Erle Robotics C++ GitBook

The delete operator

In most cases, memory allocated dynamically is only needed during specific periods of time within a program; once it is no longer needed, it can be freed so that the memory becomes available again for other requests of dynamic memory.That is, de-allocates memory that was previously allocated using new.The delete operatot takes a pointer to the memory location.

The syntaxis is the following:

delete pointer;
delete[] pointer;

The first statement releases the memory of a single element allocated using new, and the second one releases the memory allocated for arrays of elements using new and a size in brackets ([]).

The value passed as argument to delete shall be either a pointer to a memory block previously allocated with new, or a null pointer (in the case of a null pointer, delete produces no effect).

Let's see one example step by step: We are going to implement a function which returns a pointer to some memory containing the integer 5.

  • Allocate memory using new to ensure it remains allocated.
    int *getPtrToFive() {
    int *x = new int;
    *x = 5;
    return x;
  • When done, de-allocate the memory using delete. ```cpp


    using spacename std;

int getPtrToFive() { int x = new int; *x = 5; return x; }

int main() { int p = getPtrToFive(); cout << p << endl; // 5 delete p; }

If you don’t use de-allocate memory using
delete, your application will waste memory.When your program allocates memory but is
unable to de-allocate it, this is a memory leak.

So the final searched result is:
#include <iostream>
using namestapce std;

int *getPtrToFive() {
 int *x = new int;
 *x = 5;
 return x;

int main() {
 int *p;
 for (int i = 0; i < 3; ++i) {
  p = getPtrToFive();
  cout << *p << endl;
  delete p;

 return 0;

Note that to fix the memory leak, de-allocate memory within the loop. Remember to only delete if memory was allocated by new.