God forsaken linker errors...

I keep getting a damn linker error in this header file. It seams that it works the first time it is processed but every time I call it again, it pops up with another (of the same) error. Here's the code:

Code:

---

#ifndef MESSAGE_H_
#define MESSAGE_H_

#include "globaltypes.h"

// MESSAGE LIST
enum MSG
{
        MSG_NONE = 0, // default
        MSG_FAIL = 0, //
        MSG_SUCCESS = 1, //
        MSG_OK = 1, //
       
        MSG_ERROR, // string of error message
        MSG_WARNING, // string of warning message

        MSG_TOTALMESSAGETYPES
};

class MESSAGE
{
public:
        MESSAGE();
        ~MESSAGE();

        bool Dispatch( MSG Type, void *Data = NULL );
        bool DispatchOne( MSG Type, void *Data, UINT16 Number );
        bool DispatchThis( MSG Type, void *Data = NULL );
        virtual bool Device( const MSG Type, const void *Data );

private:
        UINT16 NumberID;
};

class MESSAGE_TOP
{
public:
        UINT16 Add( MESSAGE* pDevice );
        bool Dispatch( MSG Type, void *Data = NULL );
        bool DispatchOne( MSG Type, void *Data, UINT16 Number );
        MESSAGE* Get( const UINT16 Number ) const;
        UINT16 Remove( const UINT16 Number );
        void RemoveAll();
        UINT16 Size() const;

private:
        std::vector< MESSAGE* > Device;
} extern Message; // THIS IS CAUSING PROBLEMS HERE!!!

#endif

---

The error is on the line towards the end (extern Message). This is the linker error:

Code:

---

error LNK2001: unresolved external symbol "class MESSAGE_TOP Message" (?Message@@3VMESSAGE_TOP@@A)

---

And this is the error without the extern in there:

Code:

---

error LNK2005: "class MESSAGE_TOP Message" (?Message@@3VMESSAGE_TOP@@A) already defined

---

I've tried all sorts of things but I give up. This is apart of my global header, so it is known to pretty much every other part of the program.

Thanks.

Do you actually declare "MESSAGE Message;" in any .cpp file anywhere? An extern on its own is not enough. The extern just tells the rest of the code to expect that symbol to be present at link-time, but doesn't create the symbol.

Also, I'd recommend separating out the extern declaration from the class declaration:

Code:

---

class MESSAGE
{
    ...
};

extern MESSAGE Message;

---

Yes, that got it... thankyou.