thr_gc_arg
int s[2], passfd = ((struct thr_gc_arg *)arg)->passfd;
if (!(thr_gc_arg = malloc(sizeof(*thr_gc_arg))))
thr_gc_arg->passfd = thr_pass_args[0].s[0];
if ((error = pthread_create(&thr, NULL, thr_gc, thr_gc_arg)))
} *thr_gc_arg;