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Date: Sat, 19 Dec 2009 21:11:20 -0800
From: Jeremy Fitzhardinge <jeremy@goop.org>
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To: Frederic Weisbecker <fweisbec@gmail.com>
CC: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>,
       LKML <linux-kernel@vger.kernel.org>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       Paul Mackerras <paulus@samba.org>
Subject: Re: [PATCH] perf tools: Prevent from BITS_PER_LONG redefinition
References: <1261173920-11320-1-git-send-regression-fweisbec@gmail.com> <1261214767.20899.697.camel@laptop> <20091219143425.GA5003@nowhere>
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On 12/19/2009 06:34 AM, Frederic Weisbecker wrote:
> Yeah but we need it from the CPP level.
> We include such code located in kernel headers:
>
> static __always_inline unsigned long __fls(unsigned long word)
> {
> 	int num = BITS_PER_LONG - 1;
>
> #if BITS_PER_LONG == 64
> 	if (!(word&  (~0ul<<  32))) {
> 		num -= 32;
> 		word<<= 32;
> 	}
> #endif
> 	if (!(word&  (~0ul<<  (BITS_PER_LONG-16)))) {
> 		num -= 16;
> 		word<<= 16;
> 	}
>
>
> And sizeof() is not defined :)
>    

You can use if() with a constant expression instead of #if.

     J