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From: dag@chinet.UUCP (Daniel A. Glasser)
Newsgroups: comp.sys.atari.st
Subject: Re: strange bug?
Message-ID: <1914@chinet.UUCP>
Date: Thu, 26-Nov-87 10:48:24 EST
Article-I.D.: chinet.1914
Posted: Thu Nov 26 10:48:24 1987
Date-Received: Sun, 29-Nov-87 23:19:41 EST
References: <21951@ucbvax.BERKELEY.EDU>
Reply-To: dag@chinet.UUCP (Daniel A. Glasser)
Organization: Chinet - Public Access Unix
Lines: 17
Keywords: m68000 excpetion handling
Summary: Not so strange -- Read up on 68000 exception handling


Your posting indicates that you are changing a machine register in an
exception handler without restoring it.  This is a no-no in systems
programming, at least on the 68000.  You don't know what's going on
when most hardware exceptions take place, and when the exception handler
returns, whatever it was that was taking place tries to continue.  If
it needs the data in that address register that you clobbered, the system
is likely to start doing very odd things.

I suggest reading up on exception handling in a 68000 manual (though the
idea is the same as most register machines).
-- 
					Daniel A. Glasser
					...!ihnp4!chinet!dag
					...!ihnp4!mwc!dag
					...!ihnp4!mwc!gorgon!dag
	One of those things that goes "BUMP!!! (ouch!)" in the night.