Need help with linking error.

[cheZ]

I wanted to try to make a simple factoring program just to try to use a class in a separate file and try using a constructor. When I try to compile I get this error: "in function 'main' [Linked error] undefined reference to 'Factor::Factor(int)' " and "Id returned one exit status [build error] ["Factoring] error 1

Here is my main.cpp

#include <cstdlib>
#include <iostream>
#include "factor.h"

using namespace std;

int main(int argc, char *argv[])
{
int number;
cout << "Enter a number to be factored. ";
cin >> number;
Factor numb(number);
system("PAUSE");
return 0;
}

this is my header file

#ifndef FACTOR_H
#define FACTOR_H

/*
* Factors integers
*/
class Factor
{
public:
// class constructor
Factor(int);
//Factorize function
void Factorize(int);
};

and this is my class's .cpp file

#include "factor.h" // class's header file
#include <iostream>

using namespace std;

// class constructor
Factor::Factor(int a)
{
Factorize(a);
}

void Factorize (int num){
int count = 1;
int factor[num];

while (count <= num){
if (num % count == 0)
factor[count-1] = count;
else
factor[count-1] = 0;

count++;
}
count = 0;
while (count < num){
if (factor[count] != 0)
cout << factor[count] << ", ";
count++;

}
}

[ciphermagi]

Try changing:

#include <cstdlib>
#include <iostream>
#include "factor.h"

using namespace std;

int main(int argc, char *argv[])
{
    int number;
    cout << "Enter a number to be factored. ";
    cin >> number;
    Factor numb(number);
    system("PAUSE");
    return 0;
}

to:

#include <cstdlib>
#include <iostream>
#include "factor.h"

using namespace std;

Factor::Factor(int);

int main(int argc, char *argv[]){
    int number;
    cout << "Enter a number to be factored. ";
    cin >> number;
    Factor numb(number);
    cin.ignore();
    return 0;
}

[cheZ]

I tried that and got the following errors:
in line 3 "In file inlcuded from main.cpp"
in line 3:1 "unterminated #ifndef
in line 7: "Declaration of 'Factor::Factor(int)' outside of class is not a definition"

[ciphermagi]

Okay, we determined what's wrong here. You didn't end your pre-processor if statement. So take Factor::Factor(int); out of the main cpp file again, and change your header from:

#ifndef FACTOR_H
#define FACTOR_H

/*
* Factors integers
*/
class Factor
{
public:
    // class constructor
    Factor(int);
    //Factorize function
    void Factorize(int);
};

to:

#ifndef FACTOR_H
#define FACTOR_H
#endif

/*
* Factors integers
*/
class Factor
{
public:
    // class constructor
    Factor(int);
    //Factorize function
    void Factorize(int);
};

EDIT: Using code tabs would probably have made this easier to read. Might be something to look in to in the future.

[cheZ]

okay thanks, I did that and it fixed the new error message but the original linking error is still there.

[zb0S216C]

Undefined references occur when an invoked function doesn't have an associated definition. For instance, consider this example:

int Function();

int main()
{
    return Function();
}

What do you notice? I'll tell you; Function() is never defined; that is, it's never given a body. By omitting the body of a function, you fail to give the linker the information it needs to assemble the function. To fix this, you would add the following after main():

int Function()
{
    return(0);
}

To define a method (a function that resides within a class), you would qualify the method with the identifier of the class followed by the scope resolution operator, as such:

class COMyClass
{
    public:
        void MyMethod();
};

// Define the method:
void COMyClass::MyMethod()
{
    // ...
}

ciphermagi wrote:

Factor::Factor(int); (sic)

This is not a definition.

_Wazzak

[ciphermagi]

It wasn't meant to be a definition. It was meant to be a prototype.

[cheZ]

I think I have the methods defined in the factor class's .cpp file. I'm new to using classes though so maybe I have them defined incorrectly or in the wrong place

[zb0S216C]

Correct me if I'm wrong, but isn't the prototype within the class itself?

_Wazzak

[ciphermagi]

@cheZ: You do have the definitions in the class' cpp file.

@Framework: Prototyping the call forces the call to be "correct" according to the order of operations, which can force the compiler/debugger to tell you more about why it's an undefined reference.

[zb0S216C]

I know what a prototype is.

_Wazzak

[ciphermagi]

I'm not questioning that. I'm saying that in this case, I used it as a debugging tool to force the compiler to spit out different errors that can help triangulate the actual problem.