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Date:   Fri, 15 Dec 2017 08:54:20 +0900
From:   Masahiro Yamada <>
To:     Linux Kbuild mailing list <>
Cc:     Ulf Magnusson <>,
        Sam Ravnborg <>,
        Linus Torvalds <>,
        Masahiro Yamada <>,
        Mauro Carvalho Chehab <>,
        Nicholas Piggin <>,
        Kate Stewart <>,
        Markus Heiser <>,
        "open list:DOCUMENTATION" <>,
        Borislav Petkov <>,
        Linux Kernel Mailing List <>,
        Thomas Gleixner <>,
        Jonathan Corbet <>,
        Michal Marek <>,
        SeongJae Park <>,
        Greg Kroah-Hartman <>,
        Philippe Ombredanne <>,
        Max Filippov <>
Subject: Re: [PATCH 0/3] kbuild,kconfig: generate lexer/parser C files instead
 of copying _shipped files

2017-12-10 1:02 GMT+09:00 Masahiro Yamada <>:
> In Linux build system convention, pre-generated files are version-
> controlled with a "_shipped" suffix.  During the kernel building,
> they are simply shipped (copied) removing the suffix.
> From users' point of view, this approach can reduce external tool
> dependency for the kernel build,
> From developers point of view, it is tedious to manually regenerate
> such artifacts.  In fact, we see several patches to regenerate
> _shipped files.  They are noise commits.
> When we update a *.y or *.l file, it would be better to update the
> corresponding _shipped file in the same commit, but it is painful.
> If you use a different version of flex/bison, it will produce lots of
> irrelevant diffs.
> We could update _shipped files after adding various changes to the
> real sources, but it is not very nice for a git-bisect'ability.
> In case of a problem, "git bisect" would point to the commit updating
> _shipped files, but the root cause would be in another commit that
> has changed the corresponding .l or .y files.
> Some months ago, I sent RFC patches to run flex, bison, and gperf
> during the build.
> Basically Linus agreed this, but he found a problem in gperf, then
> use of gperf in kernel was removed.
> It took some months for me to come back.  This time, I installed various
> versions of flex/bison on my machine, and tested them more carefully.
> My current motivation is in Kconfig.
> There are several Kconfig patches touching *.y and *.l
> (and Linus suggested another improvement for Kconfig)
> so I want to remove zconf.lex.c_shipped and now.
> Kconfig has no problem for this switch.
> dtc and genksyms will be taken care of later because
> both of them are having shift/reduce conflicts now.
> The ambiguous grammar in dtc has been fixed in upstream, but not
> reflected to kernel yet.  We can proceed migration in sub-system base.
> Masahiro Yamada (3):
>   kbuild: add LEX and YACC variables
>   kbuild: prepare to remove C files pre-generated by flex and bison
>   kconfig: generate lexer and parser during build instead of shipping

I did not get any problem report from the 0-day bot.
I assume flex and bison are installed on their machines.

Fixed a typo pointed out by Randy,
then applied to linux-kbuild/kconfig.

Best Regards
Masahiro Yamada

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