From: Nick Desaulniers <nick.desaulniers@gmail.com>
To: Masahiro Yamada <yamada.masahiro@socionext.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: Sat, 30 Sep 2017 16:14:50 -0700 [thread overview]
Message-ID: <20170930231450.cggvysrt4zedsbkq@lostoracle.net> (raw)
In-Reply-To: <CAK7LNARwbqviGS4THmftO3mCkxpjPmQHxDbFjTsBXptyEG5cMg@mail.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, $(call hostcc-option, ...) returns always an empty string here
> whether the compiler supports the option or not.
So calling a yet-to-be defined variable results in an empty string
rather than a loud failure? Chalk that up there with language features
no one ever asked for. That kind of implicit conversion gets languages
like JavaScript (with its loose type system, not that C is without its
own implicit type conversions/promotions) in a lot of hot water.
If that's the case, why are includes not at the top of Makefiles, if
silent failure is a possibility? Is there a reason the include is so
far into the Makefile?
Is your sugguestion to raise the include or lower the HOSTCFLAGS
definition?
> > -ifeq ($(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.
next prev parent reply other threads:[~2017-09-30 23:14 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 [this message]
2017-10-01 0:38 ` Segher Boessenkool
2017-10-05 20:15 ` Masahiro Yamada
2017-10-07 20:23 ` [PATCH v2] " Nick Desaulniers
2017-10-07 20:26 ` Nick Desaulniers
2017-10-12 0:56 ` Masahiro Yamada
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