How to load the DLL from the main project c++

Question

I have created a project that uses 2 DLL's to play against each other (a DLL is a player). The game is that the first player picks a number and the second player picks another number, and then the PlayRound function compares the two numbers. My problem that am not sure how to load the DLL (run/load time). I created my first DLL (simple.dll) which has a Pick function that always returns "int 2" for simplicity:

#include "stdafx.h"
#define ASEXPORT
#include <iostream>
#include "player.h"

using namespace std;

int Pick(int Round, int MyMoves[], int OpponentMoves[])
{
    return 2;
}

This project have a header (player.h) with the following code:

#ifndef ASEXPORT
#define DLLIMPORTOREXPORT dllimport
#else
#define DLLIMPORTOREXPORT dllexport
#endif

_declspec(DLLIMPORTOREXPORT) int Pick(int Round, int MyMoves[], int OpponentMoves[]);

Not sure where to include this code do i include it in the main or in a function:

    HINSTANCE hinstLib; 
    MYPROC ProcAdd; 
    BOOL fFreeResult, fRunTimeLinkSuccess = FALSE; 

    // Get a handle to the DLL module.

    //hinstLib = LoadLibrary(TEXT(player2Name)); 

    hinstLib = LoadLibrary();
    // If the handle is valid, try to get the function address.

    if (hinstLib != NULL) 
    { 
        ProcAdd = (MYPROC) GetProcAddress(hinstLib, "simple.DLL"); 

        // If the function address is valid, call the function.

        if (NULL != ProcAdd) 
        {
            fRunTimeLinkSuccess = TRUE;
            (ProcAdd) (L"Message sent to the DLL function\n"); 
        }

        // Free the DLL module.
        fFreeResult = FreeLibrary(hinstLib); 
    } 

// Report any failures
    if (! fRunTimeLinkSuccess) 
        printf("Unable to load DLL or link to functions\n"); 
    if (! fFreeResult) 
        printf("Unable to unload DLL\n");
//

I hope I made it easy to understand

Answer 1

You can see this in my ModuleService implementation in the IndieZen core library. I treat .dll and .so as a "module". In my plugin system I have a standard that every module implements one and only one exported function, which is getModule() in my example, Pick() in your use case.

My example returns in implementation of I_Module interface. In my example, modules are collections of plugins, so the only thing you can do is get an implementation of an I_Plugin, which in turn can be used to gain access to class factories, and then these class factories construct objects (extensions) which implement pre-defined interfaces (extension points).

I know that's all overkill for your example, but the code is quite easy to follow; feel free to copy/paste the subsets you can use.

One key thing is to NOT use _declspec(DLLIMPORTOREXPORT) on the Pick function; you should only be exporting the function and not importing it. You should also not be linking these DLL's to your main application, nor should you include the DLL's header file into your main application. This will give you the flexibility of being able to import two separate DLL's that expose the same function (Pick in your case) without having linking errors. It will also give you the advantage of not knowing the names of the DLL's until runtime (where possibly you may want some configuration or GUI to let the user pick which players).

My implementation, with the reference counting, class factory, etc would give you an added advantage in that you could have two players implemented within the same DLL which could play against each other.