linux-kernel - [PATCH net] tcp: Fix -Wc23-extensions in tcp_options

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Message-Id: <20231031-tcp-ao-fix-label-in-compound-statement-warning-v1-1-c9731d115f17@kernel.org>
Date:   Tue, 31 Oct 2023 13:23:35 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     edumazet@...gle.com, davem@...emloft.net, dsahern@...nel.org,
        kuba@...nel.org, pabeni@...hat.com
Cc:     ndesaulniers@...gle.com, trix@...hat.com, 0x7f454c46@...il.com,
        fruggeri@...sta.com, noureddine@...sta.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        patches@...ts.linux.dev, Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH net] tcp: Fix -Wc23-extensions in tcp_options_write()

Clang warns (or errors with CONFIG_WERROR=y) when CONFIG_TCP_AO is set:

  net/ipv4/tcp_output.c:663:2: error: label at end of compound statement is a C23 extension [-Werror,-Wc23-extensions]
    663 |         }
        |         ^
  1 error generated.

On earlier releases (such as clang-11, the current minimum supported
version for building the kernel) that do not support C23, this was a
hard error unconditionally:

  net/ipv4/tcp_output.c:663:2: error: expected statement
          }
          ^
  1 error generated.

Add a semicolon after the label to create an empty statement, which
resolves the warning or error for all compilers.

Closes: https://github.com/ClangBuiltLinux/linux/issues/1953
Fixes: 1e03d32bea8e ("net/tcp: Add TCP-AO sign to outgoing packets")
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 net/ipv4/tcp_output.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f558c054cf6e..6064895daece 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -658,7 +658,7 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
 			memset(ptr, TCPOPT_NOP, sizeof(*ptr));
 			ptr++;
 		}
-out_ao:
+out_ao:;
 #endif
 	}
 	if (unlikely(opts->mss)) {

---
base-commit: 55c900477f5b3897d9038446f72a281cae0efd86
change-id: 20231031-tcp-ao-fix-label-in-compound-statement-warning-ebd6c9978498

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