Correctly over-loading a stringbuf to replace cout in a MATLAB mex file

You don’t really want to overload std::stringbuf, you want to overload std::streambuf or std::basic_streambuf (if you want to support multiple character types), also you need to override the overflow method as well.

But I also think you need to rethink your solution to your problem.

cout is just an ostream, so if all classes / functions takes an ostream then you can pass in anything you like. e.g. cout, ofstream, etc

If that’s too hard then I would create my own version of cout, maybe called mycout that can be defined at either compiler time or runtime time (depending on what you want to do).

A simple solution may be:

#include <streambuf>
#include <ostream>

class mystream : public std::streambuf
{
public:
    mystream() {}

protected:
    virtual int_type overflow(int_type c)
    {
        if(c != EOF)
        {
            char z = c;
            mexPrintf("%c",c);
            return EOF;
        }
        return c;
    }

    virtual std::streamsize xsputn(const char* s, std::streamsize num)
    {
        mexPrintf("*s",s,n);
        return num;
    }
};

class myostream : public std::ostream
{
protected:
    mystream buf;

public:
    myostream() : std::ostream(&buf) {}
};

myostream mycout;

And the cout version could just be:

typedef std::cout mycout;

A runtime version is a bit more work but easily doable.