linux-kernel - [PATCH 1/1] kbuild: Only enable -Wtautological-constant-out-of-range-compare for W=2

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Message-Id: <20251214131528.3648-1-david.laight.linux@gmail.com>
Date: Sun, 14 Dec 2025 13:15:28 +0000
From: david.laight.linux@...il.com
To: Nathan Chancellor <nathan@...nel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Nicolas Schier <nsc@...nel.org>,
	linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: David Laight <david.laight.linux@...il.com>
Subject: [PATCH 1/1] kbuild: Only enable -Wtautological-constant-out-of-range-compare for W=2

From: David Laight <david.laight.linux@...il.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@...il.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