Thread: Problem with invoke of hooks DLL

Hi!

I know we've had dozens of discussions on Win32 hooks, but I couldn't get any of them to work for me simply because I couldn't compile the file that references the DLL.

In the following case, I got an:
error LNK2019: unresolved external symbol "__declspec(dllimport) int __stdcall InstallHook (struct HINSTANCE __ *)" (__imp_?InstallHook@@YGHP

For now, here's what I came up with after copy-pasting from a few sources:

the one thats supposed to compile to .EXE:

Code:

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>

extern __declspec (dllimport) LRESULT CALLBACK KbProc(int, 
WPARAM, LPARAM);
extern __declspec (dllimport) BOOL WINAPI InstallHook(HMODULE ahmod);
extern __declspec (dllimport) void WINAPI RemoveHook(void);


int main(int argc, char *argv[])
{
  HMODULE hmod = LoadLibrary("Hooky.dll");
  InstallHook(hmod);

  system("pause");
  return 0;
};

The one that compiles to DLL:

Code:

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>

__declspec (dllexport) LRESULT CALLBACK KbProc(int, WPARAM, LPARAM);
__declspec (dllexport) BOOL WINAPI InstallHook(HMODULE ahmod);
__declspec (dllexport) void WINAPI RemoveHook(void);

#pragma data_seg("shared_data")
// Superglobals
HHOOK hookdata = 0;
#pragma data_seg()
#pragma comment(linker, "/SECTION:shared_data,S")

HMODULE hmodule = 0;
HWND hwindow = 0;
BOOL recycle = FALSE;
BOOL running = FALSE;
UINT timerid = 0;
void CALLBACK TimerProc(HWND hwnd, UINT uMsg, UINT idEvent, DWORD dwTime);

__declspec (dllexport) LRESULT CALLBACK KbProc(int code, WPARAM w, LPARAM l)
{
  if ( code < 0 || code != HC_ACTION )
    return CallNextHookEx(hookdata,code,w,l);

  char buff[100];

  sprintf(buff,"Values are: %d %u %u\n", code, w, l);

  MessageBox(0, buff, "ok", 0);

  switch(w)
  {
  case NULL: break;
    default: return CallNextHookEx(hookdata,code,w,l);
  }
  return TRUE;
}

__declspec (dllexport) BOOL APIENTRY DllMain (HMODULE hmod,
                       DWORD reason,
                       LPVOID na)
{
    switch (reason)
    {
      case DLL_PROCESS_ATTACH:
           hmodule = hmod;
        break;

      case DLL_PROCESS_DETACH:
        break;

      case DLL_THREAD_ATTACH:
        break;

      case DLL_THREAD_DETACH:
        break;
    }

    /* Returns TRUE on success, FALSE on failure */
    return TRUE;
}

__declspec (dllexport) BOOL WINAPI InstallHook(HMODULE ahmod)
{
  if ( hookdata != 0 )
     return FALSE;
  hookdata = SetWindowsHookEx(WH_KEYBOARD, KbProc, (HINSTANCE) ahmod, 0);
  if ( !hookdata )
     MessageBox(0, TEXT("Hook failed."), TEXT("Error"), MB_ICONEXCLAMATION); 
  return hookdata != 0;
}

__declspec (dllexport) void WINAPI RemoveHook(void)
{
  if ( hookdata != 0 )
  {
    UnhookWindowsHookEx(hookdata);
  }
}

void CALLBACK TimerProc(HWND hwnd, UINT uMsg, UINT idEvent, DWORD dwTime)
{
}

Finally, the module definition file:

Code:

LIBRARY	Hooky

EXPORTS
KbProc
InstallHook
RemoveHook