| Message ID | 20231031-tcp-ao-fix-label-in-compound-statement-warning-v1-1-c9731d115f17@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] tcp: Fix -Wc23-extensions in tcp_options_write() | expand |
On Tue, Oct 31, 2023 at 1:23 PM Nathan Chancellor <nathan@kernel.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@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, 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@kernel.org> >
On Tue, Oct 31, 2023 at 9:23 PM Nathan Chancellor <nathan@kernel.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: Reviewed-by: Eric Dumazet <edumazet@google.com>
On Tue, 31 Oct 2023 13:23:35 PDT (-0700), nathan@kernel.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@kernel.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...)
On Wed, Nov 01, 2023 at 05:41:10PM -0700, Palmer Dabbelt wrote: > On Tue, 31 Oct 2023 13:23:35 PDT (-0700), nathan@kernel.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@kernel.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. What GCC version? I cannot reproduce that error with my patch applied. I tested mainline at commit deefd5024f07 ("Merge tag 'vfio-v6.7-rc1' of https://github.com/awilliam/linux-vfio") using GCC 6 from kernel.org and I can reproduce a similar failure with ARCH=x86_64 allyesconfig: net/ipv4/tcp_output.c: In function 'tcp_options_write': net/ipv4/tcp_output.c:661:1: error: label at end of compound statement out_ao: ^~~~~~ With this change applied, the error disappears for GCC 6 and GCC 13 continues to build without error. I can try the other supported versions later, I just did an older and newer one for a quick test. > 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...) I am not opposed to this once we understand what versions are affected by this so that we have some timeline of removing this workaround. Cheers, Nathan
On Wed, 01 Nov 2023 18:07:23 PDT (-0700), nathan@kernel.org wrote: > On Wed, Nov 01, 2023 at 05:41:10PM -0700, Palmer Dabbelt wrote: >> On Tue, 31 Oct 2023 13:23:35 PDT (-0700), nathan@kernel.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@kernel.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. > > What GCC version? 12.1, though I can't get a smaller reproducer so I'm going to roll back to your change and double-check. Might take a bit... > I cannot reproduce that error with my patch applied. I tested mainline > at commit deefd5024f07 ("Merge tag 'vfio-v6.7-rc1' of > https://github.com/awilliam/linux-vfio") using GCC 6 from kernel.org and > I can reproduce a similar failure with ARCH=x86_64 allyesconfig: > > net/ipv4/tcp_output.c: In function 'tcp_options_write': > net/ipv4/tcp_output.c:661:1: error: label at end of compound statement > out_ao: > ^~~~~~ > > With this change applied, the error disappears for GCC 6 and GCC 13 > continues to build without error. I can try the other supported versions > later, I just did an older and newer one for a quick test. > >> 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...) > > I am not opposed to this once we understand what versions are affected > by this so that we have some timeline of removing this workaround. > > Cheers, > Nathan
On Wed, 01 Nov 2023 18:42:10 PDT (-0700), Palmer Dabbelt wrote: > On Wed, 01 Nov 2023 18:07:23 PDT (-0700), nathan@kernel.org wrote: >> On Wed, Nov 01, 2023 at 05:41:10PM -0700, Palmer Dabbelt wrote: >>> On Tue, 31 Oct 2023 13:23:35 PDT (-0700), nathan@kernel.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@kernel.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. >> >> What GCC version? > > 12.1, though I can't get a smaller reproducer so I'm going to roll back > to your change and double-check. Might take a bit... Looks like there was just some bug in my test scripts and the original patch wasn't actually picked up for all the configs. It's working now, so Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com> Sorry for the confusion! >> I cannot reproduce that error with my patch applied. I tested mainline >> at commit deefd5024f07 ("Merge tag 'vfio-v6.7-rc1' of >> https://github.com/awilliam/linux-vfio") using GCC 6 from kernel.org and >> I can reproduce a similar failure with ARCH=x86_64 allyesconfig: >> >> net/ipv4/tcp_output.c: In function 'tcp_options_write': >> net/ipv4/tcp_output.c:661:1: error: label at end of compound statement >> out_ao: >> ^~~~~~ >> >> With this change applied, the error disappears for GCC 6 and GCC 13 >> continues to build without error. I can try the other supported versions >> later, I just did an older and newer one for a quick test. >> >>> 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...) >> >> I am not opposed to this once we understand what versions are affected >> by this so that we have some timeline of removing this workaround. >> >> Cheers, >> Nathan
On Tue, Oct 31, 2023 at 01:23:35PM -0700, Nathan Chancellor 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. Can you please just split the A0 handlig into a separate helper, which shuld make the whole thing a lot cleaner?
