Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: Do you have to cast void pointers when dereferencing them?
Message-ID: <9186@smoke.BRL.MIL>
Date: 15 Dec 88 00:58:50 GMT
References: <2414@ssc-vax.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 16

In article <2414@ssc-vax.UUCP> dmg@ssc-vax.UUCP (David Geary) writes:
>  This runs just fine on my Sun, but gives me illegal
>pointer WARNINGS.  Under ANSI C, do I HAVE to cast
>my void pointer, or not?

Many older UNIX compilers will accept pointer to almost anything
in the context p->member_name, if the member_name has an unambiguous
structure offset.  Indeed, really old UNIX kernels (around 6th
Edition) relied heavily on this.

It's not currently legal to use anything other than a pointer to
a structure declared as having such a member_name in that context.
This applies even more strongly for void*, which has only a small
subset of permitted operations, definitely not including structure
member reference.

So, yes, write your code to say what you really mean.