variable.c:1132
static struct st_table *
check_autoload_table(av)
    VALUE av;
{
    Check_Type(av, T_DATA);
    if (RDATA(av)->dmark != (RUBY_DATA_FUNC)rb_mark_tbl ||
	RDATA(av)->dfree != (RUBY_DATA_FUNC)st_free_table) {
	rb_raise(rb_eTypeError, "wrong autoload table: %s", RSTRING(rb_inspect(av))->ptr);
    }
    return (struct st_table *)DATA_PTR(av);
}
