svn commit: r313982 - in head/sys/dev: agp al_eth an arcmsr bce beri/virtio bhnd/cores/usb buslogic ce cm cp ctau cx de ed fatm fe firewire hptiop hptmv iicbus isp le md ncr netmap ofw patm pccard ...

[Conrad Meyer]

On Sun, Feb 19, 2017 at 7:43 PM, Pedro F. Giffuni <pfg at freebsd.org> wrote:
> Author: pfg
> Date: Mon Feb 20 03:43:12 2017
> New Revision: 313982
> URL: https://svnweb.freebsd.org/changeset/base/313982
>
> Log:
>   sys/dev: Replace zero with NULL for pointers.
>
>   Makes things easier to read, plus architectures may set NULL to something
>   different than zero.

Hi Pedro,

I like the change for style reasons.

The comment about architectures with non-zero NULL is a little
misleading, though.  This change has no impact on non-zero bit pattern
NULL architectures.  The zero pointer value in C is NULL and NULL is
the zero pointer value in C.  It may have a bit pattern other than
zero (i.e., printf("%p", NULL) may be non-zero and memset(&p, 0,
sizeof(p)) is bogus in portable code) but assigning the logical zero
value is always legitimate.

After all, NULL is just a casted zero value:

#define NULL    ((void *)0)

Maybe this is moot.  I don't believe any architecture FreeBSD actually
supports has non-zero bitpattern NULL, but something weird like CHERI
might.

Best,
Conrad