realloc in c

1/*prototype of realloc*/
2void *realloc(void *ptr, size_t newsize);
3
4/*use*/
5dyn_array = realloc(dyn_array, (dyn_array_size + 1) * sizeof(int));
6
7/*
8	adds one more space to dyn_array
9    you need stdlib.h for this
10*/

1int ptr_new = *realloc(void *ptr, size_t size); 
2Where 'ptr_new' is the new pointer you want to point to the required Dynamic
3memory, 'ptr' is the already existing pointer to a dynamic memory and 'size'
4is the new size of dynamic memory that you want to allocate.
5
6Working:
7Realloc creates/allocates a new memory in heap with specified size and copies
8all the contents from the previous memory pointer to by the pointer 'ptr'.
9It the deallocates the memory in heap pointed to by the old pointer i.e, 'ptr'.
10Note: pointer 'ptr' should also point to a memory in heap.

1void *realloc(void *ptr, size_t size)

1#include <stdio.h>
2int main () {
3   char *ptr;
4   ptr = (char *) malloc(10);
5   strcpy(ptr, "Programming");
6   printf(" %s,  Address = %u\n", ptr, ptr);
7
8   ptr = (char *) realloc(ptr, 20); //ptr is reallocated with new size
9   strcat(ptr, " In 'C'");
10   printf(" %s,  Address = %u\n", ptr, ptr);
11   free(ptr);
12   return 0;
13}