Re: [PATCH v14 1/7] rust: sync: add `OnceLock`

["Benno Lossin" <lossin@kernel.org>]

On Thu Jul 3, 2025 at 6:25 PM CEST, Andreas Hindborg wrote:
> "Benno Lossin" <lossin@kernel.org> writes:
>> On Thu Jul 3, 2025 at 11:03 AM CEST, Andreas Hindborg wrote:
>>> "Benno Lossin" <lossin@kernel.org> writes:
>>>> On Wed Jul 2, 2025 at 3:18 PM CEST, Andreas Hindborg wrote:
>>>>> +impl<T: Copy> OnceLock<T> {
>>>>> +    /// Get a copy of the contained object.
>>>>> +    ///
>>>>> +    /// Returns [`None`] if the [`OnceLock`] is empty.
>>>>> +    pub fn copy(&self) -> Option<T> {
>>>>> +        if self.init.load(Acquire) == 2 {
>>>>> +            // SAFETY: As determined by the load above, the object is ready for shared access.
>>>>> +            Some(unsafe { *self.value.get() })
>>>>> +        } else {
>>>>> +            None
>>>>> +        }
>>>>
>>>> The impl can just be:
>>>>
>>>>     self.as_ref().copied()
>>>
>>> Nice. I was thinking of dropping this method and just have callers do
>>>
>>>  my_once_lock.as_ref().map(|v| v.copied())
>>>
>>> What do you think?
>>
>> There is `Option::copied`, so no need for the `.map` call.
>
> Cool.
>
>> I don't
>> really have a preference, if users always want to access it by-value,
>> then we should have `copy`.
>
> But should it be `copy` or `copied` like `Option`?

I'd say `copy`. With `copied` I'm thinking of something that turns
`OnceLock<&T>` into `OnceLock<T>`, which is weird...

---
Cheers,
Benno