Size of Structure

UNIX for Beginners Q & A UNIX for Dummies Questions & Answers
1

How can we find size of a structure with out using sizeof operator?

Thanks,
Harika

2

one way to how they are allocated in memory:

typedef 
struct 
{
     char a;
     int b;
} mystruct_t;


int main()
{
	mystruct_t arr[2]={0x0,0};
	printf("%u %u\n", &arr[1], &arr[0]);
	return 0;
}

The difference between the two addresses is how the individual structs are parked in memory.
I get

or 8 bytes, this is because both variables in the struct are word-aligned - ie on exact 4 byte boundaries.

3

another way...

#include <stdio.h>

main(void)
{
    struct one
    {
        int a;
        char b;
    } x;
    char dummy;
    printf("size of struct one is %i bytes\n", (int) &(dummy) - (int) &(x.a));
}