Something

#define ASTOBJ_CONTAINER_TRAVERSE2(container,iteratorname,continue,eval) \
        do { \
                typeof((container)->head) iterator##iteratorname; \
                typeof((container)->head) next; \
                ASTOBJ_CONTAINER_RDLOCK(container); \
                next = (container)->head; \
                while((continue) && (iterator##iteratorname = next)) { \
                        next = iterator##iteratorname->next[0]; \
                        eval; \
                } \
                ASTOBJ_CONTAINER_UNLOCK(container); \
        } while(0)