Виртуальные абстрактные базовые классы

//workermi.h
#ifndef WORKERMI_H_
#define WORKERMI_H_
 
#include <iostream>
#include <string>
 
//abstract base class
class Worker {
private:
    std::string fullname;
    long id;
protected:
    virtual void Data() const;
    virtual void Get();
public:
    Worker() : fullname("no one"), id(0L) { }
    Worker(const std::string & s, long i) : fullname(s), id(i) { }
    //~Worker();
    virtual ~Worker() = 0;
    virtual void Set() = 0;         // cleanly virtual function
    virtual void Show() const = 0;
};
 
class Waiter : virtual public Worker {
private:
    int panache;
protected:
    virtual void Data() const;
    virtual void Get();
public:
    Waiter() : Worker(), panache(0) { }
    Waiter(const std::string & s, long i, int p = 0) :
        Worker(s, i), panache(p) { }
    Waiter(const Worker & wk, int p = 0) :
        Worker(wk), panache(p) { }
    //~Waiter();
    void Set();
    void Show() const;
};
 
class Singer : virtual public Worker {
protected:
    enum { other, alto, contralto, soprano, bass,
            baritone, tenor };
    enum { Vtypes = 7 };
    virtual void Data() const;
    virtual void Get();
private:
    static char *pv [Vtypes];
    int voice;
public:
    Singer() : Worker(), voice(other) { }
    Singer(const std::string & s, long i, int v = other) :
        Worker(s, i), voice(v) { }
    Singer(const Worker & wk, int v = other) :
        Worker(wk), voice(v) { }
    //~Singer();
    void Set();
    void Show() const;
};
 
class SingingWaiter: public Waiter, public Singer {
protected:
    void Data() const;
    void Get();
public:
    SingingWaiter() { }
    SingingWaiter(const std::string & s, long i, int p = 0, int v = other) :
        Worker(s, i), Waiter(s, i, p), Singer(s, i, v) { }
    SingingWaiter(const Worker & wk, long i = 0, int v = other) :
        Worker(wk), Waiter(wk, i), Singer(wk, v) { }
    SingingWaiter(const Waiter & wt, int v = other) :
        Worker(wt), Waiter(wt), Singer(wt, v) { }
    SingingWaiter(const Singer & sg, long i = 0) :
        Worker(sg), Waiter(sg, i), Singer(sg) { }
    //~SingingWaiter();
    void Set();
    void Show() const;
};
 
#endif /* WORKERMI_H_ */

//workermi.cpp
#include "workermi.h"
 
//============================================= Worker
void Worker::Data() const {
    std::cout << "Name:" << fullname << std::endl;
    std::cout << "ID: " << id << std::endl;
}
 
void Worker::Get() {
    std::getline(std::cin, fullname);
    std::cout << "Enter ID of the worker: ";
    std::cin >> id;
    while(std::cin.get() != '\n')
        continue;
}
 
//============================================= Waiter
void Waiter::Data() const {
    std::cout << "Panache index: " << panache << std::endl;
}
 
void Waiter::Get() {
    std::cout << "Enter the Panache index: ";
    std::cin >> panache;
    while(std::cin.get() != '\n')
        continue;
}
 
void Waiter::Set() {
    std::cout << "Enter first and second name of the Waiter: ";
    Worker::Get();
    Get();
}
 
void Waiter::Show() const {
    std::cout << "The Waiter category\n";
    Worker::Data();
    Data();
}
 
//============================================= Singer
char * Singer::pv [Singer::Vtypes] = { "other", "alto", "contralto",
        "soprano", "bass", "baritone", "tenor"};
 
void Singer::Data() const {
    std::cout << "Vocal range: " << pv[voice] << std::endl;
}
 
void Singer::Get() {
    std::cout << "Enter vocal range value of the singer: " << std::endl;
    int i;
    for(i = 0; i < Vtypes; i++) {
        std::cout << i << ": " << pv[i] << " ";
        if (i % 4 == 3)
            std::cout << std::endl;
    }
    if (i%4 != 0)
        std::cout << '\n';
    std::cin >> voice;
    while(std::cin.get() != '\n')
        continue;
}
 
void Singer::Set() {
    std::cout << "Enter first and second name of the Singer: ";
    Worker::Get();
    Get();
}
 
void Singer::Show() const {
    std::cout << "The Singer category\n";
    Worker::Data();
    Data();
}
 
