stringstream->rdbuf()->pubsetbuf is not setting the buffer

Question

I am trying to modify a stringbuffer of a stringstream object without having to copy a string, using the method pubsetbuf, but it is not working. I am following the document

Answer 1

Not should set contents. pubsetbuf calls virtual setbuf

basic_streambuf* setbuf(charT* s, streamsize n);

15 Effects: implementation-defined, except that setbuf(0,0) has no effect.

16 Returns: this.

VS 2010. There is no overload of virtual method setbuf in basic_stringbuf, it uses default from basic_streambuf

virtual _Myt *__CLR_OR_THIS_CALL setbuf(_Elem *, streamsize)
    {   // offer buffer to external agent (do nothing)
    return (this);
    }