Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
Reply-To: sedat.dilek@gmail.com
In-Reply-To: <CAK8P3a0yi+MrOS=+pjCeUu==YBE_AppB8vfqdsQS-1NpSO2c4A@mail.gmail.com>
References: <20180607204927.219329-1-ndesaulniers@google.com>
 <20180607204927.219329-2-ndesaulniers@google.com> <CAK8P3a0yi+MrOS=+pjCeUu==YBE_AppB8vfqdsQS-1NpSO2c4A@mail.gmail.com>
From:   Sedat Dilek <sedat.dilek@gmail.com>
Date:   Fri, 8 Jun 2018 12:04:36 +0200
Message-ID: <CA+icZUXDoeo5ktZZPFcFyLzk3xthM-98N88QJFzesg6t+Vr5cQ@mail.gmail.com>
Subject: Re: [PATCH v4 1/3] compiler-gcc.h: add gnu_inline to all inline declarations
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Nick Desaulniers <ndesaulniers@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-efi@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        virtualization@lists.linux-foundation.org, astrachan@google.com,
        Manoj Gupta <manojgupta@google.com>,
        Greg Hackmann <ghackmann@google.com>, tstellar@redhat.com,
        Kees Cook <keescook@google.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Michal Marek <michal.lkml@markovi.net>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Will Deacon <will.deacon@arm.com>, mawilcox@microsoft.com,
        David Rientjes <rientjes@google.com>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Philippe Ombredanne <pombredanne@nexb.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Jan Kiszka <jan.kiszka@siemens.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        akataria@vmware.com, Brijesh Singh <brijesh.singh@amd.com>,
        Cao jin <caoj.fnst@cn.fujitsu.com>,
        gregkh <gregkh@linuxfoundation.org>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Juergen Gross <jgross@suse.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Matthias Kaehlcke <mka@chromium.org>,
        "Lendacky, Thomas" <thomas.lendacky@amd.com>,
        Thiebaud Weksteen <tweek@google.com>, mjg59@google.com,
        Joe Perches <joe@perches.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Jun 8, 2018 at 9:59 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> On Thu, Jun 7, 2018 at 10:49 PM, Nick Desaulniers
> <ndesaulniers@google.com> wrote:
>> Functions marked extern inline do not emit an externally visible
>> function when the gnu89 C standard is used. Some KBUILD Makefiles
>> overwrite KBUILD_CFLAGS. This is an issue for GCC 5.1+ users as without
>> an explicit C standard specified, the default is gnu11. Since c99, the
>> semantics of extern inline have changed such that an externally visible
>> function is always emitted. This can lead to multiple definition errors
>> of extern inline functions at link time of compilation units whose build
>> files have removed an explicit C standard compiler flag for users of GCC
>> 5.1+ or Clang.
>>
>> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
>> Suggested-by: H. Peter Anvin <hpa@zytor.com>
>> Suggested-by: Joe Perches <joe@perches.com>
>
> I suspect this will break Geert's gcc-4.1.2, which I think doesn't have that
> attribute yet (4.1.3 or higher have it according to the documentation.
>
> It wouldn't be hard to work around that if we want to keep that version
> working, or we could decide that it's time to officially stop supporting
> that version, but we should probably decide on one or the other.
>

Good point.
What is the minimum requirement of GCC version currently?
AFAICS x86/asm-goto support requires GCC >= 4.5?

Just FYI...
...saw the last days in upstream commits that kbuild/kconfig for
4.18-rc1 offers possibilities to check for cc-version dependencies.

- sed@ -