Pointer to a callback in a DLL

I'm calling a Dialog that has it's resources and dlg-procedure in a DLL. I'm not using a DEF file or LIB file. The function names are known, the function args are known, I'm using GetProcAddress to get a pointer to the functions I'm interested in.

'Why' I'm doing it this way is of no consequence, it's an experiment in 'learning'.

This works on _cdecl functions, but on the CALLBACK (_stdcall), I can't get a pointer to the actual dialog procedure (it returns 0).

Here's how I'm doing my pointers:

//////////////////// DLL TEST STUFF ////////////////////////////

#define   DLLPATH "../../testdll/release/testdll.dll"

//typedef some function pointers
typedef HINSTANCE        (__cdecl *INSTPROC )(void); 
typedef int              (__cdecl *VOIDPROC )(void); 
typedef LRESULT          (__stdcall *DLGROC )(HWND, UINT, WPARAM, LPARAM );

///////////////////////////////////////////////////////////////

As I said, any function that is NOT a callback returns a valid result, additionally, the dialog pops up as expected, no problems with DLL's HINSTANCE.

But without a pointer to it's dlgproc, no button messages have anywhere to go.

Here's some more test code:

 //use DLL funcs without lib or def files

                              //this works
  GetInst = (INSTPROC)GetProcAddress(Loadme,"getinst");
                              //this works
  GetID   = (VOIDPROC)GetProcAddress(Loadme,"getid");
                              //this doesn't work, rets 0
  DlgProc = (DLGPROC) GetProcAddress(Loadme,"dllProc");

  //test for result
  dllid  =(GetID)();
  dllinst=(GetInst)();

  //compare hinst            OK
  wsprintf(buf,"dllinst=%x  Loadme=%x",dllinst, Loadme);
  MessageBox(hwnd,buf,"",MB_OK);

  //check resOurce ID        OK
  wsprintf(buf,"GetID returned: %d",dllid);
  MessageBox(hwnd,buf,"",MB_OK);

  //check dllProc addr       NOGO, ret=0
  wsprintf(buf,"dllProc=%x",DlgProc);
  MessageBox(hwnd,buf,"",MB_OK);

        //    DLL instance,        resource ID,     parent,  dlgproc    
        DialogBox(Loadme  ,  MAKEINTRESOURCE(dllid),  hwnd,  DlgProc);

  //dialog loads and shows, can't get dlgproc addr 

        FreeLibrary(Loadme);
        ///////////////// END DLL TEST STUFF ///////////////

On the DLL side of things, it looks like this:

__declspec(dllexport) LRESULT CALLBACK dllProc(
                                            HWND hwnd, 
              UINT Message, 
              WPARAM wParam, 
              LPARAM lParam
              )
{

hpwnd=hwnd;

 switch (Message){

  case WM_INITDIALOG:
   MessageBox(hwnd,"At DlgProc...","",MB_OK);
  return TRUE;

  case WM_COMMAND:
   switch(LOWORD(wParam)){
       case IDEND:
    case IDCANEND:
      EndDialog(hwnd,0);
   return TRUE;
    }
 return TRUE;
 }
return FALSE;
}

Which really doesn't matter at this point, since I can't get a pointer to the callback in the first place.

If anyone happens to know the fix for getting a pointe开发者_开发百科r to the callback, I would very much appreciate your input.

Thanks for your patience.

---

You need to declare your dllProc inside an extern "C" block to prevent its name being decorated when exported, so that when you ask for a function called "dllProc" such a function is found (instead of "dllProc@blahmoocow" or whatever madness the C++ decoration produces. :-)).

Place this declaration before the dllProc definition:

extern "C"
{
    __declspec(dllexport) LRESULT CALLBACK dllProc(
           HWND hwnd, UINT Message, WPARAM wParam, PARAM lParam);
}

You can also then drop the __declspec(dllexport) from the dllProc definition.