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From: Lewis_P@cc.curtin.edu.au (Peter Lewis)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Cross Compilers for Mac ?
Message-ID: <7130.27bfdc02@cc.curtin.edu.au>
Date: 18 Feb 91 05:52:02 GMT
References: <Le9eX3w163w@ersys.uucp> <NV89-NUN.91Feb18003848@alv.nada.kth.se>
Organization: Curtin University of Technology
Lines: 51

In article <NV89-NUN.91Feb18003848@alv.nada.kth.se>, 
       nv89-nun@alv.nada.kth.se (Nicklas Ungman) writes:
> I'we also been thinking of doing some cross developing in the Mac. One way
> to cross compile is to build a stand-alone code resource. This can be done
> with both MPW C and THINK C, which are both good compilers. However, this
> prevents you from using global variables, and also limits multi segmentation.

   This is how we programmed a standalone 68000 for a micro-mouse competition
(albeit using THINK Pascal, but its basically the same).  Another problem
was that you had to be very careful about what you called, and how the
libraries worked (the silly thing crashed with and A-line trap, and it took 
us a while to find that my co-programmer (who shall remain nameless - Hi
John :-) had foolishly called Random).

> Does anyone know how to get around this problem?

   The way we solved this was to allocated a fixed space on the target
machine for globals - say $1000 bytes at $00400000, then do -
const
  globals=$00400000;
type
  gr=record
    any globals you want
  end;
  gp=^gr;

Then at the start of any procedure requiring global variables -
var g:gp;
begin
  g:=gp(globals);
  with g^ do begin
  ....
  end;
end;

   Its not particularly elegant, but it works ok.  If you dont want to
allocate a huge block of ram, you could just allocate a fixed pointer, and
use g^^.  Saddly, with C, you cant use nested procedures to mimic globals
(it wouldnt work very well with large projects anyway).
> 
> /Nixxon
HTH,
   Peter.
-- 
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