On Tue, 30 Jan 2007, Nick Piggin wrote: > Robert P. J. Day wrote: > > Add the inline function "is_power_of_2()" to log2.h, where the value > > zero is *not* considered to be a power of two. > > > > > Signed-off-by: Robert P. J. Day <[EMAIL PROTECTED]> > > > > /* > > + * Determine whether some value is a power of two, where zero is > > + * *not* considered a power of two. > > + */ > > Why the qualifier? Zero *is* not a power of 2, is it?
no, but it bears repeating since some developers might think it *is*. if you peruse the current kernel code, you'll find some tests of the simpler form: ((n & (n - 1)) == 0)) which is clearly testing for "power of twoness" but which will return true for a value of zero. that's wrong, and it's why it's emphasized in the comment. rday -- ======================================================================== Robert P. J. Day Linux Consulting, Training and Annoying Kernel Pedantry Waterloo, Ontario, CANADA http://www.fsdev.dreamhosters.com/wiki/index.php?title=Main_Page ======================================================================== - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/