Re: MMM and MCL 2.0.1

[bill@cambridge.apple.com (Bill St. Clair)]

At 10:40 AM 2/28/95, David Neves wrote:
>In article <dgaxiola-2802950129390001@silent-mobius.mit.edu>,
>dgaxiola@mit.edu (David Gabriel Gaxiola) wrote:
>
>:  I've been using MCL 2.0.1 on my PowerMac 6100 for the past few weeks with
>:  the modern memory manager on.  I've been told/read that for MCL to work
>:  right, MMM should be turned off.  I've not seen any problems so far.  Am I
>:  just setting myself up for disaster?
>We can reliably crash MCL (with MMM on) with Quicktime.  I bet anything
>that deals with the Mac Heap may cause problems.  If you are just doing
>standard Lisp stuff without using the graphics interface you might be
>successful.
>-David

Kalman has investigated this more than I, but I believe the problem
occurs if MCL's growzone procedure is called. The growzone procedure
is called when there is not enough room in the (Mac) heap to satisfy
a NewPtr or NewHandle request. MCL's growzone uses undocumented
information about how the heap is represented in order to move the
boundary between the Mac heap and the Lisp heap. The MMM changes
this undocumented representation in a way that is incompatible with
MCL.