From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>,
Kees Cook <keescook@chromium.org>,
linux-arch <linux-arch@vger.kernel.org>,
linux-kbuild <linux-kbuild@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Russell King <rmk+kernel@armlinux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
kernel-build-reports@lists.linaro.org,
kvmarm@lists.cs.columbia.edu
Subject: Re: [RFC] minimum gcc version for kernel: raise to gcc-4.3 or 4.6?
Date: Mon, 24 Apr 2017 12:17:03 +0200 [thread overview]
Message-ID: <CAMuHMdUOv-sn9vDei0qPaRe19faYJGZ1zo1X==JDyFWJW3x5=A@mail.gmail.com> (raw)
Message-ID: <20170424101703.pFH-45AvyE3aZwTbe02UIs75G44ZiXWt6ktAF1Lrclw@z> (raw)
In-Reply-To: <CAK8P3a32Y0AiKyVaotYb14uZZ1jM=nwhFD1vyP56epW1Y9KqSw@mail.gmail.com>
Hi Arnd,
On Mon, Apr 24, 2017 at 11:44 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> On Sun, Apr 23, 2017 at 10:13 PM, Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
>> On Sat, Apr 22, 2017 at 5:30 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>>> Based on what I found so far, gcc-4 can be pretty much ruled out from
>>> being the minimum version based on the number of failures I got.
>>> It's much better than 3.4 but much worse than 4.1 or 4.2 which seem
>>> fixable on MIPS and x86 at least, and may or may not work depending
>>> on configuration. So the best two possible (but conflicting) answers I
>>> have are
>>>
>>> a) There are known users on gcc-4.1, and we never break things that
>>> work for users, so gcc-4.1 (or possibly 4.0 if a user shows up) would
>>> be the minimum version.
>>> b) gcc-4.1 and 4.2 have too many problems, so users are better off
>>> when we tell them to upgrade to something newer, and a minimum
>>> version of gcc-4.3 has fewer surprises. We should remove all
>>> workarounds for pre-gcc-4.3 compilers and just force a build error
>>> message.
>>
>> If there's no real good reason (brokenness) to deprecate gcc-4.1, I would not
>> do it.I guess most people using old compilers know what they're doing.
>
> What I'm trying to find out first is whether "people regularly using 10+
> year old compilers for the latest kernels" is a strict subset of "people in
> Geert's household".
Fair enough.
>> My main motivation for keep on using gcc-4.1 is that it gives many warnings
>> that were disabled in later gcc versions. I do look at all new warnings, and
>> send patches when they are real bugs, or are trivial to silence.
>
> What kind of warnings do you see that disappeared with later versions?
> Do you know what caused them to disappear in later versions (different
> optimization decisions, warning getting disabled by default but still available
> for turning on manually, ...)? Do you know if the disabled warnings are
> still there in gcc-4.3 (I can try it out if you give me examples)?
Mostly the "may be used uninitialized" warnings. I believe they were disabled
in gcc-4.3 (4.2?) and later due to too many false positives, which is not an
issue for me, as I look at differences.
They were re-enabled lately (with much less false-positives), that's why you
see them, and fix them.
For example, do you see the warning fixed by commit 1b8c1012142d8322
("drivers: net: xgene: Simplify xgene_enet_setup_mss() to kill warning")
with gcc-4.3? Yes, that was a false positive.
Or see commit cc4a7ffe02c95f53 ("spi: fsl-lpspi: Pre-initialize ret in
fsl_lpspi_transfer_one_msg()"). That one was a real bug.
I don't see that in any of the kisskb build logs, and they use gcc-4.2.4 for
avr32. So having gcc-4.2 or gcc-4.3 in a farm won't help.
And as long as I find real bugs this way, I'd like to continue doing it.
>> BTW, below is the diff I use to avoid an ICE.
>> After that, it builds and (test)boots fine on ARAnyM ;-)
>
> I guess this means that even your builds require extra patches and you
> can't strictly build a defconfig and expect that to work ;-)
No sane people enable GFS in defconfig, so it's not affected.
