Question

I have the following code:

template <class T>
static std::string ToString(const T& t)
{
  stringstream temp;
  temp << t;
  return temp.str();
}

It compiles with no problems with Visual C++ on Windows, but when trying to compile it with GCC on Linux I get the following error:

no match for 'operator<<' in 'temp << t'

What could be the reason for that?

Thank you in advance.

Answer 1

That depends on the type T as Space_C0wb0y said.

Check out the following code

#include <sstream>
#include <iostream>

template<typename T>
static std::string ToString(const T& t){
  std::stringstream temp;
  temp << t;
  return temp.str();
}
struct empty{};
struct non_empty{
  std::string str;
  non_empty(std::string obj):str (obj){}
  friend std::ostream& operator << (std::ostream& out, const non_empty &x);
};

std::ostream& operator << (std::ostream& out, const non_empty &x){
    out << x.str;
    return out;
}

int main(){
   std::string s = ToString<double>(12.3); // this will work fine
 /*********************************************************************************
  * std::string k = ToString(empty()); // no match for 'operator<<' in 'temp << t'*
  *********************************************************************************/
   std::string t = ToString(non_empty("123")); // this works too

}

A call to ToString(empty()); gives the same error that you have got but ToString(non_empty("123")); is fine. What does that imply?