Another Delphi Invalid Pointer Operation - delphi

Question

This VCL Form program generates the Invalid Pointer Operation notice:
Uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.ComCtrls,
DcadMenu_u;
type
TForm1 = class(TForm)
MenuTestRichEdit: TRichEdit;
LoadButton: TButton;
procedure ButtonLoadClick(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm1.ButtonLoadClick(Sender: TObject);
var
menu : TDcadMenu;
item1, item2 : TDcadMenuItem;
strlist :tstringlist;
i : integer;
begin
menu := tDcadMenu.Create();
item1 := TDcadMenuItem.create ('Option1', 'Do Option1', false, false, true);
menu.add (item1);
item2 := TDcadMenuItem.create ('Option2', 'Do Option2', false, false, true);
menu.add (item2);
strlist := tstringlist.Create;
Try
For i := 0 to Menu.Count - 1 DO
begin
item1 := menu.Items[i];
strlist.Add (Item1.lblset + ' | ' + Item1.lblmsg );
end;
Form1.MenuTestRichEdit.Lines := strlist;
finally
item1.free;
item2.Free;
menu.free;
strlist.Free;
end;
end;
The code works fine and generates the item list in the Richedit component. I suspect I am freeing an object that is already being handled, but not clear on what the cause is specifically. Can someone explain this?

Answer 1

We can't see the implementation of TDcadMenu, but normally adding items to a class gives the ownership of the items to that class, so there is no need to free the items outside of the class. As #Remy comments, it is normally safe to free them before before freeing the menu object, though.
In your code you are reassigning item1, and when freeing the items, Item1 and Item2 both shares the same instance as menu.Items[1]. This means that you have a double free, which gives your invalid pointer notice.
item1.free;
item2.Free; // <- Double free of same instance