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

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Date:   Wed, 8 Jun 2022 01:19:12 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Kevin Locke <kevin@...inlocke.name>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kbuild: avoid regex RS for POSIX awk

On Tue, Jun 7, 2022 at 11:43 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>
> ---

Portable and clean solution!

Applied to linux-kbuild/fixes. Thanks.





-- 
Best Regards
Masahiro Yamada