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

[Alice Ryhl]

On Wed, Jul 2, 2025 at 5:07 PM Benno Lossin <lossin@xxxxxxxxxx> wrote:
>
> 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()
>
> Would it make sense for this function to take `self` instead & we make
> the `OnceLock` also `Copy` if `T: Copy`? Maybe not...

Atomics are not Copy.

Alice