Re: [PATCH] Raise the minimum GCC version to 5.2

From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: "Michal Suchánek" <msuchanek@suse.de>,
	"Miguel Ojeda" <miguel.ojeda.sandonis@gmail.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Joe Perches <joe@perches.com>,
	Ben Dooks <ben.dooks@codethink.co.uk>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Miguel Ojeda <ojeda@kernel.org>,
	Paul Mackerras <paulus@samba.org>,
	linux-riscv <linux-riscv@lists.infradead.org>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	Will Deacon <will@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] Raise the minimum GCC version to 5.2
Date: Tue, 4 May 2021 14:26:18 +0200	[thread overview]
Message-ID: <529aef7c-30b1-f6c5-4610-34bd869e4ad4@csgroup.eu> (raw)
In-Reply-To: <20210504121713.GT6564@kitsune.suse.cz>

Le 04/05/2021 à 14:17, Michal Suchánek a écrit :
> On Tue, May 04, 2021 at 02:09:24PM +0200, Miguel Ojeda wrote:
>> On Tue, May 4, 2021 at 11:22 AM Michal Suchánek <msuchanek@suse.de> wrote:
>>>
>>> Except it makes answering the question "Is this bug we see on this
>>> ancient system still present in upstream?" needlessly more difficult to
>>> answer.
>>
>> Can you please provide some details? If you are talking about testing
>> a new kernel image in the ancient system "as-is", why wouldn't you
>> build it in a newer system? If you are talking about  particular
>> problems about bisecting (kernel, compiler) pairs etc., details would
>> also be welcome.
> 
> Yes, bisecting comes to mind. If you need to switch the userspace as
> well the bisection results are not that solid. You may not be even able
> to bisect because the workload does not exist on a new system at all.
> Crafting a minimal test case that can be forward-ported to a new system
> is not always trivial - if you understood the problem to that extent you
> might not even need to bisect it in the first place.
> 

But you don't need to switch the userspace or the complete build tools to build a kernel with a 
newer toolchain.

All you have to do is take one from https://mirrors.edge.kernel.org/pub/tools/crosstool/

I'm doing everything under CentOS 6, and using one of those tools allows me to build latest kernel 
without breaking anything else.

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