From: Vegard Nossum vegard.nossum@oracle.com
[ Upstream commit af9c5d2e3b355854ff0e4acfbfbfadcd5198a349 ]
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__)
Signed-off-by: Vegard Nossum vegard.nossum@oracle.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Reviewed-by: Masahiro Yamada yamada.masahiro@socionext.com Reviewed-by: Daniel Santos daniel.santos@pobox.com Cc: Rasmus Villemoes linux@rasmusvillemoes.dk Cc: Ian Abbott abbotti@mev.co.uk Cc: Joe Perches joe@perches.com Link: http://lkml.kernel.org/r/20200331112637.25047-1-vegard.nossum@oracle.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 0020ee1cab37a..7837afabbd78e 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -546,7 +546,7 @@ unsigned long read_word_at_a_time(const void *addr) * 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), \