Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!zephyr.ens.tek.com!tektronix!reed!chaffee
From: chaffee@reed.bitnet (Alex Chaffee,(259),,2369505)
Newsgroups: comp.sys.mac.programmer
Subject: Re: converting tail patches to head patches...
Message-ID: <13636@reed.UUCP>
Date: 28 Nov 89 23:41:59 GMT
References: <63359@tiger.oxy.edu> <9099@hoptoad.uucp>
Sender: news@reed.UUCP
Reply-To: chaffee@shiva.JPL.NASA.GOV (Alex Chaffee)
Organization: Reed College, Portland, OR
Lines: 53
Summary: Shouldn't it go like this?

In article <9099@hoptoad.uucp> tim@hoptoad.UUCP (Tim Maroney) writes:
>      myPatch()
>      {
>      doMyStuff();
>      asm{
>          unlk      a6
>          Lea       @1,A0	; @1 is a dc.l that has the old trap stashed
>          Move.L    (A0),A0
>          Jmp       (A0)
>        }
>      }

What is the syntax one should use for setting up a dc.l from within Think
C?  With scoping as I understand it, the @1 would have to refer to somewhere
_within_ the function, and you haven't declared it...  So shouldn't it go
something like this:

long OldTrap;	/* global - some initialization routine sets this */

myPatch()
{
	doMyStuff();
	asm {
		br.s 	@2
@1		dc.l
@2		move.L	OldTrap, @1
		unlk	A6
		move.L	@1, A0
		move.L	(A0), A0
		jmp	(A0)
	}
}

I'm sure there are a dozen things wrong with the syntax (and it would be
very educational to be corrected), but how's the idea?  By the way, if this
works, I will use it instead of my old method, which is

	asm {
		move.l	OldTrap, A0	; or A1, for some traps
		unlk	A6
		jmp	(A0)
	}

(if I remember correctly).

                "Nor is it a consequence of my bed's being covered with
                 leaves that I am not hallucinating that it is."
                 - Barry Stroud
____________________
--
Alex Chaffee
chaffee@reed.UUCP
____________________