#define RMR_DEF_SIZE 0 // pass as size to have msg allocation use the default msg size
+#define RMR_VOID_MSGTYPE (-1) // unset/invalid message type and sub id
+#define RMR_VOID_SUBID (-1)
#define RMR_OK 0 // state is good
#define RMR_ERR_BADARG 1 // argument passd to function was unusable