From: Ben Peddell <killer DOT lightspeed AT bigpond DOT com>
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Newsgroups: comp.os.msdos.djgpp
Subject: Re: gprof with all zero execution times in version 2.03
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Date: Thu, 15 May 2003 17:10:17 +1000
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Andre Chrcanovic wrote:
> Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de> wrote in message news:<b9t2md$7ca$1 AT nets3 DOT rz DOT RWTH-Aachen DOT DE>...
> 
>>There, you did it.  Unless you did that *very* carefully, this almost
>>certainly is what broke the profile data collection.  Gprof relies on
>>standard timer ticks to do its work.
> 
> 
> OK. Maybe I was not very careful... I wrote the handler based on the
> information I found in the FAQ (item '18.9 How to hook hardware
> interrupts').
> 
> Is there a way to change the timer and still have the profile to work?
> Charles Sandmann mentions that "If you need your own timer routine
> then you need to chain to the original timer if you want profiling by
> time to work". I tried to use
> '_go32_dpmi_chain_protected_mode_interrupt_vector', as described in
> the 'Guide: Interrupts Overview' document, but this crashes the
> program... Is the version of the document I found in DJGPP's site not
> updated? I also tried the example code listed there and it also
> crashes...

So, you want a 5ms timer?
Why not hook the RTC interrupt?
It fires 1024 times a second by default, and you should be able to catch 
every fifth interrupt, giving a 4.88ms period.