// This file is a "Hello, world!" in C++ language by GCC for wandbox.
#include <iostream>
#include <cstdlib>
#include <thread>
#include <vector>
class FooBase
{
virtual void OnStateChange() = 0;
};

class FooBaseImpl : public FooBase {
    void OnstateChange() override {
        // stuff in static stateChange();
    }
};

class FooImpl : public FooBase
{
  void OnStateChange() { .. }
};

class Bar
{
    Bar() {
        static FooBaseImpl impl
        foovec.push_back(&impl);
    }

void test() {
   Foo::stateChange();
   for(f : foovec) f->OnStateChange();
}
vector<FooBase*> foovec;
}