Robert P. J. Day wrote:
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.
I would have thought you'd comment the broken ones, but that's just me.
--
SUSE Labs, Novell Inc.
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