Re: [PATCH v5 2/4] rust: generate a fatal error if BINDGEN_TARGET is undefined

From: Vivian Wang <wangruikang@iscas.ac.cn>
To: "Mingcong Bai" <jeffbai@aosc.io>,
	"Asuna Yang" <spriteovo@gmail.com>,
	"Nathan Chancellor" <nathan@kernel.org>,
	"Nicolas Schier" <nsc@kernel.org>,
	"Miguel Ojeda" <ojeda@kernel.org>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <lossin@kernel.org>,
	"Andreas Hindborg" <a.hindborg@kernel.org>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"Trevor Gross" <tmgross@umich.edu>,
	"Danilo Krummrich" <dakr@kernel.org>,
	"Nick Desaulniers" <nick.desaulniers+lkml@gmail.com>,
	"Bill Wendling" <morbo@google.com>,
	"Justin Stitt" <justinstitt@google.com>,
	"Paul Walmsley" <pjw@kernel.org>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	"Alexandre Ghiti" <alex@ghiti.fr>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Jason Montleon" <jmontleo@redhat.com>,
	"Han Gao" <rabenda.cn@gmail.com>,
	"Conor Dooley" <conor@kernel.org>,
	"Kexy Biscuit" <kexybiscuit@aosc.io>,
	"Xi Ruoyao" <xry111@xry111.site>
Cc: linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	rust-for-linux@vger.kernel.org, llvm@lists.linux.dev,
	linux-riscv@lists.infradead.org, linux-doc@vger.kernel.org
Subject: Re: [PATCH v5 2/4] rust: generate a fatal error if BINDGEN_TARGET is undefined
Date: Tue, 23 Dec 2025 20:46:51 +0800	[thread overview]
Message-ID: <30975f96-db5f-4072-a371-4ac252139e4e@iscas.ac.cn> (raw)
In-Reply-To: <6bd26802-e3ce-43e2-b28d-f23e13492458@aosc.io>

On 12/23/25 20:09, Mingcong Bai wrote:
> Hi Asuna,
>
> 在 2025/12/4 15:54, Asuna Yang 写道:
>> From: Asuna Yang <spriteovo@gmail.com>
>>
>> Generate a friendly fatal error if the target triplet is undefined for
>> bindgen, rather than having the compiler generate obscure error messages
>> during the build stage.
>>
>> This piece of code is copied from `scripts/Makefile.clang`.
>>
>> Before this commit, error messages might look like:
>>
>> error: unknown argument: '-mno-riscv-attribute'
>> error: unsupported argument 'medany' to option '-mcmodel=' for target
>> 'unknown'
>> error: unsupported option '-march=' for target ''
>> error: unsupported option '-mno-save-restore' for target ''
>> error: unknown target triple 'unknown'
>> panicked at bindgen/ir/context.rs:562:15:
>> libclang error; possible causes include:
>> - Invalid flag syntax
>> - Unrecognized flags
>> - Invalid flag arguments
>> - File I/O errors
>> - Host vs. target architecture mismatch
>>
>> Acked-by: Miguel Ojeda <ojeda@kernel.org>
>> Signed-off-by: Asuna Yang <SpriteOvO@gmail.com>
>
> Unfortunately, this broke build for MIPS and PowerPC, neither of which
> has support for Rust. I also feel as though it might be pointless to
> ask all architecture to define BINDGEN_TARGET, especially when such a
> target specification may not even exist upstream (in Rust or even in
> LLVM).
>
> As shown in the first patch, the original Makefile did not require
> this definition either (please do enlighten me). 

Looks like the rust/ subdir is conditional on CONFIG_RUST, so the
original rust/Makefile didn't have this problem.

Fixing this should be as simple as moving the check into rust/Makefile
instead.

Vivian "dramforever" Wang

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