linux-kernel - [PATCH v1 1/5] bitfield: Silence a clang -Wshorten-64-to-32 warning

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Message-ID: <20250403165702.396388-2-irogers@google.com>
Date: Thu,  3 Apr 2025 09:56:58 -0700
From: Ian Rogers <irogers@...gle.com>
To: Yury Norov <yury.norov@...il.com>, Rasmus Villemoes <linux@...musvillemoes.dk>, 
	Arnd Bergmann <arnd@...db.de>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>, Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>, Ian Rogers <irogers@...gle.com>, 
	Adrian Hunter <adrian.hunter@...el.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Jakub Kicinski <kuba@...nel.org>, Jacob Keller <jacob.e.keller@...el.com>, linux-arch@...r.kernel.org, 
	linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: [PATCH v1 1/5] bitfield: Silence a clang -Wshorten-64-to-32 warning

The clang warning -Wshorten-64-to-32 can be useful to catch
inadvertent truncation. In some instances this truncation can lead to
changing the sign of a result, for example, truncation to return an
int to fit a sort routine. Silence the warning by making the implicit
truncation explicit.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 include/linux/bitfield.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
index 63928f173223..cc5cfed041bb 100644
--- a/include/linux/bitfield.h
+++ b/include/linux/bitfield.h
@@ -176,7 +176,7 @@ static __always_inline __##type type##_encode_bits(base v, base field)	\
 {									\
 	if (__builtin_constant_p(v) && (v & ~field_mask(field)))	\
 		__field_overflow();					\
-	return to((v & field_mask(field)) * field_multiplier(field));	\
+	return to((__##type)((v & field_mask(field)) * field_multiplier(field))); \
 }									\
 static __always_inline __##type type##_replace_bits(__##type old,	\
 					base val, base field)		\
-- 
2.49.0.504.g3bcea36a83-goog