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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Sun, 11 Feb 2018 22:10:45 +0100
Message-ID: <CAK8P3a3DHkpbRxUTP77OoeAqRHDz-tL-qYxLfq61Wv8NUPmyjA@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 9:06 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Sun, Feb 11, 2018 at 11:53 AM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>>
>> Well, it's still not a very *big* bump. With modern distros being at
>> 7.3, and people testing pre-releases of gcc-8, something like gcc-4.5
>> is still pretty darn ancient.
>
> ... it's worth noting that our _documentation_ may claim that gcc-3.2
> is the minimum supported version, but Arnd pointed out that a few
> months ago that apparently nothing older than 4.1 has actually worked
> for a longish while, and gcc-4.3 was needed on several architectures.
>
> So the _real_ jump in required gcc version would be from 4.1 (4.3 in
> many cases) to 4.5, not from our documented "3.2 minimum".
>
> Arnd claimed that some architectures needed even newer-than-4.3, but I
> assume that's limited to things like RISC-V that simply don't have old
> gcc support at all.

Right. Also architecture specific features may need something more recent,
and in some cases like the 'initializer for anonymous union needs extra
curly braces', a trivial change would make it work, but a lot of architectures
have obviously never been built with toolchains old enough to actually
run into those cases.

Geert is the only person I know that actively uses gcc-4.1, and he actually
sent some patches that seem to get additional architectures to build on
that version, when they were previously on gcc-4.3+.

gcc-4.3 in turn is used by default on SLES11, which is still in support,
and I've even worked with someone who used that compiler to build
new kernels, since that was what happened to be installed on his
shared build server. In this case, having gcc-4.3 actively refused to
force him to use a new compiler would have saved us some
debugging trouble.

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.

      Arnd