2023-07-14 09:54:49

by Asahi Lina

Subject: [PATCH] rust: init: Implement Zeroable::zeroed()

By analogy to Default::default(), this just returns the zeroed
representation of the type directly. init::zeroed() is the version that
returns an initializer.

Signed-off-by: Asahi Lina <[email protected]>
---
rust/kernel/init.rs | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
index b4332a4ec1f4..c300ce39ac10 100644
--- a/rust/kernel/init.rs
+++ b/rust/kernel/init.rs
@@ -1354,7 +1354,14 @@ pub unsafe trait PinnedDrop: __internal::HasPinData {
/// ```rust,ignore
/// let val: Self = unsafe { core::mem::zeroed() };
/// ```
-pub unsafe trait Zeroable {}
+pub unsafe trait Zeroable: core::marker::Sized {
+ /// Create a new zeroed T.
+ ///
+ /// Directly returns a zeroed T, analogous to Default::default().
+ fn zeroed() -> Self {
+ unsafe { core::mem::zeroed() }
+ }
+}

/// Create a new zeroed T.
///

---
base-commit: 06c2afb862f9da8dc5efa4b6076a0e48c3fbaaa5
change-id: 20230714-zeroed-dd05bc737f85

Thank you,
~~ Lina

2023-07-14 10:47:02

by Alice Ryhl

Subject: Re: [PATCH] rust: init: Implement Zeroable::zeroed()

Asahi Lina <[email protected]> writes:
> +pub unsafe trait Zeroable: core::marker::Sized {
> + /// Create a new zeroed T.
> + ///
> + /// Directly returns a zeroed T, analogous to Default::default().
> + fn zeroed() -> Self {
> + unsafe { core::mem::zeroed() }
> + }
> +}

I don't think this trait needs to require `Sized`. How about the
following alternate implementation?

pub unsafe trait Zeroable {
/// Create a new zeroed T.
///
/// Directly returns a zeroed T, analogous to Default::default().
fn zeroed() -> Self
where
Self: core::marker::Sized,
{
unsafe { core::mem::zeroed() }
}
}

Then types like [T] can also implement Zeroable when T does.

If you make the above change, then you may add my
Reviewed-by: Alice Ryhl <[email protected]>

Alice

2023-07-15 10:42:21

by Benno Lossin

Subject: Re: [PATCH] rust: init: Implement Zeroable::zeroed()

> By analogy to Default::default(), this just returns the zeroed
> representation of the type directly. init::zeroed() is the version that
> returns an initializer.
>
> Signed-off-by: Asahi Lina <[email protected]>
> ---
> rust/kernel/init.rs | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
> index b4332a4ec1f4..c300ce39ac10 100644
> --- a/rust/kernel/init.rs
> +++ b/rust/kernel/init.rs
> @@ -1354,7 +1354,14 @@ pub unsafe trait PinnedDrop: __internal::HasPinData {
> /// ```rust,ignore
> /// let val: Self = unsafe { core::mem::zeroed() };
> /// ```
> -pub unsafe trait Zeroable {}
> +pub unsafe trait Zeroable: core::marker::Sized {

Note that `Sized` is in the prelude so you do not need the full path
`core::marker::`. Also same concern as Alice.

> + /// Create a new zeroed T.
> + ///
> + /// Directly returns a zeroed T, analogous to Default::default().

Please add a link to `init::zeroed()` and explain that that is the
initializer version of this function.

> + fn zeroed() -> Self {
> + unsafe { core::mem::zeroed() }

Missing `SAFETY` comment.

--
Cheers,
Benno

> + }
> +}
>
> /// Create a new zeroed T.
> ///
>
> ---
> base-commit: 06c2afb862f9da8dc5efa4b6076a0e48c3fbaaa5
> change-id: 20230714-zeroed-dd05bc737f85
>
> Thank you,
> ~~ Lina
>