Error compiling a class in C ++

I get two mistakes and I do not know why.

Statement of the exercise:

  

Implement the TAD (abstract data type) ConjuntoCadenas .

     

This TAD will consist of a structure capable of storing a set of at most 100 different strings.

     

The TAD will be implemented by a class called ConjuntoCadenas in a module named ccadenas ( ccadenas.h and ccadenas.cpp ).

     

The namespace used in this module must be modulosp2 .

     

The operations that will have this TAD defined are:

     

• leerDeFichero : You will receive as a parameter the name of a file with one string per line. The method will add the strings that appear in the file to the set.

  

• escribirAFichero : You will receive as a parameter the name of a file and what   will overwrite with the strings that the set contains.

  

• incluir : Receives a string as a parameter and adds it to the set. If the string already exists in the set it will not do anything.

  

• pertenece : It receives as a parameter a string and returns if it belongs or not to the set.

  

• eliminar : It receives as a parameter a string and if it belongs to the set it eliminates it.

  

• listar : Shows all the strings of the set per screen.

  

• vaciar : Remove all elements from the set.

  

I just made the first point to see how it started.

This is the code ccadenas.h :

#ifndef CCADENAS_H
#define CCADENAS_H

#include <iostream>
#include <fstream>
#include <string>

namespace modulosp2 {
    class ConjuntoCadenas {
        public:
        void leerDeFichero(std::string fichero);

        private:
        static const int MAX=100;
        typedef std::string TDatos[MAX];
        struct conjunto {
            int tamanyo=0;
            TDatos cadena;
        };
        conjunto datos;
        std::string linea;  
    };
}
#endif // CCADENAS_H

The code ccadenas.cpp :

#include "ccadenas.h"
#include <fstream>
#include <iostream>
#include <string>

using namespace std;

namespace modulosp2 {
    void ConjuntoCadenas::leerDeFichero(string fichero) {
        ifstream fin;

        fin.open(fichero.c_str());

        while (!fin.eof()) {
            if(datos.tamanyo<MAX) {
                lleno=false;
                getline(fin, linea);
                datos.cadena[datos.tamanyo]=linea;
                datos.tamanyo++;
            } else {
                lleno=true;
            }
        }
        fin.close();
    }
}

Which I get the following errors:

  

undefined reference to WinMain @ 16

     

error: ld returned 1 exit status

Finally the main code conjuntos.cpp :

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

using namespace modulosp2;
using namespace std;

int menu() {
    int op;
    cout<<"\t0. Fin"<<endl;
    cout<<"\t1. Leer de fichero"<<endl;
    while(op<0||op>1) {
        cout<<"\tOpcion?: "<<endl;
        cin>>op;
    }
    return op;
}

int main() {
    int op;
    string fichero;
    ConjuntoCadenas concad;
    do {
        op=menu();
        switch(op) {
            case 1:
                cout<<"\tIntroduzca el nombre del fichero"<<endl;
                getline(cin, fichero);
                concad.leerDeFichero(fichero);
            break;
        }
    }while(op!=0);
    return 0;
}

Which I get the following errors:

  

modulosp2 :: SetChains :: readFile (std :: string)

     

error: ld returned 1 exit status