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From: Arnd Bergmann <arnd@arndb.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Ard Biesheuvel <ardb@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	linux-efi <linux-efi@vger.kernel.org>
Subject: Re: [GIT PULL] EFI fixes
Date: Thu, 9 Jul 2020 11:30:27 +0200
Message-ID: <CAK8P3a1GFjM5-ENf7XL6jjUvRdJhgjzYpSGD5R7TmW6oWEhYRA@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wggLLv8dY7ViOm7rdHxVNKJUkZMuR90vXO307WkBT8qrw@mail.gmail.com>

On Wed, Jul 8, 2020 at 8:00 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Wed, Jul 8, 2020 at 9:21 AM Peter Zijlstra <peterz@infradead.org> wrote:
> > >
> > > It's perhaps yet another reason to just skip gcc-4.8 too, since
> > > apparently 4.9 works.
> > >
> > > gcc-4.9 really has a lot of advantages. It's where (I think) gcc
> > > basically supports all C11 things, including _Generic() but also
> > > __auto_type.
> >
> > +1
> >
> > Anybody for nay, or should we just do this?
>
> I'll just do it. Let's see if anybody screams with a good reason. I
> hate the whole "support old compilers", it ends up not only making for
> complex code, it tends to cause these unnecessary kinds of "guys, we
> tested this really well, but that crazy compiler had a very particular
> odd issue, and it wasn't in any test box.

Cool, thanks for changing it, this is clearly a better suited compiler
version. Aside from the added C11 features, this is also where a lot of
the optimizations changed, so code generation is more predictable
if we don't need to worry about gcc-4.8.

On the flip side, gcc-4.8 was used by old enterprise distros that
are still supported (SUSE 12, RHEL 7), whereas gcc-4.9 was only
shipped in Debian Jessie and Android releases that are both
EOL now (Android never moved beyond a buggy gcc-4.9 prerelease
but now uses clang for everything).

I don't see any technical reasons to go even further, but if
something does come up, the users of these Long-term supported
distros would be most impacted by a change:

gcc-4.9: Used in Debian 8 (Jessie), EOL June 2020
gcc-5: Used in Ubuntu 16.04 (Xenial, Mint 18, ...), EOL April 2021
gcc-6: Used in Debian 9 (Stretch), EOL 2022
gcc-7: Used in SLES 15, Ubuntu 18.04 (Bionic, Mint 19, ...)
gcc-8: Used in RHEL-8 (centos, oracle, ...), OpenWRT

The most interesting version to require in the future would be
gcc-7, which IIRC is the point at which we can just use -std=gnu99
or -std=gnu11 instead of -std=gnu89 without running into the
problem with compound literals[1].

       Arnd

[1] https://patchwork.kernel.org/patch/11195831/

  parent reply index

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-28 18:26 Ingo Molnar
2020-06-28 18:57 ` Linus Torvalds
2020-06-28 19:26   ` Ard Biesheuvel
2020-06-28 19:34     ` Borislav Petkov
2020-07-08 16:20   ` Peter Zijlstra
2020-07-08 18:00     ` Linus Torvalds
2020-07-09  8:28       ` Peter Zijlstra
2020-07-09  9:30       ` Arnd Bergmann [this message]
2020-07-09 10:34         ` Kirill A. Shutemov
2020-07-10 10:09           ` Arnd Bergmann
2020-07-10 11:00             ` Kirill A. Shutemov
2020-07-10 11:17               ` Lukas Wunner
2020-06-28 22:05 ` pr-tracker-bot
  -- strict thread matches above, loose matches on Subject: below --
2021-06-02 17:44 Ingo Molnar
2021-06-02 19:36 ` pr-tracker-bot
2021-03-21 10:47 Ingo Molnar
2021-03-21 18:45 ` pr-tracker-bot
2020-07-25 10:32 Ingo Molnar
2020-07-25 22:30 ` pr-tracker-bot
2020-04-15  9:03 Ingo Molnar
2020-04-16  0:45 ` pr-tracker-bot
2020-03-02  7:10 Ingo Molnar
2020-03-03 23:35 ` pr-tracker-bot
2020-01-18 17:16 Ingo Molnar
2020-01-18 21:05 ` pr-tracker-bot
2019-12-17 11:09 Ingo Molnar
2019-12-17 19:20 ` pr-tracker-bot
2019-11-01 17:43 Ingo Molnar
2019-11-01 19:10 ` pr-tracker-bot
2019-10-12 13:01 Ingo Molnar
2019-10-12 22:35 ` pr-tracker-bot
2019-06-29  8:23 Ingo Molnar
2019-06-29 11:45 ` pr-tracker-bot
2019-06-02 17:35 Ingo Molnar
2019-06-02 18:15 ` pr-tracker-bot
2018-12-09 21:59 Ingo Molnar
2018-12-09 23:45 ` pr-tracker-bot
2018-11-17 10:51 Ingo Molnar
2018-11-18 20:05 ` pr-tracker-bot
2017-12-06 22:05 Ingo Molnar
2017-10-27 19:10 Ingo Molnar
2017-06-02  6:46 Ingo Molnar
2017-03-07 20:21 Ingo Molnar
2017-02-02 20:54 Ingo Molnar
2017-01-15  9:53 Ingo Molnar
2016-11-14  7:50 Ingo Molnar
2016-10-22 10:36 Ingo Molnar
2016-09-13 18:08 Ingo Molnar
2016-08-12 19:17 Ingo Molnar
2016-06-10 12:36 Ingo Molnar
2016-05-06 11:07 Ingo Molnar
2015-10-03 10:11 Ingo Molnar

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