Thread: errors reported using friend

Neither of the following programs compile in MSVC++ v 6.0 but both compile, run, and give expected results in Dev-C++. Any explanation for the descrepency? Any suggested corrections to get it to compile with MSVC++?

Code:

#include <iostream> 
using namespace std; 
 
class ClassType 
{ 
  public: 
    int f; 
    int s; 
    friend ostream & operator<<(ostream &, ClassType &); 
}; 
 
ostream & operator<<(ostream & os, ClassType & ct) 
{ 
  os << ct.f << ' ' << ct.s << endl; 
  return os;  
} 
 
int main() 
{ 
   ClassType classType; 
   classType.f = 5; 
   classType.s = 89; 
   cout << classType << endl; 

   char ch;
   cin >> ch;
   return 0; 
}

error message:
C:\Program Files\Microsoft Visual Studio\MyProjects\mySamples\mySamples.cpp(78) : error C2593: 'operator <<' is ambiguous
Error executing cl.exe.

and it points to this line in main():
cout << classType << endl;

Code:

#include <iostream> 
using namespace std; 
 
class ClassType 
{ 
  public: 
    int f; 
    int s; 
    friend  ClassType operator+(ClassType &, ClassType &); 
    const ClassType & operator=(const ClassType & rhs); 
}; 
 
const ClassType & ClassType::operator =(const ClassType & rhs) 
{ 
  f = rhs.f; 
  s = rhs.s; 
} 
 
 
ClassType operator+(ClassType & lhs, ClassType & rhs) 
{ 
  ClassType temp; 
  temp.f = lhs.f + rhs.f; 
  temp.s = lhs.s + rhs.s; 
  return temp; 
} 
 
int main(int argc, char* argv[]) 
{ 
  ClassType ct1; 
  ct1.f = 5; 
  ct1.s = 89; 
  
  ClassType ct2; 
  ct2.f = 6; 
  ct2.s = 11; 
 
  ClassType ct3; 
  ct3 = ct1 + ct2; 
  cout << ct3.f << ' ' << ct3.s << endl; 
 
  char ch;
  cin >> ch;
  return 0; 
}

error message is:
C:\Program Files\Microsoft Visual Studio\MyProjects\mySamples\mySamples.cpp(20) : fatal error C1001: INTERNAL COMPILER ERROR
(compiler file 'msc1.cpp', line 1786)
Please choose the Technical Support command on the Visual C++
Help menu, or open the Technical Support help file for more information

and it relates to line:

friend ClassType operator+(const ClassType &, const ClassType &);

Both example compile fine in dev-c++ except this line:

Code:

const ClassType & operator=(ClassType & rhs);

needs to be const ClassType & for the parameter...

The first compiles fine in VC++ 7.1, and the second needs a return value for operator=, but otherwise compiles fine.

I tested it with MSVC++ 6 and I get the same errors...seems to have a problem with having operator << declared in the class and having operator << defined for ClassType, but not being part of the class...The only way i got it to work was to remove your definition of operator << and put it inside the class:

Code:

class ClassType 
{ 
  public: 
    int f; 
    int s; 
    friend ostream & operator<<(ostream & os, ClassType & ct)
{
os << ct.f << ' ' << ct.s << endl; 
 return os;  
} 
 /*
ostream & operator<<(ostream & os, ClassType & ct) 
{ 
  os << ct.f << ' ' << ct.s << endl; 
  return os;  
} 
*/

Does it work if you forward declare the function? E.g. does this work:

Code:

#include <iostream> 
using namespace std; 

class ClassType;
ostream & operator<<(ostream & os, ClassType & ct);
 
class ClassType 
{ 
  public: 
    int f; 
    int s; 
    friend ostream & operator<<(ostream &, ClassType &); 
}; 
 
ostream & operator<<(ostream & os, ClassType & ct) 
{ 
  os << ct.f << ' ' << ct.s << endl; 
  return os;  
} 
 
int main() 
{ 
   ClassType classType; 
   classType.f = 5; 
   classType.s = 89; 
   cout << classType << endl; 

   char ch;
   cin >> ch;
   return 0; 
}

There is no reason that this should present a problem, it is a compiler error in VC++ 6. Prior to 7.1, VC++ was not a very decent compiler.

Seems to work Too bad...MSVC++ 6 is the best I can get for free (legally) Dev-Cpp is pretty darn good compiler though

Originally posted by elad
my copy of Dev-C++ frequently throws an out of bounds error message if I don't do things exacly right, like type in the name of the index in a subscript operator, etc. Therefore I gave it up and started using VC++. Now I don't get the out of bounds error boxes that were so annoying, but I'm running into other problems instead. MSVC++ v 7.1 is the 2003 version of Visual Studio .NET is it not? I've been reluctant to go that route because of the added layer of complexity and proprietary(ness) that .NET brings, but maybe I'll have to bite the bullet and go for it.

Anybody with VC 6 able to come up with a work around/explanation for the second program (the + operator overaloaded as a friend function)?

Nothing says you need to do .NET programming in VC++ .NET. It lets you do it if you want, it never forces you to.

The .NET versions do not take AWAY any features/language support, they only add more. If you don't like the new stuff, don't use it.

And VC++7.1 is, according to some statistics I've seen, the most standards-compliant compiler out there.

Maybe are you right, I don't actually have MSVC 7.1 and I've not seen benchmarks since the v7.0.

[EDIT]May I ask a question? Is MSVC 7.1 really more standard-compliant than GCC 3.2? Because as far as I know (I don't know much on compilers that I don't use however), the only feature that is not supported by GCC is the export keyword.