Linking problem

Det på engelsk af hensyn til at jeg også har stilt spørgsmålet i andre forum..
Jeg bruger gcc 3.4.3, på hhv. FreeBSD 5.4 RC2 og/eller 5.3 RELEASE. Jeg kan bare ikke finde noget ordentligt dokumentation på fejlmeldingerne fra GCC.

I've implemented the statemachine pattern in AggState pasted into the bottom of this post..
I'm getting these linker errors when trying to build the main executable.

My problem is I don't really know what the errormessages mean.. Thus I can't fix the problem.
Any of you guys able to help me? Or at least point me in the direction of a better discription of the errormessage, then just the errormessage.


g++ -I/usr/local/include/mysql++/ -I/usr/local/include/ -I/usr/local/include/mysql/  -L/usr/local/lib -L/usr/local/lib/mysql  -pthread -lqosmysql -lqosthreads -lqoslog -lqoslegacynetstuff -lqoscommon -lqosmeasuring  main.cpp -o measuring
/usr/local/lib/libqosmeasuring.so: undefined reference to `typeinfo for AggState'
/usr/local/lib/libqosmeasuring.so: undefined reference to `vtable for AggState'
*** Error code 1




Code:
#ifndef _AGGSTATE_H_
#define _AGGSTATE_H_

//#include <map>
#include <list>
#include <set>
#include <functional>
#include <utility>
#include <limits>
#include <math.h>
#include <sys/time.h>
#include "Packet.h"
#include "AggregationPacket.h"
#include "../common/QoSTime.h"

class AggState
{
public:
        AggState(      std::list<AggregationPacket> *win,
                                std::list<AggregationPacket> *buf,
                                QoSTime &winStart, QoSTime &winEnd) :
                                start(winStart), end(winEnd)
        {
                this->nnp = true;
                this->win_rdy = false;
                this->win = win;
                this->buf = buf;
        }
        virtual ~AggState() {};
        /* handlePacket handles the packet, and returns the
        * next state..
        * */
        virtual AggState *handlePacket(std::list<AggregationPacket>::iterator *itPtr);
        virtual bool needsNextPacket()  { return this->nnp; }
        virtual bool windowIsReady()    { return this->win_rdy; }
        static AggState *getInitialState(
                                std::list<AggregationPacket> *win,
                                std::list<AggregationPacket> *buf,
                                QoSTime &winStart, QoSTime &winEnd);
protected:
        bool nnp;
        bool win_rdy;
        QoSTime start;
        QoSTime end;
        std::list<AggregationPacket> *win;
        std::list<AggregationPacket> *buf;
};

class AggUpState : public AggState
{
public:
        virtual ~AggUpState() {}
        AggUpState(std::list<AggregationPacket> *win,
                                std::list<AggregationPacket> *buf,
                                QoSTime &winStart, QoSTime &winEnd) :
                                                AggState(win, buf, winStart, winEnd) { }
        virtual AggState *handlePacket(std::list<AggregationPacket>::iterator *itPtr);
};
class AggPotUpState : public AggState
{
public:
        virtual ~AggPotUpState() {}
        AggPotUpState(std::list<AggregationPacket> *win,
                                std::list<AggregationPacket> *buf,
                                QoSTime &winStart,
                                QoSTime &winEnd,
                                QoSTime &goodPacketStartTime) :
                                AggState(win, buf, winStart, winEnd),
                                goodPacketStartTime(goodPacketStartTime) { }
        virtual AggState *handlePacket(std::list<AggregationPacket>::iterator *itPtr);
protected:
        QoSTime goodPacketStartTime;
};

class AggPotDownState : public AggState
{
public:
        virtual ~AggPotDownState() {}
        AggPotDownState(std::list<AggregationPacket> *win,
                                std::list<AggregationPacket> *buf,
                                QoSTime &winStart,
                                QoSTime &winEnd,
                                QoSTime &lossStartTime) :
                                AggState(win, buf, winStart, winEnd),
                                lossPacketStartTime(lossStartTime) { }
        virtual AggState *handlePacket(std::list<AggregationPacket>::iterator *itPtr);
protected:
        QoSTime lossPacketStartTime;
};

class AggDownState : public AggState
{
public:
        virtual ~AggDownState() {}
        AggDownState(std::list<AggregationPacket> *win,
                                std::list<AggregationPacket> *buf,
                                QoSTime &winStart, QoSTime &winEnd) :
                                                        AggState(win, buf, winStart, winEnd) { }
        virtual AggState *handlePacket(std::list<AggregationPacket>::iterator *itPtr);
};



#endif //_AGGSTATE_H_