From: David Dillow <dave@thedillows.org>
To: Roland Dreier <rdreier@cisco.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org,
Bart Van Assche <bart.vanassche@gmail.com>
Subject: Re: [PATCH] log2.h: Macro-ize is_power_of_2() for use in BUILD_BUG_ON
Date: Wed, 06 Jan 2010 16:15:04 -0500 [thread overview]
Message-ID: <1262812504.2265.0.camel@lap75545.ornl.gov> (raw)
In-Reply-To: <aday6kbt14a.fsf@roland-alpha.cisco.com>
On Wed, 2010-01-06 at 12:44 -0800, Roland Dreier wrote:
> > Perhaps we can avoid worrying about that via
>
> > #define BUILD_BUG_ON_NOT_POWER_OF_2(n) \
> > BUILD_BUG_ON((n != 0 && ((n & (n - 1)) == 0)))
>
> Having something so specific to this particular case makes me feel like
> maybe it's just not worth it. At least in the case I'm looking at, we
> could just have:
>
> /*
> * The code relies on FOO being a power of 2. If you break this,
> * you're dumb.
> */
> #define FOO_SHIFT 6
> #define FOO (1 << FOO_SHIFT)
>
> Your thoughts?
I'm fine with that, but now I'll probably be the dumb one to break it
some day in the future.
next prev parent reply other threads:[~2010-01-06 22:00 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-06 20:21 Roland Dreier
2010-01-06 20:33 ` Andrew Morton
2010-01-06 20:44 ` Roland Dreier
2010-01-06 21:15 ` David Dillow [this message]
2010-01-06 21:42 ` Andrew Morton
2010-01-06 23:02 ` [PATCH] Add BUILD_BUG_ON_NOT_POWER_OF_2() Roland Dreier
2010-01-06 23:09 ` Andrew Morton
2010-01-07 7:33 ` Bart Van Assche
2010-01-07 7:51 ` Roland Dreier
2010-01-07 8:36 ` Robert P. J. Day
2010-01-07 16:45 ` Stefan Richter
2010-01-06 21:23 ` [PATCH] log2.h: Macro-ize is_power_of_2() for use in BUILD_BUG_ON Roland Dreier
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