Oh wait, some mips, powerpc, s390, and tile do ;-)
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
next prev parent reply other threads:[~2017-04-24 10:17 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-16 10:56 [RFC] minimum gcc version for kernel: raise to gcc-4.3 or 4.6? Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2016-12-16 10:56 ` [PATCH 01/13] [HACK] gcc-4.5: avoid link errors for unused function pointers Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2016-12-16 10:56 ` [PATCH 02/13] KVM: arm: fix gcc-4.5 build Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2017-01-04 10:38 ` Christoffer Dall
2017-01-04 10:38 ` Christoffer Dall
2016-12-16 10:56 ` [PATCH 03/13] ARM: div64: fix building with gcc-4.5 and lower Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2016-12-16 10:56 ` [PATCH 04/13] vfio-pci: use 32-bit comparisons for register address for gcc-4.5 Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2016-12-16 15:30 ` Alex Williamson
2016-12-16 19:50 ` Arnd Bergmann
2016-12-16 10:56 ` [PATCH 05/13] clk: pxa: fix gcc-4.4 build Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2016-12-16 10:56 ` [PATCH 06/13] ARM: atomic: " Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2016-12-16 10:56 ` [PATCH 07/13] watchdog: kempld: fix gcc-4.3 build Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2016-12-16 10:56 ` [PATCH 08/13] arm/arm64: xen: avoid gcc-4.4 warning Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2016-12-16 10:56 ` [PATCH 09/13] ARM: mark cmpxchg and xchg __always_inline for gcc-4.3 Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2016-12-16 10:56 ` [PATCH 10/13] asm-generic: mark cmpxchg as " Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2016-12-16 10:56 ` [PATCH 11/13] fs: fix unsigned enum warning with gcc-4.2 Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2017-01-03 22:47 ` Brendan Gregg
2017-02-28 21:53 ` Brendan Gregg
2016-12-16 10:56 ` [PATCH 12/13] KVM: arm: avoid binary number literals for gcc-4.2 Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2017-01-04 10:39 ` Christoffer Dall
2017-01-04 10:39 ` Christoffer Dall
2016-12-16 10:56 ` [PATCH 13/13] ARM: avoid 'Q' asm constraint for gcc-4.1 and earlier Arnd Bergmann
2016-12-16 10:56 ` Arnd Bergmann
2016-12-16 11:14 ` [RFC] minimum gcc version for kernel: raise to gcc-4.3 or 4.6? Arnd Bergmann
2016-12-16 11:14 ` Arnd Bergmann
2017-04-16 19:52 ` Kees Cook
2017-04-20 10:15 ` Arnd Bergmann
2017-04-20 19:52 ` Kees Cook
2017-04-20 19:52 ` Kees Cook
2017-04-21 20:55 ` Arnd Bergmann
2017-04-21 20:55 ` Arnd Bergmann
2017-04-21 21:05 ` Kees Cook
2017-04-21 21:05 ` Kees Cook
2017-04-22 3:10 ` Maciej W. Rozycki
2017-04-22 3:10 ` Maciej W. Rozycki
2017-04-22 15:30 ` Arnd Bergmann
2017-04-22 15:30 ` Arnd Bergmann
2017-04-23 20:13 ` Geert Uytterhoeven
2017-04-23 20:13 ` Geert Uytterhoeven
2017-04-24 9:44 ` Arnd Bergmann
2017-04-24 9:44 ` Arnd Bergmann
2017-04-24 10:17 ` Geert Uytterhoeven [this message]
2017-04-24 10:17 ` Geert Uytterhoeven
2017-04-24 14:13 ` Arnd Bergmann
2017-04-24 16:53 ` Maciej W. Rozycki
2017-04-24 17:29 ` Arnd Bergmann
2017-04-24 18:16 ` Geert Uytterhoeven
2017-04-24 18:16 ` Geert Uytterhoeven
2017-04-24 18:30 ` Maciej W. Rozycki
2017-04-24 18:30 ` Maciej W. Rozycki
2017-04-24 20:30 ` Arnd Bergmann
2017-04-24 20:52 ` Kees Cook
2017-04-25 7:06 ` Geert Uytterhoeven
2017-04-25 7:06 ` Geert Uytterhoeven
2017-04-25 9:22 ` Suzuki K Poulose
2017-04-25 9:22 ` Suzuki K Poulose
2016-12-16 15:54 ` Geert Uytterhoeven
2016-12-16 15:54 ` Geert Uytterhoeven
2016-12-16 19:58 ` Arnd Bergmann
2016-12-16 19:58 ` Arnd Bergmann
2016-12-16 20:34 ` Geert Uytterhoeven
2016-12-16 20:34 ` Geert Uytterhoeven
2016-12-16 17:00 ` Sebastian Andrzej Siewior
2016-12-16 22:00 ` Arnd Bergmann
2016-12-16 22:00 ` Arnd Bergmann
2016-12-17 11:29 ` Sebastian Andrzej Siewior
2016-12-17 11:29 ` Sebastian Andrzej Siewior
2017-01-02 12:23 ` Russell King - ARM Linux
2017-01-02 12:23 ` Russell King - ARM Linux
2016-12-20 9:59 ` Heiko Carstens
2016-12-20 9:59 ` Heiko Carstens
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