sparse and ARRAY_SIZE() foolproofing

sparse and ARRAY_SIZE() foolproofing

[Alexey Dobriyan]

For every valid ARRAY_SIZE() use sparse warns about
"cannot size expression". This is somewhat annoying, because code is OK.

$ cat 1.c
#define BUILD_BUG_ON_ZERO(e) (sizeof(char[1 - 2 * !!(e)]) - 1)
#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))

int f(void)
{
        int a[42];

        return ARRAY_SIZE(a);
}
$ sparse 1.c
1.c:9:9: error: cannot size expression