rust ownership_error ai_generated true

called `Result::unwrap()` on an `Err` value: Arc::try_unwrap failed because there are still other strong references

ID: rust/rust-arc-cannot-unwrap

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82%Fix Rate
85%Confidence
50Evidence
2023-01-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1 active — — —

Root Cause

Arc::try_unwrap fails when other Arc clones still exist. You must ensure all other references are dropped first.

generic

Workarounds

  1. 88% success Ensure all other Arc clones are dropped before calling try_unwrap 
    // Drop other references first
drop(other_arc_clone);
// Now try_unwrap will succeed
let inner = Arc::try_unwrap(arc).expect("all refs should be dropped");

    Sources: https://doc.rust-lang.org/std/sync/struct.Arc.html#method.try_unwrap

  2. 85% success Use Arc::into_inner() (Rust 1.70+) which returns None instead of panicking 
    if let Some(inner) = Arc::into_inner(arc) {
    // use inner
} else {
    // other references still exist, handle gracefully
}

    Sources: https://doc.rust-lang.org/std/sync/struct.Arc.html#method.into_inner

Dead Ends

Common approaches that don't work:

  1. Use unsafe to extract the inner value regardless of reference count 95% fail

    Other references will point to freed memory causing use-after-free bugs

Error Chain

Leads to:
Preceded by:
Frequently confused with: