Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!apple!dlyons
From: dlyons@Apple.COM (David Lyons)
Newsgroups: comp.sys.apple
Subject: Re: deleting DA's from memory
Message-ID: <31983@apple.Apple.COM>
Date: 30 May 89 17:39:52 GMT
References: <8905272100.AA01113@obsolete.UUCP>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 31

In article <8905272100.AA01113@obsolete.UUCP> emerrill@pro-carolina.UUCP (Eric Merrill) writes:
>[...]
>Do I have to reboot my system disk each time I get the menus full?
>I know that there are DA's which will let me have more room to list other
>ones, but I want something to delete unneeded DA's from memory.  Thanks for
>any help!!

Under System Disk 4.0 and earlier, there is no legitimate way to remove a
DA.

Under System Disk 5.0 and later, there are two new Desk Manager calls:
RemoveCDA and RemoveNDA (just like InstallCDA and InstallNDA, only different).
These calls remove a DA from the Desk Manager's tables, but they do *not*
actually remove the DA's code from memory, because there's no safe way to do
that.  (The DA may have intercepted system vectors or toolbox functions or
installed heartbeat interrupt tasks, so that freeing up its memory could easily
crash the system.)

It would be neat if there were a way for a DA to identify itself as "removable"
and have a routine to call that unhooks the DA from the system if necessary.
But that's not happening in 5.0.


 --Dave Lyons, Apple Computer, Inc.          |   DAL Systems
   AppleLink--Apple Edition: DAVE.LYONS      |   P.O. Box 875
   AppleLink--Personal Edition: Dave Lyons   |   Cupertino, CA 95015-0875
   GEnie: D.LYONS2 or DAVE.LYONS         CompuServe: 72177,3233
   Internet/BITNET:  dlyons@apple.com    UUCP:  ...!ames!apple!dlyons

   My opinions are my own, not Apple's.