align.c

/tmp ➤ gcc foo.c -m32
/tmp ➤ ./a.out
one offset: 0
two offset: 4
three offset: 12
/tmp ➤ cat foo.c
#include <stdio.h>
#include <stdint.h>

struct foo {
    int32_t one;
    int64_t two;
    int32_t three;
};

int main(void) {
    struct foo f;
    printf("one offset: %lu\n",(unsigned long)&f.one - (unsigned long)&f);
    printf("two offset: %lu\n",(unsigned long)&f.two - (unsigned long)&f);
    printf("three offset: %lu\n",(unsigned long)&f.three - (unsigned long)&f);
}