Assign integer value to heap

Question

  #include<iostream>
  using namespace std;
  int main() 
  { 
    int i= new int;
    cout<<i;
    return 0;
  }

when i tried to assign int i value to heap it shows error: invalid conversion from 'int*' to 'int'

when i assign value to int pointer then it assign to it.why we cannot assign value to int to heap.Yes i know as much as possible avoid assigning value to heap. I looked many stackoverflow post everyone explained about int *p=new int[10]; Please someone explain this to me. Thanks for your help.

Answer 1

new int returns a pointer to int, that is, int*. Assigning it to an int is an obvious type mismatch.

The pointer returned by new T points to a memory location on the heap a.k.a. free store, which provides enough space to store one object of type T. T is an arbitrary type here.

Your code could be altered to this:

int* ptr = new int;
*ptr = 1;
cout << *ptr;    // prints 1

Don't forget to delete afterwards!

---

Note that the heap should only be used for dynamic data used beyond scope boundaries. In your case, it's way too heavyweight. Just use a good old automatic variable:

int i = 1;

Answer 2

new int;

allocates memory for a single int, initializes one int in there, and gives you a pointer to that. It doesn't give you an int but a pointer to int, hence int*.

You probably just want to do

int i = 42;

or so.

EDIT:

You can of course also do

int* i = new int;

but the way you use it, you shouldn't do that. Memory gotten via new stays allocated until you delete it; that means that you'd code a memory leak if you used new without delete.