From:	"Avi Berkovich" <berkovic AT netvision DOT net DOT il>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: memset etc.
Date:	Tue, 15 Aug 2000 03:10:34 +0300
Organization:	NetVision Israel
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References:	<8mu28b$202$1 AT nslave1 DOT tin DOT it>
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Hello

Well, you have to enable the usage of near pointers before trying to
assigned an IO mapped device address to a C++ pointer.

what you should do is:

#include <sys/nearptr.h>

__djgpp_nearptr_enable();
unsigned char *VGA = (unsigbed char *) (0xA0000 +
__djgpp_conventional_base);


This will setup your pointer and enable you to access the video ram, you
should use the function __djgpp_nearptr_disable() at the end of your
program.

Note: this method won't work under Windows NT, Linux DosEMU and other
systems which don't allow the DS selector to have an absolute maximum
length.

P.S.
There is a replacement of the function MK_FP which is used in Borland Turbo
C++ (if you're familiar with it), in the DJGPP FAQ.


Avi


ClaudioF wrote in message <8mu28b$202$1 AT nslave1 DOT tin DOT it>...
>Sorry I'm newbie. I've a little problem with a code I've ported from
Watcom:
>"General Protection Fault at eip=00002e95 etc. etc."
>
>Here's the code. It writes with memset() to the video memory:
>
>
>  ScreenPointer = (unsigned char *) 0x0a0000;
>  memset (ScreenPointer+(x + (y*320)), color, 1);              //  Here's
>the problem. I can't resolve it
> }
>

>Thanks at all.
>ByeZ

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