linux-kernel - [PATCH] x86/boot: Address clang -Wimplicit-fallthrough in vsprintf()

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Date: Thu, 16 May 2024 07:03:41 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
 x86@...nel.org
Cc: Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, 
 linux-kernel@...r.kernel.org, llvm@...ts.linux.dev, patches@...ts.linux.dev, 
 kernel test robot <lkp@...el.com>, Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH] x86/boot: Address clang -Wimplicit-fallthrough in
 vsprintf()

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@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202405162054.ryP73vy1-lkp@intel.com/
Signed-off-by: Nathan Chancellor <nathan@...nel.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@...nel.org>