Path: utzoo!attcan!uunet!cs.utexas.edu!samsung!usc!apple!keith
From: keith@Apple.COM (Keith Rollin)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Speaking of Munger...
Message-ID: <43017@apple.Apple.COM>
Date: 16 Jul 90 01:28:34 GMT
References: <233@sun13.scri.fsu.edu> <42917@apple.Apple.COM> <1990Jul13.135946.6664@eng.umd.edu>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 35

In article <1990Jul13.135946.6664@eng.umd.edu> russotto@eng.umd.edu (Matthew T. Russotto) writes:
>In article <42917@apple.Apple.COM> keith@Apple.COM (Keith Rollin) writes:
>>When Munger needs some more memory, it calls SetHandleSize. If
>>SetHandleSize returns an error (returned in register D0), Munger exits
>>immediately. This means that the error result code is still in D0, and
>>you can retrieve it with a little bit of glue code or inline assembly.
>>
>>The reason why MemError isn't set is because the Memory Manager doesn't
>>set it; that's the function of the glue code provided for those calls
>>by your development system. Your call to something like SetHandleSize
>>is really a call to subroutine that takes your parameters off the stack,
>>puts them in registers, calls the function, and puts the result code in
>>MemError.  Since Munger is written in assembly, it doesn't use this
>>little subroutine.  Hence, MemError never gets set with the result
>>code.
>
>Says Inside Mac, Volume 4:
>All Memory Manager routines (including the RecoverHandle function) return a
>result code that you can examine by calling the MemError function.
>
>And a look at the SetHandleSize function reveals that it does indeed move
>D0 to MemErr... Hmmmm.  (Unless, of course, you are running under the 64K
>Roms)

Sigh. Again, I've thrown a walk concerning Munger. Eric eventually found
the problem (he was making another Memory Manager call and erasing MemErr
from the Munger call). I had assumed that the Memory Manager didn't 
actually set MemErr because there was glue that also did it.

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"Argue for your Apple, and sure enough, it's yours" - Keith Rollin, Contusions