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Re: [patch] put ptrdiff_t in the kernel and create sys/stddef.h

On Wed, Dec 04, 2013 at 01:54:56PM -0200, Lourival Vieira Neto wrote:
 > >> > Why sys/stddef.h?  Just keep them in sys/types.h please.
 > >>
 > >> To avoid redefining ptrdiff_t on stddef.h. I think it would be more
 > >> coherent, since ptrdiff_t is a stddef.h definition and stddef.h
 > >> shouldn't include sys/types.h.
 > >
 > > Weak reason. stddef.h must not include sys/types.h, but it doesn't mean
 > > they can't both define it.
 > I didn't state that it can't be defined by both. I just said it would
 > be more coherent to define it in just one place. Why it is a bad idea?

Because doing it *right* is a bigger cleanup than you've done(*) and
the way consistent with the scheme already in place for handling these
issues is what Matt posted.

(*) A complete scheme for doing it right removes all the _BSD_FOO_T_
drivel and ifdefs scattered in userland headers in favor of:
   - a single header file that defines all the needed types prefixed
     with __, which can be included anywhere;
   - in userland, include-guarded header files akin to sys/null.h
     that define single or common groups of the names without the
     __ prefixes, e.g. <types/size_t.h>;
   - including these header files in the proper places, such as in
     standard userland header files like stddef.h;
   - in the kernel, a single header file that defines all the types
     without the __, that is or is exposed to sys/types.h but does
     not affect userland.

This is not a small undertaking; don't try it at home. :-/

It is also probably impossible to pull off cleanly until the
kernel/userland header namespace gets cleaned.

David A. Holland

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