Path: utzoo!telly!ddsw1!lll-winken!killer!texbell!uhnix1!nuchat!uunet!convex!texsun!pitstop!sun!david
From: david@sun.uucp (David DiGiacomo)
Newsgroups: gnu.gcc
Subject: Re: left-hand side cast
Message-ID: <78888@sun.uucp>
Date: 23 Nov 88 02:18:21 GMT
References: <8811221620.AA25541@ee.ecn.purdue.edu>
Organization: Sun Microsystems, Inc. - Mtn View, CA
Lines: 36

In article <8811221620.AA25541@ee.ecn.purdue.edu> lewie@EE.ECN.PURDUE.EDU
(Jeff Lewis) writes:
>Say you needed to push arbitrary sized data onto a stack:
>
>	int *sp, foo;
>	short int *sp2, bar;
>	unsigned char *sp3, biff;
>
>	*sp++ = foo;
>	sp2 = (short int *) sp;
>	*sp2++ = bar;
>	sp3 = (unsigned char *) sp2;
>	*sp3++ = biff;
>	sp = (int *) sp3;
>	...

This is not a good example to support the use of lvalue casts.  Ordinary
rvalue casts will clean it up nicely.

#define	PUSH(sp, item) \
	(* (typeof (item) *) (sp) = (item), ((sp) += sizeof (item)))

	caddr_t sp;
	int foo;
	short int bar;
	unsigned char biff;

	PUSH(sp, foo);
	PUSH(sp, bar);
	PUSH(sp, biff);
	...

The poster you quoted was probably referring to something like

	(type) complicated_expression++ = item;

where it's undesirable to realize the complicated_expression twice.