table iteration in C++ and mysql.

rahulvishwakarma · 02-13-2021, 10:39 PM

hi to all, I've mysql server in centos 6 and client in centos 7. 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 :-

Code:

void product::showAllProduct()
{
    int times;
    char choose;
    clrscr();
    drawrect();
    int l = 5;
    int qstate;
    int i = 0;
    int r = 0;
    gotoxy(15, 5);
    char ch ;
    string strQuery;
    cout << "Welcome To Electronic Store";

    gotoxy(15, 6);
    cout << "Show All Items Menu\n";

    do
    {
        gotoxy(2, 7);
        cout << "Enter P -> producname | Stock -> S |\n Rate -> R | ProductID -> I : ";
        ch = cin.get();

        cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
        if(toupper(ch) == 'P')
        {
            strQuery = "select *from tableProductRecords order by productname asc;";
        }
        else if(toupper(ch)  == 'S')
        {
            strQuery = "select *from tableProductRecords order by Stock asc;";
        }
        else if(toupper(ch) == 'R')
        {
            strQuery = "select *from tableProductRecords order by Rate asc;";
        }
        else if( toupper(ch) == 'I')
        {
            strQuery = "select *from tableProductRecords order by ProductId asc;";
        }
        mysql = Conn::connection();
        qstate = mysql_query(mysql, strQuery.c_str());
        if(!qstate)
        {
            res = mysql_store_result(mysql);
            i = process_result_set(mysql, res, 10, &times, totallen);
        }
        else
        {
            cout << " error : " << "  "<< mysql_error(mysql) << "  " << endl;
        }

        sql = "select sum(Rate) from tableProductRecords";
        mysql->reconnect = true;
        mysql = Conn::connection();
        qstate = mysql_query(mysql, sql.c_str());

        if(!qstate)
        {
            res = mysql_store_result(mysql);
            if((row = mysql_fetch_row(res)) != nullptr)
            {
                r = atoi(row[0]);
            }
            gotoxy(2, 9);
            cout << "Grand Total of Stock : "<< r;
        }
        gotoxy(29, 8);
        cin.get();
    }while(int(ch) != 10);
}

how to get rid of this segmentation fault error.

tinfoil3d · 02-14-2021, 01:40 AM

Man, there are so many languages out there, why do people have to shoot their feet off in 2021 with C and C++? Leave it to hardware and firmware designers, please.

dugan · 02-14-2021, 09:16 AM

You need more null-pointer checks.

One specific example is that you’re not checking if “res” is null.

TB0ne · 02-14-2021, 11:50 AM

Quote:

Originally Posted by rahulvishwakarma

hi to all, I've mysql server in centos 6 and client in centos 7. 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 :-

Code:

void product::showAllProduct()
{
    int times;
    char choose;
    clrscr();
    drawrect();
    int l = 5;
    int qstate;
    int i = 0;
    int r = 0;
    gotoxy(15, 5);
    char ch ;
    string strQuery;
    cout << "Welcome To Electronic Store";

    gotoxy(15, 6);
    cout << "Show All Items Menu\n";

    do
    {
        gotoxy(2, 7);
        cout << "Enter P -> producname | Stock -> S |\n Rate -> R | ProductID -> I : ";
        ch = cin.get();

        cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
        if(toupper(ch) == 'P')
        {
            strQuery = "select *from tableProductRecords order by productname asc;";
        }
        else if(toupper(ch)  == 'S')
        {
            strQuery = "select *from tableProductRecords order by Stock asc;";
        }
        else if(toupper(ch) == 'R')
        {
            strQuery = "select *from tableProductRecords order by Rate asc;";
        }
        else if( toupper(ch) == 'I')
        {
            strQuery = "select *from tableProductRecords order by ProductId asc;";
        }
        mysql = Conn::connection();
        qstate = mysql_query(mysql, strQuery.c_str());
        if(!qstate)
        {
            res = mysql_store_result(mysql);
            i = process_result_set(mysql, res, 10, &times, totallen);
        }
        else
        {
            cout << " error : " << "  "<< mysql_error(mysql) << "  " << endl;
        }

        sql = "select sum(Rate) from tableProductRecords";
        mysql->reconnect = true;
        mysql = Conn::connection();
        qstate = mysql_query(mysql, sql.c_str());

        if(!qstate)
        {
            res = mysql_store_result(mysql);
            if((row = mysql_fetch_row(res)) != nullptr)
            {
                r = atoi(row[0]);
            }
            gotoxy(2, 9);
            cout << "Grand Total of Stock : "<< r;
        }
        gotoxy(29, 8);
        cin.get();
    }while(int(ch) != 10);
}

how to get rid of this segmentation fault error.

AGAIN??
https://www.linuxquestions.org/quest...-c-4175686608/
https://www.linuxquestions.org/quest...es-4175686406/

You keep opening new threads, and never follow up in your others, and they're all incredibly similar to this one. You post incomplete code, and somehow expect us to be able to decipher what you want. You have been programming in C++ for **TEN YEARS** at this point....have you not learned how to use a debugger yet?? You say you're using Codeblocks...fairly sure it has one in there.

AGAIN: Unless you post your COMPLETE CODE, give us an ACTUAL ERROR (past the fairly-useless 'segmentation fault'), there isn't much we can tell you.