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refactor: remove bump field from ChunkIter #319

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overlookmotel wants to merge 1 commit into from
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refactor: remove bump field from ChunkIter #319

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6 changes: 1 addition & 5 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2149,10 +2149,7 @@ impl<const MIN_ALIGN: usize> Bump<MIN_ALIGN> {
pub fn iter_allocated_chunks(&mut self) -> ChunkIter<'_, MIN_ALIGN> {
// Safety: Ensured by mutable borrow of `self`.
let raw = unsafe { self.iter_allocated_chunks_raw() };
ChunkIter {
raw,
bump: PhantomData,
}
ChunkIter { raw }
Comment on lines 2149 to +2152
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Copilot AI Apr 2, 2026

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The safety comment here (“Ensured by mutable borrow of self.”) becomes incorrect if ChunkIter no longer carries a PhantomData<&'a mut Bump<MIN_ALIGN>>: the iterator only keeps an immutable borrow, and Bump exposes mutation via &self (e.g., alloc, try_alloc_layout, etc.). This means allocations can occur while the safe iterator is alive, violating the safety preconditions for producing &'a [MaybeUninit<u8>].

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}

/// Returns an iterator over raw pointers to chunks of allocated memory that
Expand Down Expand Up @@ -2388,7 +2385,6 @@ impl<const MIN_ALIGN: usize> Bump<MIN_ALIGN> {
#[derive(Debug)]
pub struct ChunkIter<'a, const MIN_ALIGN: usize = 1> {
raw: ChunkRawIter<'a, MIN_ALIGN>,
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Copilot AI Apr 2, 2026

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Removing bump: PhantomData<&'a mut Bump<MIN_ALIGN>> from ChunkIter weakens the borrow the iterator holds to an immutable borrow via ChunkRawIter (ChunkRawIter currently uses PhantomData<&'a Bump<MIN_ALIGN>>). Since Bump has allocation APIs that take &self (interior mutability), callers can allocate while a safe ChunkIter is alive, which can invalidate the returned chunk slices and lead to UB. Keep the &'a mut Bump phantom in ChunkIter, or otherwise ensure the iterator type enforces exclusive access for the duration of iteration.

Suggested change
raw: ChunkRawIter<'a, MIN_ALIGN>,
raw: ChunkRawIter<'a, MIN_ALIGN>,
bump: PhantomData<&'a mut Bump<MIN_ALIGN>>,

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bump: PhantomData<&'a mut Bump>,
}

impl<'a, const MIN_ALIGN: usize> Iterator for ChunkIter<'a, MIN_ALIGN> {
Expand Down
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