c++ - Standard functions and operations not working in class constructor -

i trying make first class constructor , seems acting strangely. class derived filebuf , reason, unable open in constructor. tried add cout statement debugging, << operator not recognized.

#include <iostream> #include "bin.h"  int main() {     bin mybin("e:\temp\test.txt");       system("pause");     return 0; } 

bin.h

#pragma once #include <fstream> #include <cstdlib> #include <cstring>  class bin : private std::filebuf {  int buffsize = 1000; char* buffer; unsigned int length; short int buffcounter;  public:     bin(std::string filename)     {         open(filename.c_str(), std::ios::in | std::ios::out | std::ios::trunc);         if (!is_open())             std::cout << "error: failed open file " << filename << std::endl;          //set io operations unbufferred, buffering managed manually         setbuf(0, 0);         //create buffer         buffer = new char[buffsize];      };        virtual ~bin()     {         delete buffer;     }; }; 

std::cout << "error: failed open file " << filename << std::endl; 

should

std::cout << "error: failed open file " << filename.c_str() << std::endl; 

std::cout doesn't accept std::string accept const char *