From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1754655AbcCBJ2z (ORCPT <rfc822;w@1wt.eu>);
	Wed, 2 Mar 2016 04:28:55 -0500
Received: from mail-out.m-online.net ([212.18.0.9]:46883 "EHLO
	mail-out.m-online.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1754213AbcCBJ2w (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 2 Mar 2016 04:28:52 -0500
X-Auth-Info: LKwvR4beBDtCEnmhJ3r230jK3TPBnpoDNEwCaJoBOju3UScgo8Ad68OBH+UEEw8o
From: Andreas Schwab <schwab@linux-m68k.org>
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@vger.kernel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/6] rtc: generic: allow building on all architectures
References: <1456851608-3374907-1-git-send-email-arnd@arndb.de>
	<1456851608-3374907-2-git-send-email-arnd@arndb.de>
	<CAMuHMdW5+jZ1n9WnCwBrGSGjUa8ziNTTqf-H15EFTQC_iwnw+Q@mail.gmail.com>
X-Yow: Okay..  I'm going home to write the ``I HATE RUBIK's CUBE
 HANDBOOK FOR DEAD CAT LOVERS''..
Date: Wed, 02 Mar 2016 10:28:40 +0100
In-Reply-To: <CAMuHMdW5+jZ1n9WnCwBrGSGjUa8ziNTTqf-H15EFTQC_iwnw+Q@mail.gmail.com>
	(Geert Uytterhoeven's message of "Wed, 2 Mar 2016 09:57:27 +0100")
Message-ID: <mvmwpplns8n.fsf@hawking.suse.de>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: 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
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."