undefined reference to

Question

This is the error I am keep getting . undefined reference to my class. I am not sure. I think I m linking them. this is how my main looks like.

    #include <iostream>
    #include "randomNumberMagnifier.h"

    using namespace std;

     int main()
      {
        randomNumberMagnifier r1, r2;

      cout << "Random Number "<< r1.getRandomNumber();
       cout << endl;


      } 

I am not sure what I am doing wrong. this is what it looks like. when I compile

      [singha1@cs1 p4]$ g++ -c randomNumberMagnifier.cpp
       [singha1@cs1 p4]$ g++ -o p4Driver.cpp
        g++: no input files
        p4Driver.cpp:(.text+0x8c): undefined reference to `randomNumberMagnifier::getRandomNumber
     collect2: ld returned 1 exit status



      #ifndef RANDOMNUMBERMAGNIFIER_H
#define RANDOMNUMBERMAGNIFIER_H

class randomNumberMagnifier
{
  int addFactor;
  int multFactor;
  bool addOn;
  bool multOn;
  int randomNumber;
  static const int MAX_ADD_FACTOR = 100;
  static const int MAX_MULT_FACTOR = 20;
  static const int MAX_RANDOM = 200;

 public:
  randomNumberMagnifier();

  //~randomNumberMagnifer();

  randomNumberMagnifier& operator=(const randomNumberMagnifier& rhs);

  randomNumberMagnifier(const randomNumberMagnifier& arandom);

  randomNumberMagnifier(bool aState, bool mState);

  int randomMagnifier();

  int getAdd();
  int getMult();

  bool getAddState();
  bool getMultState();

  int getRandomNumber();


};
#endif

Answer 1

g++ -o p4Driver.cpp

That doesn't say what it's supposed to compile to, which is what -o is supposed to be for. You want:

g++ -c randomNumberMagnifier.cpp
g++ -c p4Driver.cpp
g++ randomNumberMagnifier.o p4Driver.o -o p4Driver

Or just:

g++ randomNumberMangifier.cpp p4Driver.cpp -o p4Driver

Answer 2

you need to provide randomNumberMagnifier.o to g++ command, so it can find function definition. I tested with below command and i worked

g++ -o p4Driver p4Driver.cpp randomNumberMagnifier.o