Commit d67b3701 authored by Benno Lossin's avatar Benno Lossin
Browse files

rust: pin-init: add `zeroed()` & `Zeroable::zeroed()` functions 

`zeroed()` returns a zeroed out value of a sized type implementing
`Zeroable`.

The function is added as a free standing function, in addition to an
associated function on `Zeroable`, because then it can be marked `const`
(functions in traits can't be const at the moment).

Link: https://github.com/Rust-for-Linux/pin-init/pull/56/commits/809e4ec160579c1601dce5d78b432a5b6c8e4e40
Link: https://lore.kernel.org/all/20250523145125.523275-4-lossin@kernel.org


Signed-off-by: default avatarBenno Lossin <lossin@kernel.org>
parent c47024ba

rust/pin-init/src/lib.rs

+52 −0
Original line number Diff line number Diff line
@@ -1506,6 +1506,33 @@ fn init_zeroed() -> impl Init<Self> 
    {

        init_zeroed()

    }



    /// Create a `Self` consisting of all zeroes.

    ///

    /// Whenever a type implements [`Zeroable`], this function should be preferred over

    /// [`core::mem::zeroed()`] or using `MaybeUninit<T>::zeroed().assume_init()`.

    ///

    /// # Examples

    ///

    /// ```

    /// use pin_init::{Zeroable, zeroed};

    ///

    /// #[derive(Zeroable)]

    /// struct Point {

    ///     x: u32,

    ///     y: u32,

    /// }

    ///

    /// let point: Point = zeroed();

    /// assert_eq!(point.x, 0);

    /// assert_eq!(point.y, 0);

    /// ```

    fn zeroed() -> Self

    where

        Self: Sized,

    {

        zeroed()

    }

}



/// Marker trait for types that allow `Option<Self>` to be set to all zeroes in order to write
@@ -1534,6 +1561,31 @@ pub fn init_zeroed<T: Zeroable>() -> impl Init<T> { 
    }

}



/// Create a `T` consisting of all zeroes.

///

/// Whenever a type implements [`Zeroable`], this function should be preferred over

/// [`core::mem::zeroed()`] or using `MaybeUninit<T>::zeroed().assume_init()`.

///

/// # Examples

///

/// ```

/// use pin_init::{Zeroable, zeroed};

///

/// #[derive(Zeroable)]

/// struct Point {

///     x: u32,

///     y: u32,

/// }

///

/// let point: Point = zeroed();

/// assert_eq!(point.x, 0);

/// assert_eq!(point.y, 0);

/// ```

pub const fn zeroed<T: Zeroable>() -> T {

    // SAFETY:By the type invariants of `Zeroable`, all zeroes is a valid bit pattern for `T`.

    unsafe { core::mem::zeroed() }

}



macro_rules! impl_zeroable {

    ($($({$($generics:tt)*})? $t:ty, )*) => {

        // SAFETY: Safety comments written in the macro invocation.