diff options
Diffstat (limited to 'library/std/src/sync/once_lock.rs')
| -rw-r--r-- | library/std/src/sync/once_lock.rs | 55 |
1 files changed, 0 insertions, 55 deletions
diff --git a/library/std/src/sync/once_lock.rs b/library/std/src/sync/once_lock.rs index 813516040..37413ec62 100644 --- a/library/std/src/sync/once_lock.rs +++ b/library/std/src/sync/once_lock.rs @@ -3,7 +3,6 @@ use crate::fmt; use crate::marker::PhantomData; use crate::mem::MaybeUninit; use crate::panic::{RefUnwindSafe, UnwindSafe}; -use crate::pin::Pin; use crate::sync::Once; /// A synchronization primitive which can be written to only once. @@ -223,60 +222,6 @@ impl<T> OnceLock<T> { Ok(unsafe { self.get_unchecked() }) } - /// Internal-only API that gets the contents of the cell, initializing it - /// in two steps with `f` and `g` if the cell was empty. - /// - /// `f` is called to construct the value, which is then moved into the cell - /// and given as a (pinned) mutable reference to `g` to finish - /// initialization. - /// - /// This allows `g` to inspect an manipulate the value after it has been - /// moved into its final place in the cell, but before the cell is - /// considered initialized. - /// - /// # Panics - /// - /// If `f` or `g` panics, the panic is propagated to the caller, and the - /// cell remains uninitialized. - /// - /// With the current implementation, if `g` panics, the value from `f` will - /// not be dropped. This should probably be fixed if this is ever used for - /// a type where this matters. - /// - /// It is an error to reentrantly initialize the cell from `f`. The exact - /// outcome is unspecified. Current implementation deadlocks, but this may - /// be changed to a panic in the future. - pub(crate) fn get_or_init_pin<F, G>(self: Pin<&Self>, f: F, g: G) -> Pin<&T> - where - F: FnOnce() -> T, - G: FnOnce(Pin<&mut T>), - { - if let Some(value) = self.get_ref().get() { - // SAFETY: The inner value was already initialized, and will not be - // moved anymore. - return unsafe { Pin::new_unchecked(value) }; - } - - let slot = &self.value; - - // Ignore poisoning from other threads - // If another thread panics, then we'll be able to run our closure - self.once.call_once_force(|_| { - let value = f(); - // SAFETY: We use the Once (self.once) to guarantee unique access - // to the UnsafeCell (slot). - let value: &mut T = unsafe { (&mut *slot.get()).write(value) }; - // SAFETY: The value has been written to its final place in - // self.value. We do not to move it anymore, which we promise here - // with a Pin<&mut T>. - g(unsafe { Pin::new_unchecked(value) }); - }); - - // SAFETY: The inner value has been initialized, and will not be moved - // anymore. - unsafe { Pin::new_unchecked(self.get_ref().get_unchecked()) } - } - /// Consumes the `OnceLock`, returning the wrapped value. Returns /// `None` if the cell was empty. /// |