Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.sys.mac.programmer
Subject: Re: How to do a LEGAL tail-patch
Message-ID: <6551@hoptoad.uucp>
Date: 17 Feb 89 00:48:17 GMT
References: <1272@ccnysci.UUCP> <6541@hoptoad.uucp> <293@berlin.acss.umn.edu>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Organization: Eclectic Software, San Francisco
Lines: 23

In article <293@berlin.acss.umn.edu> grg@berlin.acss.umn.edu (George
Gonzalez) suggests a legal way to do tail patching using single stepping.
It's very clever, and it gives me nightmares just thinking about it.

As George pointed out, only one trap can use this at a time.  That in
itself is enough to disqualify it, since the old trap code that you call
might itself call another patched trap.

What if a debugger is on?  That's bound to interfere with any software
use of the trace mode bit of the status register.

What about speed?  Trace mode is generally quite slow.

What about compatibility across processor lines?

It's one of the more intriguing suggestions I've heard here, but really,
it's too weird to go into production quality software.
-- 
Tim Maroney, Consultant, Eclectic Software, sun!hoptoad!tim
"What's the ugliest part of your body?
 Some say your nose, some say your toes,
 But I think it's your mind."
-- Frank Zappa