linux-kernel - Re: [PATCH 1/4] rust: fix signature of rust_fmt

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Message-ID: <87v7suo5ay.fsf@kernel.org>
Date: Fri, 28 Feb 2025 09:13:25 +0100
From: Andreas Hindborg <a.hindborg@...nel.org>
To: "Alice Ryhl" <aliceryhl@...gle.com>
Cc: "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,  "Miguel Ojeda"
 <ojeda@...nel.org>,  "Petr Mladek" <pmladek@...e.com>,  "Steven Rostedt"
 <rostedt@...dmis.org>,  "Andy Shevchenko"
 <andriy.shevchenko@...ux.intel.com>,  "Rasmus Villemoes"
 <linux@...musvillemoes.dk>,  "Sergey Senozhatsky"
 <senozhatsky@...omium.org>,  "Andrew Morton" <akpm@...ux-foundation.org>,
  "Boqun Feng" <boqun.feng@...il.com>,  "Gary Guo" <gary@...yguo.net>,
  Björn Roy Baron <bjorn3_gh@...tonmail.com>,  "Benno
 Lossin"
 <benno.lossin@...ton.me>,  "Trevor Gross" <tmgross@...ch.edu>,  "Maarten
 Lankhorst" <maarten.lankhorst@...ux.intel.com>,  "Maxime Ripard"
 <mripard@...nel.org>,  "Thomas Zimmermann" <tzimmermann@...e.de>,  "David
 Airlie" <airlied@...il.com>,  "Simona Vetter" <simona@...ll.ch>,
  <linux-kernel@...r.kernel.org>,  <rust-for-linux@...r.kernel.org>,
  <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH 1/4] rust: fix signature of rust_fmt_argument

"Alice Ryhl" <aliceryhl@...gle.com> writes:

> Without this change, the rest of this series will emit the following
> error message:
>
> error[E0308]: `if` and `else` have incompatible types
>   --> <linux>/rust/kernel/print.rs:22:22
>    |
> 21 | #[export]
>    | --------- expected because of this
> 22 | unsafe extern "C" fn rust_fmt_argument(
>    |                      ^^^^^^^^^^^^^^^^^ expected `u8`, found `i8`
>    |
>    = note: expected fn item `unsafe extern "C" fn(*mut u8, *mut u8, *mut c_void) -> *mut u8 {bindings::rust_fmt_argument}`
>               found fn item `unsafe extern "C" fn(*mut i8, *mut i8, *const c_void) -> *mut i8 {print::rust_fmt_argument}`
>
> The error may be different depending on the architecture.
>
> Fixes: 787983da7718 ("vsprintf: add new `%pA` format specifier")
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
> ---
>  lib/vsprintf.c       | 2 +-
>  rust/kernel/print.rs | 8 ++++----
>  2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 56fe96319292..a8ac4c4fffcf 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -2285,7 +2285,7 @@ int __init no_hash_pointers_enable(char *str)
>  early_param("no_hash_pointers", no_hash_pointers_enable);
>
>  /* Used for Rust formatting ('%pA'). */
> -char *rust_fmt_argument(char *buf, char *end, void *ptr);
> +char *rust_fmt_argument(char *buf, char *end, const void *ptr);
>
>  /*
>   * Show a '%p' thing.  A kernel extension is that the '%p' is followed
> diff --git a/rust/kernel/print.rs b/rust/kernel/print.rs
> index b19ee490be58..8551631dedf1 100644
> --- a/rust/kernel/print.rs
> +++ b/rust/kernel/print.rs
> @@ -6,13 +6,13 @@
>  //!
>  //! Reference: <https://docs.kernel.org/core-api/printk-basics.html>
>
> -use core::{
> +use core::fmt;
> +
> +use crate::{
>      ffi::{c_char, c_void},
> -    fmt,
> +    str::RawFormatter,
>  };
>
> -use crate::str::RawFormatter;
> -
>  // Called from `vsprintf` with format specifier `%pA`.
>  #[expect(clippy::missing_safety_doc)]
>  #[no_mangle]

The changes in this last hunk is not mentioned in the commit message.


Best regards,
Andreas Hindborg