Re: [PATCH 1/6] rtc: generic: allow building on all architectures

[Geert Uytterhoeven]

On Wed, Mar 2, 2016 at 10:28 AM, Andreas Schwab <schwab@xxxxxxxxxxxxxx> wrote:
> Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> writes:
>
>>> +#else
>>> +#define generic_rtc_ops *(struct rtc_class_ops*)NULL
>>> +#endif
>>>
>>>  static int __init generic_rtc_probe(struct platform_device *dev)
>>>  {
>>>         struct rtc_device *rtc;
>>> +       const struct rtc_class_ops *ops;
>>> +
>>> +       ops = dev_get_platdata(&dev->dev);
>>> +       if (!ops)
>>> +               ops = &generic_rtc_ops;
>>
>> I hope no compiler version treats "&*(struct rtc_class_ops*)NULL" as
>> undefined behavior?
>
> Yes, that is guaranteed, the operations cancel each other (6.5.3.2#3: If
> the operand is the result of a unary * operator, neither that operator
> nor the & operator is evaluated and the result is as if both were
> omitted).

Thanks for confirming.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds