BasicSingleton.cpp

// Basic singleton implementation
// Requires construction to be called before usage 
// (so no lazy initialization)

// --- singleton.h
class Singleton {
public:
  Singleton();
  virtual ~Singleton();
  static Singleton *getInstance() {
    return m_activeSingleton;
  }  
  //...
private:
  static Singleton *m_activeSingleton;
};
  
// --- singleton.cpp
Singleton* Singleton::m_activeSingleton = NULL;

Singleton::Singleton()
{
  if (m_activeSingleton == NULL)
    m_activeSingleton = this;
}

Singleton::~Singleton()
{
  if (m_activeSingleton == this)
    m_activeSingleton = NULL;
}

// --- derived class

class ConsoleLog: public Singleton {
public:
   void addText(const std::string &a_text) {
      cout << a_text;
   }
  static ConsoleLog *getInstance() {
    return static_cast<ConsoleLog *>(Singleton::getInstance());
  }  
};

// --- main
void foo() {
  ConsoleLog::getInstance()->addText("Test");
}

int main(int argc, char* argv[])
{
  std::unique_ptr<ConsoleLog> consoleLog(new ConsoleLog);
  foo();
}