//============================================= SingingWaiter
 
void SingingWaiter::Data() const {
    Waiter::Data();
    Singer::Data();
}
void SingingWaiter::Get() {
    Waiter::Get();
    Singer::Get();
}
 
void SingingWaiter::Set() {
    std::cout << "Enter first and second name of the Singer: ";
    Worker::Get();
    Get();
}
 
void SingingWaiter::Show() const {
    std::cout << "The SingingWaiter category\n";
    Worker::Data();
    Data();
}

//QueWorMain.h
#include <iostream>
#include "workermi.h"
 
int main() {
    std::cout << "Hello" << std::endl;
    return 0;
}

//Console
Building target: Prta_G14_zL3
Invoking: Cross G++ Linker
g++  -o "Prta_G14_zL3"  ./QueWorMain.o ./bank.o ./queue.o ./workermi.o   
./workermi.o: In function `~Waiter':
/home/farik/Prog/Workspace/Prta_G14_zL3/Debug/../workermi.h:24: undefined reference to `Worker::~Worker()'
/home/farik/Prog/Workspace/Prta_G14_zL3/Debug/../workermi.h:24: undefined reference to `Worker::~Worker()'
./workermi.o: In function `~Singer':
/home/farik/Prog/Workspace/Prta_G14_zL3/Debug/../workermi.h:41: undefined reference to `Worker::~Worker()'
/home/farik/Prog/Workspace/Prta_G14_zL3/Debug/../workermi.h:41: undefined reference to `Worker::~Worker()'
./workermi.o: In function `~SingingWaiter':
/home/farik/Prog/Workspace/Prta_G14_zL3/Debug/../workermi.h:62: undefined reference to `Worker::~Worker()'
./workermi.o:/home/farik/Prog/Workspace/Prta_G14_zL3/Debug/../workermi.h:62: more undefined references to `Worker::~Worker()' follow
collect2: выполнение ld завершилось с кодом возврата 1
make: *** [Prta_G14_zL3] Ошибка 1

virtual ~Worker();

Building file: ../workermi.cpp
Invoking: Cross G++ Compiler
g++ -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"workermi.d" -MT"workermi.d" -o "workermi.o" "../workermi.cpp"
../workermi.cpp:43:41: предупреждение: deprecated conversion from string constant to «char*» [-Wwrite-strings]
../workermi.cpp:43:41: предупреждение: deprecated conversion from string constant to «char*» [-Wwrite-strings]
../workermi.cpp:43:41: предупреждение: deprecated conversion from string constant to «char*» [-Wwrite-strings]
../workermi.cpp:43:41: предупреждение: deprecated conversion from string constant to «char*» [-Wwrite-strings]
../workermi.cpp:43:41: предупреждение: deprecated conversion from string constant to «char*» [-Wwrite-strings]
../workermi.cpp:43:41: предупреждение: deprecated conversion from string constant to «char*» [-Wwrite-strings]
../workermi.cpp:43:41: предупреждение: deprecated conversion from string constant to «char*» [-Wwrite-strings]
Finished building: ../workermi.cpp
 
