各位大佬，虚心讨教，初学C语言~

app_lsm6dso_context_t* g_six_d = NULL;
void bt_sink_srv_event_lsm6dso_six_d(int cur_state)
{
        int old_state = g_six_d->lsm6dso_state;
        g_six_d->lsm6dso_state = cur_state;
        bool ret = true;
        switch(cur_state)
        {
            case STATE_LSM6DSO_XH:
            {
                printf("###### function = %s, line = %d.STATE_LSM6DSO_XH", __FUNCTION__, __LINE__);
                bt_sink_srv_event_callback_timeout_remove(BT_SINK_SRV_EVENT_SIX_D);
                bt_sink_srv_event_callback_timeout(BT_SINK_SRV_EVENT_SIX_D, NULL, 0, 250);
                break;
            }
            
            case STATE_LSM6DSO_XL:
            {
                printf("###### function = %s, line = %d.STATE_LSM6DSO_XL", __FUNCTION__, __LINE__);
                bt_sink_srv_event_callback_timeout_remove(BT_SINK_SRV_EVENT_SIX_D);
                bt_sink_srv_event_callback_timeout(BT_SINK_SRV_EVENT_SIX_D, NULL, 0, 250);
                break;
            }
            
            case STATE_LSM6DSO_YH:
            {
                printf("###### function = %s, line = %d.STATE_LSM6DSO_YH", __FUNCTION__, __LINE__);
                
                if(old_state == STATE_LSM6DSO_XH && cur_state == STATE_LSM6DSO_YH)
                    {
                        printf("###### function = %s, line = %d.STATE_LSM6DSO_XH-STATE_LSM6DSO_YH", __FUNCTION__, __LINE__);
                        bt_sink_srv_event_callback_timeout_remove(BT_SINK_SRV_EVENT_SIX_D);
                        bt_sink_srv_event_callback_timeout(BT_SINK_SRV_EVENT_SIX_D, NULL, 0, 250);
                    }
                
                break;
            }
                 
           
            default:
            {
                ret = false;
                break;
            }
        }
}

typedef struct {
    int  lsm6dso_state;
} app_lsm6dso_context_t;

我想在一个switch语句里面当前case下，获取上一个case状态是什么，可以怎么写，我使用一个 结构体变量在外面保存这样会死机，请问语法有什么问题吗

你找个地方定义一个int oldState = 0; 不就行了，搞个struct没啥必要。

而且struct的定义也应该放在你的变量前面。