Наследование от std::ostream

#include <iostream>
 
class DebugMessage : public std::ostream
{
public:
    DebugMessage() : std::ostream( std::cout.rdbuf() ) { }
    virtual ~DebugMessage() { *this << std::endl; }
};
 
int main(int argc, char *argv[])
{
    DebugMessage() << "hello" << 42;
 
    return 0;
}

#include <iostream>
 
class mycout : public std::ostream {
public:
  mycout() : std::ostream(std::cout.rdbuf()) { }
};
 
int main() {
  mycout z;
  mycout() << "Hello, World !!!" << std::endl;
  z<<"Heelo, World!!!"<<std::endl;
}

#include <iostream>
     
class DebugMessage
{
private:
    std::ostream& stream;
public:
    DebugMessage() : stream( std::cout ) { }
    virtual ~DebugMessage() { stream << std::endl; }
    operator std::ostream&() { return stream; }
};
     
int main(int argc, char *argv[])
{
    static_cast<std::ostream&>(DebugMessage()) << "hello" << 42;
    return 0;
}

#include <iostream>
 
class DebugMessage 
{
private: 
    std::ostream& stream;
public:
    DebugMessage() : stream( std::cout ) { }
    virtual ~DebugMessage() { stream << std::endl; }
    
    template<typename T>
    std::ostream& operator<<( const T& t ) const
    {
        return stream << t;
    }
};
 
int main(int argc, char *argv[])
{
    DebugMessage() << "hello" << 42;
    return 0;
}

template<typename T>
const DebugMessage& operator<<( const T& t ) const
{
   stream << t;
   return *this;
}

std::ostream& operator << (const std::ostream& t, const char * n){ 
   //Здесь const_cast, иначе метод write() не работает
}

ostream(cout.rdbuf()) << "Hello";

#include <iostream>
#include <cstring>
 
std::ostream& operator << ( std::ostream& t, const char * n)
{ 
    for( int i=0; i<3; ++i )
    {
        t.write( n, strlen(n) );
    }
    return t;
}
 
int main() {
    
    std::cout << "ho" << std::endl;
    
    return 0;
}

DebugMessage() << "hello" << static_cast<std::ostream&(*)(std::ostream&)>(std::endl) << 42;