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From: throopw@xyzzy.UUCP (Wayne A. Throop)
Newsgroups: comp.lang.c
Subject: Re: pointer cast question
Message-ID: <280@xyzzy.UUCP>
Date: Mon, 28-Sep-87 14:29:01 EDT
Article-I.D.: xyzzy.280
Posted: Mon Sep 28 14:29:01 1987
Date-Received: Tue, 29-Sep-87 07:08:50 EDT
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> andrew@teletron.UUCP (Andrew Scott)
> I was just curious as to why
> pointer casts exist if they basically do nothing.

IF pointer casts did basically did nothing, THEN their existance might
well be pointless.  But they *DO* do something.  They create a new value
which has the format of a pointer of the cast type.  On many machines,
where all pointers have the same format, this does nothing.  But the
conceptual operation is still important, because there are machines
where something must be done in such cases, such as casting from a short
pointer type to a long one in some PC C implementations, or from
character-granular pointer types to word-granular pointer types in some
word-oriented machines.

The cast operation doesn't guarantee the *alignment* of the result, but
it does guarantee the *format* if the alignment already makes sense.

--
Inigo hated it there.  Everybody was so dangerous, big, mean and
muscular, and so what if he was the greatest fencer in the world, who'd
know it to look at him?  He looked like a skinny Spanish guy it might be
fun to rob.  You couldn't walk around with a sign saying "Be careful,
this is the greatest fencer since the death of the Wizard of Corsica. Do
not burgle."
                        --- From The Princess Bride by William Goldman
-- 
Wayne Throop      <the-known-world>!mcnc!rti!xyzzy!throopw