Messages in this thread |  | | Subject | Re: [PATCH] compiler.h: fix error in BUILD_BUG_ON() reporting | From | Joe Perches <> | Date | Tue, 31 Mar 2020 11:20:07 -0700 |
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On Tue, 2020-03-31 at 13:26 +0200, Vegard Nossum 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__) [] > diff --git 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__)
This might be better using something like __LINE__ ## _ ## __COUNTER__
as line # is somewhat useful to identify the specific assert in a file.
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