Building target: Prta_G14_zL3
Invoking: Cross G++ Linker
g++  -o "Prta_G14_zL3"  ./QueWorMain.o ./bank.o ./queue.o ./workermi.o   
./workermi.o:(.rodata._ZTV13SingingWaiter[vtable for SingingWaiter]+0x28): undefined reference to `SingingWaiter::~SingingWaiter()'
./workermi.o:(.rodata._ZTV13SingingWaiter[vtable for SingingWaiter]+0x30): undefined reference to `SingingWaiter::~SingingWaiter()'
./workermi.o:(.rodata._ZTV13SingingWaiter[vtable for SingingWaiter]+0x70): undefined reference to `non-virtual thunk to SingingWaiter::~SingingWaiter()'
./workermi.o:(.rodata._ZTV13SingingWaiter[vtable for SingingWaiter]+0x78): undefined reference to `non-virtual thunk to SingingWaiter::~SingingWaiter()'
./workermi.o:(.rodata._ZTV13SingingWaiter[vtable for SingingWaiter]+0xd8): undefined reference to `virtual thunk to SingingWaiter::~SingingWaiter()'
./workermi.o:(.rodata._ZTV13SingingWaiter[vtable for SingingWaiter]+0xe0): undefined reference to `virtual thunk to SingingWaiter::~SingingWaiter()'
./workermi.o:(.rodata._ZTC13SingingWaiter0_6Waiter[vtable for SingingWaiter]+0x28): undefined reference to `Waiter::~Waiter()'
./workermi.o:(.rodata._ZTC13SingingWaiter0_6Waiter[vtable for SingingWaiter]+0x30): undefined reference to `Waiter::~Waiter()'
./workermi.o:(.rodata._ZTC13SingingWaiter0_6Waiter[vtable for SingingWaiter]+0x90): undefined reference to `virtual thunk to Waiter::~Waiter()'
./workermi.o:(.rodata._ZTC13SingingWaiter0_6Waiter[vtable for SingingWaiter]+0x98): undefined reference to `virtual thunk to Waiter::~Waiter()'
./workermi.o:(.rodata._ZTC13SingingWaiter16_6Singer[vtable for SingingWaiter]+0x28): undefined reference to `Singer::~Singer()'
./workermi.o:(.rodata._ZTC13SingingWaiter16_6Singer[vtable for SingingWaiter]+0x30): undefined reference to `Singer::~Singer()'
./workermi.o:(.rodata._ZTC13SingingWaiter16_6Singer[vtable for SingingWaiter]+0x90): undefined reference to `virtual thunk to Singer::~Singer()'
./workermi.o:(.rodata._ZTC13SingingWaiter16_6Singer[vtable for SingingWaiter]+0x98): undefined reference to `virtual thunk to Singer::~Singer()'
./workermi.o:(.rodata._ZTV6Singer[vtable for Singer]+0x28): undefined reference to `Singer::~Singer()'
./workermi.o:(.rodata._ZTV6Singer[vtable for Singer]+0x30): undefined reference to `Singer::~Singer()'
./workermi.o:(.rodata._ZTV6Singer[vtable for Singer]+0x90): undefined reference to `virtual thunk to Singer::~Singer()'
./workermi.o:(.rodata._ZTV6Singer[vtable for Singer]+0x98): undefined reference to `virtual thunk to Singer::~Singer()'
./workermi.o:(.rodata._ZTV6Waiter[vtable for Waiter]+0x28): undefined reference to `Waiter::~Waiter()'
./workermi.o:(.rodata._ZTV6Waiter[vtable for Waiter]+0x30): undefined reference to `Waiter::~Waiter()'
./workermi.o:(.rodata._ZTV6Waiter[vtable for Waiter]+0x90): undefined reference to `virtual thunk to Waiter::~Waiter()'
./workermi.o:(.rodata._ZTV6Waiter[vtable for Waiter]+0x98): undefined reference to `virtual thunk to Waiter::~Waiter()'
collect2: выполнение ld завершилось с кодом возврата 1
make: *** [Prta_G14_zL3] Ошибка 1

virtual ~Worker() = 0;

#include <iostream>
 
using namespace std;
 
class A
{
public:
    virtual ~A()=0;
};
 
A::~A()
{
  cout<<"class A destructor"<<endl;
}
 
class B: public A
{
public:
    virtual ~B();
};
 
B::~B()
{
    cout<<"class B destructor"<<endl;
}
 
void test()
{
    B b;
}
 
 
int main()
{
    test();
    getchar();
    return 0;
}