Re: [RFC][PATCH 01/10] put alignment macros in align.h

From: Nikita Danilov <nikita_at_clusterfs.com>
Date: 2006-08-31 02:11:44
Dave Hansen writes:
 > 

[...]

 > + */
 > +#ifndef __ASSEMBLY__
 > +#define ALIGN(x,a) (((x)+(a)-1)&~((a)-1))

This evaluates (a) twice. While in all existing call-sites (a) is
probably a constant, it's still safer to do

#define ALIGN(x,a) ({ typeof(a) __a = (a); (((x) + __a - 1) & ~(__a - 1)); })

in a generic macro and rely on compiler to optimize temporary variable
out.

Nikita.

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Received on Thu Aug 31 02:17:16 2006

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