Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watmath!orchid!rbutterworth
From: rbutterworth@orchid.UUCP
Newsgroups: comp.lang.c
Subject: Re: char (*a)[]  (was: Style [++i vs i++])
Message-ID: <10758@orchid.waterloo.edu>
Date: Sun, 20-Sep-87 11:39:15 EDT
Article-I.D.: orchid.10758
Posted: Sun Sep 20 11:39:15 1987
Date-Received: Sun, 20-Sep-87 22:39:20 EDT
References: <8298@brl-adm.ARPA> <587@cblpe.ATT.COM> <189@xyzzy.UUCP> <8655@mimsy.UUCP>
Organization: U of Waterloo, Ontario
Lines: 23
Keywords: brain dead architectures versus X3J11

In article <8655@mimsy.UUCP>, chris@mimsy.UUCP (Chris Torek) writes:
>     for (p = foo; p < &foo[10]; p++)
> is portable, and compilers must allow for it, but
>     for (p = &foo[9]; p >= foo; p--)
> is not, and compilers need not allow for it.  This does not `break
> half the code in existence' except when one tries to run it on an
> architecture in which &foo[-1] >= &foo[0] (where---surprise!---it
> already fails).

Using
    for (p = &foo[9]; p != foo; p--)
gets around this problem of the incorrect inequality.

The question is, does an expression, such as "p--", that generates
an illegal address violate the standard if that address is never
used as an address?

e.g. given "p = &foo[-1];", it is obviously wrong to use "*p",
but is there hardware for which the assignment itself would cause
a machine fault (assuming "p" is not declared as "register")?

If there aren't any such machines, why does this assignment violate
the ANSI standard?