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From: dgold@apple.UUCP
Newsgroups: comp.sys.mac
Subject: Re: A Trivial Suggestion
Message-ID: <1039@apple.UUCP>
Date: Mon, 15-Jun-87 13:55:38 EDT
Article-I.D.: apple.1039
Posted: Mon Jun 15 13:55:38 1987
Date-Received: Wed, 17-Jun-87 01:32:15 EDT
References: <869@apple.UUCP> <1499@midas.TEK.COM> <981@apple.UUCP> <1968@sphinx.uchicago.edu>
Reply-To: dgold@apple.UUCP (David Goldsmith)
Organization: Apple Computer Inc., Cupertino, USA
Lines: 21

In article <1968@sphinx.uchicago.edu> fdot@sphinx.UUCP (Tom Lippincott) writes:
>...When I run flat out of memory,
>my heap expansion procedure ends up doing a longjmp back to the main
>event loop...

This is a bad thing to do.  The Memory Manager (and the rest of the Toolbox)
expects to get control back from your GrowZone procedure.  If you unwind
the stack as you are doing, there is no guarantee the system will continue
to operate correctly.  You must signal failure by returning 0 from your
GrowZone, and cope with the error which the Memory Manager returns to its
caller.  In order to prevent failures from Toolbox components which call
SysError when out of memory, you must arrange for your GrowZone to always
have memory available to give up for use by the Toolbox.
-- 
David Goldsmith
Apple Computer, Inc.

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