Zachary, "Looking again, that one is non-trivial, but still doable.  You just need a "this means an error happened" value to initialize rl to, and return that value instead of NULL."How do you give "this means an error happened" value to struct rlimit?struct rlimit {               rlim_t rlim_cur;  /* Soft limit */               rlim_t rlim_max;  /* Hard limit (ceiling for rlim_cur) */};This is what prevents me to use custom converter.