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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 12 Jan 2021 18:35:50 -0800
Message-ID: <CAHk-=wh-+TMHPTFo1qs-MYyK7tZh-OQovA=pP3=e06aCVp6_kA@mail.gmail.com>
Subject: Re: [PATCH] compiler.h: Raise minimum version of GCC to 5.1 for arm64
To:     Will Deacon <will@kernel.org>,
        Masahiro Yamada <masahiroy@kernel.org>
Cc:     Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Android Kernel Team <kernel-team@android.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Theodore Ts'o" <tytso@mit.edu>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Florian Weimer <fweimer@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Russell King <linux@armlinux.org.uk>,
        Arnd Bergmann <arnd@kernel.org>
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On Tue, Jan 12, 2021 at 6:14 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> Ack. I'll assume I get this the usual ways from the arm64 tree..

Oh.. Actually, while you can use my ack if you decide to go this way,
I do wonder if it might not be better to introduce a notion of an
error at Kconfig time, and then we could make this whole GCC_VERSION
check be something that gets covered much earlier - when configuring
the kernel, rather than randomly (ok, very early) when building it.

We already have the CONFIG_GCC_VERSION config variable, after all.

And Kconfig already has an error functionality, which it uses for
things like compilers not found etc.

So something like

     $(error-if,CC_IS_GCC && GCC_VERSION < 90100,"Gcc version too old")

in the arm64 Kconfig file should do it.

Adding Masahiro, because I couldn't actually get it to work. I'm
probably doing something wrong, but it might also be that it cannot
depend on config variables currently (our only use is for running
shell script tests unconditionally).

           Linus