Mail Archives: djgpp/1995/01/27/18:49:14

Date: Fri, 27 Jan 95 13:21:41 EST
From: peprbv AT cfa0 DOT harvard DOT edu (Bob Babcock)
To: A DOT APPLEYARD AT fs2 DOT mt DOT umist DOT ac DOT uk
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Re: V2
Reply-To: babcock AT cfa DOT harvard DOT edu

> What are these `farptr' routines and where is information about them?

Look in sys\farptr.h which has more comments than a typical gnu file ;-(

> I don't want the supermassive rewrite job on my program which this change
> will cause me. Please!!! What <is> the matter with having the text screen
> represented as always the same addresses like now??  Ditto with knowing the
> graphics screen's address.

I think you are already in trouble.  Ever tried running one of your programs
under Windows or OS/2?  DPMI 0.9 does not allow the sort of remapping you now
depend on.  Instead, you can get a different selector which points at video
memory.  A pointer which uses a different segment register or selector is, in
PC compilers, callled a far pointer.  Gcc does not implement far pointers, so
DJ wrote some macros which expand to inline assembler to mimic the effect of
a far keyword.  I'll admit to not having actually used these macros simply
because all the code I have for direct video access was done by hand tweaking
of assembly language utput from gcc before the farptr macros were available.

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