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emphasize that ManuallyDrop is safe-to-access and unsafe-to-drop #72277

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May 17, 2020
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emphasize that ManuallyDrop is safe-to-access and unsafe-to-drop #72277

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6 changes: 5 additions & 1 deletion src/libcore/mem/manually_drop.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,6 @@ use crate::ops::{Deref, DerefMut};
use crate::ptr;

/// A wrapper to inhibit compiler from automatically calling `T`’s destructor.
///
/// This wrapper is 0-cost.
///
/// `ManuallyDrop<T>` is subject to the same layout optimizations as `T`.
Expand All @@ -11,6 +10,11 @@ use crate::ptr;
/// with [`mem::zeroed`] is undefined behavior.
/// If you need to handle uninitialized data, use [`MaybeUninit<T>`] instead.
///
/// Note that accessing the value inside a `ManuallyDrop<T>` is safe.
/// This means that a `ManuallyDrop<T>` whose content has been dropped must not
/// be exposed through a public safe API.
/// Correspondingly, `ManuallyDrop::drop` is unsafe.
///
/// # Examples
///
/// This wrapper can be used to enforce a particular drop order on fields, regardless
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