/* Join the thread */
#ifdef WIN32
        if (WaitForSingleObject(thread->handle, INFINITE) != WAIT_OBJECT_0) {
            /* Timeout/abandonment unexpected here; check $^E */
            Perl_croak(aTHX_ "PANIC: underlying join failed");
        };
#else
        if ((rc_join = pthread_join(thread->thr, &retval)) != 0) {
            /* In progress/deadlock/unknown unexpected here; check $! */
            errno = rc_join;
            Perl_croak(aTHX_ "PANIC: underlying join failed");
        };
#endif