What is Memory Leak? How can we avoid?

Data can be stored in either stack or heap memory. The stack stores local variables and parameters of the function while the heap is used for dynamic memory allocation during runtime.
A memory leak occurs when a program dynamically allocates memory but does not release it after it's no longer needed.

• In C, memory is allocated using malloc() / calloc() and released using free().
• In C++, memory is allocated using new / new[] and released using delete / delete[].

Memory Leak

#include <iostream>
using namespace std;

int main()
{

    // allocate memory
    int *ptr = new int;
    *ptr = 20;
    cout << *ptr << endl;

    // Forgot to delete memory delete ptr;
    return 0;
}

#include <stdio.h>
#include <stdlib.h>

int main()
{
    
    // allocate memory
    int *ptr = (int *)malloc(sizeof(int)); 

    *ptr = 10;
    printf("%d\n", *ptr);

    // Forgot to free memory free(ptr) is missing
    return 0;
}

Common Causes of Memory Leak

• Memory is allocated (malloc/new) but not released (free/delete).
• If a pointer to allocated memory is overwritten or goes out of scope without freeing, the memory it pointed to becomes unreachable.
• In long-running programs, even small leaks add up over time. This gradually eats up system memory, making the program slow or crash.

How to avoid memory leaks?

• Always free/ delete the memory after use.
• Don't overwrite a pointer before freeing its old memory.
• In C++, prefer smart pointers (unique_ptr, shared_ptr) to handle memory automatically.
• Use tools like Valgrind to detect leaks during testing.