linux-kernel - [PATCH 2/2] build_bug.h: remove all dummy BUILD_BUG

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Date:   Fri, 16 Nov 2018 15:19:01 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] build_bug.h: remove all dummy BUILD_BUG_ON stubs for sparse

The introduction of these dummy BUILD_BUG_ON stubs dates back to
commit 903c0c7cdc21 ("sparse: define dummy BUILD_BUG_ON definition
for sparse"). At that time, BUILD_BUG_ON() was implemented with the
negative array trick, which Sparse complains about even if the
condition can be optimized and evaluated to 0 at compile-time.

With the previous commit, the leftover negative array trick is gone.
Sparse is happy with the current BUILD_BUG_ON(), which is implemented
by using the 'error' attribute.

There might be a little room for argument about BUILD_BUG_ON_ZERO().
Sparse reports 'invalid bitfield width, -1' for non-zero value,
and 'bad integer constant expression' for non-constant value.
This is the same criteria as GCC uses. So, if those Sparse errors
occurred, they would cause errors for GCC as well. (Hence, such
errors would have been detected by the normal compile test process.)

Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
---

 include/linux/build_bug.h | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/include/linux/build_bug.h b/include/linux/build_bug.h
index d415c64..b0828f7 100644
--- a/include/linux/build_bug.h
+++ b/include/linux/build_bug.h
@@ -4,16 +4,6 @@

 #include <linux/compiler.h>

-#ifdef __CHECKER__
-#define __BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
-#define BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
-#define BUILD_BUG_ON_ZERO(e) (0)
-#define BUILD_BUG_ON_INVALID(e) (0)
-#define BUILD_BUG_ON_MSG(cond, msg) (0)
-#define BUILD_BUG_ON(condition) (0)
-#define BUILD_BUG() (0)
-#else /* __CHECKER__ */
-
 /* Force a compilation error if a constant expression is not a power of 2 */
 #define __BUILD_BUG_ON_NOT_POWER_OF_2(n)	\
 	BUILD_BUG_ON(((n) & ((n) - 1)) != 0)
@@ -64,6 +54,5 @@
  */
 #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")

-#endif	/* __CHECKER__ */

 #endif	/* _LINUX_BUILD_BUG_H */
-- 
2.7.4