On Sat, Aug 21, 2010 at 02:40:15PM -0400, Mathieu Desnoyers wrote: > * Alexey Dobriyan ([email protected]) wrote: > > On Sat, Aug 21, 2010 at 10:17:51AM -0400, Mathieu Desnoyers 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)) > > > > Sorry, this is tasteless macro. > > Let's look at the surrounding where I added this macro in kernel.h: > > > /* Force a compilation error if condition is true */ > #define BUILD_BUG_ON(condition) ((void)BUILD_BUG_ON_ZERO(condition)) > > /* Force a compilation error if condition is constant and true */ > #define MAYBE_BUILD_BUG_ON(cond) ((void)sizeof(char[1 - 2 * !!(cond)])) > > /* Force a compilation error if a constant expression is not a power of 2 */ > #define BUILD_BUG_ON_NOT_POWER_OF_2(n) \ > BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0)) > > /* Force a compilation error if condition is true, but also produce a > result (of value 0 and type size_t), so the expression can be used > e.g. in a structure initializer (or where-ever else comma expressions > aren't permitted). */ > #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); })) > #define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); })) > > > So I am guessing that you plan to rewrite all of these ?
Of course not. > Or perharps you have other suggestions ? Learn that n & (n - 1) is idiomatic way to check for power of two in C. Done that, encoding that information in identifier won't make sense. _______________________________________________ ltt-dev mailing list [email protected] http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
