[asadullah.ansari]

Quote:

Originally Posted by mr.anandc

Here my doubt is, if ptr value is 0 which is NULL, why access to b using ptr (ptr->b) is not crashing .

Thanks.

That is Now your Intelligent question!!!

#include<stdio.h>
#include<stdlib.h>
#define offsetof(s,m) (size_t)&(((s *)0)->m)
#define Off(i,j)  ((i*)0)->j


struct Data
{
 int a;
 int b;
};

int main()
{
  int OffSet=offsetof(Data, b);
  printf("%d", OffSet) ;
  return 0;
}

In above  code , You are only getting the address not accessing.


int main()
{ 
  int Add=Off(Data , b);
  printf("%d", Add) ;
  return 0;
}

In this code , now you are accessing so segmentation fault will come.