Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!sun-barr!sun!plx!evan
From: evan@plx.UUCP (Evan Bigall)
Newsgroups: comp.lang.c
Subject: Re: Correction, a[33]
Message-ID: <1949@plx.UUCP>
Date: 27 May 89 19:18:05 GMT
References: <5819@microsoft.UUCP> <17763@mimsy.UUCP> <13434@haddock.ima.isc.com> <2737@helios.ee.lbl.gov>
Reply-To: evan@plx.UUCP (Evan Bigall)
Distribution: usa
Organization: Plexus Computers; San Jose, CA
Lines: 27

In article <2737@helios.ee.lbl.gov> envbvs@epb2 (Brian V. Smith) writes:
>In article <17763@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes:
>>Similarly, &b[7] could legally be at the end of memory, pointing to nothing
>>dereferencable; all that's required is that &b[7] can be computed and stored
> ^^^^^^^^^^^^^^
>Please excuse my ignorance, but I've seen this word many times now, and it's
>not in Webster's.
>be referenced", but de-referencable?
>What does "dereferencable" mean? I could see "referencable", meaning "can

Informally, remember that addresses are often called pointers.  The verb 
"to derefrence" referrs to the action of `following' the pointer to see what
it points at.  ie: what is the contents of that particular address in memory.

From a more formal perspective * is the derefrence operator in C.  From K&R 89

	The unary operator * treats its operand as the address of the ultimate
        target, and accesses that address to fetch the contents.

So, what Chris means (imho) is that it is possible to have a legal pointer that
points to the end of memory (or just the end of a segment) but have * fail 
(coredump).

Does that help? 
-- 
Evan Bigall, Plexus Computers, San Jose, CA (408)943-2283 ...!sun!plx!evan
"I barely have the authority to speak for myself, certainly not anybody else"