I think about some test at the last bit if it is on, the number is not a power of 2
On Sun, Aug 22, 2010 at 10:38 PM, Mathieu Desnoyers <[email protected]> wrote: > * Andi Kleen ([email protected]) wrote: >> > +/* Force a compilation error if condition is constant and not a power of >> > 2 */ >> > +#define MAYBE_BUILD_BUG_ON_NOT_POWER_OF_2(n) \ >> > + MAYBE_BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0)) >> >> Looks super-ugly. IMHO just writing MAYBE_BUILD_BUG_ON(!n || n & (n - 1)) >> directly >> would be clear enough. If you really think that's unclear define a generic >> is_power_of_two() macro. > > There is already a is_power_of_two macro in log2.h, but I fear it might > incorrectly interact with "MAYBE_BUILD_BUG_ON" (for some reason passing the > constant result of a static inline is not treated as a constant by the macro, > and thus it always "passes" the test). > > So if everyone object to this new macro, I'd be tempted to just go with your > suggestion. However the fact that we already have > BUILD_BUG_ON_NOT_POWER_OF_2(n) > made me think that some people prefer to have it done as a macro. > > Other opinions ? > > Thanks, > > Mathieu > > > -- > Mathieu Desnoyers > Operating System Efficiency R&D Consultant > EfficiOS Inc. > http://www.efficios.com > -- > 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/ > _______________________________________________ ltt-dev mailing list [email protected] http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
