Function check_worker_alive

src/core/impl/system.cpp:443–451

return whether worker is alive

    //! return whether worker is alive
    bool check_worker_alive() {
        if (m_worker_pid) {
            auto wait_ret = waitpid(m_worker_pid, nullptr, WNOHANG);
            CHECK_SYS_ERR(wait_ret);
            if (!wait_ret)
                return true;
        }
        return false;
    }

    //! start worker if it is not alive
    void ensure_worker_alive() {