Thread: first DLL program

I created my first program using a DLL. I used a sample out of the Visual C++ 6 bible. That one worked fine. Their sample "DisplayAppName()" has no parameters. Then when I tried to build a function with parameters for "Multiply(int x, int y)" I could not figure out the syntax. I tried everything I could think of to include declaring my own function pointer so as to have a pointer of the correct type. I know it is not in the linking process because one works. I believe it is the syntax but cannot figure it out. Any help or hint is greatly appreciated.

IDE: Visual C++ 6.0
Using DLL wizard...


//*****************************************
//in the DLL .h file
void DisplayAppName();
int Multiply(int x, int y);


//*****************************************
//in the DLL cpp file
void DisplayAppName()
{
AFX_MANAGE_STATE(AfxGetStaticModuleState() );
CString str = AfxGetAppName();
AfxMessageBox( str );
}

int Multiply(int x, int y)
{
return x * y;
}


//****************************************
//In the client program (driver program)
void CDllTestDlg::OnButton1()
{
FARPROC pfn;

char buffer[255];
CString s;

GetCurrentDirectory(255, buffer);
s = buffer;
s.TrimRight("\\");

s += ("\\DllProj.dll");

HMODULE hm = LoadLibrary( s );

if( hm != NULL )
{
CString s1;

//this works fine
pfn = GetProcAddress(hm, "DisplayAppName");

if( pfn != NULL )
pfn();
else
{
s1.Format("Error %d", GetLastError());
MessageBox( s1 );
}

//** this does not work
//**i also tried "Multiply(int x, int y)
//** i also tried declaring my own pointer to function
//int (*multi)(int x, int y);
//multi = GetProcAdress(hm, "Multiply");
pfn = GetProcAddress(hm, "Multiply");
if( pfn != NULL )
{
s1.Format("2 * 2 = %d", pfn());
MessageBox( s1 );
}

}

}

....oops I goofed sorry.. Here it is again

Code:

//***************************************** 
//in the DLL .h file 
void DisplayAppName(); 
int Multiply(int x, int y); 


//***************************************** 
//in the DLL cpp file 
void DisplayAppName() 
{ 
    AFX_MANAGE_STATE(AfxGetStaticModuleState() ); 
    CString str = AfxGetAppName(); 
    AfxMessageBox( str ); 
} 

int Multiply(int x, int y) 
{ 
   return x * y; 
} 


//**************************************** 
//In the client program (driver program) 
void CDllTestDlg::OnButton1() 
{ 
   FARPROC pfn; 

   char buffer[255]; 
   CString s; 

   GetCurrentDirectory(255, buffer); 
   s = buffer; 
   s.TrimRight("\\"); 

   s += ("\\DllProj.dll"); 

   HMODULE hm = LoadLibrary( s ); 

   if( hm != NULL ) 
   { 
      CString s1; 

      //this works fine 
      pfn = GetProcAddress(hm, "DisplayAppName"); 

      if( pfn != NULL ) 
         pfn(); 
      else 
     { 
         s1.Format("Error %d", GetLastError()); 
         MessageBox( s1 ); 
     } 

     //** this does not work 
     //**i also tried "Multiply(int x, int y) 
     //** i also tried declaring my own pointer to function 
     //int (*multi)(int x, int y); 
     //multi = GetProcAdress(hm, "Multiply");  
     pfn = GetProcAddress(hm, "Multiply"); 
     if( pfn != NULL ) 
     { 
            s1.Format("2 * 2 = %d", pfn()); 
            MessageBox( s1 ); 
     } 

  } 

}