Manishearth commented on code in PR #6551:
URL: https://github.com/apache/arrow-rs/pull/6551#discussion_r1802146588
##########
arrow-buffer/src/util/bit_mask.rs:
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@@ -127,16 +127,16 @@ unsafe fn set_upto_64bits(
}
/// # Safety
-/// The caller must ensure all arguments are within the valid range.
+/// The caller must ensure `data` has `offset..(offset + 8)` range, and `count
<= 8`.
#[inline]
unsafe fn read_bytes_to_u64(data: &[u8], offset: usize, count: usize) -> u64 {
debug_assert!(count <= 8);
- let mut tmp = std::mem::MaybeUninit::<u64>::new(0);
+ let mut tmp: u64 = 0;
Review Comment:
@kazuyukitanimura `MaybeUninit(0)` and `0` should have no difference in
performance. For this to be an optimization, this ought to have used
`MaybeUninit::uninit()`, though that would also be unsound given that the
entire integer is not guaranteed to be initialized..
If this is intended to be an optimization, it displays a misunderstanding of
what MaybeUninit _does_.
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