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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Wed, 24 Jan 2024 10:52:25 +0100
Message-ID: <CAMuHMdWLMNj=Yvf4QxxrCxf-UBr-VXUxfJei+V2bNd0M7D1OhQ@mail.gmail.com>
Subject: Re: [PATCH 1/2] kconfig: remove unneeded symbol_empty variable
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: Yoann Congal <yoann.congal@smile.fr>, linux-kbuild@vger.kernel.org, 
	linux-kernel@vger.kernel.org, 
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>, 
	Vegard Nossum <vegard.nossum@oracle.com>
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Hi Yamada-san,

On Wed, Jan 24, 2024 at 9:10=E2=80=AFAM Masahiro Yamada <masahiroy@kernel.o=
rg> wrote:
> On Wed, Jan 24, 2024 at 12:11=E2=80=AFAM Yoann Congal <yoann.congal@smile=
fr> wrote:
> > Le 23/01/2024 =C3=A0 13:54, Geert Uytterhoeven a =C3=A9crit :
> > > On Sat, Nov 25, 2023 at 5:36=E2=80=AFPM Masahiro Yamada <masahiroy@ke=
rnel.org> wrote:
> > >> This is used only for initializing other variables.
> > >>
> > >> Use the empty string "".
> > >>
> > >> Please note newval.tri is unused for S_INT/HEX/STRING.
> > >>
> > >> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > >
> > > Thanks for your patch, which is now commit 4e244c10eab345a7
> > > ("kconfig: remove unneeded symbol_empty variable") in v6.8-rc1.
> > >
> > > When running "make <foo>_defconfig" with <foo>_defconfig an SMP
> > > defconfig without explicit configuration of CONFIG_LOG_CPU_MAX_BUF_SH=
IFT,
> > > the aforementioned commit causes a change in the generated .config:
> > >
> > > -CONFIG_LOG_CPU_MAX_BUF_SHIFT=3D12
> > > +CONFIG_LOG_CPU_MAX_BUF_SHIFT=3D0
> > >
> > > It looks like CONFIG_BASE_SMALL=3D0 is treated as a string instead of
> > > the integer number zero?
> > >
> > > init/Kconfig=3Dconfig LOG_CPU_MAX_BUF_SHIFT
> > > init/Kconfig-   int "CPU kernel log buffer size contribution (13 =3D>=
 8
> > > KB, 17 =3D> 128KB)"
> > > init/Kconfig-   depends on SMP
> > > init/Kconfig-   range 0 21
> > > init/Kconfig:   default 12 if !BASE_SMALL
> > > init/Kconfig:   default 0 if BASE_SMALL
> > >
> > > Note that reverting 4e244c10eab345a7 is not sufficient to fix the iss=
ue.
> > > Also reverting commit 6262afa10ef7cc8f ("kconfig: default to zero if
> > > int/hex symbol lacks default property") does fix it.
> >
> > (Since I'd really like 6262afa10ef7cc8f ("kconfig: default to zero if i=
nt/hex symbol lacks default property") to stay, allow me to try to help)
> >
> > The problem is quite easy to reproduce:
> >   $ make x86_64_defconfig
> >   $ grep 'LOG_CPU_MAX_BUF_SHIFT\|BASE_SMALL\|BASE_FULL' .config
> >   CONFIG_LOG_CPU_MAX_BUF_SHIFT=3D0
> >   CONFIG_BASE_FULL=3Dy
> >   CONFIG_BASE_SMALL=3D0
> > Here, CONFIG_LOG_CPU_MAX_BUF_SHIFT should be 12 not 0.
>
>
>
> I could not produce it in this way.
> I ran the same commands as yours.
>
> CONFIG_LOG_CPU_MAX_BUF_SHIFT=3D12 for me.
>
>
>
> masahiro@zoe:~/ref/linux(master)$ git describe
> v6.8-rc1-29-g615d30064886
> masahiro@zoe:~/ref/linux(master)$ git diff
> masahiro@zoe:~/ref/linux(master)$ make  x86_64_defconfig
> #
> # No change to .config
> #
> masahiro@zoe:~/ref/linux(master)$ grep
> 'LOG_CPU_MAX_BUF_SHIFT\|BASE_SMALL\|BASE_FULL' .config
> CONFIG_LOG_CPU_MAX_BUF_SHIFT=3D12
> CONFIG_BASE_FULL=3Dy
> CONFIG_BASE_SMALL=3D0

Interesting...

$ git describe
v6.8-rc1-29-g615d300648869c77
$ make  x86_64_defconfig
[...]
$ grep 'LOG_CPU_MAX_BUF_SHIFT\|BASE_SMALL\|BASE_FULL' .config
CONFIG_LOG_CPU_MAX_BUF_SHIFT=3D0
CONFIG_BASE_FULL=3Dy
CONFIG_BASE_SMALL=3D0

Does it depend on the flex/bison version?
I have Ubuntu LTS flex 2.6.4-8build2 and bison 2:3.8.2+dfsg-1build1.

Gr{oetje,eeting}s,

                        Geert

--=20
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k=
org

In personal conversations with technical people, I call myself a hacker. Bu=
t
when I'm talking to journalists I just say "programmer" or something like t=
hat.
                                -- Linus Torvalds