uses of void

[Tom Stockfisch]

I want to be able to use "void *" in a generic sorting function and I tried
something like

	sort( (void *)&foo[0], (void *)&foo[20], sizeof(foo), compare_foos );
	.
	.
	.
	void
	sort( beg, end, size, compare )
		void	*beg, *end;
		int	size;
		int	(*compare)();
	{
		int	nelements =	(end - beg) / size;

		for ( p = beg;  p < end;  p += size )
			...;
		...
	}

My compiler (4.2BSD running on a Celerity) when into an infinite loop trying
to parse

		(end - beg)

I (naively?) thought that pointer arithmetic would work with "void *", and
that it would work in the same abstract units as "sizeof()", so that all
previous generic "char *" kludges could be replaced by "void *".

What are the (proposed and current) legal operations for "void *" besides
assignment, casting, and passing as a parameter?

-- Tom Stockfisch, UCSD Chemistry
-- 

-- Tom Stockfisch, UCSD Chemistry