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Path: utzoo!watmath!clyde!rutgers!brl-adm!brl-sem!ron
From: ron@brl-sem.UUCP
Newsgroups: comp.arch
Subject: Re: catering to bad code
Message-ID: <636@brl-sem.ARPA>
Date: Thu, 19-Feb-87 14:12:52 EST
Article-I.D.: brl-sem.636
Posted: Thu Feb 19 14:12:52 1987
Date-Received: Fri, 20-Feb-87 21:24:09 EST
References: <14833@amdcad.UUCP>
Organization: Electronic Brain Research Lab
Lines: 15

In article <14833@amdcad.UUCP>, phil@amdcad.UUCP (Phil Ngai) writes:
> In a Unix system I am designing, I am considering catering to bad
> code. That is, like the VAX I propose to make location 0 contain a
> readable 0. I think that code which gets ported to a Sun machine often
> has to have this kind of thing cleaned up. 
> 
I like the GOULD approach.  The board that traps access to location 0
among other out of bound memory addresses can be set to just ignore
the attempt (the user appears to have accessed the location, but doesn't
get anything if it is outside his memory limits, 0 is never in a user
address space there), print a message in the logfile, or memory fault
the process (and print a message in the log file).  This allows you
to turn on carefull mode or revert to VAX bad-code compatibility mode.

-Ron