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References: <20231031-tcp-ao-fix-label-in-compound-statement-warning-v1-1-c9731d115f17@kernel.org>
In-Reply-To: <20231031-tcp-ao-fix-label-in-compound-statement-warning-v1-1-c9731d115f17@kernel.org>
From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Tue, 31 Oct 2023 14:49:51 -0700
Message-ID: <CAKwvOd=CsF8B2i6f6d95J=n3zAZ7P2+bddBGBt0st=Q-f-OniA@mail.gmail.com>
Subject: Re: [PATCH net] tcp: Fix -Wc23-extensions in tcp_options_write()
To:     Nathan Chancellor <nathan@kernel.org>
Cc:     edumazet@google.com, davem@davemloft.net, dsahern@kernel.org,
        kuba@kernel.org, pabeni@redhat.com, trix@redhat.com,
        0x7f454c46@gmail.com, fruggeri@arista.com, noureddine@arista.com,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        llvm@lists.linux.dev, patches@lists.linux.dev
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On Tue, Oct 31, 2023 at 1:23=E2=80=AFPM Nathan Chancellor <nathan@kernel.or=
g> wrote:
>
> Clang warns (or errors with CONFIG_WERROR=3Dy) 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@kernel.org>

Well, at least ISO fixed that in C23...I found it annoying. One day we
might have nice things.  Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>  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, stru=
ct 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-ebd6c9=
978498
>
> Best regards,
> --
> Nathan Chancellor <nathan@kernel.org>
>


--=20
Thanks,
~Nick Desaulniers