Linux kbuild/kconfig development
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From: david.laight.linux@gmail.com
To: Nathan Chancellor <nathan@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, Nicolas Schier <nsc@kernel.org>,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: David Laight <david.laight.linux@gmail.com>
Subject: [PATCH 1/1] kbuild: Only enable -Wtautological-constant-out-of-range-compare for W=2
Date: Sun, 14 Dec 2025 13:15:28 +0000	[thread overview]
Message-ID: <20251214131528.3648-1-david.laight.linux@gmail.com> (raw)

From: David Laight <david.laight.linux@gmail.com>

The kernel code style is to use !(expr) rather that (expr) == 0.
But clang complains that converting some constant expressions
(eg (0xffffu << 16)) to a boolean always evalutes to true.
This happens often in the validity checks in #defines.
Move tautological-constant-out-of-range-compare to W=2 (along with the
similar type-limits).

Signed-off-by: David Laight <david.laight.linux@gmail.com>
---
 scripts/Makefile.warn | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/Makefile.warn b/scripts/Makefile.warn
index 68e6fafcb80c..e2d467835c5b 100644
--- a/scripts/Makefile.warn
+++ b/scripts/Makefile.warn
@@ -151,7 +151,6 @@ KBUILD_CFLAGS += -Wformat-insufficient-args
 endif
 endif
 KBUILD_CFLAGS += $(call cc-option, -Wno-pointer-to-enum-cast)
-KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
 KBUILD_CFLAGS += $(call cc-option, -Wno-unaligned-access)
 KBUILD_CFLAGS += -Wno-enum-compare-conditional
 endif
@@ -179,6 +178,7 @@ KBUILD_CFLAGS += -Wno-shift-negative-value
 
 ifdef CONFIG_CC_IS_CLANG
 KBUILD_CFLAGS += -Wno-enum-enum-conversion
+KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare
 endif
 
 ifdef CONFIG_CC_IS_GCC
-- 
2.39.5


             reply	other threads:[~2025-12-14 13:15 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-12-14 13:15 david.laight.linux [this message]
2025-12-19 20:12 ` [PATCH 1/1] kbuild: Only enable -Wtautological-constant-out-of-range-compare for W=2 Nathan Chancellor
2025-12-19 20:26   ` Arnd Bergmann
2025-12-19 22:18   ` David Laight
2025-12-20 10:27     ` Arnd Bergmann
2025-12-20 12:15       ` David Laight
2025-12-22 10:20         ` Arnd Bergmann
2025-12-22 17:14           ` David Laight

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