Re: [PATCH 2/2] rust: workqueue: remove HasWork::OFFSET

[Benno Lossin]

On Sat Mar 15, 2025 at 4:37 PM CET, Tamir Duberstein wrote:
> On Sat, Mar 15, 2025 at 5:30 AM Benno Lossin <benno.lossin@xxxxxxxxx> wrote:
>>
>> On Fri Mar 14, 2025 at 9:44 PM CET, Tamir Duberstein wrote:
>> > On Fri, Mar 14, 2025 at 3:20 PM Benno Lossin <benno.lossin@xxxxxxxxx> wrote:
>> >>
>> >> On Fri Mar 7, 2025 at 10:58 PM CET, Tamir Duberstein wrote:
>> >> >      /// Returns a pointer to the struct containing the [`Work<T, ID>`] field.
>> >> >      ///
>> >> >      /// # Safety
>> >> >      ///
>> >> >      /// The pointer must point at a [`Work<T, ID>`] field in a struct of type `Self`.
>> >> > -    #[inline]
>> >> > -    unsafe fn work_container_of(ptr: *mut Work<T, ID>) -> *mut Self
>> >> > -    where
>> >> > -        Self: Sized,
>> >>
>> >> This bound is required in order to allow the usage of `dyn HasWork` (ie
>> >> object safety), so it should stay.
>> >>
>> >> Maybe add a comment explaining why it's there.
>> >
>> > I guess a doctest would be better, but I still don't understand why
>> > the bound is needed. Sorry, can you cite something or explain in more
>> > detail please?
>>
>> Here is a link: https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility
>>
>> But I realized that the trait wasn't object safe to begin with due to
>> the `OFFSET` associated constant. So I'm not sure we need this. Alice,
>> do you need `dyn HasWork`?
>
> I wrote a simple test:

[...]

> so I don't think adding the Sized bound makes sense - we'd end up
> adding it on every item in the trait.

Yeah the `Sized` bound was probably to make the cast work, so let's
remove it.

---
Cheers,
Benno