Re: [PATCH 1/4] rust: fix signature of rust_fmt_argument

[Andreas Hindborg <a.hindborg@kernel.org>]

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

> On Fri, Feb 28, 2025 at 9:20 AM Andreas Hindborg <a.hindborg@kernel.org> wrote:
>>
>> "Alice Ryhl" <aliceryhl@google.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@google.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.
>
> The diff is rendered pretty poorly, but this is just importing
> integers from crate::ffi instead of core::ffi, and I do believe that
> the commit message makes it clear that this is needed.

I see, thanks for clarifying. Consider including the clarification in
the commit message.


Best regards,
Andreas Hindborg