Message-ID:	<3BB4E801.32F49852@cyberoptics.com>
From:	Eric Rudd <rudd AT cyberoptics DOT com>
Organization:	CyberOptics
X-Mailer:	Mozilla 4.72 [en] (Win95; U)
X-Accept-Language:	en,pdf
MIME-Version:	1.0
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Heap structure
References:	<3BA1292B DOT C593DFD8 AT cyberoptics DOT com> <9p25as$rra$1 AT milzis DOT latnet DOT lv>
Lines:	27
Date:	Fri, 28 Sep 2001 16:13:37 -0500
NNTP-Posting-Host:	38.196.93.9
X-Trace:	client 1001711620 38.196.93.9 (Fri, 28 Sep 2001 17:13:40 EDT)
NNTP-Posting-Date:	Fri, 28 Sep 2001 17:13:40 EDT
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp
Reply-To:	djgpp AT delorie DOT com

Antonijs Kipans wrote:

> As I stumbled over this myself, there is one unexpected possibility - you
> trie to fprintf() into UNOPEN file!

My program had opened and closed the same file for appending several times
before the bomb occurred, and the file contents were plausible, so I doubt
that was the problem here.

The debugging tools were not of much help because the side effects of the bug
disappeared as soon as I enabled the debugging code.  (Specifically,
whenever I increased malloc_debug to 1 or higher to detect the bug, the
program executed normally and malloc_verify() returned 1 -- how
frustrating!)   By inspection, I eventually did find some errors in my code,
and after I fixed them the program didn't bomb anymore.  Thanks to all who
offered their help.

-Eric

> "Eric Rudd" <rudd AT cyberoptics DOT com> wrote in message
> news:3BA1292B DOT C593DFD8 AT cyberoptics DOT com...
> > I have a DJGPP program that is bombing with a SIGSEGV error.  I have
> > reason to believe that the program has an array overflow that is
> > corrupting the structure of the heap.  (The program actually bombs in a
> > malloc call inside fprintf, but at this point I have no convincing
> > reason to believe that a system function bug is to blame.)

- Raw text -