消息队列返回的是什么

int user_mq_recv(rt_mq_t mq, const void *buffer, rt_size_t size,rt_size_t timeout)
{
       rt_err_t result;
       result = rt_mq_recv(mq, buffer, size, timeout);
       if(result == RT_EOK)
       {
           rt_kprintf("rx_mq RT_EOK\n");
       }
       else if (result == -RT_EFULL)
       {
           rt_kprintf("rx_mq RT_EFULL\n");
       }
       else if (result == -RT_ENOMEM)
       {
           rt_kprintf("rx_mq RT_ENOMEM\n");
       }
       else
       {
          rt_kprintf("rx_mq err:%d\n", result);
       }
       return result;
}