rb_next_class_serial  178 class.c            RCLASS_SERIAL(obj) = rb_next_class_serial();
rb_next_class_serial 1453 internal.h     rb_serial_t rb_next_class_serial(void);
rb_next_class_serial   65 vm_method.c        RCLASS_SERIAL(klass) = rb_next_class_serial();