Re: Linker cannot find CFrameWnd::_GetBaseMessageMap

Hello newsgroup,

[I posted this to microsoft.public.vc.mfc some days before, but noone was
able to help me.]

I'm experiencing a quite strange phenomenon: I have a class derived from
CFrameWnd inside a static library (the following code shows the definition
of the template version; in my code I use CFrameWnd for t_BaseFrameClass).
The reason why I want to use the template is that I want to be able to use
the CHelperMixin class for MDI and SDI projects.

[The following code depends on MFC 4.2 (Visual C 6.0). Also you'll have to
define _AFXDLL in order to compile it]

#include <afxwin.h>

template<class t_BaseFrameClass>
class CHelperMixin: public t_BaseFrameClass
{
  typedef t_BaseFrameClass TBaseFrameClass;
protected:
  static const AFX_MSGMAP* PASCAL _GetBaseMessageMap();
  virtual const AFX_MSGMAP* GetMessageMap() const;
};

template<class t_BaseFrameClass>
inline const AFX_MSGMAP* PASCAL
CHelperMixin<t_BaseFrameClass>::_GetBaseMessageMap ()
{
  return &TBaseFrameClass::messageMap;
}

template<class t_BaseFrameClass>
inline const AFX_MSGMAP* CHelperMixin<t_BaseFrameClass>::GetMessageMap()
const
{
  // Define an empty message map (just for demonstration).
  static const AFX_MSGMAP_ENTRY messageEntries[] =
  {
  END_MESSAGE_MAP()

  static const AFX_MSGMAP messageMap =
  {
    TBaseFrameClass::_GetBaseMessageMap,
    &messageEntries[0]
  };
  return &messageMap;
}

class CMyMainFrame : public CHelperMixin<CFrameWnd>
{
};

int main ()
{
  CMyMainFrame MyMainFrame;
  return 0;
}

Everything compiles fine, but I get a linker error:
error LNK2001: Unresolved external
"protected: static struct AFX_MSGMAP const * __stdcall
CFrameWnd::_GetBaseMessageMap(void)"

Strange enough, if I provide this method in one of my source files,
everything seems to be OK. I wonder how this could happen. Shouldn't the
linker complain about multiple definitions of this method? Surely this
method is part of the static libraries of MFC!

Thanks in advance,
Stuart