+linux-kernel
+#define DECLARE_EWMA(name, _factor, _weight)> > > > > \
+> > struct ewma_##name {> > > > > > > \
+> > > unsigned long internal;> > > > > > \
+> > };> > > > > > > > > \
+> > static inline void ewma_##name##_init(struct ewma_##name *e)> > \
+> > {> > > > > > > > > \
+> > > BUILD_BUG_ON(!__builtin_constant_p(_factor));> > > \
+> > > BUILD_BUG_ON(!__builtin_constant_p(_weight));> > > \
+> > > BUILD_BUG_ON(!is_power_of_2(_factor));> > > > \
+> > > BUILD_BUG_ON(!is_power_of_2(_weight));> > > > \
So this seemed fine to me, but for some reason the compiler is saying
the BUILD_BUG_ON(!is_power_of_2(x)) fails, if and only if (!)
CONFIG_GCOV_PROFILE_ALL is enabled, which seems to boil down to the
compiler option -fprofile-arcs.
I'm going to replace this with just the code itself, i.e.
/* both must be a power of 2 */
BUILD_BUG_ON(_factor & (_factor - 1));
BUILD_BUG_ON(_weight & (_weight - 1));
but should I have expected this?
johannes
On Fri, Aug 14, 2015 at 10:29:04AM +0200, Johannes Berg wrote:
+linux-kernel
quoted
+#define DECLARE_EWMA(name, _factor, _weight)> > > > > \
+> > struct ewma_##name {> > > > > > > \
+> > > unsigned long internal;> > > > > > \
+> > };> > > > > > > > > \
+> > static inline void ewma_##name##_init(struct ewma_##name *e)> > \
+> > {> > > > > > > > > \
+> > > BUILD_BUG_ON(!__builtin_constant_p(_factor));> > > \
+> > > BUILD_BUG_ON(!__builtin_constant_p(_weight));> > > \
+> > > BUILD_BUG_ON(!is_power_of_2(_factor));> > > > \
+> > > BUILD_BUG_ON(!is_power_of_2(_weight));> > > > \
So this seemed fine to me, but for some reason the compiler is saying
the BUILD_BUG_ON(!is_power_of_2(x)) fails, if and only if (!)
CONFIG_GCOV_PROFILE_ALL is enabled, which seems to boil down to the
compiler option -fprofile-arcs.
I'm going to replace this with just the code itself, i.e.
/* both must be a power of 2 */
BUILD_BUG_ON(_factor & (_factor - 1));
BUILD_BUG_ON(_weight & (_weight - 1));
but should I have expected this?
It might have something to do with the fact that is_power_of_2() being
an inline function, perhaps with this compiler option it translates to
something that can't be used in the context BUILD_BUG_ON() uses it in.
There is a BUILD_BUG_ON_NOT_POWER_OF_2() macro you could use.
Michal Kubecek
On Fri, 2015-08-14 at 11:00 +0200, Michal Kubecek wrote:
quoted
but should I have expected this?
It might have something to do with the fact that is_power_of_2()
being an inline function, perhaps with this compiler option it
translates to something that can't be used in the context
BUILD_BUG_ON() uses it in.
Evidently, yeah.
There is a BUILD_BUG_ON_NOT_POWER_OF_2() macro you could use.
Good point, I'll do that, thanks.
johannes