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Fix GC race condition #21

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Fix GC race condition #21

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8549b24
Fix GC race condition
brianjenkins94 Mar 31, 2026
1affec4
Update mpmc.ts
brianjenkins94 Mar 31, 2026
e1921c0
Update json_buffer.ts
brianjenkins94 Apr 1, 2026
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18 changes: 16 additions & 2 deletions src/lib/json_buffer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -604,7 +604,15 @@ class SharedJsonBufferImpl<T extends Proxyable> extends Serializable {
return Reflect.get(target, prop, receiver);
}
if (prop === "__ptr") return target.__ptr;
if (prop === "toJSON") return () => this.toJSON(target.__ptr);
if (prop === "toJSON")
return () => {
// Clear caches that may be stale from another thread's GC
// compacting the shared buffer and recycling addresses.
this.stringCache.clear();
this.proxyCache.clear();
this.propertyHints.clear();
return this.toJSON(target.__ptr);
};

const ptr = target.__ptr;
if (ptr === 0) return undefined;
Expand Down Expand Up @@ -1211,7 +1219,13 @@ class SharedJsonBufferImpl<T extends Proxyable> extends Serializable {
if (prop === CONSOLE_VIEW) return () => this.toConsoleView(target.__ptr);
if (prop === toSerialized) return () => this[toSerialized]();
if (prop === "__ptr") return target.__ptr;
if (prop === "toJSON") return () => this.toJSON(target.__ptr);
if (prop === "toJSON")
return () => {
this.stringCache.clear();
this.proxyCache.clear();
this.propertyHints.clear();
return this.toJSON(target.__ptr);
};
if (prop === Symbol.iterator) {
return () => new ArrayCursor(this, target.__ptr);
}
Expand Down
16 changes: 14 additions & 2 deletions src/lib/sync/mpmc.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -289,9 +289,15 @@ export class Receiver<T> extends ChannelHandle<T> {
: { ok: false, error: ERR_SPURIOUS };
}

// Deep-copy under sendLock to prevent concurrent GC from
// compacting the SharedArrayBuffer while we traverse the proxy.
const sendToken = await this.internals.sendLock.acquire();
const copied = typeof (val as any)?.toJSON === "function" ? (val as any).toJSON() : val;
sendToken[Symbol.dispose]();

// Handover: Item token consumed -> Slot token released
this.internals.slotsAvailable[INTERNAL_SEMAPHORE_CONTROLLER].release(1);
return { ok: true, value: val };
return { ok: true, value: copied };
}

blockingRecv(): Result<T, Error> {
Expand Down Expand Up @@ -320,8 +326,14 @@ export class Receiver<T> extends ChannelHandle<T> {
: { ok: false, error: ERR_SPURIOUS };
}

// Deep-copy under sendLock to prevent concurrent GC from
// compacting the SharedArrayBuffer while we traverse the proxy.
const sendToken = this.internals.sendLock.blockingAcquire();
const copied = typeof (val as any)?.toJSON === "function" ? (val as any).toJSON() : val;
sendToken[Symbol.dispose]();

this.internals.slotsAvailable[INTERNAL_SEMAPHORE_CONTROLLER].release(1);
return { ok: true, value: val };
return { ok: true, value: copied };
}

async *[Symbol.asyncIterator](): AsyncGenerator<T, void, void> {
Expand Down