From:	Damian Yerrick <Bullcr_pd_yerrick AT hotmail DOT comRemoveBullcr_p>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: tracking an elusive crash
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On Sun, 03 Sep 2000 12:38:46 -0500, April <awhite AT user DOT rose DOT com>
wrote:

>I am working with btree code based on a text book.  I get an elusive
>crash that I cannot track down nor get any useful info post-crash.
>
>djgpp gcc version 2.95.2 19991024
>win95
>
>The worst crash reboots the computer, the second worst gives a fatal
>error 'you program has commited an illegal instruction'.  Obviously in
>both cases there is no call stack to symify.

You've hit upon a bug so bad it crashes Windows's DOS box.  Try
running it in plain DOS (press F8 right before the clouds come up when
starting your computer) with CWSDPMI.EXE in your .../djgpp/bin folder.
CWSDPMI is a bit better at catching null pointer and other memory bugs

>I have tried to run the program in dos mode (ie. booted to dos)

Good.

>but the GPF gives no callstack, and if I can believe the IP address,
>when I locate it in the map file I finaly created, it is inside
>libc.a(exceptn.o).

I recently had this happen to me:  mine turned out to be a stack
overflow from infinite recursion due to an invalid tree structure
in a data file.

>What can I try?

Try increasing the stack size.  If that helps (larger data sizes
without a crash), try switching to an algorithm that uses less stack.

Try printf() debugging so you can trace the flow of the program.

-- 
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  that renders the sufferer barely able to perform the simplest
  task.  2. A disease, multiple sclerosis (see).

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