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doubly-linked-list: improve leak check #2043

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Feb 26, 2025
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doubly-linked-list: improve leak check #2043

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3 changes: 1 addition & 2 deletions exercises/practice/doubly-linked-list/tests/step_4_leak_test_2.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,8 +19,7 @@ fn drop_no_leaks() {
drop(list);

let allocated_after = ALLOCATED.load(SeqCst);
let leaked_bytes = allocated_before - allocated_after;
assert!(leaked_bytes == 0);
Comment on lines -22 to -23
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Was there any particular reason for choosing subtraction over equality in the past? It seems like a really strange decision.

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Looking at it more closely, it just looks like a logic error. Even if there was a reason for the subtraction, the order should have been reversed. There's no conceivable reason for allocated_before to ever be larger than allocated_after.

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Original PR is here, I can't find any discussion on that.

assert_eq!(allocated_before, allocated_after);
}

// Defines a wrapper around the global allocator that counts allocations
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