linux-kernel - Re: [PATCH 2/3] kbuild: rust: apply `CONFIG

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Date: Wed, 22 May 2024 19:13:41 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Wedson Almeida Filho <wedsonaf@...il.com>, 
	Alex Gaynor <alex.gaynor@...il.com>, Nathan Chancellor <nathan@...nel.org>, 
	Nicolas Schier <nicolas@...sle.eu>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...sung.com>, 
	Alice Ryhl <aliceryhl@...gle.com>, linux-kbuild@...r.kernel.org, 
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
	patches@...ts.linux.dev
Subject: Re: [PATCH 2/3] kbuild: rust: apply `CONFIG_WERROR` to all Rust targets

On Tue, May 21, 2024 at 5:05 PM Miguel Ojeda
<miguel.ojeda.sandonis@...il.com> wrote:
>
> On Tue, May 21, 2024 at 6:15 AM Masahiro Yamada <masahiroy@...nelorg> wrote:
> >
> > Rust started to do something different from C.
> >
> > KBUILD_HOSTCFLAGS is not affected by any CONFIG option.
> >
> > The reason is because HOSTCC is needed for building Kconfig.
> > If the flags for HOSTCC is changed by a CONFIG option,
> > it would be a chicken-egg problem.
> > Also, some host programs might be compiled even
> > without .config at all. (e.g. scripts/unifdef)
> >
> > I know Rust will not become a part of the core infrastructure
> > of the build system, but IMHO, host programs should not be
> > affected by any CONFIG option.
> >
> > I do not like this patch.
>
> Thanks Masahiro -- yeah, I can see how it makes sense for C host
> programs, and consistency with those may be best, even if it is not
> used for core infrastructure in the case of Rust.
>
> Do you think it would be OK if we do it only for everything else, i.e.
> no host programs?


What does "everything else" mean exactly?


I just noticed that $(rust_common_flags) is passed
not only to RUSTC but also to RUSTDOC.


It seems to be intentional because it explicitly says
"requires kernel .config".


@echo  '  rustdoc   - Generate Rust documentation'
@echo  '     (requires kernel .config)'


This is different from how other "make htmldocs" etc. work.

Why is the .config required for generating documentation?









> That covers most of the Rust things so far and would
> have helped with the warning I linked above (which is why I would like
> to change this -- one can pass the flag manually, of course, but
> having more targets affected by `CONFIG_WERROR` means more developers
> will have it enabled and thus notice earlier).
>
> (I am also thinking whether it could make sense to eventually
> explicitly mark the C host programs that would be exempt from
> `CONFIG_WERROR` so that we could apply it to everything else -- I
> guess it could be easy to get wrong and/or forget when new ones are
> added.)
>
> Cheers,
> Miguel



-- 
Best Regards
Masahiro Yamada