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

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Message-ID: <CAKwvOd=CsF8B2i6f6d95J=n3zAZ7P2+bddBGBt0st=Q-f-OniA@mail.gmail.com>
Date:   Tue, 31 Oct 2023 14:49:51 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     edumazet@...gle.com, davem@...emloft.net, dsahern@...nel.org,
        kuba@...nel.org, pabeni@...hat.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
Subject: Re: [PATCH net] tcp: Fix -Wc23-extensions in tcp_options_write()

On Tue, Oct 31, 2023 at 1:23 PM Nathan Chancellor <nathan@...nel.org> wrote:
>
> 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>

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@...gle.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, 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>
>


-- 
Thanks,
~Nick Desaulniers