Question

I have to do one project and I was given dll and a header file with implemented functions needed for the project. I was told just to add the header file to the project but this way i get unresolve externals error if i try to use functions referenced in header. So what needs to be done to make everything work? Visual Studio 2010.
Here are the files i have: http://www.ipix.lt/images/33871682.png
And this is header file:

#ifndef __BIM482_RADAR__
#define __BIM482_RADAR__

int BIM482OpenRadar();
int BIM482AddPlane(double x, double y);
int BIM482SetPlaneColor(int planeidx, int coloridx);
int BIM482SetPlanePos(int planeidx, double x, double y);
void BIM482UpdateRadar();

#endif // __BIM482_RADAR__

I need to initiate gui with OpenRadar and pass information with those functions. How to start this thing?

Answer 1

You don’t have a .lib-file to link against.

Maybe this can help you

http://www.coderetard.com/2009/01/21/generate-a-lib-from-a-dll-with-visual-studio/

or this:

http://support.microsoft.com/default.aspx?scid=kb;en-us;131313

or this:

http://www.asawicki.info/news_1420_generating_lib_file_for_dll_library.html

when you have generated the lib-file ,you must use __declspec(dllimport) on yuor functions in the header file.

An alternative to all of the above is to use LoadLibrary(…) in your source and write wrapper function for those function in the dll and call those dll funcions via GetProcAddress(…).

struct
{
   HMODULE hDll;

   int   (*BIM482OpenRadar)     (); 
   int   (*BIM482AddPlane)      (double x, double y); 
   int   (*BIM482SetPlaneColor) (int planeidx, int coloridx); 
   int   (*BIM482SetPlanePos)   (int planeidx, double x, double y); 
   void  (*BIM482UpdateRadar)   (); 
} dll_funcs = {0};

bool ExitRadar( LPCTSTR szDllPath )
{
   if (dll_funcs.hDll)
      FreeLibrary( dll_funcs.hDll );

   return true;
}

bool InitRadar( LPCTSTR szDllPath )
{
   if (dll_funcs.hDll)
      return true;
   dll_funcs.hDll = LoadLibrary( szDllPath );
   if (!dll_funcs.hDll)
      return false;

   dll_funcs.BIM482OpenRadar     = (int(*)())GetProcAddress( dll_funcs.hDll ,("BIM482OpenRadar") );
   dll_funcs.BIM482AddPlane      = (int(*)(double,double))GetProcAddress( dll_funcs.hDll ,("BIM482AddPlane") );
   dll_funcs.BIM482SetPlaneColor = (int(*)(int,int))GetProcAddress( dll_funcs.hDll ,("BIM482SetPlaneColor") );
   dll_funcs.BIM482SetPlanePos   = (int(*)(int,double,double))GetProcAddress( dll_funcs.hDll ,("BIM482SetPlanePos") );
   dll_funcs.BIM482UpdateRadar   = (void(*)())GetProcAddress( dll_funcs.hDll ,("BIM482UpdateRadar") ); 
   return true;
}

int   BIM482OpenRadar     () 
{ return (*dll_funcs.BIM482OpenRadar)(); }; 

int   BIM482AddPlane      (double x, double y)
{ return (*dll_funcs.BIM482AddPlane)( x ,y ); }

int   BIM482SetPlaneColor (int planeidx, int coloridx )
{ return (*dll_funcs.BIM482SetPlaneColor)( planeidx ,coloridx ); }

int   BIM482SetPlanePos   (int planeidx, double x, double y) 
{ return (*dll_funcs.BIM482SetPlanePos)( planeidx ,x ,y ); }

void  BIM482UpdateRadar   ()
{ return (*dll_funcs.BIM482UpdateRadar)(); }