inet_ntoa内存问题

浏览数：21 / 时间：2015年06月09日

最近写的一个程序,大致用到以下代码:

    WSADATA wsaData;

    WSAStartup (MAKEWORD( 2, 2 ),&wsaData);

    struct addrinfo *aiList=0;
    sockaddr_in addr;
    char *ip;

    while (TRUE)
    {
        if (0==getaddrinfo("www.qq.com",0,0,&aiList))
        {
            addr=*(struct sockaddr_in *)aiList->ai_addr;
            ip=inet_ntoa(addr.sin_addr);
        }
        //............................       
    }

多次循环之后,发现inet_ntoa破坏栈空间.搜索了一下,inet_ntoa返回的字符串是临时装在一个静态分配的缓冲区里面，下一次调用此函数的时候缓冲区会被重写

http://blog.csdn.net/litingli/article/details/5461535

MSDN:

The string returned by inet_ntoa resides in memory that is allocated by Windows Sockets. The application should not make any assumptions about the way in which the memory is allocated. The string returned is guaranteed to be valid only until the next Windows Sockets function call is made within the same thread. Therefore, the data should be copied before another Windows Sockets call is made.

但是仍然不知道为什么会破坏栈,覆盖了局部变量.

解决方案:

    WSADATA wsaData;

    WSAStartup (MAKEWORD( 2, 2 ),&wsaData);

    struct addrinfo *aiList=0;
    sockaddr_in addr;
    in_addr in;
    char buffer[32];

    unsigned char *bytes = (unsigned char *) &in;
    __snprintf (buffer, sizeof (buffer), "%d.%d.%d.%d",bytes[0], bytes[1], bytes[2], bytes[3]);