apple/pkl · error

fatal: failed to attach response dispatch thread to isolate.

Error message

fatal: failed to attach response dispatch thread to isolate.

What it means

Fatal check in libpkl's pkl_dispatch_worker: before polling for Pkl responses, the worker thread must attach to the GraalVM isolate via graal_attach_thread; a non-zero return means the native thread could not join the isolate, so the process aborts. Typically caused by isolate teardown concurrent with dispatch or resource exhaustion.

Solutions

1. Ensure pkl_close is not racing the dispatch worker (close only after stopping message traffic).
2. Check GraalVM native-image logs for isolate creation/attach limits.

When it happens

Trigger: Thrown at libpkl/src/main/c/pkl.c:68 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apple/pkl@f3efcbfc9b (2026-09-08). Data as JSON: /api/errors/c796a20a0d7d1e5c. Report an issue: GitHub.

Appendix: source

Thrown at libpkl/src/main/c/pkl.c:68

};

/**
 * Polls for messages coming from Pkl and sends them back to the handler.
 *
 * Ensures that calls into Pkl are wrapped with graal_attach_thread/graal_detach_thread, and
 * calls back to the handler are _not_ inside the GraalVM thread context.
 */
#ifdef _WIN32
static DWORD WINAPI pkl_dispatch_worker(LPVOID arg) {
#else
static void* pkl_dispatch_worker(void *arg) {
#endif
	const pkl_exec_t *pexec = (pkl_exec_t*) arg;

	for (;;) {
		graal_isolatethread_t *thread;
		if (graal_attach_thread(pexec->isolate, &thread) != 0) {
			fprintf(stderr,
					"fatal: failed to attach response dispatch thread to isolate.\n");
			abort();
		}

		char *message = NULL;
		const int length = pkl_internal_poll_response(thread, &message);

		if (graal_detach_thread(thread) != 0) {
			fprintf(stderr,
					"fatal: failed to detach response dispatch thread from isolate.\n");
			abort();
		}

		if (length < 0) {
			// pkl_internal_server_stop has been called and the queue is drained
			break;
		}
		pexec->handler(length, message, pexec->userData);

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