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Date: Tue, 24 Jan 2012 13:46:31 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Andrew Morton <akpm@linux-foundation.org>
CC: Cyrill Gorcunov <gorcunov@gmail.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
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        Serge Hallyn <serge.hallyn@canonical.com>,
        Kees Cook <keescook@chromium.org>, Tejun Heo <tj@kernel.org>,
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        Alexey Dobriyan <adobriyan@gmail.com>, Ingo Molnar <mingo@elte.hu>,
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        Eric Dumazet <eric.dumazet@gmail.com>,
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Subject: Re: [patch 2/4] [RFC] syscalls, x86: Add __NR_kcmp syscall v4
References: <20120124064719.GA29735@moon> <4F1E57F3.6020607@zytor.com> <20120124071716.GC29735@moon> <20120124162031.a3956058.kamezawa.hiroyu@jp.fujitsu.com> <20120124073842.GE29735@moon> <20120124164008.aa1714bd.kamezawa.hiroyu@jp.fujitsu.com> <20120124084823.GF29735@moon> <CAHGf_=r=zwj4=yjCekYZVRsTwjohJ8F8cP4rnZx6UL9kKNTc+g@mail.gmail.com> <20120124202606.GC2546@moon> <m18vkwj0dw.fsf@fess.ebiederm.org> <20120124205039.GB2278@moon> <20120124132222.d78bc0d4.akpm@linux-foundation.org> <20120124134510.75f2c63f.akpm@linux-foundation.org>
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On 01/24/2012 01:45 PM, Andrew Morton wrote:
> On Tue, 24 Jan 2012 13:22:22 -0800
> Andrew Morton <akpm@linux-foundation.org> wrote:
> 
>> static int kcmp_task_pointers(void *task1, void *task2, size_t field_offset,
>> 				enum you_forgot_to_name_the_enum type)
>> {
>> 	void **field1 = t1 + field_offset;	/* points to a pointer in the task_struct */
>> 	void **field2 = t1 + field_offset;
> 
> On reflection, this was being too cute.  It would be better to make the
> function type-safer and just put up with the local typecasts:
> 
> static int kcmp_task_pointers(struct task_struct *task1,
> 			struct task_struct *task2, size_t field_offset,
> 			enum you_forgot_to_name_the_enum type)
> {
> 	void **field1 = (void *)t1 + field_offset;
> 	void **field2 = (void *)t2 + field_offset;
> 

Arithmetic on void pointers?

	-hpa