c++ - How do I resolve the "undefined reference to `vtable for <<ClassName>>" error? -

i c++ beginner. have singleton 'manager' class shown below , following error when build project in eclipse:

../src/manager.hpp:28: undefined reference 'vtable manager'

[the below code minimum (almost) run in dev environment or ides if want try , reproduce error.]

manager.hpp

#include <iostream> #include <vector> #include <cstdio> #include <cstring> #include <unistd.h>  #include "stream_state.h"   class manager {     public:        static manager* getinstance();        std::vector<stream_state> m_statelist;      // why can not remove std::?         virtual ~manager();      // virtual destructor      private:        manager(){};                               // error points here - why so?        manager(manager const&){};        static manager* psingleton; }; 

manager.cpp

#include "manager.hpp"  manager* manager::psingleton = 0;  manager* manager::getinstance() {     if (psingleton == null){         psingleton = new manager;     }     return psingleton; }  // other member function implementations 

main.cpp

#include <iostream> #include <stdlib.h> #include "manager.hpp"  int main(int argc, char** argv) {      manager* managerobj;     managerobj = manager::getinstance();     // other code     return 0; } 

stream_state.h

struct stream_state {    file* sp;    bool locked; }; 

what have tried (and didn't work):
1. changed constructor manager class to:
manager::manager(){}; error: extra qualification 'manager::' on member 'manager'

2. removed std:: line std::vector<stream_state> m_statelist; vector<stream_state> m_statelist; error: vector not name type

can please explain me undefined reference 'vtable manager' error (and, if possible no necessary, vector not name type error)?

i see declaration ~manager() don't see definition. needs in manager.cpp.

i believe getting obscure message because vtable holds addresses of virtual functions. have 1 virtual function , haven't defined it.

i can't reproduce vector error. once add ~manager::manager() { } manager.cpp, version compiles fine.