[GitHub] [arrow-rs] viirya commented on a diff in pull request #2061: Use `read_volatile` in `BitChunkIterator.next`

[GitBox <gi...@apache.org>]

viirya commented on code in PR #2061:
URL: https://github.com/apache/arrow-rs/pull/2061#discussion_r920756928


##########
arrow/src/util/bit_chunk_iterator.rs:
##########
@@ -333,7 +333,7 @@ impl Iterator for BitChunkIterator<'_> {
             // the constructor ensures that bit_offset is in 0..8
             // that means we need to read at most one additional byte to fill in the high bits
             let next = unsafe {
-                std::ptr::read_unaligned(raw_data.add(index + 1) as *const u8) as u64
+                std::ptr::read_volatile(raw_data.add(index + 1) as *const u8) as u64

Review Comment:
   I think the doc is for `read_unaligned` usage that accesses the buffer pointer as u64:
   
   ```
   let current = unsafe { std::ptr::read_unaligned(raw_data.add(index)).to_le() };
   ```
   
   For accessing `next`, we only read a byte and case the byte to u64. So it is not a problem.
   
   



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