test.cxx

#include <iostream>
#include <functional>
#include <vector>
#include <cstdint>
struct Base
{
  std::vector<std::function<void(void)>> fOnInit{};
  Base()
  {
    std::cout << "Calling Base constructor\n";
  }
  void onInit()
  {
    for (auto& f: fOnInit)
      f();
  }
};

// return a lambda expression whose return type is the class generated
#define MKCLASS(NAME)							\
  []()									\
  {									\
    struct temp : public virtual Base					\
  {									\
    uint32_t f ## NAME[64*256];						\
    temp()								\
    {									\
									\
      fOnInit.push_back([this]()					\
      {									\
	std::cout << "Setting up f"#NAME" at "<< &(this->f##NAME)	\
		  <<"\n";						\
      });								\
    }									\
    } tempobj;								\
  return tempobj;							\
  }


template<auto... bases>
struct All: public decltype(bases())...
{
};

int main()
{
  All<MKCLASS(Foo), MKCLASS(Bar), MKCLASS(Baz)> a;
  a.onInit();
  std::cout << &(a.fFoo) << "\n";
  std::cout << &(a.fBar) << "\n";
  std::cout << &(a.fBaz) << "\n";
  std::cout << sizeof(a.fOnInit) << "\n";
  std::cout << sizeof(a)*1.0/4/64/256 << "\n";
}

/*
output 
Calling Base constructor
Setting up fFoo at 0x7ffdc1a96958
Setting up fBar at 0x7ffdc1aa6960
Setting up fBaz at 0x7ffdc1ab6968
0x7ffdc1a96958
0x7ffdc1aa6960
0x7ffdc1ab6968
24
3.00073
*/