Question

#include<iostream>
using namespace std;
struct data {
  int x;
  data *ptr;
};

int main() {
 int i = 0;
  while( i >=3 ) {
    data *pointer = new data;  // pointer points to the address of data
    pointer->ptr = pointer;    // ptr contains the address of pointer
    i++;
  }
 system("pause");
}

Let us assume after iterating 3 times :

 ptr had address = 100 after first loop
 ptr had address = 200 after second loop
 ptr had address = 300 after third loop

Now the questions are :

1. Do all the three addresses that were being assigned to ptr exist in the memory after the program gets out of the loop ?
2. If yes , what is the method to access these addresses after i get out of the loop ?

Answer 1

For starters, there will be no memory allocated for any ptr with the code you have.

int i = 0;
while( i >= 3)

This will not enter the while loop at all.

However, if you are looking to access the ptr contained inside the struct then you can try this. I am not sure what you are trying to achieve by assigning the ptr with its own struct object address. The program below will print the value of x and the address assigned to ptr.

#include<iostream>
using namespace std;
struct data {
  int x;
  data *ptr;
};

int main() {
 int i = 0;
 data pointer[4];
  while( i <=3 ) {
    pointer[i].x = i;
    pointer[i].ptr = &pointer[i];  
    i++;
  }

for( int i = 0; i <= 3; i++ )
{
   cout<< pointer[i].x << endl;
   cout<< pointer[i].ptr << endl;
}

}

OUTPUT:

0
0xbf834e98
1
0xbf834ea0
2
0xbf834ea8
3
0xbf834eb0

Personally, when I know the number of iterations I want to do, I choose for loops and I use while only when I am looking to iterate unknown number of times before a logical expression is satisfied.