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Merged
merged 2 commits into from
May 7, 2025
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Comment on Rc abort-guard strategy without naming unrelated fn #140483

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dd20225
Update rc.rs docs
baumanj Apr 29, 2025
6a4af82
Update rc.rs docs
baumanj May 6, 2025
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10 changes: 5 additions & 5 deletions library/alloc/src/rc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3536,11 +3536,11 @@ impl<T> Default for Weak<T> {
}
}

// NOTE: We checked_add here to deal with mem::forget safely. In particular
// if you mem::forget Rcs (or Weaks), the ref-count can overflow, and then
// you can free the allocation while outstanding Rcs (or Weaks) exist.
// We abort because this is such a degenerate scenario that we don't care about
// what happens -- no real program should ever experience this.
// NOTE: If you mem::forget Rcs (or Weaks), drop is skipped and the ref-count
// is not decremented, meaning the ref-count can overflow, and then you can
// free the allocation while outstanding Rcs (or Weaks) exist, which would be
// unsound. We abort because this is such a degenerate scenario that we don't
// care about what happens -- no real program should ever experience this.
//
// This should have negligible overhead since you don't actually need to
// clone these much in Rust thanks to ownership and move-semantics.
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