composition versus inheritance.cpp

#include <cstdio>

class A {
  double X;
  int Y;
};

class B {
  A base;
  int Z;
};

class C: A {
    int Z;
};

int main() {
  printf("sizeof(A) = %lu, alignof(A) = %lu\n", sizeof(A), alignof(A));
  printf("sizeof(B) = %lu, alignof(B) = %lu\n", sizeof(B), alignof(B));
  printf("sizeof(C) = %lu, alignof(C) = %lu\n", sizeof(C), alignof(C));
  return 0;
}
/*
sizeof(A) = 16, alignof(A) = 8
sizeof(B) = 24, alignof(B) = 8
sizeof(C) = 16, alignof(C) = 8
*/

gistfile1.cpp

#include <cstdio>

class A {
public:
  double X;
  int Y;
};

class B {
  A base;
  int Z;
};

class C: A {
    int Z;
};

int main() {
  printf("sizeof(A) = %lu, alignof(A) = %lu\n", sizeof(A), alignof(A));
  printf("sizeof(B) = %lu, alignof(B) = %lu\n", sizeof(B), alignof(B));
  printf("sizeof(C) = %lu, alignof(C) = %lu\n", sizeof(C), alignof(C));
  return 0;
}
/*
sizeof(A) = 16, alignof(A) = 8
sizeof(B) = 24, alignof(B) = 8
sizeof(C) = 24, alignof(C) = 8
*/