C++ wrapper to GNU Readline

I'm trying to write a c++ wrapper for GNU Readline to be able to use custom completion easily, but I'm running into a small problem and can't think of a solution (I'm pretty new to c++).

class ReadLine {

public:

    ReadLine();
    ~ReadLine();

    std::string exec ();
    void enableHistory ();

private:
    std::vector<std::string> keywordList;
    bool history;

private:
    static char** my_completion (const char*, int, int);
    void* xmalloc (int);

    char* generator (const char*, int);
    char* dupstr (std::string);

};

cpp file:

std::string ReadLine::exec(){

    rl_attempted_completion_function = my_completion;

    std::string buf = "";

    buf = readline("Command>>");
    //enable auto-complete
    rl_bind_key('\t',rl_complete);

    if (buf[0]!=0)
        add_history(buf.c_str());

    return buf;
}




char** ReadLine::my_completion (const char* text, int start, int end) {


    char** matches;

    matches = NULL;

    if (start == 0) 
        matches = rl_completion_matches(text, my_generator);

    return matches;


}

My problem is the line

matchs = rl_completion_matches（text，my_generator）

Obviously throws an error: call to non-static member function without an object argumentbut I don't want to make the generator static, and I can't find the parameters it should take, because I won't have access to the class members in it (I need to use a keyword list to generate the keywords).

What do you suggest?