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

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Date:   Wed, 13 Jan 2021 15:02:32 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Will Deacon <will@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Theodore Ts'o <tytso@....edu>,
        Florian Weimer <fweimer@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Russell King <linux@...linux.org.uk>,
        Arnd Bergmann <arnd@...nel.org>
Subject: Re: [PATCH] compiler.h: Raise minimum version of GCC to 5.1 for arm64

On Tue, Jan 12, 2021 at 06:35:50PM -0800, Linus Torvalds wrote:
> On Tue, Jan 12, 2021 at 6:14 PM Linus Torvalds
> <torvalds@...ux-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.

$(error-if) seems to expect a y/n as a condition. We do have $(failure)
and $(success) but they translate a (shell) command's return code to
y/n. Even with something like:

config GCC_IS_OLD
	def_bool CC_IS_GCC && GCC_VERSION < ...

I can't get $(error-if,GCC_IS_OLD) to expand the config value, no matter
what other. GCC_VERSION is also a config option in your example.

I'll queue Will's patch in the meantime.

-- 
Catalin