mfcclrlinkerafx

Compiling MFC application with /clr (step1: linking against dynamic DLLs)

I have successfully upgraded an MFC application which was compiled with an old version of Developer Studio to Visual Studio 2008. A very small number of changes were needed because of some breaking changes in MFC. Now that everything works, I'd like to take the next step and compile the solution with /clr.

To do so, I have found useful information on the MSDN web site:

Here are the steps I have taken:

  1. Set the Runtime Library to Multi-threaded Debug DLL (/MDd).
  2. Set the Use of MFC to Use MFC in a Shared DLL.

However, doing so prevents me from linking the project:

  1. The reference to afxData can no longer be resolved; somehow, afxData is only visible when linking statically against MFC. In my code, I have the following declaration:

    extern AFX_DATA AUX_DATA afxData;

    which works fine with the statically linked MFC version.

  2. The references to _afxThreadState and _afxWinState cannot be resolved either.

Here are the full error messages :

error LNK2001: unresolved external symbol "struct AUX_DATA afxData" (?afxData@@3UAUX_DATA@@A)
error LNK2001: unresolved external symbol "class CThreadLocal<class _AFX_THREAD_STATE> _afxThreadState" (?_afxThreadState@@3V?$CThreadLocal@V_AFX_THREAD_STATE@@@@A)
error LNK2001: unresolved external symbol "class CProcessLocal<class _AFX_WIN_STATE> _afxWinState" (?_afxWinState@@3V?$CProcessLocal@V_AFX_WIN_STATE@@@@A)

in case this might be related to the name mangling...

So, what can I do in order to dynamically link against MFC, but still reference afxData, _afxThreadState and _afxWinState?

Solution

  • When using MFC in a shared DLL, AUX_DATA must be dllimported.

    extern __declspec(dllimport) AUX_DATA afxData

    For thread state, rather than using template classes, use one of these

    AFX_MODULE_THREAD_STATE* pState = _AFX_CMDTARGET_GETSTATE()->m_thread;
AFX_THREAD_STATE* pState = AfxGetThreadState();

    Depending on the state information you require. For example, see here for some members that were moved to module state to fix a bug. Note that AfxGetModuleThreadState exists but is undocumented and could be changed in a future version.

    Win state does not ring a bell, how is it used? There is probably a new way to accomplish it.