From:	"Stefan Viljoen" <rylan AT intekom DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: calling a pointer
Date:	Mon, 9 Aug 1999 23:26:01 +0300
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References:	<37ADD81B DOT 4840 AT iquest DOT net>
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Mike Nansgar <dkw AT iquest DOT net> wrote in message
news:37ADD81B DOT 4840 AT iquest DOT net...
> I am writing VESA VBE 2.0 routines using a combination of DJGPP and
> NASM. It seems as if my code (which calls the NEAR p-mode code) half
> works; it does set the page because when I write to the video, it sets
> the right pixels. But immediately after setting them it crashes with a
> GPF at my 'rep stosd' instruction! The same 'rep stosd' works perfectly
> when used with the set bank interrupt. Any help would be greatly
> appreciated. Thanks in advance!

I have encountered something similar when I was converting demo code from
real mode TASM to protected mode DJGPP + NASM - the problem was that my rep
stosd instructions worked perfectly, but as soon as I linked in Allegro into
the converted program, it started cracking up with a GPF at the rep stosd
just as your program is doing. If I remember right it had something to do
with allegro changing the descriptor in DS  (Shawn?) - I seem to remember
fixing it by recording the DS selector in a variable, and switching this
back before a rep stosd, and then replacing it again afterward. Some
instructions that I dropped totally in the real / protected mode switch
included some compound instructions that required implied registers that I
could not use in protected mode like in real mode - I broke these up into
simpler instructions, like a mov and an inc for something like stos...


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