Memory alignment demonstration thingie

memory-alignment.c

#include <stddef.h>
#include <stdio.h>

#define STR(x) #x

typedef struct 
{
    // === funny little waste of memory due to alignment (or lack thereof) ===
    //  my CPU can only address bytes in multiples of four
    //  using a non-multiple of 4 number of bytes for the "name" field makes
    //  age be placed in the next offset that is a multiple of 4, namely 20 in this case
    char name[17];
    int age;
} Person;

int main()
{
    Person old_dude = {"Very old dude", 123};
    Person* pointer_to_dude = &old_dude;

    unsigned char* dude_as_byte_array = (unsigned char*)pointer_to_dude;

    size_t offset_of_age_in_bytes = offsetof(Person, age);

    int dudes_age = *(dude_as_byte_array + offset_of_age_in_bytes);
    
    printf("%s: %lu\n", STR(offset_of_age_in_bytes), offset_of_age_in_bytes);
    printf("Dude's age is %d\n", dudes_age);
}