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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Tue, 7 Dec 2021 15:21:29 -0800
Message-ID: <CAKwvOdk9VNenJJN5HnPpGgsHT+OsRsgPGSesQgqMP2aLPWy0NQ@mail.gmail.com>
Subject: Re: [PATCH 15/19] Kbuild: add Rust support
To:     Miguel Ojeda <ojeda@kernel.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        linux-kbuild@vger.kernel.org
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, Alex Gaynor <alex.gaynor@gmail.com>,
        Finn Behrens <me@kloenk.de>,
        Adam Bratschi-Kaye <ark.email@gmail.com>,
        Wedson Almeida Filho <wedsonaf@google.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Sven Van Asbroeck <thesven73@gmail.com>,
        Gary Guo <gary@garyguo.net>,
        Boris-Chengbiao Zhou <bobo1239@web.de>,
        Boqun Feng <boqun.feng@gmail.com>,
        Douglas Su <d0u9.su@outlook.com>,
        Dariusz Sosnowski <dsosnowski@dsosnowski.pl>,
        Antonio Terceiro <antonio.terceiro@linaro.org>,
        Daniel Xu <dxu@dxuuu.xyz>
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On Tue, Dec 7, 2021 at 2:45 PM Nick Desaulniers <ndesaulniers@google.com> wrote:
>
> On Mon, Dec 6, 2021 at 6:07 AM Miguel Ojeda <ojeda@kernel.org> wrote:
> >
>
> ... snip ...
>
> Miguel and team,
> I'm happy to see progress here! Just some quick notes after a first pass.
>
> Testing this series applied on mainline, I see:
> $ make LLVM=1 -j72 defconfig
> $ grep RUST .config
> CONFIG_HAS_RUST=y
> CONFIG_RUSTC_VERSION=14000
> # CONFIG_RUST is not set
> ...
> $ make LLVM=1 -j72 menuconfig
> # enable CONFIG_RUST
> $ make LLVM=1
> ...
>   CALL    scripts/checksyscalls.sh
> error: @path is unstable - use -Z unstable-options to enable its use
>
> error: @path is unstable - use -Z unstable-options to enable its use
> $ rustc --version
> rustc 1.40.0 (73528e339 2019-12-16)
>
> Can we update some Kconfig checks to fix that?

After now reading though the Documentation/ patch:

$ rustup update
$ rustc --version
rustc 1.57.0 (f1edd0429 2021-11-29)
$ make LLVM=1 -j72
...
make[1]: *** No rule to make target
'/usr/local/google/home/ndesaulniers/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/lib.rs',
needed by 'rust/core.o'.  Stop.

Maybe I'm holding it wrong, let me reread the Documentation/ again.

I still think CONFIG_RUST shouldn't be selectable unless
CONFIG_RUSTC_VERSION is either a blessed version, or above some
minimal value (like we do for CONFIG_GCC_VERSION, CONFIG_LD_VERSION,
CONFIG_CLANG_VERSION, LLD_VERSION, etc).

Also, it looks like I don't have bindgen installed. Anything we can do
there to help the developer out, as in informing them that it's
necessary perhaps via a Kconfig check? I don't think I should be able
to select CONFIG_RUST if I don't have bindgen installed. (Same comment
about version check probably applies, too).  Installing bindgen
doesn't change the error I'm observing above though.
-- 
Thanks,
~Nick Desaulniers