c# - C++ plugin for Unity "EntryPointNotFoundExeption"

Question

I need some serious help here... I'm trying to either get my member functions exported so I can call them in C#

WMIWrapper.h

#ifndef _WMIWRAPPER_H_
#define _WMIWRAPPER_H_

#include <Windows.h>  
#include <sstream>  
#include <iostream>
#include <WbemCli.h>  

using std::endl;
using std::wstring;
using std::wstringstream;

#pragma comment(lib, "wbemuuid.lib")  

static class WMIWrapper 
{  
public:
    __declspec(dllexport) WMIWrapper();
    __declspec(dllexport) ~WMIWrapper();

    __declspec(dllexport) wstring CreateCOM();
    __declspec(dllexport) wstring CreateService();
__declspec(dllexport) wstring GetMonitors();

private:
    IWbemLocator* _locator;
    IWbemServices* _service;
    IEnumWbemClassObject* _monitors;
};

#endif

WMIWrapper.cpp

#include "WMIWrapper.h"


extern "C" {

    WMIWrapper::WMIWrapper()
    {
        _locator = NULL;
        _service = NULL;
    }

    WMIWrapper::~WMIWrapper()
    {
        if(_service != NULL)
            _service->Release();
        if(_locator != NULL)
            _locator->Release();
    }

    wstring WMIWrapper::CreateCOM()
    {
        wstringstream ERRStream (wstringstream::in | wstringstream::out);
        HRESULT hRes = CoInitializeEx(NULL, COINIT_MULTITHREADED);  
        if(FAILED(hRes))  
        {  
            ERRStream << "Unable to launch COM: 0x" << std::hex << hRes << endl;
            return L"";  
        }  

        hRes = CoInitializeSecurity(NULL, -1, NULL, NULL, RPC_C_AUTHN_LEVEL_CONNECT, RPC_C_IMP_LEVEL_IMPERSONATE, NULL, EOAC_NONE, 0);
        if(FAILED(hRes))
        {
            ERRStream << "Unable to set security level for COM: " << std::hex << hRes << endl;
            return L"";
        }

        if(FAILED(hRes = CoCreateInstance(CLSID_WbemLocator, NULL, CLSCTX_ALL, IID_PPV_ARGS(&_locator))))  
        {  
            ERRStream << "Unable to create a WbemLocator: " << std::hex << hRes << endl;  
            return L"";  
        }

        const std::wstring& myWString = ERRStream.str();
        const LPCWSTR p = myWString.c_str();
        return p;

    }

    wstring WMIWrapper::CreateService()
    {
        wstringstream ERRStream (wstringstream::in | wstringstream::out);
        HRESULT hRes;
        if(_locator == NULL || FAILED(hRes = _locator->ConnectServer(L"root\CIMV2", NULL, NULL, NULL, WBEM_FLAG_CONNECT_USE_MAX_WAIT, NULL, NULL, &_service)))  
        {  
            ERRStream << "Unable to connect to "CIMV2": " << std::hex << hRes << endl;  
            return L"";  
        }  

        const std::wstring& myWString = ERRStream.str();
        const LPCWSTR p = myWString.c_str();
        return p;
    }

    wstring WMIWrapper::GetMonitors()
    {
        HRESULT hRes;
        wstringstream ssMonitorDescription;
        if(_locator == NULL 
            || _service == NULL
            || FAILED(hRes = _service->ExecQuery(L"WQL", L"SELECT * FROM Win32_DesktopMonitor", WBEM_FLAG_FORWARD_ONLY, NULL, &_monitors)))
        {
            //ERRStream << "Unable to retrieve desktop monitors: " << std::hex << hRes << endl;
            return L"";
        }

        IWbemClassObject* clsObj = NULL;
        int numElems;
        while((hRes = _monitors->Next(WBEM_INFINITE, 1, &clsObj, (ULONG*)&numElems)) != WBEM_S_FALSE)
        {
            if(FAILED(hRes))
                break;

