DLL Calling Problem?

I have a problem when i call the dll from VB.The message box appears but after i click ok i get the error message "bad dll calling convention".How can i solve this.
The Dll code

Code:

---

#include "stdafx.h"
void car(HWND h)
{
        MessageBox(h,"OK","KO",MB_OK);
}

---

Def File

Code:

---

LIBRARY "brisi.DLL"
EXPORTS
        car @2

---

And in VB a declare the function and call it:

Code:

---

Public Declare Sub car Lib "brisi.dll" (ByVal h As Long)
car Form1.hWnd

---

Try using:

Code:

---

#include "stdafx.h"
void __declspec(dllexport) car(HWND h)
{
        MessageBox(h,"OK","KO",MB_OK);
}

---

for your code, and

Code:

---

LIBRARY "brisi.DLL"
EXPORTS
        car

---

for your .def file.

If i dont pass a parameter to a function dll in c++ a can get a return from it. if i do this

extern "C" __declspec( dllexport ) long returnNothing(long nDays)
{
return nDays;
}

i get bad dll calling convention.

any help heres the declare.

Declare Function returnNothing Lib "D:\DEVELOP\ALL16_32\myproj\Debug\myproj.dll" (ByVal nDays As Long) As Long

help!!!

Code:

---

extern "C" __stdcall __declspec(dllexport) long returnNothing(long nDays) {
    return nDays;
}

---

The __stdcall may need to go after the __declspec.

extern "C" void __stdcall car(HWND h)
{
//code
}


will work. the extern "C" tells the compiler to do some name mangling thing so VB can understand it, and __stdcall means the func will clear up the stack afterwards, which VB requires.

def file:

LIBRARY "yourdll.dll"
EXPORTS
car

extern "C" int __declspec(dllexport) CALLBACK returnNothing (int nDays)
{
return nDays;
}


vb:

Declare Function returnNothing Lib "D:\DEVELOP\ALL16_32\myproj\Debug\myproj.dll" Alias "_returnNothing@4" (ByVal nDays As Integer) As Integer


ps:

As a real problem with Long any suggestions

If you use a .DEF file then you don't actually need the extern "C", since it causes the linker to rename the external references anyway.

yeah, but its really weird, i've tried it with just __stdcall and a DEF file, and it doesn't work from VB for me. having extern "C" works though.

Yep, got that working extern "C" _cdecl and _dllexport

Another problem arouse with VB, cannot send a LONG to c++ dll and return it .. any thoughts.?

Cheers

do you mean something like:

Declare Sub AddOne Lib "lala.dll" (Num as Long)

the c++ func should be:

extern "C" void __stdcall AddOne(long *num)
{
*num ++;
}

the thing you're probably doing wrong is not declaring the number as a pointer in the C++ function if you simply do
..(long num) then any changes won't affect the original number.

extern "C" long __stdcall AddOne(long *num)
{
return *num;
}

What, does this work, i'll try it in VB.
Cheers