Path: utzoo!utgpu!watmath!att!dptg!rutgers!iuvax!purdue!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.lang.c
Subject: Re: comp.std.c
Keywords: ANSI C, hardware protection, out-of-bounds pointers
Message-ID: <10884@smoke.BRL.MIL>
Date: 31 Aug 89 00:27:58 GMT
References: <426@maytag.waterloo.edu>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 12

In article <426@maytag.waterloo.edu> lhf@aries5 (Luiz H. deFigueiredo) writes:
>Now I ask, it is possible/legal to do the analogous thing for a-1 as in
>	char *head=a-1;		/* Here! */

The Standard does not guarantee that this will work, although it might work
uner some circumstances under some implementations.

The asymmetry between last+1 (guaranteed) and first-1 (not guaranteed) is
due to the former only requiring one byte safety allowance while the latter
requires an entire array member amount of safety allowance.  It was
considered sufficient to guarantee just one way of traversing an array,
and the readily implementable choice was made.