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Date: Sun, 22 Aug 2010 21:27:05 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: LKML <linux-kernel@vger.kernel.org>, ltt-dev@lists.casi.polymtl.ca,
        Linus Torvalds <torvalds@linux-foundation.org>,
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Subject: Re: [PATCH for -tip 1/2] kernel.h: add MAYBE_BUILD_BUG_ON_NOT_POWER_OF_2
Message-ID: <20100822192705.GE1771@one.firstfloor.org>
References: <20100821141750.770348530@efficios.com> <20100821142215.023431313@efficios.com>
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> +/* Force a compilation error if condition is constant and not a power of 2 */
> +#define MAYBE_BUILD_BUG_ON_NOT_POWER_OF_2(n)		\
> +	MAYBE_BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))

Looks super-ugly. IMHO just writing MAYBE_BUILD_BUG_ON(!n || n & (n - 1)) directly
would be clear enough. If you really think that's unclear define a generic
is_power_of_two() macro.

-Andi