On Sun, Aug 21, 2010 at 10:44:28 +0300, Alexey Dobriyan wrote: > 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.
I don't get it, do you suggest to call it BUILD_BUG_ON_SMART_PANTS() and have people look it up every time to see what it does and do a git-blame to see who's sense of taste interferes with coding or do you suggest to paste the "BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))" every time so that people learn how to write C? Regards, -- Alex _______________________________________________ ltt-dev mailing list [email protected] http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
