mfc中调用curl_slist_free_all时报错：读取位置 0x3d646e65 时发生访问冲突

环境：Win7 64位+VS2008
问题：在mfc中进行libcurl编程的时候，发现无法释放发送给服务端的header信息

问题代码如下

//释放资源curl_slist_free_all(headers);

报错：0x586244d6 处最可能的异常: 0xC0000005: 读取位置 0x3d646e65 时发生访问冲突

完整代码

ReturnInfo CCSDNDlg::LoginServer(CString strUser,CString strPass){    ReturnInfo returnInfo;    returnInfo.bReturn = FALSE;    CURL *curl;    CURLcode res;    struct curl_slist *headers = NULL;    curl_global_init(CURL_GLOBAL_ALL);    curl = curl_easy_init();    if(curl){        //初始化cookie引擎        curl_easy_setopt(curl, CURLOPT_COOKIEFILE, "");        curl_easy_setopt(curl,CURLOPT_FOLLOWLOCATION, 1L);        //http请求头        headers = curl_slist_append(headers,"User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64; rv:25.0) Gecko/20100101 Firefox/25.0"); //模拟浏览器        headers = curl_slist_append(headers,"Host:passport.csdn.net");        headers = curl_slist_append(headers,"Accept:*/*");        headers = curl_slist_append(headers,"Accept-Language:zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3");        headers = curl_slist_append(headers,"Accept-Encoding:gzip, deflate");        headers = curl_slist_append(headers,"X-Requested-With:XMLHttpRequest");        headers = curl_slist_append(headers,"Referer:https://passport.csdn.net/account/loginbox?callback=logined&hidethird=1&from=http%3a%2f%2fwww.csdn.net%2f");        headers = curl_slist_append(headers,"Connection:keep-alive");        //设置要发往服务器的cookie        curl_easy_setopt(curl, CURLOPT_COOKIEJAR, "mycookie.txt");      //把服务器发过来的cookie保存到mycookie.txt        //发送http请求头        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);        char url[128];        sprintf(url,"http://passport.csdn.net/ajax/accounthandler.ashx?t=log&u=%s&p=%s&remember=0&f=http%3A%2F%2Fwww.csdn.net%2F&rand=0.47590136872096434",strUser,strPass);        curl_easy_setopt(curl, CURLOPT_URL,url);        string content;        //设置回调函数        res = curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writer);        res = curl_easy_setopt(curl, CURLOPT_WRITEDATA, &content);        //执行http请求        res = curl_easy_perform(curl);        string returnVal;        Utf8ToMb((char*)content.c_str(),content.length(),returnVal);        int pos = returnVal.find("\"status\":true");        if ( pos >= 0){            returnInfo.bReturn = TRUE;        }else{            int nStartPos = returnVal.find("error\":");            int nEndPos   = returnVal.find("data\":",nStartPos);            returnInfo.strErrorInfo = returnVal.substr(nStartPos+8,nEndPos-nStartPos-11);        }        //释放资源        curl_easy_cleanup(curl);        curl_slist_free_all(headers);        headers = NULL;    }    curl_global_cleanup();    return returnInfo;}