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: <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) | | +----------------------------------------+------------------------------+