linux-kernel - Re: [PATCH v2] kbuild: fix SIGPIPE error message for AR=gcc-ar and AR=llvm-ar

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Date:   Thu, 27 Oct 2022 09:36:57 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, Jiri Slaby <jirislaby@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nicolas Schier <nicolas@...sle.eu>, Tom Rix <trix@...hat.com>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH v2] kbuild: fix SIGPIPE error message for AR=gcc-ar and AR=llvm-ar

On Thu, Oct 27, 2022 at 9:28 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> Jiri Slaby reported that building the kernel with AR=gcc-ar shows:
>   /usr/bin/ar terminated with signal 13 [Broken pipe]
>
> Nathan Chancellor reported the latest AR=llvm-ar shows
>   error: write on a pipe with no reader
>
> The latter occurs since LLVM commit 51b557adc131 ("Add an error message
> to the default SIGPIPE handler").
>
> The resulting vmlinux is correct, but it is better to silence it.
>
> 'head -n1' exits after reading the first line, so the pipe is closed.
>
> Use 'sed -n 1p' to eat the stream till the end.
>
> Fixes: 321648455061 ("kbuild: use obj-y instead extra-y for objects placed at the head")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1651
> Reported-by: Jiri Slaby <jirislaby@...nel.org>
> Reported-by: Nathan Chancellor <nathan@...nel.org>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>

Looks great! Thanks all.
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>
> Changes in v2:
>   - Update commit description to mention llvm-ar
>
>  Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index e90bb2b38607..e9e7eff906a5 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1218,7 +1218,7 @@ quiet_cmd_ar_vmlinux.a = AR      $@
>        cmd_ar_vmlinux.a = \
>         rm -f $@; \
>         $(AR) cDPrST $@ $(KBUILD_VMLINUX_OBJS); \
> -       $(AR) mPiT $$($(AR) t $@ | head -n1) $@ $$($(AR) t $@ | grep -F -f $(srctree)/scripts/head-object-list.txt)
> +       $(AR) mPiT $$($(AR) t $@ | sed -n 1p) $@ $$($(AR) t $@ | grep -F -f $(srctree)/scripts/head-object-list.txt)
>
>  targets += vmlinux.a
>  vmlinux.a: $(KBUILD_VMLINUX_OBJS) scripts/head-object-list.txt autoksyms_recursive FORCE
> --
> 2.34.1
>


-- 
Thanks,
~Nick Desaulniers