Re: ptrdiff_t in the kernel

[David Young <dyoung%pobox.com@localhost>]

On Wed, Dec 04, 2013 at 12:07:42PM -0200, Lourival Vieira Neto wrote:
> >>> No, <stddef.h> is not allowed in the kernel.  Symbols from it are
> >>> provided via other means.
> >>
> >> I know. In fact, I'm asking if it would be alright to allow that.
> >> AFAIK, it would be inoffensive if available in the kernel.
> >
> > Actually, it would be offensive.
> 
> Why?

I would also like to know why that would be offensive!

I'm always disappointed when I have to write something like this in order
to share code between the userland and kernel,

        #if defined(_KERNEL) || defined(_STANDALONE)
        #include <sys/types.h>  /* for bool, size_t---XXX not right? */
        #else
        #include <stdbool.h>    /* for bool */
        #include <sys/types.h>  /* for size_t */
        #endif

Apparently, <stddef.h> is the correct header for size_t, so that is more
properly written like this,

        #if defined(_KERNEL) || defined(_STANDALONE)
        #include <sys/types.h>  /* for bool, size_t---XXX not right? */
        #else
        #include <stdbool.h>    /* for bool */
        #include <stddef.h>  /* for size_t */
        #endif

I would prefer for this to suffice both for the kernel and userland:

        #include <stdbool.h>    /* for bool */
        #include <stddef.h>  /* for size_t */

ISTM that the reasons things are not that simple are merely historical
reasons, but I am open to other explanations.

Dave

-- 
David Young
dyoung%pobox.com@localhost    Urbana, IL    (217) 721-9981