Call a dll for Labview: Function not found in library

[steinhagelvoll]

Hello,

I am trying to call a very simple .dll form Labview. I compiled the .dll for x64 using Visual Studio 2010, because I am using Labview(64-bit). I did everything exactly the way I read it in several Tutorials. But the "Call Library Function Node" doesn't create a popup menu with the avalible functions like it is supposed to do. The Import Wizard doesn't find any functions neither. What is wrong with my .dll?

I added a block marked 'extern "C" ' into my source file, but it still won't work.

Thanks

Matthias

[.aCe.]

You need to define an entry point to the DLL

BOOL APIENTRY DllMain( HANDLE hModule,
                        DWORD  ul_reason_for_call,
                        LPVOID lpReserved )
{
    return TRUE;
}

Also add extern "C" __declspec(dllexport) to your functions

More details here: http://www.ni.com/white-paper/3056/en

[steinhagelvoll]

I read this article before, but I don't understand it. Where do I add the entry? In the *.cpp or in the *.h? If I simply copy it I get several syntax errors. I added the extern "C" already to the source file. If I add it to the header-file I get another error.

They should have added the source files so it would be a lot easier to understand.

Thanks

Matthias

[smercurio_fc · Accepted solution]

You did not read the article correctly. Re-read Step 3. In the .cpp file you add "__declspec(dllexport)" before the function's body. In the header file you add extern "C" at the beginning of the prototype. This is to deal with the name-decorating that C++ compilers do.

[steinhagelvoll]

---

@.aCe. wrote:

More details here: http://www.ni.com/white-paper/3056/en

---

This Tutorial is a little outdated. Visual Studio creates a file called 'dllmain.cpp' which contains the BOOL APIENTRY DllMain function. Therefore I did not need to add it to my source file. The solution was to add an ' extern "C" __declspec(dllexport)' before the declaration and "__declspec(dllexport)" before the definition of the function.

Thank you very much

Matthias