On 30 August 2017 at 03:26, Michal Nazarewicz <min...@mina86.com> wrote: > 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-abbo...@mev.co.uk >> >> Signed-off-by: Joe Stringer <j...@ovn.org> >> Cc: Ian Abbott <abbo...@mev.co.uk> >> Cc: Arnd Bergmann <a...@arndb.de> >> Cc: Michal Nazarewicz <min...@mina86.com> >> Cc: Kees Cook <keesc...@chromium.org> >> Cc: Andrew Morton <a...@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 <min...@mina86.com>
Thanks, I applied this change and send a v2 with your ack.
