linux-kernel - [Patch v4 1/2] linux/build

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Message-Id: <20191009214502.637875-2-rikard.falkeborn@gmail.com>
Date:   Wed,  9 Oct 2019 23:45:01 +0200
From:   Rikard Falkeborn <rikard.falkeborn@...il.com>
To:     rikard.falkeborn@...il.com
Cc:     akpm@...ux-foundation.org, bp@...en8.de, joe@...ches.com,
        johannes@...solutions.net, keescook@...omium.org,
        linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
        yamada.masahiro@...ionext.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [Patch v4 1/2] linux/build_bug.h: Change type to int

Having BUILD_BUG_ON_ZERO produce a value of type size_t leads to awkward
casts in cases where the result needs to be signed, or of smaller type
than size_t. To avoid this, cast the value to int instead and rely on
implicit type conversions when a larger or unsigned type is needed.

Suggested-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Reviewed-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@...il.com>
---
Changes in v4:
  - Added Kees and Masahiros reviewed-by tags.
Changes in v3:
  - This patch is new in v3

 include/linux/build_bug.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/build_bug.h b/include/linux/build_bug.h
index 0fe5426f2bdc..e3a0be2c90ad 100644
--- a/include/linux/build_bug.h
+++ b/include/linux/build_bug.h
@@ -9,11 +9,11 @@
 #else /* __CHECKER__ */
 /*
  * Force a compilation error if condition is true, but also produce a
- * result (of value 0 and type size_t), so the expression can be used
+ * result (of value 0 and type int), so the expression can be used
  * e.g. in a structure initializer (or where-ever else comma expressions
  * aren't permitted).
  */
-#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:(-!!(e)); }))
+#define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
 #endif /* __CHECKER__ */
 
 /* Force a compilation error if a constant expression is not a power of 2 */
-- 
2.23.0