Messages in this thread | | | From | Michal Nazarewicz <> | Subject | Re: [PATCH] compiler: Don't perform compiletime_assert with -O0. | Date | Wed, 30 Aug 2017 12:26:44 +0200 |
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On Tue, Aug 29 2017, Joe Stringer wrote: > Recent changes[0] to make use of __compiletime_assert() from > container_of() increased the usage of this macro, allowing developers to > notice type conflicts in usage of container_of() at compile time. > However, the implementation of __compiletime_assert relies on compiler > optimizations to report an error. This means that if a developer uses > "-O0" with any code that performs container_of(), the compiler will > always report an error regardless of whether there is an actual problem > in the code. > > This patch disables compile_time_assert when optimizations are disabled > to allow such code to compile with CFLAGS="-O0". > > Example compilation failure: > > ./include/linux/compiler.h:547:38: error: call to ‘__compiletime_assert_94’ declared with attribute error: pointer type mismatch in container_of() > _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) > ^ > ./include/linux/compiler.h:530:4: note: in definition of macro ‘__compiletime_assert’ > prefix ## suffix(); \ > ^~~~~~ > ./include/linux/compiler.h:547:2: note: in expansion of macro ‘_compiletime_assert’ > _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) > ^~~~~~~~~~~~~~~~~~~ > ./include/linux/build_bug.h:46:37: note: in expansion of macro ‘compiletime_assert’ > #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) > ^~~~~~~~~~~~~~~~~~ > ./include/linux/kernel.h:860:2: note: in expansion of macro ‘BUILD_BUG_ON_MSG’ > BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \ > ^~~~~~~~~~~~~~~~ > > [0] http://lkml.kernel.org/r/20170525120316.24473-7-abbotti@mev.co.uk > > Signed-off-by: Joe Stringer <joe@ovn.org> > Cc: Ian Abbott <abbotti@mev.co.uk> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Michal Nazarewicz <mina86@mina86.com> > Cc: Kees Cook <keescook@chromium.org> > Cc: Andrew Morton <akpm@linux-foundation.org> > --- > include/linux/compiler.h | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index eca8ad75e28b..b67e5ec9b810 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -517,7 +517,8 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s > # define __compiletime_error_fallback(condition) do { } while (0) > #endif > > -#define __compiletime_assert(condition, msg, prefix, suffix) \ > +#ifdef __OPTIMIZE__ > +# define __compiletime_assert(condition, msg, prefix, suffix) \ > do { \ > bool __cond = !(condition); \ > extern void prefix ## suffix(void) __compiletime_error(msg); \ > @@ -525,6 +526,9 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s > prefix ## suffix(); \ > __compiletime_error_fallback(__cond); \ > } while (0) > +#else > +# define __compiletime_assert(condition, msg, prefix, suffix)
+# define __compiletime_assert(condition, msg, prefix, suffix) \ + do { } while (0)
With that fix,
Acked-by: Michal Nazarewicz <mina86@mina86.com>
> +#endif > > #define _compiletime_assert(condition, msg, prefix, suffix) \ > __compiletime_assert(condition, msg, prefix, suffix)
-- Best regards ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ «If at first you don’t succeed, give up skydiving»
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