Re: [PATCH v3 3/3] rust: alloc: Add doctest for `ArrayLayout`

[Danilo Krummrich <dakr@kernel.org>]

On Tue, Dec 17, 2024 at 04:23:12PM -0800, Jimmy Ostler wrote:
> Add a rustdoc example and Kunit test to the `ArrayLayout` struct's
> `ArrayLayout::new()` function.
> 
> This patch depends on the first patch in this series in order for the
> kunit test to compile.
> 
> Suggested-by: Boqun Feng <boqun.feng@gmail.com>
> Link: https://github.com/Rust-for-Linux/linux/issues/1131
> Signed-off-by: Jimmy Ostler <jtostler1@gmail.com>


Reviewed-by: Danilo Krummrich <dakr@kernel.org>

> ---
>  rust/kernel/alloc/layout.rs | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/rust/kernel/alloc/layout.rs b/rust/kernel/alloc/layout.rs
> index 4b3cd7fdc816..0e053dcc7941 100644
> --- a/rust/kernel/alloc/layout.rs
> +++ b/rust/kernel/alloc/layout.rs
> @@ -43,6 +43,25 @@ pub const fn empty() -> Self {
>      /// # Errors
>      ///
>      /// When `len * size_of::<T>()` overflows or when `len * size_of::<T>() > isize::MAX`.
> +    ///
> +    /// # Examples
> +    ///
> +    /// ```
> +    /// # use kernel::alloc::layout::{ArrayLayout, LayoutError};
> +    /// let layout = ArrayLayout::<i32>::new(15)?;
> +    /// assert_eq!(layout.len(), 15);
> +    ///
> +    /// // Errors because `len * size_of::<T>()` overflows
> +    /// let layout = ArrayLayout::<i32>::new(isize::MAX as usize);
> +    /// assert!(layout.is_err());
> +    ///
> +    /// // Errors because `len * size_of::<i32>() > isize::MAX`,
> +    /// // even though `len < isize::MAX`
> +    /// let layout = ArrayLayout::<i32>::new(isize::MAX as usize / 2);
> +    /// assert!(layout.is_err());
> +    ///
> +    /// # Ok::<(), Error>(())
> +    /// ```
>      pub const fn new(len: usize) -> Result<Self, LayoutError> {
>          match len.checked_mul(core::mem::size_of::<T>()) {
>              Some(size) if size <= ISIZE_MAX => {
> -- 
> 2.47.1
>