obj: use ref-counting in set objects

obj/set.c

@@ -20,7 +20,7 @@ static kern_status_t set_get_child_at(object_t *obj, size_t at, object_t **out)
 	size_t i = 0;
 	queue_foreach(object_t, child, &set->s_list, ob_list) {
 		if (i == at) {
-			*out = child;
+			*out = object_ref(child);
 			return KERN_OK;
 		}
 
@@ -42,7 +42,7 @@ static kern_status_t set_get_child_named(object_t *obj, const char *name, object
 		}
 
 		if (!strcmp(child_name, name)) {
-			*out = child;
+			*out = object_ref(child);
 			return KERN_OK;
 		}
 	}
@@ -104,6 +104,7 @@ kern_status_t set_add_object(object_t *set_obj, object_t *obj)
 		}
 	}
 
+	object_ref(obj);
 	queue_push_back(&set->s_list, &obj->ob_list);
 	return KERN_OK;
 }
@@ -116,6 +117,7 @@ kern_status_t set_remove_object(object_t *set_obj, object_t *obj)
 	
 	struct set *set = object_data(set_obj);
 	queue_delete(&set->s_list, &obj->ob_list);
+	object_deref(obj);
 
 	return KERN_OK;
 }