Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752822AbdI1Kxc (ORCPT ); Thu, 28 Sep 2017 06:53:32 -0400 Received: from conssluserg-06.nifty.com ([210.131.2.91]:65148 "EHLO conssluserg-06.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751778AbdI1Kxa (ORCPT ); Thu, 28 Sep 2017 06:53:30 -0400 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-06.nifty.com v8SArGHA013669 X-Nifty-SrcIP: [209.85.161.175] X-Google-Smtp-Source: AOwi7QCKLKg20J1dj1aI4AeDZq6CH+UkJNZvB/ObIHZJB/WDFfm49J0bwvCPIBVktAWbIe70k/AB/z4QKeGhlsRpDso= MIME-Version: 1.0 In-Reply-To: <20170926022835.30916-1-nick.desaulniers@gmail.com> References: <20170926022835.30916-1-nick.desaulniers@gmail.com> From: Masahiro Yamada Date: Thu, 28 Sep 2017 19:52:35 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] kbuild: clang: remove crufty HOSTCFLAGS To: Nick Desaulniers Cc: Behan Webster , dl9pf@gmx.de, Mark Charlebois , Matthias Kaehlcke , Greg Hackmann , Michael Davidson , Michal Marek , Linux Kbuild mailing list , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2413 Lines: 77 Hi Nick, 2017-09-26 11:28 GMT+09:00 Nick Desaulniers : > When compiling with `make CC=clang HOSTCC=clang`, I was seeing warnings > that clang did not recognize -fno-delete-null-pointer-checks for HOSTCC > targets. These were added in commit 61163efae020 ("kbuild: LLVMLinux: > Add Kbuild support for building kernel with Clang"). That patch wraps > that flag in cc-option for KBUILD_CFLAGS, but not hostcc-option for > HOSTCFLAGS. Either hostcc-option did not exist, or the author was not > setting HOSTCC to clang as well as CC when authored. > > It's not clear why the other warnings were disabled, and just for > HOSTCFLAGS, but I can remove them, add -Werror to HOSTCFLAGS and compile > with clang just fine. > > Signed-off-by: Nick Desaulniers > --- > * It may also be worthwhile keep the old flags, and simply wrap > everything in hostcc-option. > > Makefile | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > diff --git a/Makefile b/Makefile > index d1119941261c..2e908969e0d8 100644 > --- a/Makefile > +++ b/Makefile > @@ -301,16 +301,12 @@ HOST_LFS_LIBS := $(shell getconf LFS_LIBS) > HOSTCC = gcc > HOSTCXX = g++ > 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. > HOSTCXXFLAGS := -O2 $(HOST_LFS_CFLAGS) > HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) > HOST_LOADLIBES := $(HOST_LFS_LIBS) > > -ifeq ($(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. > # Decide whether to build built-in, modular, or both. > # Normally, just do built-in. > -- Best Regards Masahiro Yamada