set_intersection working on integers, but not on chars, even though it's void*

I have made a set ADT implementation with set_intersection being one of the functions.

It works well on integers, it goes through both testing systems it shall go through, but when I am trying to use it on chars it isn't working at all. Even though it is made with void * support.

set_t *set_intersection(set_t *a, set_t *b) {

    set_t *inter = set_create(a->cmpfunc);

    set_iter_t *iterA = set_createiter(a);
    set_iter_t *iterB;

    void *itemA = set_next(iterA);
    void *itemB;

    while(itemA != NULL) {
        iterB = set_createiter(b);
        itemB = set_next(iterB);
        while (itemB != NULL) {
            if (itemA == itemB) {
                set_add(inter, itemA);
                break;
            }
            itemB = set_next(iterB);
        }
        set_destroyiter(iterB);
        itemA = set_next(iterA);
    }
    set_destroyiter(iterA);


    list_sort(inter->list);
    return inter;
}

Using this struct:

struct set {
    list_t *list;
    cmpfunc_t cmpfunc;
    int size;
};

This is what's happening when trying to do intersect on 2 sets with characters:

Working on integers: