On Sun, Feb 19, 2017 at 7:43 PM, Pedro F. Giffuni <p...@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
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