Question

What can i do with the error: 997 (io pending) when invoking: RegisterEventSource?

Thanks for help!

procedure TForm1.Button111Click(Sender: TObject);
var
  StringToAdd: String;
  hEventLog: THandle;
  p: PChar;
  EventID: Word;
  CategoryID: Word;
  wynik: Boolean;
  errnumber: cardinal;
begin
  hEventLog := RegisterEventSource(nil, PChar('app'));

  errnumber := 0;
  errnumber := GetLastError();  //<==997
  showmessage (IntToStr(errnumber));

  if hEventLog > 0 then
  begin
    p := PChar('Test');
    wynik :=
    ReportEvent(
    hEventLog,
    EVENTLOG_INFORMATION_TYPE, // Event Type
    22, // Event Category ID
    500, // Event ID
    nil, // User SID (optional)
    1, // Number of strings
    0, // Size of Binary Data
    @p, // String to be merged with Text in Ressource DLL 
    nil // Address of Binary Data
    );
    errnumber := GetLastError(); //<==997
    showmessage (IntToStr(errnumber));

    DeRegisterEventSource(hEventLog);
  end;
end;

Answer 1

You aren’t testing whether or not hEventLog is NULL before calling GetLastError. You should only call GetLastError if the API call failed, as described in the documentation.

My guess is that RegisterEventSource actually succeeds and you are getting the error code from the failure of another API call that happened earlier in the execution of your program.