segmentation fault in c ++ with mysql connector

Good morning, I'm very new in the programming environment and I'm doing some test programs.

I'm using c ++ in codeblocks and mysql connector. This is a segment of the code. What I want to do is send the value of the variable "t" that increases each cycle. But I get segmentation fault before I get to the last if (! Qstate).

I hope you can help me find my mistake or any suggestion to avoid it. Greetings.

#include <iostream>
#include <unistd.h>
#include <mysql++/mysql++.h>
#include <wiringPi.h>
#include <fstream>
#include <string.h>
#include <sstream>
#include <string>
#include <cstring>

using namespace std;

int main()
{



MYSQL*  conn;
MYSQL_ROW row;
MYSQL_RES* res;

int qstate; //stores query status after execution

conn = mysql_init(0);

if(conn)            // if SUCCEEDED
{
    cout<<"connection object ok"<<endl;
    }
else
{
    cout << "conn object problem!" <<mysql_error(conn) << endl;

    conn = mysql_real_connect(conn,"localhost","root","1234","prueba2",0,NULL,0);
    }

if(conn)            // if SUCCEEDED
{
    cout<<"connection to database done!!"<<conn<<endl;

    //before select, it will insert first. So new record will be displayed

 wiringPiSetup();
pinMode(0,OUTPUT);
pinMode(24,INPUT);



int a = 0;
    for (a = 0; a = 1; a+ digitalRead(24))
    {
float t;

    if(digitalRead(24) == HIGH)
    {

    int i = 0;
    for (i = 0;i<3;i++)
        {
    digitalWrite(0,HIGH);
    delay(900);
    cout <<"Enciende"<<endl;
    digitalWrite(0,LOW);
    delay(900);
    cout <<"Apaga"<<endl;
        }
        t=t+a;
    cout<<t<<endl;
    }


    stringstream ss;
    ss<<t<<endl;

    string t2 = ss.str();

   string query="insert into tabla2 (id) values('"+ t2+"')";

    //const char converst string object to const char as it is requires in mysql_query(conn,q)
    const char * q = query.c_str();

    cout<<"query is: "<<q<<endl;
    qstate = mysql_query(conn,q);



    if(!qstate) //if insert succeeded
        cout<<"record inserted successfully..."<<endl;
    else
        cout<<"query problem: "<<mysql_error(conn)<<endl;
    // dasdsa
    //now lets run select query on db table
    qstate = mysql_query(conn,"select * from tabla2");

    if(!qstate)  //means nonzero
    {
       //get records from conn object to res* pointer
       res = mysql_store_result(conn);
       //now read an display record one @ time
       while(row=mysql_fetch_row(res))
       {
        cout<<"id: "<<row[0]<<endl;



    }
    }

else
    {
        cout << "query execution problem!" <<mysql_error(conn) << endl;
    }
   //its done
   }
    }
 else
 {
    cout << "conn object problem!" <<mysql_error(conn) << endl;

}

return 0;
}