俺が思いついた不自然な振る舞い方
class CBase {
protected:
CBase(int &instance_counter):InstanceCounter(instance_counter)
{InstanceCounter++;}
int &InstanceCounter;
public:
int get_count() {InstanceCounter;}
virtual ~CBase(){InstanceCounter--;}
};
class CDerivedA: public CBase {
　static int countA;
public:
CDerivedA() : CBase(countA) {}
protected:
CDerivedA(int &count) : CBase(count) {}
};
class CDerivedB: public CDerivedA {
　static int countB;
public:
CDerivedB() : CDerivedA(countB) {}
};