How to create an Instance of a class on heap memory

Question

A class type called "Pair" has already been defined for you. You need to write a function called pairFactory that creates an instance of Pair on the heap. Do not create the object on the stack. Then, your function needs to return a pointer to that created object.

I have written the code for pairFactory. It seems to run, but I get an InfraError. Please help me find my mistake. Also, I need to create the object in heap memory.

#include <iostream>

// This class Pair has already been defined for you.
// (You may not change this definition.)
class Pair {
public:
  int first, second;
  void check() {
    first = 5;
    std::cout << "Congratulations! The check() method of the Pair class \n has executed. (But, this isn't enough to guarantee \n that your code is correct.)" << std::endl;
  }
};

Pair *pairFactory() {
  //
    Pair P;
    P.check();
  // (You can use as many lines as you want.)
  return &P;
}

// Your function should be able to satisfy the tests below. You should try
// some other things to convince yourself. If you have a bug in this problem,
// the usual symptom is that after you submit, the grader will crash with a
// system error. :-)
int main() {
    Pair *p;
    p = new pairFactory();

  // This function call should work without crashing:
  p->check();

  // Deallocating the heap memory. (Assuming it was made on the heap!)
  delete p;

  std::cout << "If you can see this text, the system hasn't crashed yet!" << std::endl;

  return 0;
}

Answer 1

You've got it backwards. Your factory needs to allocate on the heap. What you're doing is returning the address of a function-local object that doesn't exist anymore.

Pair *pairFactory() {
  return new Pair;
}

And then in your main function:

Pair *p = pairFactory();