Path: utzoo!attcan!uunet!ateng!chip
From: chip@ateng.ateng.com (Chip Salzenberg)
Newsgroups: comp.arch
Subject: Re: NULL pointers (was: Software Distribution)
Keywords: software distribution, null pointers
Message-ID: <1988Sep29.141726.14882@ateng.ateng.com>
Date: 29 Sep 88 18:17:25 GMT
References: <978@esunix.UUCP> <3112@pt.cs.cmu.edu>
Organization: A T Engineering, Tampa, FL
Lines: 14

According to bsy@PLAY.MACH.CS.CMU.EDU (Bennet Yee):
>Of course, if your machine core dumps on dereferencing NULL, just trap the
>fault (SIGSEGV), check the instruction that caused the trap, and patch up
>and return if it was due to dereferencing NULL; otherwise dump core.

It is not not always possible to restart faulted instructions.  The 68000,
for example, is not capable of restarting an instruction after a bus fault.
This problem has been fixed in the 68010 and all its successors; but if
an intermediate language doesn't work on the 68000, it can hardly be called
"universal".
-- 
Chip Salzenberg                <chip@ateng.uu.net> or <uunet!ateng!chip>
A T Engineering                My employer may or may not agree with me.
	  The urgent leaves no time for the important.