Path: utzoo!attcan!uunet!convex!killer!mit-eddie!bloom-beacon!apple!mjohnson
From: mjohnson@Apple.COM (Mark Johnson)
Newsgroups: comp.sys.mac.programmer
Subject: Re: SlotVInstall problem
Message-ID: <20875@apple.Apple.COM>
Date: 19 Nov 88 02:06:04 GMT
References: <10050047@eecs.nwu.edu> <10050050@eecs.nwu.edu>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 35

In article <10050050@eecs.nwu.edu> jln@eecs.nwu.edu (John Norstad) writes:
>
>I discovered the reason why my SlotVInstall call failed in MPW C - 
>it's bad glue in the MPW library {Libraries}Interface.o.  I thought 
>it worthwhile to alert people to the problem, hence this follow-up posting.
>
>The header file Retrace.h defines SlotVInstall as follows:
>
>pascal OSErr SlotVInstall (VBLBlockPtr, theSlot)
>   QElemPtr VBLBLockPtr;
>   short theSlot;
>   extern;
>   
>I set a breakpoint on the SlotVInstall trap using MacsBug and 
>discovered that the glue code is the following:
>
>   movea.l  (a7)+,a1
>   movea.l  (a7)+,a0
>   move.w   (a7)+,d0
>   _SlotVInstall
>   move.w   d0,(a7)
>   jmp      (a1)
>   
>This glue code is popping the two parameters in the wrong order.
>The trap is getting both a bad pointer to the parameter block and
>a bad slot number.  The second and third lines of code above 
>should be interchanged.
>
>I've checked both the MPW 2.0 and 2.0.2 Interface.o libraries, and
>the have the same bad glue.
>

This problem with the MPW interface file is documented in Tech Note #200
on page 13.  It has been corrected in MPW 3.0 which is available from APDA
in beta form.