marshal.c:384
static void
w_uclass(obj, base_klass, arg)
    VALUE obj, base_klass;
    struct dump_arg *arg;
{
    VALUE klass = CLASS_OF(obj);

    w_extended(klass, arg);
    klass = rb_class_real(klass);
    if (klass != base_klass) {
	w_byte(TYPE_UCLASS, arg);
	w_unique(rb_class2name(klass), arg);
    }
}
