Question

When I run the following code in Microsoft visual studio it outputs junk values (memory addresses?) but when it is run in g++ it outputs what I intend it to (with a few changes like changing srand). How do I fix it to work in visual studio? I only have a few months coding experience and this issue has been bugging me for awhile now.

class Vehicle
{
    protected:
        int * vin;
        double * gasMileage;

    public:
        Vehicle();
        Vehicle(int v, double g);

        virtual void display(){cout<<"vin: "<<*vin<<endl<<"gasMileage: " <<*gasMileage<<endl;}
        virtual double calcGasUsed(int milesDriven){return *gasMileage * milesDriven;}

        int getVin(){return *vin;}
        double getGasMileage(){return *gasMileage;}

        void changeVin(int newvin) {vin=&newvin;}
        void changeGasMileage(double newGasMileage){gasMileage=&newGasMileage;}
        void drive();
};

class Suv:public Vehicle
{
    protected:
        bool *fourWDStatus;
        double * fourWDGasMileage;

    public:
        Suv();
        Suv(int v, double g,bool status, double fwdg);

        void display();
        double calcGasUsed(Suv&, int milesDriven);
        bool getFourWDStatus(){return *fourWDStatus;}
        double getfourWDGasMileage(){return *fourWDGasMileage;}

        void changeFourWDStatus(bool status) {fourWDStatus=&status;}
        void changeFourWDGasMileage(double newGasMileage){fourWDGasMileage=&newGasMileage;}

};
Vehicle::Vehicle()
{
    this->vin=0000;
    this->gasMileage=00;
}
Vehicle::Vehicle(int v, double g)
{
    this->vin=&v;
    this->gasMileage=&g;
}
Suv::Suv(int v, double g,bool status, double fwdg)
{
    this->vin=&v;
    this->gasMileage=&g;
    this->fourWDStatus=&status;
    this->fourWDGasMileage=&fwdg;
}
Suv::Suv()
{
    this->vin=0000;
    this->gasMileage=00;
    this->fourWDStatus=false;
    this->fourWDGasMileage=00;
}
void Suv::display()
{
    Vehicle::display();
    cout<<"fourWDStatus: "<<*fourWDStatus<<endl<<"fourWDGasMileage: "<<*fourWDGasMileage<<endl;
}
void Vehicle::drive()
{
    int r=rand()%10000;
    cout<<calcGasUsed(r)<<endl;

}
double Suv::calcGasUsed(Suv&, int milesDriven)
{
    double x;
    if (*fourWDStatus== true)
    {
        x= ((*fourWDGasMileage) * (milesDriven));
        return x;
    }
    else
    {
        x=((*gasMileage) * (milesDriven));
        return x;
    }
}

void main()
{
    cout << "test";
    srand(NULL);
    Suv A(300,12.2,false,16.6);
    Suv B(200,15.5,false,20.1);
    B.changeFourWDStatus(true);
    Vehicle C(111,20.5);
    C.drive();
    C.display();
    B.display();
    Vehicle arrOfCars[]={A,B,C};
    A.drive();
    B.drive();
    C.drive();
    system("pause");

}

Answer 1

The members Vehicle::vin, Vehicle::gasMileage as well as Suv::fourWDStatus and Suv::fourWDGasMileage are not correctly initialized pointers.

From the code you posted it seems you would be better off by changing them from pointers to regular variables (and adjusting the methods appropriately).

EDIT: If using pointers is a part of assignment, you have to initialize them correctly. This means, in your case, allocating a memory in constructors. It could be this way:

Vehicle::Vehicle()
{
    this->vin = new int(0);
    this->gasMileage = new double(0.0);
}

Vehicle::Vehicle(int v, double g)
{
    this->vin = new int(v);
    this->gasMileage = new double(g);
}

Suv::Suv(int v, double g,bool status, double fwdg) : Vehicle(v, g)
{        
    this->fourWDStatus = new bool(status);
    this->fourWDGasMileage = new double(fwdg);
}

Suv::Suv() : Vehicle(0, 0.0)
{
    this->fourWDStatus = new bool(false);
    this->fourWDGasMileage = new double(0.0);
}