Malloc function in c

Question

I made a program in c that uses malloc function. Code:

#include<stdio.h>
#include<stdbool.h>
#include<malloc.h>

int main(){
    int n;
    int *ptr,i,sum;
    sum = 0;
    printf("Enter the number = ");
    scanf("%d",&n);
    ptr = (int *)(malloc(10));
    for(i=0;i<n;i++){
        scanf("%d",ptr+i);
        sum += *(ptr+i);
    }
    printf("The sum of the numbers is = %i",sum);
}

I have used malloc function to allocate a memory of 10 bytes .How is it possible that 10 integers are stored in 10 bytes....

integers normally take 4 bytes and you are writing out of the bounds — Pooya, Apr 29 '16 at 16:52
*"How is it possible that 10 integers are stored in 10 bytes...."* It's not. — Baum mit Augen, Apr 29 '16 at 16:52
you have to add the size of the datatype: `ptr = malloc(sizeof(int) * n);` — jboockmann, Apr 29 '16 at 16:57
You do not storing 10 ints in 10 bytes space with your code. Actually you do not storing any int in your 10 bytes space either. — , Apr 29 '16 at 17:18
@piling: But yes, he does: `scanf("%d",ptr+i);`, writing beyond the limits of the array, if n is > 2... — Aconcagua, Apr 30 '16 at 05:21

score 1 · Answer 1 · answered Apr 29 '16 at 16:52

1

It is possible by luck.

You write outside the allocated area and consequently your program has UB (Undefined Behavior).

However, the program may appear to work in some situations but in general it may crash at any time.

answered Apr 29 '16 at 16:52

Support Ukraine

42,271
4
38
63

Malloc function in c

1 Answers1