Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!mailrus!uflorida!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: wait ((char *) 0)
Keywords: aack thppt wait union
Message-ID: <9185@smoke.BRL.MIL>
Date: 15 Dec 88 00:41:10 GMT
References: <gables.352@umigw.miami.edu> <9142@smoke.BRL.MIL> <gables.359@umigw.miami.edu> <685@auspex.UUCP> <1886@loral.UUCP> <5147@bsu-cs.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 18

In article <5147@bsu-cs.UUCP> dhesi@bsu-cs.UUCP (Rahul Dhesi) writes:
>My 4.3BSD manual allows wait(0).
>[This probably ought to be wait((union wait *)0) ].

No, it ought to be wait((int*)0).
wait() has always required a pointer to int;
when non-null, the pointed-to int was filled in with
the least significant 8 bits meaning one thing and
the next 8 bits meaning another (see manual for
details).  Berkeley's attempt to describe this with
a union was totally bogus, because the order of the
bitfields is implementation-dependent, and the true
meaning of the lowest 16 bits of the int pointed to
by wait was system-INdependent.  Vendors of 4BSD-
based systems either had to make sure that the union
was kludged to fit their particular C compiler's
allocation of bitfields, or else have customer code
written according to the original definition break.
I'm pretty sure IEEE 1003.1 went with int*.