            VARIANT vRet;
            VariantInit(&vRet);
            if(SUCCEEDED(clsObj->Get(L"Description", 0, &vRet, NULL, NULL)) && vRet.vt == VT_BSTR)
            {
                //std::wcout <<  L"Description: " << vRet.bstrVal << endl;
                ssMonitorDescription << "Description: " << vRet.bstrVal << endl;
                VariantClear(&vRet);
            }
        }

        clsObj->Release();

        return ssMonitorDescription.str();
    }
}

Interface.cpp

#include "WMIWrapper.h"

extern "C" 
{
    __declspec( dllexport ) wstring GetMonitor()
    {
        WMIWrapper* wmiWrapper = new WMIWrapper();
        wmiWrapper->CreateCOM();
        wmiWrapper->CreateServiceW();
        return wmiWrapper->GetMonitors();
    }
}

Unity Script

using UnityEngine;
using System.Runtime.InteropServices;
using System;


public class HardwareDiagnostics : MonoBehaviour {

    //[DllImport("WMIWrapper", EntryPoint="CreateCOM", CharSet = CharSet.Unicode)]
    //static extern String CreateCOM();
    //
    //[DllImport("WMIWrapper", EntryPoint="CreateService", CharSet = CharSet.Unicode)]
    //static extern String CreateService();
    //
    //[DllImport("WMIWrapper", EntryPoint="GetMonitors", CharSet = CharSet.Unicode)]
    //static extern String GetMonitors();
    [DllImport("WMIWrapper", EntryPoint = "GetMonitor", CharSet = CharSet.Unicode)]
    static extern string GetMonitor();

    // Use this for initialization
    void Start () {
        Debug.Log(GetMonitor());
        Debug.Log ("Cock");

    }

    // Update is called once per frame
    void Update () {

    }


}

So I'm trying to call those member functions from the Unity script and I'm getting the EntryPointNotFoundExeption error. I thought maybe it was because you couldn't export member functions, so I tried writing that "Interface.cpp" to execute those functions and return the result but that returns the same error.

UPDATE

Per suggestion I have changed my C++ functions to this format

void WMIWrapper::CreateCOM(wchar_t* err, int errLength)
    {
        .../Determine wstringstream ERRStream


        wcscpy_s(err, errLength, ERRStream.str().c_str());

    }

And my C# like so:

public class HardwareDiagnostics : MonoBehaviour {

    [DllImport( "WMIWrapper", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Unicode)]
    private static extern void CreateCOM(StringBuilder str, int length);

    [DllImport( "WMIWrapper", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Unicode)]
    private static extern void CreateService(StringBuilder str, int length);

    [DllImport( "WMIWrapper", CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Unicode)]
    private static extern void GetMonitors(StringBuilder str, int length);

    // Use this for initialization
    void Start () {
        StringBuilder buffer = new StringBuilder(255);

        CreateCOM(buffer, buffer.Capacity);
        Debug.Log(buffer.ToString());

        CreateService(buffer, buffer.Capacity);
        Debug.Log(buffer.ToString());

        GetMonitors(buffer, buffer.Capacity);
        Debug.Log(buffer.ToString());

    }

    // Update is called once per frame
    void Update () {

    }


}

HOWEVER, I'm still getting "EntryPointNotFoundExeption" when calling the first function, CreateCOM();

Answer 1

Is this windows? Because you are missing your

Bool WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID);

definition if it is windows.

See chapter 21 of "Programming Windows: Fifth Edition" by Charles Petzold.

If you don't have it. Get it. All windows programmers should read it.

The DllMain function is called when the library first begins and when it terminates. The first parameter to DllMain is the instance handle of the library. If your library uses resources that require an instance handle (such as DialogBox), you should save hInstance as a global variable. The last parameter to DllMain is reserved by the system...

A fdwReason value of DLL_PROCESS_ATTACH indicates that the dynamic-link library has been mapped into the address space of a process. This is a cue for the lib rary to do any initialization tasks it requires to service subsequent requests from the process....

If the initialization is successful, DllMain should return a nonzero value. Returning 0 will cause Windows to not run the program.

When fdwReason has a value of DLL_PROCESS_DETACH, it means that the DLL is no longer needed by the process.. clean up...

Later versions of Visual Studio, may do this for you--I am not sure about that part.

Also, you will get an EntryPointNotFound exception if your function names are being mangled. The reason your function names are being mangled even with the extern "C" declaration is because you have placed extern "C" around class methods. In order for that to work without the mangled names you have to do C style function declarations.

i.e.

#ifdef _cplusplus
extern "C" {
#endif

__declspec(dllexport) wstring CreateCOM();

...

outside the context of a class. By having those declared as class members, the names will still be mangled, even with the extern "C" declaration.