From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Nick Desaulniers <nick.desaulniers@gmail.com>
Cc: Behan Webster <behanw@converseincode.com>,
dl9pf@gmx.de, Mark Charlebois <charlebm@gmail.com>,
Matthias Kaehlcke <mka@chromium.org>,
Greg Hackmann <ghackmann@google.com>,
Michael Davidson <md@google.com>, Michal Marek <mmarek@suse.com>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
llvmlinux@lists.linuxfoundation.org
Subject: Re: [PATCH] kbuild: clang: remove crufty HOSTCFLAGS
Date: Fri, 6 Oct 2017 05:15:50 +0900 [thread overview]
Message-ID: <CAK7LNARTo+esxqmoLrXufRoP7qbJprwVOYiRB-a2jRd=AZ0sXg@mail.gmail.com> (raw)
In-Reply-To: <20170930231450.cggvysrt4zedsbkq@lostoracle.net>
Hi Nick.
2017-10-01 8:14 GMT+09:00 Nick Desaulniers <nick.desaulniers@gmail.com>:
> On Thu, Sep 28, 2017 at 07:52:35PM +0900, Masahiro Yamada wrote:
>> 2017-09-26 11:28 GMT+09:00 Nick Desaulniers <nick.desaulniers@gmail.com>:
>> > HOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 \
>> > + $(call hostcc-option,-fno-delete-null-pointer-checks) \
>> > -fomit-frame-pointer -std=gnu89 $(HOST_LFS_CFLAGS)
>>
>> You call hostcc-option
>> before Kbuild.include is included around line 341.
>>
>> So, $(call hostcc-option, ...) returns always an empty string here
>> whether the compiler supports the option or not.
>
> So calling a yet-to-be defined variable results in an empty string
> rather than a loud failure? Chalk that up there with language features
> no one ever asked for. That kind of implicit conversion gets languages
> like JavaScript (with its loose type system, not that C is without its
> own implicit type conversions/promotions) in a lot of hot water.
>
> If that's the case, why are includes not at the top of Makefiles, if
> silent failure is a possibility? Is there a reason the include is so
> far into the Makefile?
Kbuild.include depends on some other variables.
You can not include it at the top of the Makefile.
> Is your sugguestion to raise the include or lower the HOSTCFLAGS
> definition?
In this case, you do not need to move any of them.
-fno-delete-null-pointer-checks has never enabled
for host-tools before.
Just remove it to keep the current behavior.
>> > -ifeq ($(shell $(HOSTCC) -v 2>&1 | grep -c "clang version"), 1)
>> > -HOSTCFLAGS += -Wno-unused-value -Wno-unused-parameter \
>> > - -Wno-missing-field-initializers -fno-delete-null-pointer-checks
>> > -endif
>>
>> The logic is very strange in the first place.
>>
>> Even very old GCC supports -fno-delete-null-pointer-checks,
>> but clang does not.
>>
>> Here, -fno-delete-null-pointer-checks is added only when
>> we are using clang for HOSTCC. This is opposite.
>>
>> I guess we can remove all of them
>> unless somebody can explain the rationale.
>
> +llvm-linux
>
> I suppose maybe different ARCH's have different host binaries made
> during the build? I tested x86_64 and arm64. The commit message that
> added them missed any context or justification.
According to
http://llvm.linuxfoundation.org/index.php/Main_Page
llvm-linux was only successful for x86, arm(64)
at that time.
If you tested x86_64 and arm64, and saw no problem,
it is fine.
--
Best Regards
Masahiro Yamada
next prev parent reply other threads:[~2017-10-05 20:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-26 2:28 [PATCH] kbuild: clang: remove crufty HOSTCFLAGS Nick Desaulniers
2017-09-28 10:52 ` Masahiro Yamada
2017-09-30 23:14 ` Nick Desaulniers
2017-10-01 0:38 ` Segher Boessenkool
2017-10-05 20:15 ` Masahiro Yamada [this message]
2017-10-07 20:23 ` [PATCH v2] " Nick Desaulniers
2017-10-07 20:26 ` Nick Desaulniers
2017-10-12 0:56 ` 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='CAK7LNARTo+esxqmoLrXufRoP7qbJprwVOYiRB-a2jRd=AZ0sXg@mail.gmail.com' \
--to=yamada.masahiro@socionext.com \
--cc=behanw@converseincode.com \
--cc=charlebm@gmail.com \
--cc=dl9pf@gmx.de \
--cc=ghackmann@google.com \
--cc=linux-kbuild@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=llvmlinux@lists.linuxfoundation.org \
--cc=md@google.com \
--cc=mka@chromium.org \
--cc=mmarek@suse.com \
--cc=nick.desaulniers@gmail.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).