What is relloc() ?
relloc() function is used to change the size of the memory block without losing the old data.
syntax:
void *realloc(void *ptr, size_t newSize);
On failure, realloc return NULL
Example of malloc():
int *ptr = (int *)malloc(sizeof(int));
Example of realloc():
ptr = (int *)realloc(ptr, 2*sizeof(int));
- This will allocate memory space of 2*sizeof(int).
- Also, this function moves the contents of the old block to a new block and the data of the old block is not lost.
- We may lose the data when the new size is smaller than the old size.
- Newly allocated bytes are unitialised.
Example:
#include<stdio.h>
#include<stdlib.h>
int main(){
int i;
int *ptr = (int *)malloc(2*sizeof(int));
if(ptr == NULL){
printf("Memory not available!");
exit(1);
}
printf("Enter the two numbers: \n");
for(i=0; i<2; i++){
scanf("%d",ptr+i);
}
ptr = (int *)realloc(ptr, 4*sizeof(int));
if(ptr == NULL){
printf("Memory not available!");
exit(1);
}
printf("Enter two more integer: \n");
for(i=2; i<4; i++){
scanf("%d",ptr+i);
}
for(i=0; i<4; i++){
printf("%d ",*(ptr+i));
}
return 0;
}
Output:
Enter the two numbers:
1
2
Enter two more integer:
3
4
1 2 3 4
