How to find size of structure without using sizeof operator in C?

Question

How can I wwap value two variables without using third variable or +/- operator?

Answer 1

Evaluate Size of Structure Without using Sizeof Operator.

Sizeof operator is used to evaluate the size of any data type or any variable in c programming. Using sizeof operator is straight forward way of calculating size but following program will explain you how to calculate size of structure without using sizeof operator.

#include<stdio.h>

struct
  {
  int num1,num2;
  char s1;
  int *ptr;
  int abc[5];
}a[2];

void main()
  {
  int start,last;
  start = &a[1].num1;
  last = &a[0].num1;
  printf("\nSize of Structure : %d Bytes",start-last);
}

Output :

Size of Structure : 17 Bytes

Answer 2

#include <stdio.h>
typedef  struct
{
   int a;
   int b;
}str;


int main()
{
   str x;
   str *ptr  = &x;

   printf("%u", (char*)(ptr+1) - (char*)ptr);

   return 0;
}

Output = 8