Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!uflorida!haven!ncifcrf!nlm-mcs!adm!smoke!gwyn
From: gwyn@smoke.ARPA (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: A cast pointer is NOT an lvalue!? (ANSI C)
Keywords: X3J11, pointers, cast, lvalue
Message-ID: <8663@smoke.ARPA>
Date: 9 Oct 88 00:32:50 GMT
References: <479@midgard.mn.org>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 16

In article <479@midgard.mn.org> dal@syntel.UUCP (Dale Schumacher) writes:
>   value = *((long *) argp)++;

Rather than answer your questions directly, let me explain what is wrong
with this attempted usage.

A cast is the same as assignment to an unnamed temporary variable.
The ++ in your example would have to increment the temporary variable,
not the original variable argp.  That is clearly not what you wanted.

The result of a cast has never been an lvalue for just this reason.
Some compilers have been sloppy about this.

Anyway, you should be using either the old <varargs.h> or the new
<stdarg.h> macros to pick up arguments from a variable argument list.
What you were trying to do cannot be done portably any other way.