From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andreas Schwab <schwab@linux-m68k.org>
Subject: Re: [PATCH 1/6] rtc: generic: allow building on all architectures
Date: Wed, 02 Mar 2016 10:28:40 +0100
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	(Geert Uytterhoeven's message of "Wed, 2 Mar 2016 09:57:27 +0100")
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To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Arnd Bergmann <arnd@arndb.de>, Alexandre Belloni <alexandre.belloni@free-electrons.com>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, Kyle McMartin <kyle@mcmartin.ca>, RTCLINUX <rtc-linux@googlegroups.com>, Alessandro Zummo <a.zummo@towertech.it>, "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>, Linux-sh list <linux-sh@vger.kernel.org>, Parisc List <linux-parisc@vger.kernel.org>, linux-m68k <linux-m68k@lists.linux-m68k.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>

Geert Uytterhoeven <geert@linux-m68k.org> 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).

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
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"And now for something completely different."