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

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Message-ID: <CANiq72kHwAeQ+vhFqg9tiQA-QHEK_xvP_Sro-_c5LJ2XDzjzxQ@mail.gmail.com>
Date:   Tue, 4 May 2021 14:09:24 +0200
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     Michal Suchánek <msuchanek@...e.de>
Cc:     Ben Dooks <ben.dooks@...ethink.co.uk>,
        Albert Ou <aou@...s.berkeley.edu>,
        Arnd Bergmann <arnd@...db.de>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Miguel Ojeda <ojeda@...nel.org>, Will Deacon <will@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Joe Perches <joe@...ches.com>,
        Paul Mackerras <paulus@...ba.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] Raise the minimum GCC version to 5.2

On Tue, May 4, 2021 at 11:22 AM Michal Suchánek <msuchanek@...e.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.

> Sure, throwing out old compiler versions that are known to cause
> problems makes sense. Updating to latest just because much less so.

I definitely did not argue for "latest compiler" or "updating just because".

> One of the selling point of C in general and gcc in particular is
> stability. If we need the latest compiler we can as well rewrite the
> kernel in Rust which has a required update cycle of a few months.

Rust does not have a "required update cycle" and it does not break old
code unless really required, just like C and common compilers.

Concerning GCC, they patch releases for ~2.5 years, sure, but for many
projects that is not nearly enough. So you still need custom support,
which is anyway what most people care about.

> Because some mainline kernel features rely on bleeding edge tools I end
> up building mainline with current tools anyway but if you do not need
> BTF or whatever other latest gimmick older toolchains should do.

It would be better to hear concrete arguments about why "older
toolchains should do", rather than calling things a gimmick.

Cheers,
Miguel