Layout de memória de structs e classes

layout.cpp

//16B
struct message {
  int x; //4B
  int y; //4B
  int z; //4B
  int w; //4B
};

//16B
struct pack1 {
  message m1;
};

//16 + 8 + 8
struct pack2 {
  message m1;
  message *m2;
  message &m3;
};

std::cout << sizeof(pack1) << std::endl; //16
std::cout << sizeof(pack2) << std::endl; //32