如何从C++ std :: basic_ostream派生并使<< operator virtual？

#include<iostream>
#include<ostream>

class MyOStream : public std::basic_ostream<char> {
public:
    MyOStream(std::basic_streambuf<char>* sb) : std::basic_ostream<char>(sb) {}
};

class MyOStream : public std::basic_ostream<char> {
public:
    MyOStream(std::basic_streambuf<char>* sb) : std::basic_ostream<char>(sb) {}

    virtual MyOStream& operator<<(const char* s) {
        // 在这里实现你的代码
        return *this;
    }
};

class MyOStream : public std::basic_ostream<char> {
public:
    MyOStream(std::basic_streambuf<char>* sb) : std::basic_ostream<char>(sb) {}

    virtual MyOStream& operator<<(const char* s) {
        std::string str(s);
        std::transform(str.begin(), str.end(), str.begin(), ::toupper);
        write(str.c_str(), str.size());
        return *this;
    }
};

int main() {
    MyOStream my_ostream(std::cout.rdbuf());
    my_ostream << "Hello, World!"<< std::endl;
    return 0;
}