Oops, quite right. I was originally thinking of if ((rc = pthread_mutex_lock(mtx))) err("mutex_lock failed: %s", strerror(rc)); but decided to sw

Oops, quite right. I was originally thinking of if ((rc = pthread_mutex_lock(mtx))) err("mutex_lock failed: %s", strerror(rc)); but decided to switch to a better-known function at the last minute and completely lost the point.