Messages in this thread |  | | From | Masahiro Yamada <> | Date | Wed, 1 Apr 2020 02:31:37 +0900 | Subject | Re: [PATCH] compiler.h: fix error in BUILD_BUG_ON() reporting |
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On Tue, Mar 31, 2020 at 8:28 PM Vegard Nossum <vegard.nossum@oracle.com> wrote: > > compiletime_assert() uses __LINE__ to create a unique function name. > This means that if you have more than one BUILD_BUG_ON() in the same > source line (which can happen if they appear e.g. in a macro), then > the error message from the compiler might output the wrong condition. > > For this source file: > > #include <linux/build_bug.h> > > #define macro() \ > BUILD_BUG_ON(1); \ > BUILD_BUG_ON(0); > > void foo() > { > macro(); > } > > gcc would output: > > ./include/linux/compiler.h:350:38: error: call to ‘__compiletime_assert_9’ declared with attribute error: BUILD_BUG_ON failed: 0 > _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) > > However, it was not the BUILD_BUG_ON(0) that failed, so it should say 1 > instead of 0. With this patch, we use __COUNTER__ instead of __LINE__, so > each BUILD_BUG_ON() gets a different function name and the correct > condition is printed: > > ./include/linux/compiler.h:350:38: error: call to ‘__compiletime_assert_0’ declared with attribute error: BUILD_BUG_ON failed: 1 > _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > > Cc: Daniel Santos <daniel.santos@pobox.com> > Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> > Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> Cc: Ian Abbott <abbotti@mev.co.uk> > Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com> > --- > include/linux/compiler.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index 5e88e7e33abec..034b0a644efcc 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -347,7 +347,7 @@ static inline void *offset_to_ptr(const int *off) > * compiler has support to do so. > */ > #define compiletime_assert(condition, msg) \ > - _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) > + _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > > #define compiletime_assert_atomic_type(t) \ > compiletime_assert(__native_word(t), \ > -- > 2.16.1.72.g5be1f00a9.dirty >
-- Best Regards Masahiro Yamada
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