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Message-ID: <mhng-df0ad8f4-f79c-427c-9798-8682fca4f516@palmer-ri-x1c9a> Date: Wed, 01 Nov 2023 17:41:10 -0700 (PDT) From: Palmer Dabbelt <palmer@...belt.com> To: nathan@...nel.org CC: edumazet@...gle.com, davem@...emloft.net, dsahern@...nel.org, kuba@...nel.org, pabeni@...hat.com, 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@...nel.org Subject: Re: [PATCH net] tcp: Fix -Wc23-extensions in tcp_options_write() On Tue, 31 Oct 2023 13:23:35 PDT (-0700), 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> > --- > 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, This gives me a linux/net/ipv4/tcp_output.c:663:2: error: expected statement } on GCC for me. So I think something like diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index f558c054cf6e..ca09763acaa8 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -659,6 +659,11 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp, ptr++; } out_ao: + /* + * Labels at the end of compound statements are a C23 feature, so + * introduce a block to avoid a warning/error on strict toolchains. + */ + {} #endif } if (unlikely(opts->mss)) { should do it (though it's still build testing...)
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