gistfile1.txt

chavao@ubuntu:~/Desktop/cpp/proj$ g++ -c -g rumo.cpp
chavao@ubuntu:~/Desktop/cpp/proj$ g++ -g -g main.cpp
main.cpp: In function ‘int main()’:
main.cpp:8: error: aggregate ‘Rumo r’ has incomplete type and cannot be defined
chavao@ubuntu:~/Desktop/cpp/proj$ 

main.cpp

#include <iostream>
using namespace std;

class Rumo;

int main()
{
    Rumo r;
    cout << "Valor: " << r.obterValor() << endl;

    return 0;
}

rumo.cpp

#include <iostream>
using namespace std;

class Rumo
{
    private:
        int valor;
    public:
        void setValor(int v);
        int obterValor() const; 
};

int Rumo::obterValor() const
{
    return valor;
}

void Rumo::setValor(int v)
{
    valor = v;
}