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Use inline const blocks to create arrays of MaybeUninit. #125995

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Merged
merged 2 commits into from
Jun 5, 2024
Merged

Use inline const blocks to create arrays of MaybeUninit. #125995

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ac96fa4
Use inline const instead of unsafe to construct arrays in `MaybeUnini…
kpreid May 13, 2024
ec8fa17
Use inline const instead of unsafe to implement `MaybeUninit::uninit_…
kpreid May 13, 2024
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17 changes: 5 additions & 12 deletions library/core/src/mem/maybe_uninit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -120,12 +120,8 @@ use crate::slice;
/// use std::mem::{self, MaybeUninit};
///
/// let data = {
/// // Create an uninitialized array of `MaybeUninit`. The `assume_init` is
/// // safe because the type we are claiming to have initialized here is a
/// // bunch of `MaybeUninit`s, which do not require initialization.
/// let mut data: [MaybeUninit<Vec<u32>>; 1000] = unsafe {
/// MaybeUninit::uninit().assume_init()
/// };
/// // Create an uninitialized array of `MaybeUninit`.
/// let mut data: [MaybeUninit<Vec<u32>>; 1000] = [const { MaybeUninit::uninit() }; 1000];
///
/// // Dropping a `MaybeUninit` does nothing, so if there is a panic during this loop,
/// // we have a memory leak, but there is no memory safety issue.
Expand All @@ -147,10 +143,8 @@ use crate::slice;
/// ```
/// use std::mem::MaybeUninit;
///
/// // Create an uninitialized array of `MaybeUninit`. The `assume_init` is
/// // safe because the type we are claiming to have initialized here is a
/// // bunch of `MaybeUninit`s, which do not require initialization.
/// let mut data: [MaybeUninit<String>; 1000] = unsafe { MaybeUninit::uninit().assume_init() };
/// // Create an uninitialized array of `MaybeUninit`.
/// let mut data: [MaybeUninit<String>; 1000] = [const { MaybeUninit::uninit() }; 1000];
/// // Count the number of elements we have assigned.
/// let mut data_len: usize = 0;
///
Expand Down Expand Up @@ -348,8 +342,7 @@ impl<T> MaybeUninit<T> {
#[must_use]
#[inline(always)]
pub const fn uninit_array<const N: usize>() -> [Self; N] {
// SAFETY: An uninitialized `[MaybeUninit<_>; LEN]` is valid.
unsafe { MaybeUninit::<[MaybeUninit<T>; N]>::uninit().assume_init() }
[const { MaybeUninit::uninit() }; N]
}

/// Creates a new `MaybeUninit<T>` in an uninitialized state, with the memory being
Expand Down