Path: utzoo!utgpu!attcan!uunet!seismo!sundc!pitstop!sun!decwrl!labrea!eos!ames!pacbell!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.sys.mac
Subject: Re: Calling CODE segments
Message-ID: <5478@hoptoad.uucp>
Date: 29 Sep 88 01:37:17 GMT
References: <17742@glacier.STANFORD.EDU>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Distribution: na
Organization: Eclectic Software, San Francisco
Lines: 42

In article <17742@glacier.STANFORD.EDU> leeke@glacier.UUCP (Steven D. Leeke)
writes:
>LSC reqires me to use their RememberA4/SetupA4 stuff on entry in the
>CODE segment and RestoreA4 on exit to get at the globals (if any) in
>the CODE segment - so I do. e.g. the CODE segment's main looks like:
>
>void main(p1,p2,p3,...,entryPoints)
>{
>	RememberA4();
>	SetupA4();
>	/* ... */
>	RestoreA4();
>};

Look at page 85 of the User's Manual.  You need to call RememberA0(), not
RememberA4().  They're very different macros.  Things are getting trashed
because A4 is set to something silly, so all your global accesses are writing
into random memory locations.

>This seems to work well until I try to draw something from within the
>"main" program (I don't draw in the code segment) - usually activating
>or updating a window when a dialog the CODE segment loaded is being drawn.

That's probably just the way it happens; change a few variables and you might
have problems with drawing controls or dragging windows instead.  But if you
really want to know whether A5 is problematic, just drop into MacsBug or TMON
at the beginning of the main program callback routine, and see if A5 is the
same as the low-memory global CurrentA5.  I'm pretty sure there is no reason
to explicitly set A5 to CurrentA5 inside the callback routine, since the
code resource shouldn't modify A5.  But if you want, setting A5 to CurrentA5
in the callback routine couldn't hurt.

>I've tried to use SetupA5 right after SetupA4 when I start my CODE segment,
>for what it's worth, but it doesn't seem to make a difference.  I'm not
>an experienced ASM hacker period - especially on the Mac.

This, I think, confirms my feelings that your problems are with A4.
-- 
Tim Maroney, Consultant, Eclectic Software, sun!hoptoad!tim
"I see little divinity about them or you.  You talk to me of Christianity
 when you are in the act of hanging your enemies.  Was there ever such
 blasphemous nonsense!" - Shaw, "The Devil's Disciple"