realloc(), free()

realloc() function in C

• When memory is not available for malloc) (or calloc), (the memory can be re-allocated by the function reloc). (For short, it does change the size of the memory.
• Let's see the syntax of realloc() function.

ptr=realloc(ptr, new-size)

free() function in C

• The memory occupied by malloc() or calloc() functions must be released by calling free() function. Otherwise, it will consume memory until program exit.
• Let's see the syntax of free() function.
• free(ptr)

Use of free()

#include <stdio.h>

#include <stdlib.h>

int main()

{

    int *ptr, i , n1, n2;

    printf("Enter size: ");

    scanf("%d", &n1);

    ptr = (int*) malloc(n1 * sizeof(int));

    printf("Addresses of previously allocated memory: ");

    for(i = 0; i < n1; ++i)

         printf("%u\n",ptr + i);

    printf("\nEnter the new size: ");

    scanf("%d", &n2);

    // rellocating the memory

    ptr = realloc(ptr, n2 * sizeof(int));

    printf("Addresses of newly allocated memory: ");

    for(i = 0; i < n2; ++i)

         printf("%u\n", ptr + i);

  

    free(ptr);

    return 0;

}

Output will be

Enter size: 2

Addresses of previously allocated memory:26855472

26855476

Enter the new size: 4

Addresses of newly allocated memory:26855472

26855476

26855480

26855484