🚀 go-pugleaf

Hi,
I tried to reproduce the behavior in a very simple test app,
I did not use shared memory or wait for events...
Here's the complete code:

"Client" Application with a button and the following handler:


//exported from the DLL
typedef void (*PPost)(HWND h, unsigned int message);

void __fastcall TForm1::Button1Click(TObject *Poster)
{
   HWND h = FindWindow("TForm2", NULL);

   if(h != NULL)
   {
      HINSTANCE hinst = LoadLibrary("HookDll.dll");

      if(hinst != NULL)
      {
         PPost Post = (PPost)GetProcAddress(hinst, "_Post");
         if(Post != NULL)
            Post(h, WM_USER+1);
         else
            MessageBox(NULL, "GetProcAddress failed", "", 0);
         FreeLibrary(hinst);
      }
      else
         MessageBox(NULL, "LoadLibrary failed", "", 0);
   }
   else
      MessageBox(NULL, "Window TForm2 not found", "", 0);
}




HookDll with the following code:



#include <vcl.h>
#pragma hdrstop


HINSTANCE theInst = NULL;

HHOOK hMessageHook = NULL;

#pragma argsused
int WINAPI DllEntryPoint(HINSTANCE hinst,
                         unsigned long reason,
                         void* lpReserved)
{
   if(reason == DLL_PROCESS_ATTACH)
   {
      MessageBox(NULL, "Process Attached", "", 0);

      if(theInst == NULL)
         theInst = hinst;
   }
   else if(reason == DLL_PROCESS_DETACH)
   {
      MessageBox(NULL, "Process Detached", "", 0);
   }

   return TRUE;
}


LRESULT CALLBACK GetMsgProc(int code, WPARAM wParam, LPARAM lParam)
{
   if(code == HC_ACTION)
   {
      MSG* msg = (MSG*)lParam;

      if(msg->message == WM_USER+1)
      {
         MessageBox(NULL, "Received the message", "", 0);

         HWND h = (HWND)msg->lParam;

         /* this works
         char buffer[100];
         GetClassName(h, buffer, 99);

         //show the class name
         MessageBox(NULL, buffer, "", 0);
         */

         //because of this line LoadLibrary fails
         TWinControl* ctrl = FindControl(h);
         //((TForm*)ctrl)->Color = clRed;
      }
   }

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


extern "C" __declspec(dllexport)
void Post(HWND hwnd, unsigned int message)
{
   //hook the target application
   hMessageHook =
   SetWindowsHookEx(WH_GETMESSAGE,
                    (HOOKPROC)GetMsgProc,
                    theInst,
                    GetWindowThreadProcessId(hwnd, NULL));

   if(hMessageHook == NULL)
   {
      MessageBox(0, "Failed to hook", "", 0);
      return;
   }

   PostMessage(hwnd, message, 0, (long)hwnd);

   //instead of waiting for a return event
   MessageBox(NULL, "Block client app", "", 0);

   BOOL r = UnhookWindowsHookEx(hMessageHook);
   if(r == 0)
      MessageBox(0, "Failed to unhook", "", 0);
}



The "Server" app has a dummy form with classname "TForm2".

any ideas?
Nick