Question

Alright, so my simple DLL Hellow World function

#include "stdafx.h"

extern "C" void HelloWorld()
{
   MessageBox( NULL, TEXT("Hello World"), 
            TEXT("In a DLL"), MB_OK);
}

isn’t getting called by my simple hello world app:

case IDM_ABOUT:

            hinstDLL = LoadLibrary(L"phantasyhook.dll");
            if (hinstDLL != NULL)
            {
                HelloWorld = (FARPROC) GetProcAddress(hinstDLL, "HelloWorld");

                if (HelloWorld != NULL)
                    HelloWorld();

                else
                    MessageBox(NULL, L"is null", L"dll Error", MB_OK);

                FreeLibrary(hinstDLL);
            }

            break;

It opens the “is null” MessageBox, thought it should open up the Hello World one. What am I doing wrong?

Answer 1

You need to mark that a function should be exported by a DLL for other code to be able to load it. You can do by adding the __declspec(dllexport) or a module definition file.

extern "C" __declspec(dllexport) void HelloWorld()