From: Nathan Chancellor <natechancellor@gmail.com>
To: Stephen Boyd <swboyd@chromium.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>,
Michal Marek <michal.lkml@markovi.net>,
linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org,
clang-built-linux@googlegroups.com,
Peter Smith <peter.smith@linaro.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Douglas Anderson <dianders@chromium.org>
Subject: Re: [PATCH v2] kbuild: Check for unknown options with cc-option usage in Kconfig and clang
Date: Thu, 25 Jul 2019 10:01:04 -0700 [thread overview]
Message-ID: <20190725170104.GB80773@archlinux-threadripper> (raw)
In-Reply-To: <20190725154730.80169-1-swboyd@chromium.org>
On Thu, Jul 25, 2019 at 08:47:30AM -0700, Stephen Boyd wrote:
> If the particular version of clang a user has doesn't enable
> -Werror=unknown-warning-option by default, even though it is the
> default[1], then make sure to pass the option to the Kconfig cc-option
> command so that testing options from Kconfig files works properly.
> Otherwise, depending on the default values setup in the clang toolchain
> we will silently assume options such as -Wmaybe-uninitialized are
> supported by clang, when they really aren't.
>
> A compilation issue only started happening for me once commit
> 589834b3a009 ("kbuild: Add -Werror=unknown-warning-option to
> CLANG_FLAGS") was applied on top of commit b303c6df80c9 ("kbuild:
> compute false-positive -Wmaybe-uninitialized cases in Kconfig"). This
> leads kbuild to try and test for the existence of the
> -Wmaybe-uninitialized flag with the cc-option command in
> scripts/Kconfig.include, and it doesn't see an error returned from the
> option test so it sets the config value to Y. Then the Makefile tries to
> pass the unknown option on the command line and
> -Werror=unknown-warning-option catches the invalid option and breaks the
> build. Before commit 589834b3a009 ("kbuild: Add
> -Werror=unknown-warning-option to CLANG_FLAGS") the build works fine,
> but any cc-option test of a warning option in Kconfig files silently
> evaluates to true, even if the warning option flag isn't supported on
> clang.
>
> Note: This doesn't change cc-option usages in Makefiles because those
> use a different rule that includes KBUILD_CFLAGS by default (see the
> __cc-option command in scripts/Kbuild.incluide). The KBUILD_CFLAGS
> variable already has the -Werror=unknown-warning-option flag set. Thanks
> to Doug for pointing out the different rule.
>
> [1] https://clang.llvm.org/docs/DiagnosticsReference.html#wunknown-warning-option
> Cc: Peter Smith <peter.smith@linaro.org>
> Cc: Nathan Chancellor <natechancellor@gmail.com>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Douglas Anderson <dianders@chromium.org>
> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Commit message wording looks better to me, thanks for the change!
I think we might also want to add:
Cc: stable@vger.kernel.org # 4.19+
in addition to Doug's suggested fixes tag because my patch has been
AUTOSEL'd by Sasha:
https://lore.kernel.org/lkml/20190719040732.17285-44-sashal@kernel.org/
https://git.kernel.org/sashal/linux-stable/c/a28859fa4fea5a834a53d86d51e502012ce09c57
Alternatively, I can just mention that this patch needs to be picked up
in addition to that one when it is formally sent out in a stable review.
Cheers,
Nathan
next prev parent reply other threads:[~2019-07-25 17:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-25 15:47 [PATCH v2] kbuild: Check for unknown options with cc-option usage in Kconfig and clang Stephen Boyd
2019-07-25 16:41 ` Doug Anderson
2019-07-25 17:01 ` Nathan Chancellor [this message]
2019-07-29 10:02 ` Masahiro Yamada
2019-07-29 14:23 ` Stephen Boyd
2019-07-30 14:28 ` Masahiro Yamada
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190725170104.GB80773@archlinux-threadripper \
--to=natechancellor@gmail.com \
--cc=clang-built-linux@googlegroups.com \
--cc=dianders@chromium.org \
--cc=linux-kbuild@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=michal.lkml@markovi.net \
--cc=ndesaulniers@google.com \
--cc=peter.smith@linaro.org \
--cc=swboyd@chromium.org \
--cc=yamada.masahiro@socionext.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).