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fix: bump pointer/bump chunk debug assertion #313

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Merged
fitzgen merged 4 commits into from
Feb 26, 2026
+17 −4
Merged

fix: bump pointer/bump chunk debug assertion #313

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f9bbf55
fix: bump pointer/bump chunk debug assertion
my4ng Feb 23, 2026
271edf7
fix: incorrect pre-aligned pointer debug_assert
my4ng Feb 24, 2026
f9c9b8f
test: add regression test
my4ng Feb 26, 2026
fda1558
fix: add `ChunkFooter` alignment
my4ng Feb 26, 2026
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8 changes: 4 additions & 4 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -296,6 +296,7 @@ pub struct Bump<const MIN_ALIGN: usize = 1> {
}

#[repr(C)]
#[repr(align(16))]
#[derive(Debug)]
struct ChunkFooter {
// Pointer to the start of this chunk allocation. This footer is always at
Expand Down Expand Up @@ -475,10 +476,10 @@ const SUPPORTED_ITER_ALIGNMENT: usize = 16;
const CHUNK_ALIGN: usize = SUPPORTED_ITER_ALIGNMENT;
const FOOTER_SIZE: usize = mem::size_of::<ChunkFooter>();

// Assert that `ChunkFooter` is at most the supported alignment. This will give a
// Assert that `ChunkFooter` is at the supported alignment. This will give a
// compile time error if it is not the case
const _FOOTER_ALIGN_ASSERTION: () = {
assert!(mem::align_of::<ChunkFooter>() <= CHUNK_ALIGN);
assert!(mem::align_of::<ChunkFooter>() == CHUNK_ALIGN);
};

// Maximum typical overhead per allocation imposed by allocators.
Expand Down Expand Up @@ -908,7 +909,7 @@ impl<const MIN_ALIGN: usize> Bump<MIN_ALIGN> {
let ptr = round_mut_ptr_down_to(footer_ptr.cast::<u8>(), MIN_ALIGN);
debug_assert_eq!(ptr as usize % MIN_ALIGN, 0);
debug_assert!(
data.as_ptr() < ptr,
data.as_ptr() <= ptr,
"bump pointer {ptr:#p} should still be greater than or equal to the \
start of the bump chunk {data:#p}"
);
Expand Down Expand Up @@ -1908,7 +1909,6 @@ impl<const MIN_ALIGN: usize> Bump<MIN_ALIGN> {
is_pointer_aligned_to(ptr, MIN_ALIGN),
"bump pointer {ptr:#p} should be aligned to the minimum alignment of {MIN_ALIGN:#x}"
);

// This `match` should be boiled away by LLVM: `MIN_ALIGN` is a
// constant and the layout's alignment is also constant in practice
// after inlining.
Expand Down
13 changes: 13 additions & 0 deletions tests/all/tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -234,3 +234,16 @@ fn bump_is_send() {
fn assert_send(_: impl Send) {}
assert_send(Bump::new());
}

#[test]
fn test_debug_assert_data_le_bump_ptr_pr_313() {
let bump = Bump::new();
bump.set_allocation_limit(Some(1));
bump.alloc_layout(Layout::from_size_align(0, 16).unwrap());
}

#[test]
fn test_debug_assert_ptr_align_pr_313() {
let bump = Bump::<16>::with_min_align();
bump.alloc(0u8);
}