Re: pointer arithmetic on a pointer to void

On Thu, 10 Oct 2013 17:47:43 -0500
"Craig A. Berry" <[email protected]> wrote:

> Since what we have now is dubious from a sC standards viewpoint,
> wouldn't it be better to just make it a pointer to char in the first
> place

Absolutely right on all counts.  The only valid uses of void* are 

1.  compare with NULL 
2.  convert to char*
3.  convert back to the type it points to

In olden times, as I'm sure you remember, the standard library declared
ordinary buffers to be char*, and the compiler never complained if you
happened to send int* (because, say, you're reading ints).  With the
introduction of functional prototypes in C89, that was no longer
possible because the compiler would not "convert" int* to char* for
you.  So ANSI invented void* to stand in for char*'s old role, albeit
in a more limited form.  char* retained its elevated status: anything
could be cast to and from char* in order to gain byte-addressability.  

Pointer arithmetic on void* is invalid for the perfectly good reason
that the void type has no size.  

The choice between redefining the pointer to char* or casting void* to
char* is one of convenience.  If your one-liner makes the compiler
happy, I'd say that's most convenient.  

Thanks for pointing it out.  I'm surprised it hasn't cropped up
before. 

--jkl