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Return unexpected termination error instead of panicing in Thread::join #137480

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Merged
merged 3 commits into from
Feb 28, 2025
Merged

Return unexpected termination error instead of panicing in Thread::join #137480

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db1f0d0
Return error on unexpected termination in `Thread::join`.
fuzzypixelz Feb 23, 2025
1ccdc06
Remove speculation on cause of error
fuzzypixelz Feb 24, 2025
7058f62
Use `.expect(..)` instead
fuzzypixelz Feb 25, 2025
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6 changes: 5 additions & 1 deletion library/std/src/thread/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1739,7 +1739,11 @@ struct JoinInner<'scope, T> {
impl<'scope, T> JoinInner<'scope, T> {
fn join(mut self) -> Result<T> {
self.native.join();
Arc::get_mut(&mut self.packet).unwrap().result.get_mut().take().unwrap()
if let Some(packet) = Arc::get_mut(&mut self.packet) {
packet.result.get_mut().take().unwrap()
} else {
Err(Box::new("thread terminated unexpectedly (e.g. due to OS intervention)"))
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Let's not speculate if we don't have anything else to go on:

Suggested change
Err(Box::new("thread terminated unexpectedly (e.g. due to OS intervention)"))
Err(Box::new("thread terminated unexpectedly"))

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Not sure if this is the right type to return.

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I do think it'd be better to return an impl Error {} type that implements Display rather than just a Box<str>.

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Hmm. The std::thread::Result type states that its Err variant indicates that a thread has panicked with. So now it seems to me that I'm breaking the API, technically.

We should either use .except(..) instead, or change the documentation of std::thread::Result.

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It seems doubtful to me anyone relies on specifically that element of the API guarantee such that they can distinguish between unexpected termination and panic. Nonetheless you are correct this would technically be an API change, so I think that I could accept the .expect and then libs-team ACP could be pursued appropriately.

}
}
}

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