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Avoid allocations and copying in Vec::leak #89337

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Merged
merged 4 commits into from
Oct 15, 2021
Merged

Avoid allocations and copying in Vec::leak #89337

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58b1a12
Avoid allocations and copying in Vec::leak
mbrubeck Sep 28, 2021
1fca2ce
Additional docs about Vec::leak behavior
mbrubeck Sep 28, 2021
129af04
Mention Rust version in Vec::leak docs.
m-ou-se Oct 12, 2021
df15b28
Remove potentially unsound note on reconstructing a leaked Vec.
m-ou-se Oct 12, 2021
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8 changes: 5 additions & 3 deletions library/alloc/src/vec/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1952,8 +1952,9 @@ impl<T, A: Allocator> Vec<T, A> {
/// `'a`. If the type has only static references, or none at all, then this
/// may be chosen to be `'static`.
///
/// This function is similar to the [`leak`][Box::leak] function on [`Box`]
/// except that there is no way to recover the leaked memory.
/// As of Rust 1.57, this method does not reallocate or shrink the `Vec`,
/// so the leaked allocation may include unused capacity that is not part
/// of the returned slice.
///
/// This function is mainly useful for data that lives for the remainder of
/// the program's life. Dropping the returned reference will cause a memory
Expand All @@ -1976,7 +1977,8 @@ impl<T, A: Allocator> Vec<T, A> {
where
A: 'a,
{
Box::leak(self.into_boxed_slice())
let mut me = ManuallyDrop::new(self);
unsafe { slice::from_raw_parts_mut(me.as_mut_ptr(), me.len) }
}

/// Returns the remaining spare capacity of the vector as a slice of
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