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From: wert@iapetus.rice.edu@rice.EDU (Scott Comer)
Newsgroups: net.micro.mac
Subject: Re: _Debugger trap failure
Message-ID: <199@dione.rice.EDU>
Date: Mon, 28-Jul-86 19:19:36 EDT
Article-I.D.: dione.199
Posted: Mon Jul 28 19:19:36 1986
Date-Received: Wed, 30-Jul-86 00:35:29 EDT
References: <5401@ut-sally.UUCP>
Sender: root@rice.EDU
Reply-To: wert@iapetus.UUCP (Scott Comer)
Organization: Rice University, Houston
Lines: 43
Keywords: MacDB, What Apple meant to say was...

In article <5401@ut-sally.UUCP> brian@ut-sally.UUCP (Brian H. Powell) writes:
>
>     I was just reading the MacsBug version 5.1 documentation that came
>in Supplement Volume I, Issue 3 (the March/June 1986 supplement).  I noticed
>on one of the pages that they don't want anyone using Line-1111 traps anymore
>to break into a debugger.  (They will interfere with the 68881.)  (And by the
>way, this warning was in the December/February supplement also, but I didn't
>notice it then.)
>     Fine, I thought.  I am always ready to follow the Apple Guidelines.  I'll
>just change this "dc.w $ff00" statement to the approved "_Debugger" trap.
>Assemble; link.  Run.
>     Boom.  A bomb box (with a debugger installed!)  ID=12.  The old dsCoreErr.
>Unimplemented trap.  My debugger was virtually helpless.  Reboot.
>
>     You see, Apple doesn't really have an $a9ff (_debugger) trap.  They fake
>it in the debugger.  I think it only works with the new 5.* series MacsBugs.
>I was using a Mac+ with MacNub A debugged by a 128K Mac running MacDB A.  I'm
>using a (Darin Adler) NoQuiche system, version 3.2.
>     Conclusion:
>	The documentation is misleading.  Just thought you'd want to know.

Well, this message was somewhat misleading as well.

1) There is a A9FF trap. It invokes the DS Alert (ID=12) which is what
happened to you.

2) Since the documentation was for Macsbug and NOT MacNub, it might not
apply. Or there might be bugs. I remember that MacNub and MacDB have never
tracked Macsbug very closely. I have been using the A9FF trap for over a
year, with whatever the current version of Macsbug has been at the time (4.*
and now 5.1*. It has always worked.

3) Macsbug installs its own trap handler (in place of the system A line trap
dispatch routine) and catches the A9FF trap inline, without using the trap
dispatch table. Your debugger may do this differently, or not at all.

If you are just doing debugging, there really is nothing wrong with using F
line traps to do it. One advantage to using the A line debugger trap is that
you can turn it off from within the debugger. Also, eventually you will have
to find another debugging method, so you might as well start right now.
Apple is just covering their *ss.

scott