Question

Just a tiny question:

Can you tell me what’s the issue here in this code ? It should print out 9 but it does 4.8921e-270, however, when uncommenting line 4, it works just fine, too.
I don’t understand what might be wrong here. Thank you !

Code:

double& foo() {
  double x = 9;
  double &y = x;
  //cout << y << "\n";
  return y;
}

int main() {
  cout << foo() << "\n";
}

Result:
4.8921e-270

Answer 1

It is a bad idea to return references/pointers to objects on the stack. They are likely destroyed when you leave the function. Try returning it as per value:

double foo() {
  double x = 9;
  double &y = x;
  //cout << y << "\n";
  return y;
}

Now the return value is copied instead of a reference to an object that is probably not existing anymore.