how to iterate table in C++ and Mysql

[rahulvishwakarma]

hi to all, I've centos 6 server and client as centos 7 and in that codeblocks 20.
I" am building a small project and I want to iterate in table as output of a sql query in mysql server. Now when i iterate a complete table and after that 10-15 lines it gives segmentation fault. here is mine program and output :-

unsigned long product::displayProduct(string header)
{
    unsigned long l = 0, l2 = 0;

    int times;
    int intch;
    int length = 0;
    string prdin = "";
    string prd2 = "";
    string sql;
    string strbillno;
    int x1 = 24;
    unsigned long  prdid;
    int lines;
    char ch, escpch;
    bool flag = false;

    struct winsize w;


    mysql = Conn::connection();
    mysql->reconnect = true;
    clrscr();
    prdin.clear();
    do
    {
        ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
        clrscr();
        drawrect();

        mysql = Conn::connection();

        get->printMenu(productRecords, header);
        gotoxy(2, 5);
        cout << "Enter Product Name : ";
        gotoxy(x1 + prdin.length(), 5);
        gotoxy(x1, 5);
        ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
        for(int i = x1; i < w.ws_col-1; i++)
        {
            cout << " ";
        }
        gotoxy(x1, 5);
        cout << prdin;
        char ch = getc->getche();
        intch = int(ch);
        string prdsearch;
        if(intch == 27)
        {
            return 0;
        }
        if( intch == 127 && prdin.length() > 0)
        {
            gotoxy(x1, 5);
            for(int x = x1; x < w.ws_col - 1; x++)
            {
                cout << " ";
            }

            prdin = prdin.substr(0, prdin.length() -1);
            gotoxy(x1, 5);
            cout << prdin;
        }
        else if(intch == 10 && prdin.length() == 0)
        {
            prdid = 0;
            return prdid;
        }
        else if (intch == 9)
        {
            sql = "select productid from tableProductRecords where productname like '"+prdin+"%' order by productid asc;";
            qstate = mysql_query(mysql, sql.c_str());

            if(!qstate)
            {
                ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
                clrscr(2, 10, w.ws_col-1, w.ws_row-1);
                res = mysql_store_result(mysql);
                prdids.clear();
                while((row = mysql_fetch_row(res)) != nullptr)
                {
                    prdids.push_back(atoi(row[0]));
                }

                iter = prdids.begin();
                while((int(escpch = getc->getch())) == 9 && iter <= prdids.end())
                {
                    int i = 0;
                    strprdid = std::to_string(*iter++);
                    gotoxy(55, 40);
                    cout << "*iter  = " << *iter;
                    cin.get();
                    sql = "select productname, stock, rate, productid from tableProductRecords where productname like '"+prdin+"%';";
                    mysql = Conn::connection();
                    qstate = mysql_query(mysql, sql.c_str());
                    if(!qstate)
                    {
                        ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
                        clrscr(1, 10, w.ws_col, w.ws_row);
                        drawrect();
                        res = mysql_store_result(mysql);
                        sqlp->process_result_set(mysql, res, 10, &times, totallen);
                        length = *totallen;
                    }
                    mysql = Conn::connection();
                    sql = "select productname, stock, rate, productId  from tableProductRecords where productid = '"+strprdid+"';";
                    qstate = mysql_query(mysql, sql.c_str());
                    if(!qstate )
                    {
                        res = mysql_store_result(mysql);
                        if((row = mysql_fetch_row(res)) != nullptr)
                        {
                            gotoxy(x1, 5);
                            for(int y = x1; y < length + 7 ; y++)
                            {
                                cout << " ";
                            }
                            gotoxy(x1, 5);
                            prd2 = row[0];
                            cout << row[0];
                            gotoxy(x1,6);
                            for(int y = x1; y < length + 7; y++)
                            {
                                cout << " ";
                            }
                            gotoxy(x1, 6);
                            cout << atoi(row[1]);


                            gotoxy(x1, 7);
                            for(int y = x1; y < length + 7; y++)
                            {
                                cout << " ";
                            }
                            gotoxy(x1, 7);
                            cout << atoi(row[2]);

                            gotoxy(x1, 8);
                            for(int y = x1; y < length + 7; y++)
                            {
                                cout << " ";
                            }
                            gotoxy(x1, 8);

                            prdid = atol(row[3]);
                            cout << prdid;
                            gotoxy(x1 + prdin.length() , 5);
                        }

                    }
                    else
                    {
                        gotoxy(1, 11);
                        cout << "error : " << mysql_error(mysql);
                        cin.get();
                    }
                    if(iter == prdids.end())
                    {
                        iter = prdids.begin();
                    }
                    gotoxy(x1, 5);
                    for(int itr = x1; itr < length + 7; itr++)
                    {
                        cout << " ";
                    }
                    gotoxy(x1, 5);
                    cout << prd2;
                    gotoxy(2, 9);
                    for(int i = x1; i < length + 7; i++)
                    {
                        cout << " ";
                    }
                    gotoxy(2,9);
                    cout <<"search string : " << prdin;
                    gotoxy(x1, 5);
                }
            }
        }

        else
        {
            prdin += ch;
        }
    }while(intch != 10);

    return prdid;
}

how to get rid of this segmentation fault error.