Yeah this is nuts. It's like someone just discovered casting so they can be really clever and use the first pointer in an array for something non-pointy.

I can't make any sense of the aversion to a struct. Use a struct. You don't have to give its type a name, if that's the motivation here.

The reason the struct is avoided here is so the array can be typed to its element type (rather than casting to and from `void*`).

With a struct we would need one struct for each element type - at least prior to C23 which provides a better approach where we can declare the same struct multiple times in a translation unit.

    #define Array(T) struct array_##T { size_t len; T *elems; }