incrementing after a cast

[Garry Wiegand]

In a recent article kanner at 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 at cu-arpa.cs.cornell.edu)