Ever wanted to read the debug information an application sends out?

This little codesnippet will ask for the ProcessID (PID) of the application you want to catch debug information from. I did not have time to write some code for it right now, so in the meantime use the taskmanager and get the PID there. :)


Type
  TDebugThread = Class(TThread)
  Private
    { Private declarations }
  Protected
    { Protected declarations }
    Procedure Execute; override;
  Public
    { Public declarations }
    Constructor Create;
    Destructor Destroy; override;
  End;

  TForm1 = class(TForm)
    Memo1: TMemo;
    TreeView1: TTreeView;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
    DebugThread : TDebugThread;
  public
    { Public declarations }
    Procedure BeginCompile(Sender: TObject);
  end;


var
  Form1: TForm1;

Implementation


Procedure TForm1.FormCreate(Sender: TObject);
Begin
   DebugThread := TDebugThread.Create;
End;

procedure TForm1.FormDestroy(Sender: TObject);
Begin
   DebugThread.Terminate;
End;

Procedure TDebugThread.Execute;
Var
  DebugEvent : _Debug_Event;
  ReadLen    : DWord;
  StrBuffer  : pChar;
  UniBuffer  : WideString;

  S : String;
  DbgHandle  : THandle;
  OpenHandle : THandle;

  // ProcessNode : TTreeNode;
  ThreadNode  : TTreeNode;

Begin
   S := InputBox('Process', 'Handle', '0');
   DbgHandle := StrToIntDef(S, 0);
   OpenHandle := OpenProcess(PROCESS_ALL_ACCESS, True, DbgHandle);

   IF (DebugActiveProcess(DbgHandle)) Then Form1.Caption := 'Debug ok'
      Else Form1.Caption := 'Debug failed';


   Form1.TreeView1.Items.Clear;
   ThreadNode := Form1.TreeView1.Items.AddChild(NIL, 'Threads');
   // ProcessNode := Form1.TreeView1.Items.AddChild(NIL, 'Processes');

   While (not Terminated) do
   Begin
      Sleep(0);

      IF (WaitForDebugEvent(DebugEvent, 100)) Then
      Begin
         IF (not Application.Terminated) Then
         Begin
            Case DebugEvent.dwDebugEventCode of
              OUTPUT_DEBUG_STRING_EVENT : Begin
                                             IF (DebugEvent.DebugString.fUnicode = 0) Then
                                             Begin
                                                StrBuffer := StrAlloc(DebugEvent.DebugString.nDebugStringLength);
                                                ReadProcessMemory(OpenHandle{DebugEvent.dwProcessId}, @DebugEvent.DebugString.lpDebugStringData^, StrBuffer, DebugEvent.DebugString.nDebugStringLength, ReadLen);
                                                Form1.Memo1.Lines.Add(IntToStr(ReadLen)+' - STR - '+StrPas(StrBuffer));

                                                StrDispose(StrBuffer);
                                             End
                                              Else
                                               Begin
                                                  SetLength(UniBuffer, DebugEvent.DebugString.nDebugStringLength);
                                                  ReadProcessMemory(DebugEvent.dwProcessId, DebugEvent.DebugString.lpDebugStringData, @UniBuffer[1], DebugEvent.DebugString.nDebugStringLength, ReadLen);
                                                  UniBuffer := Copy(UniBuffer, 1, ReadLen);

                                                  Form1.Memo2.Lines.Add(IntToStr(DebugEvent.DebugString.nDebugStringLength)+' - UNI - '{+UniBuffer});
                                               End;
                                          End;
              CREATE_THREAD_DEBUG_EVENT : Begin
                                             Form1.TreeView1.Items.AddChild(ThreadNode, IntToStr(DebugEvent.CreateThread.hThread));
                                          End;
            End;
         End;

         ContinueDebugEvent(DebugEvent.dwProcessId, DebugEvent.dwThreadId, DBG_CONTINUE);
      End
       Else Sleep(50);
   End;

   CloseHandle(OpenHandle);
End;

Constructor TDebugThread.Create;
Begin
   Inherited Create(False);
   FreeOnTerminate := True;
End;

Destructor TDebugThread.Destroy;
Begin
   Inherited Destroy;
End;

End.