Safer determination of static array size

[Florian Weimer]

On 08/09/2013 03:26 PM, Marcin Sobieszczanski wrote:
> Linux kernel does it this way:
>
> /* Force a compilation error if condition is true, but also produce a
>     result (of value 0 and type size_t), so the expression can be used
>     e.g. in a structure initializer (or where-ever else comma expressions
>     aren't permitted). */
> #define BUILD_BUG_ON_ZERO(e) (sizeof(char[1 - 2 * !!(e)]) - 1)
>
> /* &a[0] degrades to a pointer: a different type from an array */
> #define __must_be_array(a) \
>     BUILD_BUG_ON_ZERO(__builtin_types_compatible_p(typeof(a), typeof(&a[0])))
>
> #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))

Thanks, this is what I was looking for!

-- 
Florian Weimer / Red Hat Product Security Team