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

From: Catalin Marinas <catalin.marinas@arm.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Florian Weimer <fweimer@redhat.com>,
	Arnd Bergmann <arnd@kernel.org>, Theodore Ts'o <tytso@mit.edu>,
	Peter Zijlstra <peterz@infradead.org>,
	Will Deacon <will@kernel.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	Android Kernel Team <kernel-team@android.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] compiler.h: Raise minimum version of GCC to 5.1 for arm64
Date: Wed, 13 Jan 2021 15:02:32 +0000	[thread overview]
Message-ID: <20210113150232.GA27045@gaia> (raw)
In-Reply-To: <CAHk-=wh-+TMHPTFo1qs-MYyK7tZh-OQovA=pP3=e06aCVp6_kA@mail.gmail.com>

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@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.

$(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

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