linux-kernel - Re: [PATCH 0/3] kbuild,kconfig: generate lexer/parser C files instead of copying

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Date:   Fri, 15 Dec 2017 08:54:20 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Cc:     Ulf Magnusson <ulfalizer@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Markus Heiser <markus.heiser@...marit.de>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Borislav Petkov <bp@...e.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jonathan Corbet <corbet@....net>,
        Michal Marek <michal.lkml@...kovi.net>,
        SeongJae Park <sj38.park@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Max Filippov <jcmvbkbc@...il.com>
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 <yamada.masahiro@...ionext.com>:
> 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.
> https://lkml.org/lkml/2017/8/19/49
>
> 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 zconf.tab.c_shipped 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