Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1207399 > unrolled thread

GCOV_PROFILE_ALL breaks BUILD_BUG_ON(!is_power_of_2(8))

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  GCOV_PROFILE_ALL breaks BUILD_BUG_ON(!is_power_of_2(8)) Johannes Berg <johannes@sipsolutions.net> - 2015-08-14 10:30 +0200
    Re: GCOV_PROFILE_ALL breaks BUILD_BUG_ON(!is_power_of_2(8)) Michal Kubecek <mkubecek@suse.cz> - 2015-08-14 11:10 +0200
      Re: GCOV_PROFILE_ALL breaks BUILD_BUG_ON(!is_power_of_2(8)) Johannes Berg <johannes@sipsolutions.net> - 2015-08-14 11:10 +0200

#1207399 — GCOV_PROFILE_ALL breaks BUILD_BUG_ON(!is_power_of_2(8))

+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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [next] | [standalone]

#1207426

On Fri, Aug 14, 2015 at 10:29:04AM +0200, Johannes Berg wrote:
> +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?

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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [prev] | [next] | [standalone]

#1207430

On Fri, 2015-08-14 at 11:00 +0200, Michal Kubecek wrote:

> > 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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web