linux-kernel - Re: [PATCH] kbuild: avoid regex RS for POSIX awk

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Message-ID: <CA+icZUXEswwLtmz-njhJydO33tcAPSnZ5PJkfigzpFrQ6pzP4Q@mail.gmail.com>
Date:   Wed, 8 Jun 2022 20:58:46 +0200
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     Kevin Locke <kevin@...inlocke.name>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kbuild: avoid regex RS for POSIX awk

On Tue, Jun 7, 2022 at 7:31 AM Kevin Locke <kevin@...inlocke.name> wrote:
>
> In 22f26f21774f8 awk was added to deduplicate *.mod files.  The awk
> invocation passes -v RS='( |\n)' to match a space or newline character
> as the record separator.  Unfortunately, POSIX states[1]
>
> > If RS contains more than one character, the results are unspecified.
>
> Some implementations (such as the One True Awk[2] used by the BSDs) do
> not treat RS as a regular expression.  When awk does not support regex
> RS, build failures such as the following are produced (first error using
> allmodconfig):
>
>       CC [M]  arch/x86/events/intel/uncore.o
>       CC [M]  arch/x86/events/intel/uncore_nhmex.o
>       CC [M]  arch/x86/events/intel/uncore_snb.o
>       CC [M]  arch/x86/events/intel/uncore_snbep.o
>       CC [M]  arch/x86/events/intel/uncore_discovery.o
>       LD [M]  arch/x86/events/intel/intel-uncore.o
>     ld: cannot find uncore_nhmex.o: No such file or directory
>     ld: cannot find uncore_snb.o: No such file or directory
>     ld: cannot find uncore_snbep.o: No such file or directory
>     ld: cannot find uncore_discovery.o: No such file or directory
>     make[3]: *** [scripts/Makefile.build:422: arch/x86/events/intel/intel-uncore.o] Error 1
>     make[2]: *** [scripts/Makefile.build:487: arch/x86/events/intel] Error 2
>     make[1]: *** [scripts/Makefile.build:487: arch/x86/events] Error 2
>     make: *** [Makefile:1839: arch/x86] Error 2
>
> To avoid this, use printf(1) to produce a newline between each object
> path, instead of the space produced by echo(1), so that the default RS
> can be used by awk.
>
> [1]: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/awk.html
> [2]: https://github.com/onetrueawk/awk
>
> Fixes: 22f26f21774f ("kbuild: get rid of duplication in *.mod files")
> Signed-off-by: Kevin Locke <kevin@...inlocke.name>

Tested-by: Sedat Dilek <sedat.dilek@...il.com> # LLVM-14 (x86-64)

-Sedat-

> ---
>  scripts/Makefile.build | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 1f01ac65c0cd..cac070aee791 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -251,8 +251,8 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
>
>  # To make this rule robust against "Argument list too long" error,
>  # ensure to add $(obj)/ prefix by a shell command.
> -cmd_mod = echo $(call real-search, $*.o, .o, -objs -y -m) | \
> -       $(AWK) -v RS='( |\n)' '!x[$$0]++ { print("$(obj)/"$$0) }' > $@
> +cmd_mod = printf '%s\n' $(call real-search, $*.o, .o, -objs -y -m) | \
> +       $(AWK) '!x[$$0]++ { print("$(obj)/"$$0) }' > $@
>
>  $(obj)/%.mod: FORCE
>         $(call if_changed,mod)
> --
> 2.35.1
>