struct packed aligned

#include <stdio.h>
#include <stdlib.h>

int main ()
{

    struct st1{
        char a;
        char* a1;
        char* a2;
    };

    struct st2{
        char a;
        char* a1 __attribute__ ((packed));
        char* a2 __attribute__ ((packed));
    };

    struct st3{
        int a;
        char* a1;
        char* a2;
    };

    struct st4{
        int a;
        char* a1 __attribute__ ((packed));
        char* a2 __attribute__ ((packed));
    };

    struct st5{
        char a __attribute__ ((aligned (16)));
        char* a1 __attribute__ ((aligned (16)));
        char* a2 __attribute__ ((aligned (16)));
    };

    struct st6{
        char a;
        char* a1;
        char* a2;
    } __attribute__ ((aligned (32)));


    printf("sizeof int: %zu\n", sizeof(int));
    printf("sizeof char*: %zu\n", sizeof(char*));

    printf("(1) %zu\n", sizeof (struct st1));
    printf("(2) %zu\n", sizeof (struct st2));
    printf("(3) %zu\n", sizeof (struct st3));
    printf("(4) %zu\n", sizeof (struct st4));
    printf("(5) %zu\n", sizeof (struct st5));
    printf("(6) %zu\n\n", sizeof (struct st6));


}

/*
output:

sizeof int: 4
sizeof char*: 8
(1) 24
(2) 17
(3) 24
(4) 20
(5) 48
(6) 32

*/