Multiple definition with 2 header files

I am using CodeBlocks.

In C++, I have 3 header files and 3 cpp files like below.

Base.h

class Base
{
public:
    virtual int funky(int x, int y);
};

Base.cpp

 int funky(int x, int y) {
  return x+y;
}

FirstClass.h

class FirstClass: public Base
{
public:
    virtual int funky(int x, int y);
};

FirstClass.cpp

int funky(int x, int y) {
  return x+y;
}

SecondClass.h

class SecondClass: public Base
{
public:
    virtual int funky(int x, int y);
};

SecondClass.cpp

int funky(int x, int y) {
  return x+y;
}

In this condition I take error of "multiple definition." But, I have to use these functions with the same names. I tried

int funky (int x, int y) override;
 

but it did not work.

I need all three function, because when I want to call them like below and if they are defined like above, I cannot reach them.

 vector<Base> BASE =  {FirstClass(), SecondClass()};
 BASE[1]->funky(1,2)

Do you have any suggestion? I am open to another approach to this problem. Thank you.

In the above code sample, you defining funky in two different cpp files but have declared in your class. So following should be the correct format:

FirstClass.cpp

int FirstClass::funky(int x, int y) {
  return x+y;
}

SecondClass.cpp

int SecondClass::funky(int x, int y) {
  return x+y;
}

main.cpp

FirstClass a;
SecondClass b;

cout<<a.funky(1,2)<<" "<<b.funky(3,4)<<endl;