Thread: abstract class member cannot be overladed?

I'm getting the following error when I compile:

Code:

error: 'virtual const int Base::getX() const' and 'virtual const int Base::getY() const' cannot be overloaded

Here's a look at the files in question:

main.cpp

Code:

#include <iostream>
#include "derived.h"
 
int main(){
 
  Derived( 1, 1 );
 
  return 0;
}

derived.h

Code:

#ifndef DERIVED_H_
#define DERIVED_H_
 
#include <iostream>
 
class Base{
  public:
    Base( int x, int y ) : x(x), y(y) {}
    virtual const int getX() const = 0; // Error is with these two lines
   virtual const int getY() const = 0;
 
  protected:
    int x, y;
};
 
class Derived : public Base{
  public:
    Derived( int x, int y );
    const int getX() const;
    const int getY() const;
    const int getZ() const;
 
    friend std::ostream& operator<<( std::ostream& os, const Derived& d );
    friend class Modifier;
 
  private:
    int z;
    void setZ( int val );
};
 
#endif

derived.cpp

Code:

#include "derived.h"
 
Derived::Derived( int x, int y )
: Base(x,y), z( x ) {}
 
const int Derived::getX() const{ return x; }
const int Derived::getY() const{ return y; }
const int Derived::getZ() const{ return z; }
 
void Derived::setZ( int val ){ z = val; }
 
std::ostream& operator<<( std::ostream& os, const Derived& d ){
  os << d.x << " " << d.y << " " << d.z;
  return os;
}

I am afraid that I cannot duplicate the error.

???

The screwy thing is i only get the error on 1 computer and the code compiles just fine on another... ?

Is there any cases where you can't overload base class members in this fashion (I'm not aware of any). This really sucks because I need it to compile on the machine that's giving me the error.

What OS/Compiler version?

gg

cygwin/g++

Let's try this with just one file:

Code:

#include <iostream>

class Base{
public:
    Base( int x, int y ) : x(x), y(y) {}
    virtual const int getX() const = 0;
    virtual const int getY() const = 0;

protected:
    int x, y;
};

class Derived : public Base {
public:
    Derived( int x, int y );
    const int getX() const;
    const int getY() const;
    const int getZ() const;

    friend std::ostream& operator<<( std::ostream& os, const Derived& d );
    friend class Modifier;

private:
    int z;
    void setZ( int val );
};

int main() {
    Derived( 1, 1 );

    return 0;
}

Derived::Derived( int x, int y ) : Base(x,y), z( x ) {}

const int Derived::getX() const { return x; }
const int Derived::getY() const { return y; }
const int Derived::getZ() const { return z; }

void Derived::setZ( int val ){ z = val; }

std::ostream& operator<<( std::ostream& os, const Derived& d ) {
    os << d.x << " " << d.y << " " << d.z;
    return os;
}

Do you get any compilation errors when compiling the above program?

Do you get any compilation errors when compiling the above program?

No. I even copied the contents of the files into new files in a new directory, compiled and everything was OK.

But if I go back into the troubled files and compile I get the error. Now what the heck is the deal with that? I mean, they're identical now.

???

EDIT: also, the Makefile is identical too.

Maybe try a make clean and then rebuild from scratch, though I would think that stale object files would only cause a linking error.

In the old directory (where the problem was), there's also some dependencies that have since been renamed (i.e. old_dependancy.d is no longer needed, and has been replaced by new_dependancy.d. Those dependancies came from old_dependancy.cpp and new_dependancy.cpp respectively).

The only thing I can think of is that make is relying on the info old_dependancy.d has, and can't resolve something.

It is make that is throwing the error....

yea, I was cleaning the directory, but I was getting rid of the old dependancies. I guess that was the problem.

EDIT: make that "wasn't" getting rid of the old dependancies.