Logical error with overloaded operator C++ - c++

Question

I've been making a class called Complex for storing and working with complex numbers. I'm having issues where my overloaded + and * functions return an obscenely large number, which I can only presume has something to do with pointers, but I'm very new to using them. I've copied the output here:
c1: 1 - i5
c2: -4 + i3
c1 + c2: -9.25596e+061 - i9.255
c1 * c2: -9.25596e+061 - i9.255
Press any key to continue . . .
Here is the class architecture:
// Complex.h
#include <iostream>
#include <cmath>
using namespace std;
class Complex
{
friend std::ostream &operator<<(std::ostream &, const Complex &);
friend std::istream &operator>>(std::istream &, Complex &);
friend Complex &operator+(const Complex &, const Complex &);
friend Complex &operator+(const Complex &, const double &);
friend Complex &operator+(const double &, const Complex &);
friend Complex &operator*(const Complex &, const Complex &);
friend Complex &operator*(const Complex &, const double &);
friend Complex &operator*(const double &, const Complex &);
public:
explicit Complex(double re=0, double im=0);
void setReal(double re);
void setImag(double im);
double &getReal();
double &getImag();
~Complex();
private:
double real;
double imag;
};
And here I have the relevant portions of my program:
// Complex.cpp
#include "Complex.h"
ostream &operator<<(ostream &output, const Complex &num)
{
output << num.real << (num.imag >= 0 ? " + i" : " - i") << abs(num.imag);
return output;
}
Complex &operator+(const Complex &num1, const Complex &num2)
{
Complex sum(num1.real + num2.real, num1.imag + num2.imag); // Create new complex by summing elements
return sum;
}
Complex &operator*(const Complex &num1, const Complex &num2)
{
Complex prod(num1.real * num2.real - num1.imag * num2.imag, num1.real * num2.imag + num1.imag * num2.real); // Create new complex by expansion
return prod;
}
Complex::Complex(double re, double im)
{
real = re;
imag = im;
}
int main() {
Complex c1(1.0, -5.0);
Complex c2(-4.0, 3.0);
cout << "c1: " << c1 << endl;
cout << "c2: " << c2 << endl;
cout << "c1 + c2: " << c1 + c2 << endl;
cout << "c1 * c2: " << c1 * c2 << endl;
system("pause");
}
I feel bad bothering you guys about this. Do you possibly know of a site that does a good job of explaining concepts for C++ like pointers, least-privilege, polymorphism, inheritance, etc?
Sorry for asking basic questions on here, but it's hard to find resources that explain this stuff clearly.

Answer 1

Wrong return type:
Complex &operator+(const Complex &num1, const Complex &num2)
^^^^^^^^^
You're creating a temporary Complex and returning it by reference, and then it gets destroyed so you have a dangling reference. Since operator+ is constructing a new object and returning it, it should return it by value... so the signature should be:
Complex operator+(Complex const&, Complex const& );

Answer 2

The problem is that most of your overloaded operators return a reference to a local var, which is destroyed when the operator function returns, leaving you with a dangling reference. Try changing your operators to return a Complex rather than a Complex &:
Complex operator+(const Complex &num1, const Complex &num2)
{
Complex sum(num1.real + num2.real, num1.imag + num2.imag); // Create new complex by summing elements
return sum;
}