class A : B, std::enable_shared_from_this<A>
{
public:
    A();
    virtual ~A();
public:
    void initStr(std::string str=""){m_STR = str;};
private:
    std::string m_STR;
};

struct A : B, std::enable_shared_from_this<A> {
    A();
    virtual ~A();

    void initStr(std::string str = {}) { m_STR = str; }

private:
    std::string m_STR;
};

class A : public B, public std::enable_shared_from_this<A>
{
public:
    A();
    virtual ~A();
public:
    void initStr(std::string str=""){m_STR = str;};
private:
    std::string m_STR;
};