Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: comp.lang.c
Subject: Re: structure element offsets
Message-ID: <7377@utzoo.UUCP>
Date: Thu, 4-Dec-86 13:51:58 EST
Article-I.D.: utzoo.7377
Posted: Thu Dec  4 13:51:58 1986
Date-Received: Thu, 4-Dec-86 13:51:58 EST
References: <1096@spice.cs.cmu.edu>
Organization: U of Toronto Zoology
Lines: 24
Keywords: structure, offset

> ...In other words a cast such as (type1 *)(type2 *)x
> will not always give a meaningful answer...

True.

> According to K&R all
> that is required is that (type *)(long *)x == x.

False.  Please cite chapter and verse.  I believe what you are thinking
of is (type *)(char *)x == x, which is (by K&R) valid.  Your example falls
down if, for example, "type" is "char" and the format of "long *" is not
precise enough to point to an individual char within a long.

Or perhaps you were thinking of (type *)(long)x == x ?  That would make me
nervous but it is technically valid.

> ... for good or ill,
> C has been defined such that all members-of-structures share the
> same name-space...

Not modern C, which puts each structure's members in a separate name space.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,decvax,pyramid}!utzoo!henry