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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Mon, 12 Feb 2018 11:44:26 +0100
Message-ID: <CAK8P3a3-63He=LPtqyskQn_J-8VKUTpoFXLPjUU7Vjoj1MYfLA@mail.gmail.com>
Subject: Re: [RFC PATCH 4/7] kconfig: support new special property shell=
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Kees Cook <keescook@chromium.org>,
        Ulf Magnusson <ulfalizer@gmail.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Nicolas Pitre <nicolas.pitre@linaro.org>,
        "Luis R . Rodriguez" <mcgrof@suse.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Sam Ravnborg <sam@ravnborg.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Pavel Machek <pavel@ucw.cz>,
        linux-s390 <linux-s390@vger.kernel.org>,
        Jiri Kosina <jkosina@suse.cz>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Tejun Heo <tj@kernel.org>, Ingo Molnar <mingo@kernel.org>,
        "Van De Ven, Arjan" <arjan.van.de.ven@intel.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>
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On Sun, Feb 11, 2018 at 10:50 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Sun, Feb 11, 2018 at 1:19 PM, Kees Cook <keescook@chromium.org> wrote:
>> On Sun, Feb 11, 2018 at 1:10 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>>>
>>> In my tests last year, I identified gcc-4.6 as a nice minimum level, IIRC
>>> gcc-4.5 was unable to build some of the newer ARM targets.
>>
>> But yes, if Linus wants 4.5 over 4.3, I would agree with Arnd: let's
>> take it to 4.6 instead.
>
> So it sounds like Arnd knows what the distros have.
...
> If no distro is on 4.5, then there's no reason to pick that. The
> reason I mentioned 4.5 is because that's the "asm goto" point, afaik,
> and that is likely to be a requirement in the near future.

Looking at old distros with long support cycles:

Red Hat have either gcc-4.1 (EL5, extended support ends 2020) or
gcc-4.4 (EL6, regular support ends 2020, extended support ends 2024):
https://access.redhat.com/solutions/19458
EL7 uses gcc-4.8 and will be supported until 2024 (no extended support
planned)

SUSE have gcc-4.3 (SLES11, extended support ends 2022) or gcc-4.8
(SLES12, support ends 2024, extended support ends 2027):
https://www.suse.com/lifecycle/

Debian Jessie (oldstable) comes with gcc-4.8 and is supported until June 2018,
extended support until 2020
Debian  Wheezy (oldoldstable) uses gcc-4.6 or 4.7 depending on the
architecture, extended support ends May 2018.

Ubuntu 14.04 is supported until 2019 and uses gcc-4.8

The latest Android SDK provides (known broken) versions of gcc-4.8 and
gcc-4.9 as well as clang.

OpenWRT 14.07 Barrier Breaker uses gcc-4.8, 12.07 Attitude
Adjustment 12.09 used gcc-4.6, but it's very unlikely that anyone
cares about building new kernels with either.

Most embedded distros just build everything from source and are
used to adapting to new requirements.

From that list above, it sounds like going all the way to gcc-4.8 would
be a better candidate than 4.5 or 4.6, if we decide that 4.3 and 4.4 are
both no longer desirable to support.

> If SLES11 is 4.3, that's obviously a concern. Although Arnd seemed to
> imply that that had already caused problems, so...

The problems are mainly an excessive amount of false-positive
warnings, which makes it tricky to new warnings when you make
a mistake.

          Arnd