Xref: utzoo comp.bugs.4bsd:1670 comp.std.c:4187
Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!sdrc!thor!scjones
From: scjones@thor.UUCP (Larry Jones)
Newsgroups: comp.bugs.4bsd,comp.std.c
Subject: Re: Bug in users command
Message-ID: <136@thor.UUCP>
Date: 24 Jan 91 20:40:57 GMT
References: <6182:Jan2222:06:3991@kramden.acf.nyu.edu> <18981@rpp386.cactus.org> <1991Jan24.060113.22461@tkou02.enet.dec.com>
Followup-To: comp.std.c
Organization: SDRC, Cincinnati
Lines: 20

In article <1991Jan24.060113.22461@tkou02.enet.dec.com>, diamond@jit345.swstokyo.dec.com (Norman Diamond) writes:
> [ Given "char (*a)[N];", are "(char *)a", "&(*a)[0]", and "*a" equivalent? ]
> 
> No.  The last two yield pointers to the same char object, the first char in *a.
> 
> The first one coerces a pointer-to-array to a pointer-to-char value.
> The standard guarantees that you can take a pointer-to-something, cast it to
> a pointer-to-char, cast it back to a pointer-to-something, and the result is
> equivalent to the original pointer.  It does not guarantee that the value
> with type pointer-to-char can actually be used for anything.

To rephrase, "Is a pointer to an array, when cast to the array element
type, equivalent to a pointer to the first element of the array?"

I believe that the standard imposes sufficient constraints on the
implementation that the answer to that question must be "yes".
----
Larry Jones, SDRC, 2000 Eastman Dr., Milford, OH  45150-2789  513-576-2070
Domain: scjones@thor.UUCP  Path: uunet!sdrc!thor!scjones
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