[PATCH v3] rust: Implement Display for Box

[PATCH v3] rust: Implement Display for Box

[Guangbo Cui]

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)
+    }
+}
+
 impl<T, A> fmt::Debug for Box<T, A>
 where
     T: ?Sized + fmt::Debug,
-- 
2.34.1

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

[Danilo Krummrich]

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
> 

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

[Guangbo Cui]

On Sun, Nov 03, 2024 at 09:46:40PM +0100, Danilo Krummrich wrote:
> 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].

Thanks dakr, I forgot it last week. Fix it in v4.

> 
> 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
> >