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From: steele@unc.cs.unc.edu (Oliver Steele)
Newsgroups: comp.sys.mac
Subject: Re: Fatal HyperCard Bug
Message-ID: <1665@unc.cs.unc.edu>
Date: Fri, 16-Oct-87 11:39:01 EDT
Article-I.D.: unc.1665
Posted: Fri Oct 16 11:39:01 1987
Date-Received: Sat, 17-Oct-87 20:44:42 EDT
References: <1632@unc.cs.unc.edu> <183@scdpyr.UUCP>
Reply-To: steele@unc.UUCP (Oliver Steele)
Distribution: na
Organization: University of North Carolina, Chapel Hill
Lines: 46
Keywords: fatal, bug, hypercard, croak, die, break, ugly death

faulkner@scdpyr.UUCP (Bill Faulkner) writes:
>In article <1632@unc.cs.unc.edu>, steele@unc.cs.unc.edu (Oliver Steele) writes:
>> How to break HyperCard:
>> 
>> 1) Cut a bitmapped image from somewhere.
>> 2) Put yourself in a situation where you have about 600K free in
>>    the application heap in the Finder.
>> 3) Enter HyperCard 1.0.1.
>> 4) Make sure you're at painting or above.
>> 5) Paste.
>
>Funny, thing happened when I thought I would try this.  Hypercard performed
>exactly how I expected.  This is what I did.

Mr. Faulkner then describes a set of steps in which he follows the above
except for step 2.

The bug has to do with how HyperCard recovers, or fails to recover, from a
situation in which it can't find enough memory to use painting tools but
is asked (indirectly, by means of a PICT paste) to do so anyway.  If
HyperCard *does* have enough memory to use painting tools, you're
obviously not going to see any problem.  You aren't going to see a failure
to recover from a memory shortage if there is no memory shortage.

>[...] so maybe the previous poster did not have enough
>memory and Hypercard was working OK.

Indeed I didn't have enough memory; that was why I listed step 2 as
necessary to reproduce the bug.  Hypercard was not working OK:  an
application shouldn't go into an infinite loop drawing and erasing a
dialogue box when there isn't enough memory.  It should just refuse to
perform, tell you that it can't perform, tell you why it can't perform,
and either exit to the Finder or close a document or let you pick up where
you left off.  This is particularly important with an application, such as
HyperCard, that requires a fair amount of memory; it shouldn't assume,
just because it's running on a machine with at least 1Meg of memory, that
that entire 1Meg is free for its personal use.

I'm sorry if I was unclear on this in my earlier posting.

------------------------------------------------------------------------------
Oliver Steele				  ...!{decvax,ihnp4}!mcnc!unc!steele
							steele%unc@mcnc.org

	"'As it were' means 'I think that I sound very erudite.'
	 'Per se' is Latin for 'as it were.'  As it were."