Re: [PATCH] rust: types: Add `try_from_foreign()` method

[Martin Rodriguez Reboredo <yakoyoku@gmail.com>]

On 1/22/24 13:26, Obei Sideg wrote:
> Currently `ForeignOwnable::from_foreign()` only
> works for non-null pointers for the existing
> impls (e.g. Box, Arc). It may create a few
> duplicate code like:
> 
> ```rust
> // `p` is a maybe null pointer
> if p.is_null() {
>    None
> } else {
>    Some(unsafe { T::from_foreign(p) })
> }
> ``
> 
> Link: Rust-for-Linux/linux#1059
> 
> Cc: Alice Ryhl <aliceryhl@google.com>
> Cc: Matt Gilbride <mattgilbride@google.com>
> Cc: Miguel Ojeda <ojeda@kernel.org>
> Signed-off-by: Obei Sideg <linux@obei.io>
> ---
> [...]
> +    unsafe fn try_from_foreign(ptr: *const core::ffi::c_void) -> Option<Self>;
>   }
>   
>   impl<T: 'static> ForeignOwnable for Box<T> {
> @@ -68,6 +80,14 @@ unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self {
>           // call to `Self::into_foreign`.
>           unsafe { Box::from_raw(ptr as _) }
>       }
> +
> +    unsafe fn try_from_foreign(ptr: *const core::ffi::c_void) -> Option<Self> {
> +        if ptr.is_null() {
> +            None
> +        } else {
> +            Some(Self::from_foreign(ptr))
> +        }
> +    }
> [...]

Shouldn't have `Box::try_from_foreign` been the default implementation
of `ForeignOwnable::try_from_foreign`?