Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!faatcrl!jprad
From: jprad@faatcrl.UUCP (Jack Radigan)
Newsgroups: comp.sys.amiga
Subject: Re: 2091 address zero problems
Keywords: Nope nada zip zilch
Message-ID: <1511@faatcrl.UUCP>
Date: 20 Jul 90 05:12:18 GMT
References: <38936@sequent.UUCP> <3343@usceast.UUCP> <26032@usc.edu>
Organization: FAA Technical Center, Atlantic City NJ
Lines: 21

papa@pollux.usc.edu (Marco Papa) writes:

>Of course this bug is NOT very easy to find since it can't be found on a
>68000.  I.e. sdb  or cpr (the debuggers) can't be used to check for a "read"
>access in low memeory. They can only be used to monitor write access. This
>is also the reason why all those other tools like memwatch are useless, since 
>they also can only check for write access, not read.  The only useful tool is 
>Bryce's Enforcer (on the DevCon '90 disk) that can be used on any system 
>with an MMU and that can check for incorrect read access on low memeory.

Hmm, I follow what you're saying, but even if you can't track reads, most
code (at least mine) does also write to this pointers.  Ok, for data tables
and such other cases you'll be limited to reads.  Maybe I am doing this, but
not in any area that I can think of off-hand.  Besides, if it was strictly
related to a dereferenced pointer read, it should still fail on an A1000 by
setting location zero to any non-zero value, especially an odd value.  but,
in this particular case it doesn't fail...

I'm still looking around for malformed code, but haven't found it yet.

  -jack-