diff options
Diffstat (limited to 'rust')
| -rw-r--r-- | rust/kernel/lib.rs | 2 | ||||
| -rw-r--r-- | rust/kernel/sync/arc.rs | 27 |
2 files changed, 28 insertions, 1 deletions
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 1a10f7c0ddd9..4bde65e7b06b 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -13,8 +13,10 @@ #![no_std] #![feature(allocator_api)] +#![feature(coerce_unsized)] #![feature(core_ffi_c)] #![feature(receiver_trait)] +#![feature(unsize)] // Ensure conditional compilation based on the kernel configuration works; // otherwise we may silently break things like initcall handling. diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs index e2eb0e67d483..dbc7596cc3ce 100644 --- a/rust/kernel/sync/arc.rs +++ b/rust/kernel/sync/arc.rs @@ -17,7 +17,11 @@ use crate::{bindings, error::Result, types::Opaque}; use alloc::boxed::Box; -use core::{marker::PhantomData, ops::Deref, ptr::NonNull}; +use core::{ + marker::{PhantomData, Unsize}, + ops::Deref, + ptr::NonNull, +}; /// A reference-counted pointer to an instance of `T`. /// @@ -82,6 +86,23 @@ use core::{marker::PhantomData, ops::Deref, ptr::NonNull}; /// obj.use_reference(); /// obj.take_over(); /// ``` +/// +/// Coercion from `Arc<Example>` to `Arc<dyn MyTrait>`: +/// +/// ``` +/// use kernel::sync::Arc; +/// +/// trait MyTrait {} +/// +/// struct Example; +/// impl MyTrait for Example {} +/// +/// // `obj` has type `Arc<Example>`. +/// let obj: Arc<Example> = Arc::try_new(Example)?; +/// +/// // `coerced` has type `Arc<dyn MyTrait>`. +/// let coerced: Arc<dyn MyTrait> = obj; +/// ``` pub struct Arc<T: ?Sized> { ptr: NonNull<ArcInner<T>>, _p: PhantomData<ArcInner<T>>, @@ -96,6 +117,10 @@ struct ArcInner<T: ?Sized> { // This is to allow [`Arc`] (and variants) to be used as the type of `self`. impl<T: ?Sized> core::ops::Receiver for Arc<T> {} +// This is to allow coercion from `Arc<T>` to `Arc<U>` if `T` can be converted to the +// dynamically-sized type (DST) `U`. +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::CoerceUnsized<Arc<U>> for Arc<T> {} + // SAFETY: It is safe to send `Arc<T>` to another thread when the underlying `T` is `Sync` because // it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs // `T` to be `Send` because any thread that has an `Arc<T>` may ultimately access `T` directly, for |