using a DLL function in a header file

[Guest]

I'm using a .NET Windows Forms Applications project.
I'm using LoadLibrary & GetProcAddress to use a DLL function.
This is all done in the main cpp file.
I would like to use this DLL function in a .h file. So I code :
(Proc2) (0x378, 12)....... (where Proc2 is the function)
I get a compiler error : C2065 : 'Proc2' : undeclared identifier.
I'm guessing I'm not calling this function properly - how can I fix this
problem ?

When I write a program that contains a main cpp file that loads the DLL
function &
defines Proc2 via GetProcAddress, & finally uses it in this same file, then
Proc2 runs correctly.
So I'm guessing when this code is split into a cpp & a .h file, I need to
call Proc2 differently ??
The reason I'm splitting the use of the Proc2 function into a header file,
is back that's where the event hamdler for a button click from the GUI is
located.
Any advice is appreciated.
Thanks,
AK

 

[Tamas Demjen]

You can't use the header file directly. You have to define a function
pointer type, and then create a function pointer yourself. For example,
if your function's prototype is

int Proc2(int, int);

Then you have to do the following:

typedef int (*PtrProc2)(int, int);
PtrProc2 Proc2 = (PtrProc2)GetProcAddress(DllHandle, "Proc2");
int result = Proc2(0x378, 12);

Tom

 

[Guest]

Hi Tom,

Thanks for the help. But I have this code you suggest already in the
Form1.cpp file :

typedef void (_stdcall *MyOut32)(short,short);
typedef short (_stdcall *MyInp32)(short);

HINSTANCE hinstLib;
MyInp32 ProcAdd1;
MyOut32 ProcAdd2;
//LoadLibrary loads the DLL which is in the systems folder & in the same
folder as qq.exe
hinstLib = LoadLibrary("Inpout32.dll");
//the Inp32 & Out32 functions defined in the DLL are now called ProcAdd1 &
ProcAdd2
ProcAdd1 = (MyInp32) GetProcAddress(hinstLib, "Inp32");
ProcAdd2 = (MyOut32) GetProcAddress(hinstLib, "Out32");

(ProcAdd2)(0x378, 0);


The only difference is all this code except for the last line :
(ProcAdd2)(0x378, 0);
is placed in the Form1.cpp, while the last line is placed in the event
handler of a button function which is located in Form1.h

I don't understand why the compiler understands the creation of ProcAdd2,
yet complains about it's use in the header file ??

AK

 

[Guest]

Tom,

Yes - I understand & have changed this. I have created a new class
'parallelport' that I intend to use inside the Form1 class (specifically
inside the function for the event handler of radial button #1). I wrote this
class in a new header file : "parallel port class.h" . It contains a single
member function 'setup' that defines ProcAdd2. I include this parallel port
class.h file in the Form1.h file, and this should give accessability of
parallelport class methods & variables to the Form1 class, right ?

Next, in Form1.h, I create an instance of the parallelport class called
'pp' & use pp.setup to define ProcAdd2 inside the Form1.h class. I still get
ProcAdd2 as undeclared identifier and identifier not found; compiler errors
C2065 & C3861. I have tried different codes & this code gives the least
amount of trouble & is one which makes sense to me, but I still can't execute
the simple instruction :
(ProcAdd2) (0x378, 0);

Below is the part of the code - I guess we can't attach a project file in
these discussions . I can't find the problem - maybe there is a better way
to implement this event handler ?

Regards,
Arie

****************parallel port class.h :

#include "stdafx.h"
#include <windows.h>
#include "Windows.h"


typedef void (_stdcall *MyOut32)(short,short);
typedef short (_stdcall *MyInp32)(short);

class parallelport
{
public :
void setup(void)
{
HINSTANCE hinstLib;
MyInp32 ProcAdd1;
MyOut32 ProcAdd2;

//LoadLibrary loads the DLL which is in the systems folder & in the same
folder as qq.exe
hinstLib = LoadLibrary("Inpout32.dll");
//the Inp32 & Out32 functions defined in the DLL are now called ProcAdd1 &
ProcAdd2
ProcAdd1 = (MyInp32) GetProcAddress(hinstLib, "Inp32");
ProcAdd2 = (MyOut32) GetProcAddress(hinstLib, "Out32");
}

private :
MyInp32 ProcAdd1;
MyOut32 ProcAdd2;

};


***************inside Form1.h :

#include "parallel port class.h"

parallelport pp;

public __gc class Form1 : public System::Windows::Forms::Form
{
public:
Form1(void)
....

private: System::Void radioButton1_Click(System::Object * sender,
System::EventArgs * e)
{
bool r1=radioButton1->Checked;
bool r2=radioButton2->Checked;

// X in & Y in leads to 0000 0000 out the parallel port
if (r1==0 && r2==0)
{
pp.setup();
(ProcAdd2)(0x378, 0);}