Path: utzoo!attcan!uunet!husc6!mailrus!ames!oliveb!apple!keith
From: keith@Apple.COM (Keith Rollin)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Problems with XCMDs in MPW Object Pascal 3.0
Message-ID: <27155@apple.Apple.COM>
Date: 12 Mar 89 07:21:25 GMT
References: <4321@sdcc3.ucsd.EDU> <26942@apple.Apple.COM> <877@internal.Apple.COM> <15634@cup.portal.com>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 74

In article <15634@cup.portal.com> Greg_Mark_Finnegan@cup.portal.com writes:
>
>I have one related question (and onother somewhat unrelated):
>
>Is it possible to create a multisegment XCMD? Let's say for example I want
>to somehow shoehorn a small spreadsheet (about 90K) into an XCMD. Can I
>do it (easily)?

Well, I suppose that it could be done. There are two ways that you could do
it, but neither qualify as being easy:

	1) create a multisegmented XCMD
	2) create a 90K XCMD

MPW will allow you to compile and link a code segment that is 90K in size.
However, there is major limitation when doing so: all intra segment calls
must involve a distance no greater than 32K. This comment only applies to
Pascal and C programmers. I am not an assembly language programmer so I don't
know if there is a PC relative addressing mode that allows 32-bit offsets
when calling subroutines. If there is, then you could write your XCMD in
assembly with no problems.

Creating a multisegmented XCMD is also nasty. You would have to handle the
loading of the other segments by yourself. This would amount to writing
several XCMDs, with the main one loading in and calling the others as needed.
This could be done with small subroutines.

I've heard that the LightSpeed development systems allow one to easily
create multisegmented DA's. I don't know how this is done, but perhaps their
techniques would apply to your problem.

If I were in your situation, I would re-examine what I was trying to do. If
I had 90K of code that I wanted to execute, I'd write an application, not
and XCMD that runs under HyperCard.


>Here's a question for the MPW compiler hacks out there: What is the most
>efficient base index of arrays in MPW 3.0 Pascal 0 or 1?

I just looked at the output of the following program. Neither array base
seemed offer any advantage over the other. However, I seem to recal an
instance where a zero-based array was better, but I can't remember what the
circumstances were:

VAR
        t1: array [0..10] of integer;
        t2: array [1..10] of integer;
        i: integer;
        
begin
        t1[0] := 1;
        t1[1] := 2;
        t2[1] := 3;
        t2[2] := 4;
        
        i := 0;
        t1[i] := 5;
        
        i := 1;
        t1[i] := 6;
        t2[i] := 7;
end.

>Thanks in advance.
>
>Greg.


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