marshal.c:666
static VALUE
dump(arg)
    struct dump_call_arg *arg;
{
    w_object(arg->obj, arg->arg, arg->limit);
    if (arg->arg->dest) {
	rb_io_write(arg->arg->dest, arg->arg->str);
	rb_str_resize(arg->arg->str, 0);
    }
    return 0;
}
