From: Frederic Weisbecker <fweisbec@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: 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
Date: Sat, 19 Dec 2009 15:34:29 +0100 [thread overview]
Message-ID: <20091219143425.GA5003@nowhere> (raw)
In-Reply-To: <1261214767.20899.697.camel@laptop>
On Sat, Dec 19, 2009 at 10:26:07AM +0100, Peter Zijlstra wrote:
> On Fri, 2009-12-18 at 23:05 +0100, Frederic Weisbecker wrote:
> > +#ifndef BITS_PER_LONG
> > /* CHECKME: Not sure both always match */
> > #define BITS_PER_LONG __WORDSIZE
> > +#endif
>
> Why use __WORDSIZE if you're not sure?
>
> (8*sizeof(long)) is simple and unambiguous.
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 :)
next prev parent reply other threads:[~2009-12-19 14:34 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-18 22:05 [PATCH] perf tools: Prevent from BITS_PER_LONG redefinition Frederic Weisbecker
2009-12-19 9:26 ` Peter Zijlstra
2009-12-19 14:34 ` Frederic Weisbecker [this message]
2009-12-20 5:11 ` Jeremy Fitzhardinge
2009-12-30 21:45 ` Frederic Weisbecker
2009-12-31 11:09 ` Jeremy Fitzhardinge
2010-01-02 17:01 ` Frederic Weisbecker
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