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From: garry@batcomputer.tn.cornell.edu (Garry Wiegand)
Newsgroups: comp.lang.c
Subject: Re: incrementing after a cast
Message-ID: <1706@batcomputer.tn.cornell.edu>
Date: Thu, 4-Dec-86 18:15:58 EST
Article-I.D.: batcompu.1706
Posted: Thu Dec  4 18:15:58 1986
Date-Received: Fri, 5-Dec-86 06:19:00 EST
Reply-To: garry%cadif-oak@cu-arpa.cs.cornell.edu
Organization: Cornell Engineering && Flying Moose Graphics
Lines: 36

In a recent article kanner@apple.UUCP (Herbert Kanner) wrote:
>...
>		L = *((sometype *) chp)++;
>...
>Our problem arises with the allegation that K&R makes this construct
>illegal...

This was some discussion on the net a few months about whether this ought
to be legitimate.  The context I would use it in is trying to recycle
"valuable" register variables to point to different things during the life
of a routine. For example, if I happen to know that A and B never overlap
during execution, and that my machine only has 1 available-to-C register,
I might want to do:

	    ...
	    register	char	*A;
#           define	B	((float *)A)
	    ...

and expect both *A++ and *B++ to work and to be in registers for me. If
I know that a pointer and an int take the same space and instructions on
my machine I might also want to get away with:

	    register	char	*A;
#	    define	B	((int)A)
	    ...
	    ... *A++; ...
	    ...
	    ... B = 27;

Unfortunately, that's not the way things stand on any compiler I have access
to - your compiler must be exceptionally forgiving.

I think the new spec doesn't disturb the status quo.

garry wiegand   (garry%cadif-oak@cu-arpa.cs.cornell.edu)