Question

I’m trying to write a .dll library for .dll injection purposes. And because of this fact, it must have a routine called DllMain, since this is what will be used as the entry point. I think my problem may be stemming from the fact that I’m linking in a static library that I’ve wrote which utilizes a threads and mutexes from afxmt.h. Because somewhere down the line, the inclusion of this is causing the linker to link from mfcs100ud.lib which apparently contains its own version of DllMain.

Here is the file that is giving me trouble:

dllmain.cpp

#include "stdafx.h"
#include <stdio.h>
#include "NamedPipeLogger.h"

static CNamedPipeLogger m_PipeLogger("Log.txt");

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

Here is the stdafx.h file that dllmain.cpp is including.

stdafx.h

#pragma once

#define _AFXDLL
#include <Afx.h>

#include "targetver.h"

#define WIN32_LEAN_AND_MEAN             // Exclude rarely-used stuff from Windows headers

Here is my Error message:

Error 32 error LNK2005: _DllMain@12 already defined in
dllmain.obj D:\xxxxx\xxxxx\xxxxxx\mfcs100ud.lib(dllmodul.obj)

Am I just screwed here because I cannot change the name of my Dll entry point to something other than DllMain?

Answer 1

Well, I guess I threw in the towel on this one (sort of). I was able to at least get by all my problems. I just had to stop using some of the Microsoft classes.

I touched on this in the problem description, but I recall starting to have difficulty with compiling as soon as I started including:

#include <afxmt.h>
#include <afxwin.h>

So I went through and figured out what exactly I was using that required these includes. I was using the AfxBeginThread() method, and the classes CMutex and CCriticalSection. So I figured maybe if I could just get away from any of the proprietary windows stuff that maybe my problems would go away. That means removing all includes of , , and and then address the compilation errors with more standard c++ code. Here is what I did:

• Instead of using AfxBeginThread() I used CreateThread().
• Instead of using CMutex and CCriticalSection I used the CRITICAL_SECTION structure with its accompanying routines.

After this I was able to compile the .dll and it worked fine.