Undefined reference to vtable

Question

When building my C++ program, I'm getting the error message

undefined reference to 'vtable...

What is the cause of this problem? How do I fix it?

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It so happens that I'm getting the error for the following code (The class in question is CGameModule.) and I cannot for the life of me understand what the problem is. At first, I thought it was related to forgetting to give a virtual function a body, but as far as I understand, everything is all here. The inheritance chain is a little long, but here is the related source code. I'm not sure what other information I should provide.

Note: The constructor is where this error is happening, it'd seem.

My code:

class CGameModule : public CDasherModule {  public:   CGameModule(Dasher::CEventHandler *pEventHandler, CSettingsStore *pSettingsStore, CDasherInterfaceBase *pInterface, ModuleID_t iID, const char *szName)   : CDasherModule(pEventHandler, pSettingsStore, iID, 0, szName)   {        g_pLogger->Log("Inside game module constructor");          m_pInterface = pInterface;    }    virtual ~CGameModule() {};    std::string GetTypedTarget();    std::string GetUntypedTarget();    bool DecorateView(CDasherView *pView) {       //g_pLogger->Log("Decorating the view");       return false;   }    void SetDasherModel(CDasherModel *pModel) { m_pModel = pModel; }     virtual void HandleEvent(Dasher::CEvent *pEvent);    private:      CDasherNode *pLastTypedNode;     CDasherNode *pNextTargetNode;     std::string m_sTargetString;     size_t m_stCurrentStringPos;     CDasherModel *m_pModel;     CDasherInterfaceBase *m_pInterface; }; 

Inherits from...

class CDasherModule; typedef std::vector<CDasherModule*>::size_type ModuleID_t;  /// \ingroup Core /// @{ class CDasherModule : public Dasher::CDasherComponent {  public:   CDasherModule(Dasher::CEventHandler * pEventHandler, CSettingsStore * pSettingsStore, ModuleID_t iID, int iType, const char *szName);    virtual ModuleID_t GetID();   virtual void SetID(ModuleID_t);   virtual int GetType();   virtual const char *GetName();    virtual bool GetSettings(SModuleSettings **pSettings, int *iCount) {     return false;   };   private:   ModuleID_t m_iID;   int m_iType;   const char *m_szName; }; 

Which inherits from....

namespace Dasher {   class CEvent;   class CEventHandler;   class CDasherComponent; };  /// \ingroup Core /// @{ class Dasher::CDasherComponent {  public:   CDasherComponent(Dasher::CEventHandler* pEventHandler, CSettingsStore* pSettingsStore);   virtual ~CDasherComponent();    void InsertEvent(Dasher::CEvent * pEvent);   virtual void HandleEvent(Dasher::CEvent * pEvent) {};    bool GetBoolParameter(int iParameter) const;   void SetBoolParameter(int iParameter, bool bValue) const;    long GetLongParameter(int iParameter) const;   void SetLongParameter(int iParameter, long lValue) const;    std::string GetStringParameter(int iParameter) const;   void        SetStringParameter(int iParameter, const std::string & sValue) const;    ParameterType   GetParameterType(int iParameter) const;   std::string     GetParameterName(int iParameter) const;   protected:   Dasher::CEventHandler *m_pEventHandler;   CSettingsStore *m_pSettingsStore; }; /// @}   #endif 

Answer 1

The GCC FAQ has an entry on it:

The solution is to ensure that all virtual methods that are not pure are defined. Note that a destructor must be defined even if it is declared pure-virtual [class.dtor]/7.

Therefore, you need to provide a definition for the virtual destructor:

virtual ~CDasherModule() { } 

Answer 2

For what it is worth, forgetting a body on a virtual destructor generates the following:

undefined reference to `vtable for CYourClass'.

I am adding a note because the error message is deceptive. (This was with gcc version 4.6.3.)