[PATCH vkd3d 2/5] include: Avoid using a field reference as a truth value.

[Giovanni Mascellani]

Hi,

On 17/12/21 18:48, Zebediah Figura wrote:
> --- a/include/private/rbtree.h
> +++ b/include/private/rbtree.h
> @@ -133,7 +133,7 @@ static inline struct rb_entry *rb_postorder_next(struct rb_entry *iter)
>   /* iterate through the tree using a tree entry */
>   #define RB_FOR_EACH_ENTRY(elem, tree, type, field) \
>       for ((elem) = RB_ENTRY_VALUE(rb_head((tree)->root), type, field); \
> -         &(elem)->field; \
> +         (elem) != RB_ENTRY_VALUE(0, type, field); \
>            (elem) = RB_ENTRY_VALUE(rb_next(&elem->field), type, field))

Couldn't we take the chance to just avoid constructing dangling pointers 
(which is, as I read the C standard, undefined behavior)? That would 
amount, for example, to using

(elem) = (rb_next(&(elem)->field) ? 
RB_ENTRY_VALUE(rb_next(&(elem)->field), type, field) : NULL)

as iteration expression, similarly for the initialization expression and 
just checking that elem is not NULL for the condition expression.

Thanks, Giovanni.