🔒 Locked

GetProcAddress Function Returns NULL For Hook Proc

Started by LlamaFood Nov 24, 2004 at 12:17 PM 3 replies 1.2k views

Original Post

Nov 24, 2004 at 12:17 PM

I'm making a global hook but for some reason GetProcAddress is returning NULL. Here's my WM_CREATE msg:

case WM_CREATE:
	HOOKPROC KBhkprc; 
	static HINSTANCE DLL;
	DLL=LoadLibrary((LPCTSTR)("c:\\hook.dll"));
	KBhkprc=(HOOKPROC)GetProcAddress(DLL,"KBHkPrc");
	if(KBhkprc==NULL) {
		MessageBox(0,"GetProcAdress Returns NULL",0,MB_OK);
	}
	kbhook=SetWindowsHookEx(WH_SYSMSGFILTER,KBhkprc,DLL,0);

And here's my DLL header:

#include <windows.h>

__declspec(dllexport) LRESULT __cdecl KBHkPrc(int code,WPARAM wParam,LPARAM lParam);

SiCrane

Mod

473

SiCrane

Nov 24, 2004 at 12:19 PM

I'm guessing it's a name mangling issue. Try declaring your KBHkPrc() function as extern "C" in your DLL or using a .DEF file to create the exports.

Jimmy Valavanis

Nov 24, 2004 at 12:55 PM

and to be source that DLL is loaded add:

	DLL=LoadLibrary((LPCTSTR)("c:\\hook.dll"));	if(DLL==NULL) {		MessageBox(0,"Can not load DLL",0,MB_OK);                return();	}	KBhkprc=(HOOKPROC)GetProcAddress(DLL,"KBHkPrc");	if(KBhkprc==NULL) {		MessageBox(0,"GetProcAdress Returns NULL",0,MB_OK);	}	kbhook=SetWindowsHookEx(WH_SYSMSGFILTER,KBhkprc,DLL,0);

chollida1

Nov 24, 2004 at 1:02 PM

SiCrane is correct. Alternativly you could export your method using a defs file.

Try opeingin your dll in dependancy walker and see the name it exports.

Cheers
Chris

hplus0603

Mod

3,014

hplus0603

Nov 24, 2004 at 1:05 PM

Use dumpbin to figure out the actual name of your function. Or depends.exe. Both come with Visual Studio.

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.