#include <iostream>

#include <stddef.h>

template <typename CountedType>
class ObjectCounter {
  private:
    static size_t count;    // number of existing objects

  protected:
    // default constructor
    ObjectCounter() {
        ++count;
    }

    // copy constructor
    ObjectCounter (ObjectCounter<CountedType> const&) {
        ++count;
    }

    // destructor
    ~ObjectCounter() {
        --count;
    }

  public:
    // return number of existing objects:
    static size_t live() {
        return count;
    }
};

// initialize counter with zero
template <typename CountedType>
size_t ObjectCounter<CountedType>::count = 0;


template <typename CharT>
class MyString : public ObjectCounter<MyString<CharT> > {
  //...
};

int main()
{
    MyString<char> s1, s2;
    MyString<wchar_t> ws;

    std::cout << "number of MyString<char>:    "
              << MyString<char>::live() << std::endl;
    std::cout << "number of MyString<wchar_t>: "
              << ws.live() << std::endl;
}