diff options
| -rw-r--r-- | rust/kernel/alloc/kbox.rs | 40 |
1 files changed, 39 insertions, 1 deletions
diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs index b77d32f3a58b..e043bf2f4687 100644 --- a/rust/kernel/alloc/kbox.rs +++ b/rust/kernel/alloc/kbox.rs @@ -57,12 +57,50 @@ use pin_init::{InPlaceWrite, Init, PinInit, ZeroableOption}; /// assert!(KVBox::<Huge>::new_uninit(GFP_KERNEL).is_ok()); /// ``` /// +/// [`Box`]es can also be used to store trait objects by coercing their type: +/// +/// ``` +/// trait FooTrait {} +/// +/// struct FooStruct; +/// impl FooTrait for FooStruct {} +/// +/// let _ = KBox::new(FooStruct, GFP_KERNEL)? as KBox<dyn FooTrait>; +/// # Ok::<(), Error>(()) +/// ``` +/// /// # Invariants /// /// `self.0` is always properly aligned and either points to memory allocated with `A` or, for /// zero-sized types, is a dangling, well aligned pointer. #[repr(transparent)] -pub struct Box<T: ?Sized, A: Allocator>(NonNull<T>, PhantomData<A>); +#[cfg_attr(CONFIG_RUSTC_HAS_COERCE_POINTEE, derive(core::marker::CoercePointee))] +pub struct Box<#[cfg_attr(CONFIG_RUSTC_HAS_COERCE_POINTEE, pointee)] T: ?Sized, A: Allocator>( + NonNull<T>, + PhantomData<A>, +); + +// This is to allow coercion from `Box<T, A>` to `Box<U, A>` if `T` can be converted to the +// dynamically-sized type (DST) `U`. +#[cfg(not(CONFIG_RUSTC_HAS_COERCE_POINTEE))] +impl<T, U, A> core::ops::CoerceUnsized<Box<U, A>> for Box<T, A> +where + T: ?Sized + core::marker::Unsize<U>, + U: ?Sized, + A: Allocator, +{ +} + +// This is to allow `Box<U, A>` to be dispatched on when `Box<T, A>` can be coerced into `Box<U, +// A>`. +#[cfg(not(CONFIG_RUSTC_HAS_COERCE_POINTEE))] +impl<T, U, A> core::ops::DispatchFromDyn<Box<U, A>> for Box<T, A> +where + T: ?Sized + core::marker::Unsize<U>, + U: ?Sized, + A: Allocator, +{ +} /// Type alias for [`Box`] with a [`Kmalloc`] allocator. /// |