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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Sat, 9 Apr 2022 10:47:54 +0900
Message-ID: <CAK7LNAS6ap9dR=kzRgQgt+d7FBBbVrwEqGU9g_pFD+nzMUt+gQ@mail.gmail.com>
Subject: Re: [PATCHv1] kbuild: support W=e to make build abort in case of warning
To:     Randy Dunlap <rdunlap@infradead.org>
Cc:     Nick Desaulniers <ndesaulniers@google.com>,
        Yann Droneaud <ydroneaud@opteya.com>,
        Michal Marek <michal.lkml@markovi.net>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
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On Sat, Apr 9, 2022 at 5:36 AM Randy Dunlap <rdunlap@infradead.org> wrote:
>
>
>
> On 4/8/22 13:29, Nick Desaulniers wrote:
> > On Fri, Apr 8, 2022 at 4:06 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >>
> >> On Fri, Apr 8, 2022 at 5:46 PM Yann Droneaud <ydroneaud@opteya.com> wrote:
> >>>
> >>> When developing new code/feature, CONFIG_WERROR is most
> >>> often turned off, especially for people using make W=12 to
> >>> get more warnings.
> >>>
> >>> In such case, turning on -Werror temporarily would require
> >>> switching on CONFIG_WERROR in the configuration, building,
> >>> then switching off CONFIG_WERROR.
> >>>
> >>> For this use case, this patch introduces a new 'e' modifier
> >>> to W= as a short hand for KCFLAGS+=-Werror" so that -Werror
> >>> got added to the kernel (built-in) and modules' CFLAGS.
> >>>
> >>> Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
> >>> ---
> >>>  Makefile                   |  1 +
> >>>  scripts/Makefile.extrawarn | 13 +++++++++++--
> >>>  2 files changed, 12 insertions(+), 2 deletions(-)
> >>>
> >>> Changes since v0[0]:
> >>>
> >>>  - rebase on top of commit 64a91907c896 ("kbuild: refactor scripts/Makefile.extrawarn")
> >>>  - document use case after commit 3fe617ccafd6 ("Enable '-Werror' by default for all kernel builds")
> >>>
> >>> [0] https://lore.kernel.org/all/1422803720-14723-1-git-send-email-ydroneaud@opteya.com/
> >>
> >>
> >> I remembered the previous submission, I liked it, but I had lost it.
> >>
> >> It seems already 7 years ago, (before I became the Kbuild maintainer).
> >> Thanks for coming back to this.
> >>
> >>
> >> I like this, but I will wait some time for review comments.
> >
> > Dunno, this seems pretty simple:
> >
> > $ ./scripts/config -e WERROR
> > $ make ... W=12
>
> Yeah, that's about what I was thinking too..


But, you cannot change the .config
when you build external modules.

"make W=e" might be useful for people who strive to
keep their downstream modules warning-free.


W=e is the same pattern.
I do not see much downside.


(BTW, I do not like CONFIG_WERROR.)


-- 
Best Regards
Masahiro Yamada