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Find size of structure variable(any variable) without using sizeof operator in C

This is one of the interview question, beginners could note, below is one of the way how we can find size of structure without using sizeof operator in C

It is explained with simple program as follows

#include<stdio.h>
struct test
{
 int a;
 char c;
 double d;
};

int main()
{
struct test *p;
int size=0;
/*
 * initialize struct pointer with
 * zero after type casting it to of type (struct test *)
 */

p=(struct test *)0;

/* by adding one to p gives size of struct */
size =(int)(p+1);

printf("without using sizeof %d\n", size);

/* verify result with sizeof operator */
printf("with using sizeof %d\n", sizeof(struct test));

return 0;
}

same way we can find size of other variables as well :-)


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