uint64_t sl_cas (skiplist_t *sl, void *key, uint64_t expectation, uint64_t new_val) {
TRACE("s1", "sl_cas: key %p skiplist %p", key, sl);
TRACE("s1", "sl_cas: expectation %p new value %p", expectation, new_val);
uint64_t sl_cas (skiplist_t *sl, void *key, uint64_t expectation, uint64_t new_val) {
TRACE("s1", "sl_cas: key %p skiplist %p", key, sl);
TRACE("s1", "sl_cas: expectation %p new value %p", expectation, new_val);