actual values).  The problem is that only a very small amount of time
>has elapsed yet the upper 16 bits are all ones when they were
>previously all zeros
>
>One last bit of info.  The Dell XPS-T500 (P3 500 Mhz) machine is
>booted to MS-DOS and the program is run.  The DJGPP version is 281 (I
>think).
>
>Am I doing something stupid?  Has anyone else experienced this
>problem?  Any help would be much appreciated.
>
>I've included the below function that uses uclock().  The program
>stops because bit 31 is set in diff_time.  The display shows the upper
>16 bits are set in diff_time and endtime.
>
>#include <time.h> // needed for uclock()
>
>int delay_clock(unsigned long max_ticks) {
>
>  unsigned long int
>    diff_time;
>  
>  uclock_t
>    starttime,
>    endtime;
>
>  starttime = uclock();
>  endtime = starttime;
>
>  diff_time = (unsigned long int) (endtime - starttime);
>  while ( diff_time < max_ticks) {
>    endtime = uclock();
>    diff_time = (unsigned long int) (endtime - starttime);
>    if ((diff_time & 0x80000000) == 0x80000000) {
>      printf("Error: uclock timer has/will overflow\n");
>      printf( "starttime=%08lx, endtime=%08lx, diff_time=%08lx\n",
>        (unsigned long int) starttime, (unsigned long int) endtime,
>diff_time);
>      exit(1);
>    } // crazy timer
>  } /* while delay */
>
>  return 0;
>} /* delay_clock */
>