Глубокое копирование присваиванием по умолчанию? Как?

// strngbad.h -- flawed string class definition
#include <iostream>
#ifndef STRNGBAD_H_
#define STRNGBAD_H_
#define _CRT_SECURE_NO_WARNINGS
class StringBad
{
private:
    char * str;                // pointer to string
    int len;                   // length of string
    static int num_strings;    // number of objects
public:
    StringBad(const StringBad&);
    StringBad(const char * s); // constructor
    StringBad();               // default constructor
    ~StringBad();              // destructor
// friend function
    friend std::ostream & operator<<(std::ostream & os, 
                       const StringBad & st);
};
#include <cstring>                    // string.h for some
using std::cout;
// initializing static class member
int StringBad::num_strings = 0;
// class methods
// construct StringBad from C string
StringBad::StringBad(const char * s)
{
    len = std::strlen(s);             // set size
    str = new char[len + 1];          // allot storage
    std::strcpy(str, s);              // initialize pointer
    num_strings++;                    // set object count
    cout << num_strings << ": \"" << str
        << "\" object created";    // For Your Information
    cout << "; address str " << &str << "\n";
}
StringBad::StringBad()                // default constructor
{
    len = 4;
    str = new char[4];
    std::strcpy(str, "C++");          // default string
    num_strings++;
    cout << num_strings << ": \"" << str
        << "\" default object created";  // FYI
    cout << "; address str " << &str << "\n";
}
StringBad::StringBad(const StringBad&sb)//copy constructor
{
    this->len = sb.len;
    str = new char[len + 1];
    std::strcpy(str, sb.str);
    num_strings++;
    cout << num_strings << ": \"" << str
        << "\" object created by copy constructor";    // For Your Information
    cout << "; address str " << &str << "\n";
}
StringBad::~StringBad()               // necessary destructor
{
    cout << "\"" << str << "\" object deleted, ";    // FYI
    --num_strings;                    // required
    cout << num_strings << " left"; // FYI
    cout << "; address str " << &str << "\n";
    delete[] str;                    // required
}
std::ostream & operator<<(std::ostream & os, const StringBad & st)
{
    os << st.str;
    return os;
}
#endif

using std::cout;
#include "strngbad.h"
 
void callme1(StringBad &);  // pass by reference
void callme2(StringBad);    // pass by value
 
int main()
{
    using std::endl;
    {
        cout << "Starting an inner block.\n";
        StringBad headline1("Celery Stalks at Midnight");
        StringBad headline2("Lettuce Prey");
        StringBad sports("Spinach Leaves Bowl for Dollars");
        cout << "headline1: " << headline1 << endl;
        cout << "headline2: " << headline2 << endl;
        cout << "sports: " << sports << endl;
        callme1(headline1);
        cout << "headline1: " << headline1 << endl;
        callme2(headline2);
        cout << "headline2: " << headline2 << endl;
        cout << "Initialize one object to another:\n";
        StringBad sailor = sports;
        cout << "sailor: " << sailor << endl;
        cout << "Assign one object to another:\n";
        StringBad knot;
        knot = headline1;
        cout << "knot: " << knot << endl; 
        cout << "Exiting the block.\n";
    }
    cout << "End of main()\n";
    std::cin.get();
    return 0;
}
 
void callme1(StringBad & rsb)
{
    cout << "String passed by reference:\n";
    cout << "    \"" << rsb << "\"\n";
}
 
void callme2(StringBad sb)
{
    cout << "String passed by value:\n";
    cout << "    \"" << sb << "\"\n";
}