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From: meissner@dg_rtp.UUCP (Michael Meissner)
Newsgroups: comp.lang.c
Subject: Re: zero length array
Message-ID: <1287@dg_rtp.UUCP>
Date: Fri, 6-Mar-87 13:46:24 EST
Article-I.D.: dg_rtp.1287
Posted: Fri Mar  6 13:46:24 1987
Date-Received: Sun, 8-Mar-87 06:32:26 EST
References: <4498@brl-adm.ARPA> <1987Feb25.201816.29714@gpu.utcs.toronto.edu>
Reply-To: meissner@dg_rtp.UUCP (Michael Meissner)
Organization: Data General (Languages @ Research Triangle Park, NC.)
Lines: 24

In article <1987Feb25.201816.29714@gpu.utcs.toronto.edu> woods@gpu.utcs.UUCP (Greg Woods) writes:
> In article <4498@brl-adm.ARPA> Dizio@udel.edu writes:
> >   Is the following a portable way of finding out where a field
> >within a structure is located?
> >
> >    & (((struct any_struct_tag *) 0)->any_field)
> 
> Not that I know of, though the expression without "&" is usefull in sizeof().
> 
> Some compilers will refuse to cast NULL, specifically Lattice C up to 2.15(?)
> As far as I know all Unix compilers will cast NULL.
> 
> You might want to cast one(1) instead.  Lattice will accept this.
> 
> 						Greg Woods.

I believe the harris compiler also has problems with this.  Also any
implementation which does not produce all zero bits for integer 0 -> pointer
(or vica versa) would have problems with this.  That's why offsetof was
created in ANSI.
-- 
	Michael Meissner, Data General	Uucp: ...mcnc!rti-sel!dg_rtp!meissner

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