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fix Box::into_unique #78446

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Merged
merged 1 commit into from
Oct 29, 2020
Merged

fix Box::into_unique #78446

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9 changes: 2 additions & 7 deletions library/alloc/src/boxed.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -724,15 +724,10 @@ impl<T: ?Sized, A: AllocRef> Box<T, A> {
// Box is recognized as a "unique pointer" by Stacked Borrows, but internally it is a
// raw pointer for the type system. Turning it directly into a raw pointer would not be
// recognized as "releasing" the unique pointer to permit aliased raw accesses,
// so all raw pointer methods have to leak the box. Turning *that* to a raw pointer
// so all raw pointer methods have to go through `Box::leak`. Turning *that* to a raw pointer
// behaves correctly.
let b = mem::ManuallyDrop::new(b);

// The box is unitiliazed later when moving out the allocator. The pointer is stored
// beforehand.
let ptr = b.0;
let alloc = unsafe { ptr::read(&b.1) };
(ptr, alloc)
(Unique::from(Box::leak(b)), alloc)
}

/// Returns a reference to the underlying allocator.
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