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Ensure the coordinator thread terminates before its channels drop #145894

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Merged
merged 2 commits into from
Aug 28, 2025
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Ensure the coordinator thread terminates before its channels drop #145894

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Ensure the coordinator thread terminates first
zetanumbers Aug 26, 2025
dd07459
Comment on intentional field order
zetanumbers Aug 26, 2025
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7 changes: 5 additions & 2 deletions compiler/rustc_codegen_ssa/src/back/write.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1957,10 +1957,13 @@ impl<B: ExtraBackendMethods> Drop for Coordinator<B> {
pub struct OngoingCodegen<B: ExtraBackendMethods> {
pub backend: B,
pub crate_info: CrateInfo,
pub codegen_worker_receive: Receiver<CguMessage>,
pub shared_emitter_main: SharedEmitterMain,
pub output_filenames: Arc<OutputFilenames>,
// Field order below is intended to terminate the coordinator thread before two fields below
// drop and prematurely close channels used by coordinator thread. See `Coordinator`'s
// `Drop` implementation for more info.
pub coordinator: Coordinator<B>,
pub codegen_worker_receive: Receiver<CguMessage>,
pub shared_emitter_main: SharedEmitterMain,
Comment on lines +1965 to +1966
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A comment saying the field order is intentional would be helpful for future readers.

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Field order below is intended to terminate the coordinator thread before two fields below drop and prematurely close channels used by coordinator thread. See Coordinator's Drop implementation for more info.

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Manually implementing Drop is also common when a specific drop order is required.

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Maybe wrap intended fields in some comment block? This way new added fields to this struct didn't mix up with this description. Or maybe better impl drop for OngoingCodegen to enforce drop order, instead of comments.

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@klensy I think the current state is alright, but feel free to open a follow-up to make things nicer

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@zetanumbers zetanumbers Aug 27, 2025 •
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Manually implementing Drop is also common when a specific drop order is required.

I think better place for moved fields then would be inside of Coordinator. Idk, maybe i should do that instead? That would probably be more manageable.

}

impl<B: ExtraBackendMethods> OngoingCodegen<B> {
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