linux-kernel - Re: [PATCH] kbuild: fix 'Broken pipe' message for AR=gcc-ar

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Date:   Mon, 24 Oct 2022 12:15:38 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, Jiri Slaby <jirislaby@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nicolas Schier <nicolas@...sle.eu>,
        linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        clang-built-linux <llvm@...ts.linux.dev>, eng.stk@...o.pt
Subject: Re: [PATCH] kbuild: fix 'Broken pipe' message for AR=gcc-ar

On Sun, Oct 23, 2022 at 12:53 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> Since commit 321648455061 ("kbuild: use obj-y instead extra-y for
> objects placed at the head"), 'make AR=gcc-ar' shows the following
> message:
>
>   /usr/bin/ar terminated with signal 13 [Broken pipe]

Not just AR=gcc-ar, but also AR=llvm-ar:

error: write on a pipe with no reader

Link: https://github.com/ClangBuiltLinux/linux/issues/1651
Reported-by: Nathan Chancellor <nathan@...nel.org>
Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>

Note that due to
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8017ce50641c303b9b5d96f3c10229ecfd770a70
we should send a backport to stable like:
https://github.com/engstk/op8/commit/6f2688e3eb4ec06b276e541640d4f06364b68442

>
> The resulting vmlinux is correct, but it is better to silence this.
>
> '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")
> Reported-by: Jiri Slaby <jirislaby@...nel.org>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index f41ec8c8426b..0e42a7982826 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 $@ | grep -F --file=$(srctree)/scripts/head-object-list.txt)
> +       $(AR) mPiT $$($(AR) t $@ | sed -n 1p) $@ $$($(AR) t $@ | grep -F --file=$(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