Re: [PATCH v3] rust: Implement Display for Box

[Danilo Krummrich <dakr@kernel.org>]

On Tue, Oct 29, 2024 at 10:28:38PM +0800, Guangbo Cui wrote:
> Currently `impl Display` is missing for `Box<T, A>`, as a result,
> things like using `Box<..>` directly as an operand in `pr_info!()`
> are impossible, which is less ergonomic compared to `Box` in Rust
> std.
> 
> Therefore add `impl Display` for `Box`.
> 
> Suggested-by: Boqun Feng <boqun.feng@gmail.com>
> Link: https://github.com/Rust-for-Linux/linux/issues/1126
> Signed-off-by: Guangbo Cui <2407018371@qq.com>
> ---
> Changes in v3:
> - Update `fmt` implementation to clarify that it does not call itself infinitely.
> - Link to v2: https://lore.kernel.org/rust-for-linux/tencent_F71CE9D125A8C6191D8CF95B3A4F3BB2F506@qq.com
> Changes in v2:
> - Add missing tag: Suggested-by.
> - Update the patch title and the changelogs.
> - Link to v1: https://lore.kernel.org/rust-for-linux/tencent_CA5A5D6268F0D1419BAFA6AFB4EB5A37920A@qq.com
> 
>  rust/kernel/alloc/kbox.rs | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs
> index d69c32496..a496a866d 100644
> --- a/rust/kernel/alloc/kbox.rs
> +++ b/rust/kernel/alloc/kbox.rs
> @@ -427,6 +427,16 @@ fn deref_mut(&mut self) -> &mut T {
>      }
>  }
>  
> +impl<T, A> fmt::Display for Box<T, A>
> +where
> +    T: ?Sized + fmt::Display,
> +    A: Allocator,
> +{
> +    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
> +        <T as fmt::Display>::fmt(&**self, f)

Since you went with this variant,

> +    }
> +}
> +
>  impl<T, A> fmt::Debug for Box<T, A>

please also change it for `Debug` in a separate patch, as requested in [1].

With that,

Acked-by: Danilo Krummrich <dakr@kernel.org>

[1] https://lore.kernel.org/all/a335869c-6bc4-49c1-b6a8-1c4ca4e98b20@kernel.org/

>  where
>      T: ?Sized + fmt::Debug,
> -- 
> 2.34.1
>