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Date: Tue, 23 May 2017 13:24:15 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Ian Abbott <abbotti@mev.co.uk>
Cc: Michal Nazarewicz <mina86@mina86.com>, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>,
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        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Johannes Berg <johannes.berg@intel.com>,
        Alexander Potapenko <glider@google.com>
Subject: Re: [PATCH v2] kernel.h: handle pointers to arrays better in
 container_of()
Message-ID: <20170523112415.nmbazvqmlhy343f2@hirez.programming.kicks-ass.net>
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On Tue, May 23, 2017 at 11:32:02AM +0100, Ian Abbott wrote:

> > #define container_of(ptr, type, member) (				\
> > 	_Static_assert(__builtin_types_compatible_p(			\
> >             typeof(*ptr), typeof( ((type *)0)->member )), "WUT"),	\
> > 	((type *)((char *)(ptr) - offsetof(type, member)));		\
> > )
> 
> It's a fine suggestion (if more parentheses are added), but _Static_assert
> is a C11 feature, and I thought the kernel was using gnu89 (unless it's been
> updated since).

We have BUILD_BUG_ON() that should be similar in functionality.