To: djgpp AT sun DOT soe DOT clarkson DOT edu
Cc: dridge AT MIT DOT EDU
Subject: Tricky Debugging Problem
Date: Tue, 29 Mar 94 20:48:48 EST
From: Matthew Eldridge <dridge AT MIT DOT EDU>


First a word of thanks to DJ for the great port, and to Csaba for the
LIBGRX stuff.  It makes my life a lot easier.

Now for a question:  I'm working on a graphics application that
does some Virtual Reality sorts of things, including texture mapping
among others.  It is a memory hog to say the least.  Recent experimentation
has introduced a very large buffer (~2MB) which is being used 
as an accumulation buffer for images being anti-aliased.

My machine unfortunately has a rather pitiful 4MB of memory, and
this big chunk of memory makes the machine thrash furiously as
it runs.  This I can deal with.  More importantly, it *seems* to
break the code somewhere.  My display memory has started getting
crap dumped into it sporadically, and other things get munged,
as if a pointer has run amok.

I'm using Csaba's stuff to put my ET4000/w321 into 640x480 24bit
color mode, and just blasting the data directly in via
address 0xe0000000.

I'd like to say my code isn't the culprit, but everytime someone
says this they are wrong.  What I would like is a way to catch pointer
references into screen memory and into this buffer that are done by
anything other than the couple of pointers that are suposed to be
touching these areas.

Is there any good way to do this?

Thanks in advance for any help you can send my way

-Matthew
dridge AT athena DOT mit DOT edu