Hi Christoph, On Fri, Nov 03, 2023 at 01:22:05AM -0700, Christoph Hellwig wrote: > On Tue, Oct 31, 2023 at 01:23:35PM -0700, Nathan Chancellor 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. > > Can you please just split the A0 handlig into a separate helper, which > shuld make the whole thing a lot cleaner? Is something like this (I think I got all the pointer manipulation correct...) what you had in mind? I am happy to send that as a v2 if the netdev folks would prefer it over this small change (along with some guidance about the function name, if it should be something different). Cheers, Nathan diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index f558c054cf6e..6f2a5e3bb7b3 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -601,6 +601,43 @@ static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb, } #endif +static void process_tcp_ao_options(struct tcp_sock *tp, + const struct tcp_request_sock *tcprsk, + struct tcp_out_options *opts, + struct tcp_key *key, __be32 **ptr) +{ +#ifdef CONFIG_TCP_AO + u8 maclen = tcp_ao_maclen(key->ao_key); + + if (tcprsk) { + u8 aolen = maclen + sizeof(struct tcp_ao_hdr); + + *(*ptr)++ = htonl((TCPOPT_AO << 24) | (aolen << 16) | + (tcprsk->ao_keyid << 8) | + (tcprsk->ao_rcv_next)); + } else { + struct tcp_ao_key *rnext_key; + struct tcp_ao_info *ao_info; + + ao_info = rcu_dereference_check(tp->ao_info, + lockdep_sock_is_held(&tp->inet_conn.icsk_inet.sk)); + rnext_key = READ_ONCE(ao_info->rnext_key); + if (WARN_ON_ONCE(!rnext_key)) + return; + *(*ptr)++ = htonl((TCPOPT_AO << 24) | + (tcp_ao_len(key->ao_key) << 16) | + (key->ao_key->sndid << 8) | + (rnext_key->rcvid)); + } + opts->hash_location = (__u8 *)(*ptr); + *ptr += maclen / sizeof(**ptr); + if (unlikely(maclen % sizeof(**ptr))) { + memset(*ptr, TCPOPT_NOP, sizeof(**ptr)); + (*ptr)++; + } +#endif +} + /* Write previously computed TCP options to the packet. * * Beware: Something in the Internet is very sensitive to the ordering of @@ -629,37 +666,7 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp, opts->hash_location = (__u8 *)ptr; ptr += 4; } else if (tcp_key_is_ao(key)) { -#ifdef CONFIG_TCP_AO - u8 maclen = tcp_ao_maclen(key->ao_key); - - if (tcprsk) { - u8 aolen = maclen + sizeof(struct tcp_ao_hdr); - - *ptr++ = htonl((TCPOPT_AO << 24) | (aolen << 16) | - (tcprsk->ao_keyid << 8) | - (tcprsk->ao_rcv_next)); - } else { - struct tcp_ao_key *rnext_key; - struct tcp_ao_info *ao_info; - - ao_info = rcu_dereference_check(tp->ao_info, - lockdep_sock_is_held(&tp->inet_conn.icsk_inet.sk)); - rnext_key = READ_ONCE(ao_info->rnext_key); - if (WARN_ON_ONCE(!rnext_key)) - goto out_ao; - *ptr++ = htonl((TCPOPT_AO << 24) | - (tcp_ao_len(key->ao_key) << 16) | - (key->ao_key->sndid << 8) | - (rnext_key->rcvid)); - } - opts->hash_location = (__u8 *)ptr; - ptr += maclen / sizeof(*ptr); - if (unlikely(maclen % sizeof(*ptr))) { - memset(ptr, TCPOPT_NOP, sizeof(*ptr)); - ptr++; - } -out_ao: -#endif + process_tcp_ao_options(tp, tcprsk, opts, key, &ptr); } if (unlikely(opts->mss)) { *ptr++ = htonl((TCPOPT_MSS << 24) |
On Fri, Nov 3, 2023 at 1:22 AM Christoph Hellwig <hch@infradead.org> wrote: > > On Tue, Oct 31, 2023 at 01:23:35PM -0700, Nathan Chancellor 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. > > Can you please just split the A0 handlig into a separate helper, which > shuld make the whole thing a lot cleaner? Just a note; mainline is currently red over this for us since 1e03d32bea8e spent all of ~3 days in linux-next before getting merged into mainline. Whatever the fix is, it would be great to get it into mainline ASAP.
Normally the kernel keeps the ifdef outside the function body and adds a stub. But this already looks like a huge imrpovement over the existing version to me.
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)) {
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@kernel.org> --- net/ipv4/tcp_output.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- base-commit: 55c900477f5b3897d9038446f72a281cae0efd86 change-id: 20231031-tcp-ao-fix-label-in-compound-statement-warning-ebd6c9978498 Best regards,