Building the Linux kernel with Clang and LLVM
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From: Nathan Chancellor <nathan@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,  Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	 x86@kernel.org
Cc: Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>,
	 linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
	patches@lists.linux.dev,  kernel test robot <lkp@intel.com>,
	Nathan Chancellor <nathan@kernel.org>
Subject: [PATCH] x86/boot: Address clang -Wimplicit-fallthrough in vsprintf()
Date: Thu, 16 May 2024 07:03:41 -0700	[thread overview]
Message-ID: <20240516-x86-boot-fix-clang-implicit-fallthrough-v1-1-04dc320ca07c@kernel.org> (raw)

After enabling -Wimplicit-fallthrough for the x86 boot code, clang
warns:

  arch/x86/boot/printf.c:257:3: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]
    257 |                 case 'u':
        |                 ^

Clang is a little more pedantic than GCC, which does not warn when
falling through to a case that is just break or return. Clang's version
is more in line with the kernel's own stance in deprecated.rst, which
states that all switch/case blocks must end in either break,
fallthrough, continue, goto, or return. Add the missing break to silence
the warning.

Fixes: dd0716c2b877 ("x86/boot: Add a fallthrough annotation")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202405162054.ryP73vy1-lkp@intel.com/
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 arch/x86/boot/printf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/boot/printf.c b/arch/x86/boot/printf.c
index c0ec1dc355ab..51dc14b714f6 100644
--- a/arch/x86/boot/printf.c
+++ b/arch/x86/boot/printf.c
@@ -254,6 +254,8 @@ int vsprintf(char *buf, const char *fmt, va_list args)
 		case 'd':
 		case 'i':
 			flags |= SIGN;
+			break;
+
 		case 'u':
 			break;
 

---
base-commit: dd0716c2b87792ebea30864e7ad1df461d4c1525
change-id: 20240516-x86-boot-fix-clang-implicit-fallthrough-fc5c9bb19765

Best regards,
-- 
Nathan Chancellor <nathan@kernel.org>


             reply	other threads:[~2024-05-16 14:03 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-05-16 14:03 Nathan Chancellor [this message]
2024-05-16 23:08 ` [PATCH] x86/boot: Address clang -Wimplicit-fallthrough in vsprintf() Justin Stitt
2024-05-17  9:51 ` Borislav Petkov
2024-05-17 15:18   ` Nathan Chancellor
2024-05-23 11:57     ` Borislav Petkov
2024-05-23 23:12       ` Kees Cook
2024-05-24 16:39         ` Borislav Petkov

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