消息队列在线程间传输消息后使用串口打印乱码

发布于 2023-10-28 14:19:04 浏览：526 订阅该版

BUG反馈
学习消息队列时，手写一个简单的消息队列案例，发现串口打印出乱码，字符编码设置都是utf-8。

```c
/*
 * Copyright (c) 2006-2023, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2023-10-26     RT-Thread    first version
 */

#include <rtthread.h>
#include <string.h>
#define DBG_TAG "main"
#define DBG_LVL DBG_LOG
#include <rtdbg.h>

rt_thread_t th1 = RT_NULL;
rt_thread_t th2 = RT_NULL;

rt_mq_t mq = RT_NULL;

const char *str1 = "ABCDE";
const char *str2 = "abcde";

void th1_entry(void *arg)
{
    rt_err_t ret = -1;
    char buf[32];
    while (1)
    {
        //成功返回0， 不返回接收消息的长度
        ret = rt_mq_recv(mq, buf, sizeof(buf), RT_WAITING_FOREVER);
        rt_kprintf("th1->%s,len->%d\n", buf, ret);
    }

}
void th2_entry(void *arg)
{

rt_kprintf("5秒钟之后发送邮箱\n");
    rt_thread_mdelay(5000);
    rt_kprintf("发送邮箱\n");
    //发送的是一个指针
    rt_mq_send(mq, str1, strlen(str1));
    rt_mq_send(mq, str2, strlen(str2));
}
int main(void)
{
    mq = rt_mq_create("mq", 32, 10, RT_IPC_FLAG_PRIO);
    if (RT_NULL == mq)
    {
        LOG_E("rt_mq_create failed...\n");
        return -RT_ERROR;
    }

th1 = rt_thread_create("th1", th1_entry, RT_NULL, 512, 20, 10);
    if (th1 != RT_NULL)
    {
        rt_thread_startup(th1);
    }
    th2 = rt_thread_create("th1", th2_entry, RT_NULL, 512, 20, 10);
    if (th2 != RT_NULL)
    {
        rt_thread_startup(th2);
    }

return RT_EOK;
}
```

![消息队列串口打印结果.png](https://oss-club.rt-thread.org/uploads/20231028/a66d16dcbf9a11835053190621aebe37.png)

排查后个人觉得是系统bug。在rt_mq_create创建一个消息队列时，为消息池每个消息节点初始化后没有使用memset清0，导致调用rt_mq_send_wait时 执行到rt_memcpy(msg + 1, buffer, size);只拷贝size个数据，其他未清零的数据在rt_mq_recv函数中被rt_memcpy(buffer, msg + 1, size > mq->msg_size ? mq->msg_size : size);原样拷贝给buffer，所以打印出了乱码。
并且rt_mq_recv成功接收消息时返回0，与文档描述（返回接收字符个数）不符。

解决：我在rt_mq_send_wait函数的rt_memcpy(msg + 1, buffer, size);语句之前添加memset(msg + 1, 0, mq->msg_size);语句，头文件添加#include <string.h>后问题得到解决。

![修改.png](https://oss-club.rt-thread.org/uploads/20231028/9e20f823d7d1339984a37d2f674d3afe.png.webp)

![修改后结果.png](https://oss-club.rt-thread.org/uploads/20231028/cc630a7f23e4e2a0c22beb992b25e052.png)