Question

I have two classes with inheritance at the minute, one is a base class and contains polymorphism, it is the interface:

#include <vector>
#ifndef _Signal_h
#define _Signal_h
using namespace std;

typedef vector<double> DIMENTIONS_2;

class Signal {

public:

    Signal();
    Signal(const int N, const int M)
    {
        this->width = N;
        this->height = M;
    };

    virtual vector<DIMENTIONS_2> splitSignal(vector<double> &theData) const = 0;
    virtual vector<DIMENTIONS_2> filterSignal(vector<DIMENTIONS_2>&blocks) const = 0;
    virtual vector<double> returnRawSignal() const = 0;

    virtual int zerocross() const = 0;
    virtual double energy() const = 0;
    virtual int zerocrossmap() = 0;
    virtual bool readSignal() const = 0;

protected:

    vector<double> rawSignal;
    int width;
    int height;
};

#endif

And one of the classes that inherits and implements from this:

#include "Signal.h"

#ifndef _Audio_h
#define _Audio_h

typedef vector<double> DIMENTIONS_2;

class Audio : public Signal {

  public:

     Audio();
     Audio(const int N, const int M);

     vector<DIMENTIONS_2> splitSignal(vector<double>&data, int N, int M);
     vector<DIMENTIONS_2> filter(vector<DIMENTIONS_2> &data, double sumthres, double zerothres);

     double energy(vector<double> &blocks);

     int zerocross(vector<double> &block);

     int zerocrossmap(vector<double> &strippedData);

     template<typename T>
     int sign(T n);
 };


 #endif

The Audio class has implementation (.cpp) but whenever I try to compile using this:

g++ Signal.h Audio.h Audio.cpp main.cpp 

I get the following error:

Undefined symbols for architecture x86_64:
“Signal::Signal()”, referenced from:
Audio::Audio() in ccdjMubM.o
Audio::Audio() in ccdjMubM.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status

Any ideas?

Answer 1

The constructor Signal() was not implemented. Just added that and it should solve your issue.