Trouble loading from .dll file

[slavik262]

Hi. I'm fairly new to the Win32API with several years of C and C++ experience. I'm currently trying to make a key hook (just for amusement/learning purposes) and I'm having some trouble. Since I want to make the hook global, it needs to be built into a separate .dll file. The main program loads the .dll fine, but when I call GetProcAddress(), the function addresses are not returned. Here's the code for the .dll

#include <windows.h>
#include <tchar.h>

HHOOK hHook;

__declspec(dllexport) LRESULT CALLBACK KeyHookProc(int code, WPARAM wParam, LPARAM lParam)
{
	//Return things we shouldn't handle
	if(code < 0)
		CallNextHookEx(hHook, code, wParam, lParam);

	return CallNextHookEx(hHook, code, wParam,lParam);
}

__declspec(dllexport) BOOL CALLBACK KeyHookSetup(HINSTANCE hDLL, HOOKPROC procPtr)
{
	hHook = SetWindowsHookEx(WH_KEYBOARD, procPtr, hDLL, 0);
	if(hHook == NULL)
	{
		MessageBox(NULL, _T("Could not start hook"), _T("Error"), MB_OK | MB_ICONERROR);
		return FALSE;
	}

	return TRUE;
}

__declspec(dllexport) BOOL CALLBACK KeyHookFree(void)
{
	if(UnhookWindowsHookEx(hHook) != 0)
	{
		MessageBox(NULL, _T("Could not free hook"), _T("Error"), MB_OK | MB_ICONERROR);
	}

	return TRUE;
}

and here's the code for getting function pointers from the .dll

hDLL = LoadLibrary(_T("Hook_DLL.dll"));

if(hDLL == NULL)
{
	MessageBox(NULL, _T("DLL could not be loaded."), _T("Error"),
	MB_OK|MB_ICONERROR);
}

keyHookProc = (HOOKPROC)GetProcAddress((HMODULE)hDLL, "KeyHookProc");
keyHookSetup = (SETHOOKPROC)GetProcAddress((HMODULE)hDLL, "KeyHookSetup");
keyHookFree = (FREEHOOKPROC)GetProcAddress((HMODULE)hDLL, "KeyHookFree");

if(keyHookProc == NULL)
{
	MessageBox(NULL, _T("keyHookProc could not be loaded."), _T("Error"),
		MB_OK|MB_ICONERROR);
}
if(keyHookSetup == NULL)
{
	MessageBox(NULL, _T("keyHookSetup could not be loaded."), _T("Error"),
		MB_OK|MB_ICONERROR);
}
if(keyHookFree == NULL)
{
	MessageBox(NULL, _T("keyHookFree could not be loaded."), _T("Error"),
		MB_OK|MB_ICONERROR);
}

I've tried everything I can possibly think of. The application is compiling in C++. I originally had extern "C" {} around the .dll functions to avoid name mangling, but am now compiling the .dll in C instead to avoid any possible issues. I'm using Visual C++ 2008 as a build environment.

Yes, I do realize that HookKeyProc() is not finished, but I want to get the functions loading first. Thanks for all help in advance.

[Disch]

iirc for DLLs with VS you need to make a .def file which outlines the functions you want exposed.

Somewere in the project settings there's an option for a .def file to use.

The def file I used for some other lib I worked on looked like this. I copied this from elsewhere so I don't really know the significant of the library name.

LIBRARY   in_NotSoFatso

EXPORTS
winampGetInModule2

I guess under 'EXPORTS' you just list all the functions you want externally linked (winampGetInModule2 was a function in my dll)

[slavik262]

The problem has been solved due to help on another forum. However, I appear to have a new one.

My hook is only working on the thread level, and not the global level. According to MSDN, to make the thread run on a global level you call SetWindowsHookEx() with a final parameter of 0. Despite my call being:

SetWindowsHookEx(WH_KEYBOARD, procPtr, hDLL, 0)

The hook procedure is only called when a keyboard message is passed to the window (I have verified this with breakpoints. The only time the function is called is when my window has focus and a key is pressed.) procPtr points to a function in a dll, and that dll's handle is hDLL. I don't see what the problem is. Would it be a problem that I'm calling SetWindowsHookEx() from inside of a dll function?

[george135]

> Since I want to make the hook global, it needs to be built into a separate .dll file

No, you don't need DLL

[slavik262]

According to http://msdn.microsoft.com/en-us/library/ms644960(VS.85).aspx :

You must place a global hook procedure in a DLL separate from the application installing the hook procedure.

Regardless, that's not answering my question. Does anybody have any idea why it's still only working on the thread level?

[writetonsharma]

slavik262:

you want the code for global hooks, tell me you email.
i created it some time back.

george135:

to create windows hooks, they should be in dll only. because windows injects the dll code in the applications and which cant be done using a .exe file.

[writetonsharma]

Disch:

he has already exported the functions so he doesnt need a .def file. we need to use either a .def file to export the functions or export the functions in .h/.cpp files.

[kbw]

Check your DLL using depends. You can confirm that you're DLL is exporting its functions.

[binaryboy]

slavik262

I don't know why your hook procedure cannot get keyboard events that handled by other threads, it's so strange..

but you can Replace
SetWindowsHookEx(WH_KEYBOARD, procPtr, hDLL, 0)

with
SetWindowsHookEx(WH_KEYBOARD_LL, procPtr, hDLL, 0)

you can get all low-level keyboard events...

look at this:
http://msdn.microsoft.com/en-us/library/ms644985(VS.85).aspx