请教高手关于Segmentation Fault!

[mtzhang_sh]

linux下写了一个log文件的功能，利用消息队列实现log信息的传输，有多个进程写入log消息，一个线程来读取log信息并写入log文件，然后当log文件大于5MB时，新建一个新的log文件并继续记录log信息。目前正常启动记录都没问题，问题出在新建log文件的时候，旧的log文件顺利关闭，新log文件已经建立，但是马上就出现了segmentation fault! 查了好久，也没找到原因，请教诸位高手帮忙分析下，谢谢！代码如下：

uint32_t get_file_size(const char *path)
{
uint32_t file_size;
fseek(My_sys_log.fd, 0L, SEEK_END );
file_size=ftell(My_sys_log.fd);
return file_size;
}

int create_ipc_qid()
{
int msgqid;

msgqid = msgget(MSGKEY, IPC_CREAT|0666); /*检查消息队列是否存在*/
if(msgqid < 0)
{
msgqid = msgget(MSGKEY,IPC_CREAT|0666);/*创建消息队列*/
if(msgqid <0)
{
printf("failed to create msq | errno=%d [%s]\n",errno,strerror(errno));
exit(-1);
}
}
return msgqid;
}

void send_message(int qid, char *text)
{
ipc_msg MSG;
memset(&MSG, 0, sizeof(MSG));
MSG.msg_type = Msg_type;
strcpy(MSG.mtext, text);
//把一条消息添加到消息队列,IPC_NOWAIT表示队列满不等待，返回EAGAIN错误
if((msgsnd(qid, &MSG, sizeof(MSG)-sizeof(long), IPC_NOWAIT)) ==-1)
//if((msgsnd(qid, &MSG, sizeof(MSG)-sizeof(long), 0)) ==-1)
{
perror("msgsnd");
exit(1);
}
}

ipc_msg read_message(int qid)
{
ipc_msg MSG;
int ret;
memset(&MSG, 0, sizeof(MSG));
//IPC_NOWAIT: 调用进程会立即返回。若没有收到消息则立即返回 -1。
ret=msgrcv(qid, &MSG, sizeof(MSG)-sizeof(long), (long)Msg_type,0);
if(ret==-1)
{
printf("recv message err\n");
perror("msgrcv");
exit(1);
//return -1;
}
return MSG;
}

void remove_queue(int qid)
{
msgctl(qid, IPC_RMID, 0);
}

uint8_t syslog_init()
{
DIR *dirptr = NULL;
char *log_init="Create new syslog file sucessful!\n";
memset(My_sys_log.file_path,'\0',40);
time_z now;
Time_get(&now);
printf("get time now\n");
printf("file flag is %d\n",file_flag);
if(dirptr = opendir("/media/My_SDcard/Debug") == NULL)
{
printf("not have /media/My_SDcard/Debug folder\n");
system("mkdir /media/My_SDcard/Debug ");
}
else
{
printf("open dir sucessful\n");
closedir(dirptr);
}
// sprintf(s_log_info.file_path,"/media/mmcblk0p1/Debug/S1_Debug_%d_%d_%d_%d_%d_%d.txt",now.year+2000,now.mon,now.day,now.hour,now.min,now.sec);
//sprintf(s_log_info.file_path,"/media/My_SDcard/Debug/S1_Debug_%d_%02d_%02d_%02d_%02d_%02d.txt",now.year,now.mon,now.day,now.hour,now.min,now.sec);
if(file_flag==0)
sprintf(My_sys_log.file_path,"/media/My_SDcard/Debug/S1_Debug_2017_12_25_19_17_31.txt");
else
//sprintf(My_sys_log.file_path,"/media/My_SDcard/Debug/S1_Debug_%d_%02d_%02d_%02d_%02d_%02d.txt",now.year,now.mon,now.day,now.hour,now.min,now.sec);
sprintf(My_sys_log.file_path,"/media/My_SDcard/Debug/S1_Debug_2017_12_25_19_18_31.txt");

printf("file path is %s\n",My_sys_log.file_path);

My_sys_log.fd = fopen(My_sys_log.file_path,"a+");
printf("open the log file init ucessful\n");
//printf("s_log_info.fd=%x\n",My_sys_log.fd);
if(My_sys_log.fd == NULL)
{
perror("fail to fopen syslog file");
return -1;
}
else
{
fwrite(log_init,strlen(log_init),1,My_sys_log.fd);
fflush(My_sys_log.fd);
printf("write the initial log,new file fd is %d\n",My_sys_log.fd);
}
return true;
}

void *Evl_Engine_Thread_entry(void *argv)
{
uint32_t file_size;
//int len=0;
//PNode Msg_Node;
//Frame Msg_Frame_W;
int fpclose;
ipc_msg Log_Msg;
char *buf;
int temp1=0;
//time_z now;
//char *log_init="Create new syslog file sucessful!\n";

while(1)
{
file_size = get_file_size(My_sys_log.file_path); //得到已经打开文件的大小
//len = GetSize(Msg_Queue);
printf("my file size is %d\n",file_size);
if(file_size > FILE_SIZE_MAX) //文件大于5M重新打开新的文件
//if(1)
{

printf("file size is largger than 5MB\n");
fpclose = fclose(My_sys_log.fd);
printf("close the file %d,fpclose is %d\n",My_sys_log.fd,fpclose);
file_flag = 1;
syslog_init();
}
else
{

Log_Msg = read_message(MSG_QID);
printf("write date\n");
buf = Log_Msg.mtext;
printf("log msg is %s\n",buf);
fwrite(buf,strlen(buf),1,My_sys_log.fd);
//printf("write msg sucessful\n");
fflush(My_sys_log.fd);
}

}
}

[northwesternwind]

file_path 的定义是40大小？你数数你保存的文件名字是多少字节？

[mtzhang_sh]

file_path的长度改为100个，还是同样的问题。 其实新的log文件已经建立了，而且也成功写入了第一句Create new syslog file sucessful!，测试结果是到消息队列读取的时候就出现了segmentation fault。但是这个消息队列读取在log文件不到5M的时候一直正常的，只是在新建log文件后读取消息产生了异常，感觉前后两种情况下消息队列没有什么变化啊，怎么会出现了段错误了 下面是出现错误时候的提示信息： my file size is 5242884 file size is largger than 5MB close the file 294992,fpclose is 0 get time now file flag is 1 open dir sucessful file path is /media/My_SDcard/Debug/S1_Debug_2017_12_25_19_18_31.txt open the log file init ucessful write the initial log,new file fd is 294992 my file size is 34 Segmentation fault

[northwesternwind]

引用 2 楼 weixin_41463332 的回复:

file_path的长度改为100个，还是同样的问题。 其实新的log文件已经建立了，而且也成功写入了第一句Create new syslog file sucessful!，测试结果是到消息队列读取的时候就出现了segmentation fault。但是这个消息队列读取在log文件不到5M的时候一直正常的，只是在新建log文件后读取消息产生了异常，感觉前后两种情况下消息队列没有什么变化啊，怎么会出现了段错误了 下面是出现错误时候的提示信息： my file size is 5242884 file size is largger than 5MB close the file 294992,fpclose is 0 get time now file flag is 1 open dir sucessful file path is /media/My_SDcard/Debug/S1_Debug_2017_12_25_19_18_31.txt open the log file init ucessful write the initial log,new file fd is 294992 my file size is 34 Segmentation fault

两个办法排查： 1. 用gdb打开core文件 2. 用valgrind执行下程序，会检查出内存越界的地方。