Re: git: 8b83d7e0ee54 - main - Make -Wunused-but-set-variable a fatal error for clang 13+ for kernel builds.

From: FreeBSD User <freebsd_at_walstatt-de.de>
Date: Tue, 19 Apr 2022 07:02:21 UTC 
On Mon, 18 Apr 2022 23:11:52 GMT
John Baldwin <jhb@FreeBSD.org> wrote:

> The branch main has been updated by jhb:
> 
> URL:
> https://cgit.FreeBSD.org/src/commit/?id=8b83d7e0ee54416b0ee58bd85f9c0ae7fb3357a1
> 
> commit 8b83d7e0ee54416b0ee58bd85f9c0ae7fb3357a1
> Author:     John Baldwin <jhb@FreeBSD.org>
> AuthorDate: 2022-04-18 23:06:27 +0000
> Commit:     John Baldwin <jhb@FreeBSD.org>
> CommitDate: 2022-04-18 23:06:27 +0000
> 
>     Make -Wunused-but-set-variable a fatal error for clang 13+ for kernel
> builds. 
>     Reviewed by:    imp, emaste
>     Differential Revision:  https://reviews.freebsd.org/D34949
> ---
>  sys/conf/kern.mk | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/sys/conf/kern.mk b/sys/conf/kern.mk
> index f97be774ea10..b86149ab4618 100644
> --- a/sys/conf/kern.mk
> +++ b/sys/conf/kern.mk
> @@ -42,9 +42,6 @@ CWARNEXTRA?=	-Wno-error=tautological-compare
> -Wno-error=empty-body \ -Wno-error=pointer-sign
>  CWARNEXTRA+=	-Wno-error=shift-negative-value
>  CWARNEXTRA+=	-Wno-address-of-packed-member
> -.if ${COMPILER_VERSION} >= 130000
> -CWARNFLAGS+=	-Wno-error=unused-but-set-variable
> -.endif
>  .endif	# clang
>  
>  .if ${COMPILER_TYPE} == "gcc"
> 

Hello,

this setting results in a kernel build failure:

[...]
/usr/src/sys/dev/uart/uart_core.c:348:6: error: variable 'rxp' set but not used
[-Werror,-Wunused-but-set-variable] int rxp;
[...]

and, when having set 
makeoptions     WITH_EXTRA_TCP_STACKS=YES
in the kernel definition/configuration:

[...]
--- rack_bbr_common.o ---
/usr/src/sys/modules/tcp/bbr/../../../netinet/tcp_stacks/rack_bbr_common.c:399:16:
error: variable 'inp' set but not used [-Werror,-Wunused-but-set-variable]
struct inpcb *inp;
[...]


Kind regards,

Oliver