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Message-ID: <20230802192605.5ddb32bb.gary@garyguo.net>
Date: Wed, 2 Aug 2023 19:26:05 +0100
From: Gary Guo <gary@...yguo.net>
To: Miguel Ojeda <ojeda@...nel.org>
Cc: Wedson Almeida Filho <wedsonaf@...il.com>,
Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Benno Lossin <benno.lossin@...ton.me>,
Alice Ryhl <aliceryhl@...gle.com>,
Andreas Hindborg <a.hindborg@...sung.com>,
rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
patches@...ts.linux.dev
Subject: Re: [PATCH 2/2] rust: enable `no_mangle_with_rust_abi` Clippy lint
On Sun, 30 Jul 2023 00:03:17 +0200
Miguel Ojeda <ojeda@...nel.org> wrote:
> Introduced in Rust 1.69.0 [1], this lint prevents forgetting to set
> the C ABI when using `#[no_mangle]` (or thinking it is implied).
>
> For instance, it would have prevented the issue [2] fixed by commit
> c682e4c37d2b ("rust: kernel: Mark rust_fmt_argument as extern "C"").
>
> error: `#[no_mangle]` set on a function with the default (`Rust`) ABI
> --> rust/kernel/print.rs:21:1
> |
> 21 | / unsafe fn rust_fmt_argument(
> 22 | | buf: *mut c_char,
> 23 | | end: *mut c_char,
> 24 | | ptr: *const c_void,
> 25 | | ) -> *mut c_char {
> | |________________^
> |
> = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#no_mangle_with_rust_abi
> = note: requested on the command line with `-D clippy::no-mangle-with-rust-abi`
> help: set an ABI
> |
> 21 | unsafe extern "C" fn rust_fmt_argument(
> | ++++++++++
> help: or explicitly set the default
> |
> 21 | unsafe extern "Rust" fn rust_fmt_argument(
> | +++++++++++++
>
> Thus enable it.
>
> In rare cases, we may need to use the Rust ABI even with `#[no_mangle]`
> (e.g. one case, before 1.71.0, would have been the `__rust_*`
> functions). In those cases, we would need to `#[allow(...)]` the lint,
> since using `extern "Rust"` explicitly (as the compiler suggests)
> currently gets overwritten by `rustfmt` [3].
>
> Link: https://github.com/rust-lang/rust-clippy/issues/10347 [1]
> Link: https://github.com/Rust-for-Linux/linux/pull/967 [2]
> Link: https://github.com/rust-lang/rustfmt/issues/5701 [3]
> Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
Reviewed-by: Gary Guo <gary@...yguo.net>
> ---
> Makefile | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/Makefile b/Makefile
> index 658ec2b8aa74..93bf3eca3ead 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -467,6 +467,7 @@ export rust_common_flags := --edition=2021 \
> -Dclippy::let_unit_value -Dclippy::mut_mut \
> -Dclippy::needless_bitwise_bool \
> -Dclippy::needless_continue \
> + -Dclippy::no_mangle_with_rust_abi \
> -Wclippy::dbg_macro
>
> KBUILD_HOSTCFLAGS := $(KBUILD_USERHOSTCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS)
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