线程堆栈错误

Question

我在代码中遇到问题，无法弄清楚。我有三个线程，线程1以十六进制输入两个数字，线程2和3将这两个数字与最后两个数字交换并打印结果。

错误消息：

运行时检查失败＃2 - 围绕堆栈变量 'STR' 已损坏。

DWORD WINAPI changevalue(LPVOID lpParam) 
{ 
    WaitForSingleObject(inThread,INFINITE); //Input thread 
    printf("thread 1 and 2 running \n"); 

    int num = 0; 
    num = (int)lpParam; 
    int i = 0; 

    char str[10] ={0}; 
    char a,b; 
    _itoa(num,str,16); 

    while (str[i] != NULL) 
    { 
     i++; //Get location of last char.. 
    } 
    //Exchange first two digits with last two. 
    a = str[0]; 
    b = str[1]; 

    str[0] = str[i-2]; 
    str[1] = str[i-1]; 
    str[i-2] = a; 
    str[i-1] = b; 
    printf("num=%s\n",str); 
    //long numl=strtol(str,&stop,16); 
    //printf("num = %x\n", numl); 
    //We can also take input to a string then manuplate it, and 
    //then print it in form of a string only. 
    //But int is used since it is mentioned in the statement. 
    printf("thread 1 and 2 exit......\n "); 
    return TRUE; 
} 

Answer 1

如果lParam是0，调用_itoa(num, str, 16)将导致单个字符的字符串"0"。

在这种情况下，i将1，和str[i - 2] = a将写前的字符串，从而破坏堆栈。

更一般地，范围从0到15（含）的lParam的值将触发该问题。