linux-kernel - Re: [PATCH] compiler.h: Raise minimum version of GCC to 5.1 for arm64

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Date:   Fri, 15 Jan 2021 15:24:07 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Ard Biesheuvel <ardb@...nel.org>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Florian Weimer <fweimer@...hat.com>,
        Arnd Bergmann <arnd@...nel.org>,
        "Cc: Android Kernel" <kernel-team@...roid.com>,
        "Theodore Ts'o" <tytso@....edu>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] compiler.h: Raise minimum version of GCC to 5.1 for arm64

On Thu, Jan 14, 2021 at 4:30 PM Joe Perches <joe@...ches.com> wrote:
>
> KASAN v5 instead of all the old versions
> gcc 7.1 supports fallthrough.

Considering that most people won't even enable KASAN, I think that's
not a huge reason to then force people to potentially upgrade their
compilers.

That said, I do think that it might be good to just try to standardize
on the KASAN v5 code - but that could easily be done by simply making
KASAN depend as a feature on having a newer compiler version.

So the KASAN option itself could just have something like

       depends on !CC_IS_GCC || GCC_VERSION >= 70000

in it, which would allow us to just say "only v5 need apply".

As to "fallthrough", I think it's more than enough that lots of people
build with compilers that support it, and then any warnings they see
will be fixed. No need to force upgrades - it doesn't buy kernel
developers anything.

          Linus