Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!oliveb!apple!voder!pyramid!cbmvax!vu-vlsi!swatsun!jackiw
From: jackiw@cs.swarthmore.edu (Nick Jackiw)
Newsgroups: comp.sys.mac.programmer
Subject: Re: LSC - how to find if the debugger is running?
Message-ID: <2547@ilium.cs.swarthmore.edu>
Date: 14 Mar 89 16:39:19 GMT
References: <1806@viscous.sco.COM>
Reply-To: jackiw@ilium.UUCP (Nick Jackiw)
Organization: Visual Geometry Project, Swarthmore College, PA
Lines: 49

In article <1806@viscous.sco.COM> jamesm@sco.COM (James M. Moore) writes:
> I'd like to be able to do somthing like this in LSC 3.0:
> 
> 	if (DebuggerIsActive())
> 		DebugStr("\pNow in Macsbugs");
> 	...
> 
> at the beginning of my main() procedure.  This would be useful during
> the debugging process, as I like to be able to go in and set
> breakpoints before my code starts executing.  How do I tell if the
> debugger is running?
> 

I assume you aren't talking about LSC's debugger, which I know nothing
about (hence my assumption). For Macsbug et al., this should do the trick:

The normal trap which the debugger invokes is $A9FF.  Macsbug, TMON, etc.
all patch this to point to something other than the in-ROM debugger (the
empty dialog box with a '>' prompt, which--I think--accepts only DM,
SM, and G commands [display mem, set mem, and go]).  

So what you want to do is determine whether trap $A9FF invokes the built-in
debugger (worthless for breakpoints) or something else (i. e. your better-
debugger-of-choice). Taking a clean (debugger-free) system, write a little
program to print out the result of NGetTrapAddress($FF,ToolTrap) [cf. IM
IV-234].  This is the address which a debuggerless Mac will hit; let's say
it's X.  Your DebuggerIsActive function is now the comparison
NGetTrapAddress($FF,ToolTrap)<>X; i. e. whether someone has patched this
to a different (and presumably better) debugger.

Caveat: Never used LSC. LSP's DebugStr and other debugger commands CHECK
whether Macsbug is installed before executing anyway (I think...maybe this
only applies to their menu-invoked debugger calls).

Hope this helps.


> -- 
> ** James Moore **
> ** Internet:  jamesm@sco.com **
> ** uucp:  {decvax!microsoft | uunet | ucbvax!ucscc | amd}!sco!jamesm **
> ** Nil clu no suim ar bith ag SCO ceard a bhfuil me ag scriobh anois. **


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|  nicholas jackiw  | jackiw%campus.swarthmore.edu@swarthmr.bitnet           |
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"Ah...I've got this CHRONIC pain."                             _True Believer_