linux-kernel - Re: kbuild: check the minimum compiler version in Kconfig

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Date:   Wed, 16 Nov 2022 15:11:57 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Nathan Chancellor <natechancellor@...il.com>, ojeda@...nel.org,
        sedat.dilek@...il.com, clang-built-linux <llvm@...ts.linux.dev>,
        Manoj Gupta <manojgupta@...gle.com>
Subject: Re: kbuild: check the minimum compiler version in Kconfig

On Wed, Nov 16, 2022 at 3:10 PM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> On Wed, Nov 16, 2022 at 2:56 PM Florian Fainelli <f.fainelli@...il.com> wrote:
> >
> > On 11/16/22 14:48, Nick Desaulniers wrote:
> > > On Wed, Nov 16, 2022 at 1:48 PM Florian Fainelli <f.fainelli@...il.com> wrote:
> > >>
> > >> Hi Masahiro, Nick,
> > >>
> > >> The compiler version check performed with
> > >> aec6c60a01d3a3170242d6a99372a388e1136dc6 ("kbuild: check the minimum
> > >> compiler version in Kconfig") can be defeated and prevent running the
> > >> *config targets if specifying LLVM=1 on the command line, in that way:
> > >>
> > >> BR_BINARIES_DIR=/local/users/fainelli/buildroot-llvm/output/arm64/images
> > >> LLVM=1 LLVM_IAS=1 PKG_CONFIG_PATH="" /usr/bin/make -j49 -C
> > >> /local/users/fainelli/buildroot-llvm/output/arm64/build/linux-custom
> > >> HOSTCC="/usr/bin/gcc"
> > >> HOSTCC="/local/users/fainelli/buildroot-llvm/output/arm64/host/bin/ccache
> > >> /usr/bin/gcc -O2
> > >> -I/local/users/fainelli/buildroot-llvm/output/arm64/host/include
> > >> -DNDEBUG -L/local/users/fainelli/buildroot-llvm/output/arm64/host/lib
> > >> -Wl,-rpath,/local/users/fainelli/buildroot-llvm/output/arm64/host/lib"
> > >> ARCH=arm64
> > >> INSTALL_MOD_PATH=/local/users/fainelli/buildroot-llvm/output/arm64/target
> > >> CROSS_COMPILE="/local/users/fainelli/buildroot-llvm/output/arm64/host/bin/aarch64-linux-"
> > >> WERROR=0
> > >> DEPMOD=/local/users/fainelli/buildroot-llvm/output/arm64/host/sbin/depmod
> > >> INSTALL_MOD_STRIP=1 HOSTCC="/usr/bin/gcc" menuconfig
> > >>     UPD     scripts/kconfig/mconf-cfg
> > >>     HOSTCC  scripts/kconfig/mconf.o
> > >>     HOSTCC  scripts/kconfig/lxdialog/checklist.o
> > >>     HOSTCC  scripts/kconfig/lxdialog/inputbox.o
> > >>     HOSTCC  scripts/kconfig/lxdialog/menubox.o
> > >>     HOSTCC  scripts/kconfig/lxdialog/textbox.o
> > >>     HOSTCC  scripts/kconfig/lxdialog/util.o
> > >>     HOSTCC  scripts/kconfig/lxdialog/yesno.o
> > >>     HOSTLD  scripts/kconfig/mconf
> > >> ***
> > >> *** Compiler is too old.
> > >> ***   Your Clang version:    10.0.0
> > >> ***   Minimum Clang version: 10.0.1
> > >> ***
> > >> scripts/Kconfig.include:44: Sorry, this compiler is not supported.
> > >>
> > >> Here, the compiler check is actually checking the host compiler clang
> > >> version installed on my Ubuntu 20.04 system, as opposed to the cross
> > >> compiler clang version that is being used.
> > >
> > > LLVM=1 will use `clang` as found by your $PATH.  Where did you express
> > > to make what the "cross compiler clang version" is? (And why do you
> > > set HOSTCC three times)
> >
> > We are setting CROSS_COMPILE to express the cross compiler clang prefix
> > to use.
>
> Can you try setting CLANG_PREFIX rather than CROSS_COMPILE (to the same value)?
>
> CLANG_PREFIX=/local/users/fainelli/buildroot-llvm/output/arm64/host/bin/aarch64-linux-

sorry, I meant LLVM_PREFIX

>
>
> >
> > Setting HOSTCC three times is done by buildroot, it does it through make
> > flags, and then variables passed to make etc. clearly we could change
> > that, but that's out of scope is not it?
> > --
> > Florian
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers



-- 
Thanks,
~Nick Desaulniers