Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!bellcore!decvax!genrad!mit-eddie!think!harvard!seismo!rochester!pt.cs.cmu.edu!k.cs.cmu.edu!gjs
From: gjs@k.cs.cmu.edu (Gregory Stein)
Newsgroups: net.micro.mac
Subject: Re: System Error 02 ???
Message-ID: <721@k.cs.cmu.edu>
Date: Thu, 16-Jan-86 16:44:05 EST
Article-I.D.: k.721
Posted: Thu Jan 16 16:44:05 1986
Date-Received: Sun, 19-Jan-86 04:16:02 EST
References: <470@ssc-vax.UUCP>
Organization: Carnegie-Mellon University, CS/RI
Lines: 29


    A system error 2 is the Mac reporting an address error. (It
can't recover from this, so it bombs.)  This is usually caused by
problems with pointers.  Say, for example, you have a pointer
to an integer.  When you get the value of the integer by saying
something like my_ptr^, the Mac will return the integer at the
address in the pointer variable my_ptr.  Now, the problem occurs
when this address has an odd value.  The 68000 can only retrieve
the integer value from an even address.  The same sort of thing
occurs for long integers -- they must have an even address, too.
So, what happened is that somewhere in your program an attempt
was made to get an integer or long integer value from an odd
address.
    I can't see the Modula 2 compiler generating code to do
this, so my best guess is that you did some sort of call to
the resource manager to get a resource (this includes things
such as GetNewDialog and GetNewWindow) but the resource wasn't
there.  In this case, the GetResource call will return a handle
containing 0.  When a routine attempts to use this handle it
looks at address 0 for another address.  This address is most
likely odd in your case, so the Mac crashes.
    My suggestion would be to look for calls that return handles
and put a test for a nil handle after the call.

			Greg Stein
			..!ucbvax!gjs@k.cs.cmu.edu

These dumb signature lines -- why do we do it?
	A communist plot to weed out comedians.