Xref:	news2.mv.net comp.os.msdos.djgpp:628
From:	fenric AT clark DOT net (Andrew McCaffrey)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Issues with nearptr's.
Date:	27 Jan 1996 05:15:33 GMT
Organization:	the beginning of all beginnings
Lines:	29
Message-ID:	<4eccdl$90b@clarknet.clark.net>
References:	<JTSILLA DOT 96Jan26100052 AT atlas DOT ccs DOT neu DOT edu> <31096ecf DOT sandmann AT clio DOT rice DOT edu>
NNTP-Posting-Host:	explorer.clark.net
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Charles Sandmann (sandmann AT clio DOT rice DOT edu) wrote:
> > I'd like to use nearptr's to access physical memory currently occupied
> > by video hardware. SOunds pretty simple, no? Well, I've read rumours
> > that there are dangers involved in setting the NEARPTR flag in my crt0 flags.
> 
> The only known dangers are that a stray pointer can destroy the interrupt
> table, DOS, driver data, Windows, or anything else in memory.  If you always
> program without bugs, you have nothing to worry about :-)
> 
> > One problem I have noticed is that when running under gdb, gdb
> > crashes when I use this flag and try to print out large data structures.
> > Are there any other possible issues? What's really going on in there?
> 
> This really shouldn't be related, and I don't know why this would make
> a difference.  With nearptrs you could overwrite GDB's memory, but this
> might actually be seen with the default non-move sbrk anyway, since the
> debugger and program could end up with their memory laid out ABABAB.

I've written a couple of graphic routines with nearptrs and they run fine 
under dos and cwsdpmi, but when I try to run them under gdb, I get a 
segmentation violation signal.  

-- 
+------------------------Andrew McCaffrey+[fenric AT clark DOT net]------------+
|Doctor: But I don't exist in your world!|"Anybody remotely interesting |
|Brigade-Leader: Then you won't feel the |is mad in one way or another."|
|bullets when we shoot you.              |    - The Seventh Doctor      | 
|       Doctor Who - Inferno (1970)      |                              |
+----------------------------------------+------------------------------+

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