delphi如果列表为空list循环的问题

如果列表为空

for i:=0 to list.count -1
这样就不循环了
如果不减一，又怕越界，怎么办？

 repeat
    ShowMessage('aa');
  until list.count = 0 ;

if List.Count > 0 then
  for i:=0 to list.count -1
  begin
    {......}
  end;

procedure TForm1.Button1Click(Sender: TObject);
var
  List: TStringList;
  s: string;
begin
  List := TStringList.Create;
  for s in List do
    ShowMessage(s);
  List.Free;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  List: TList;
  p: Pointer;
begin
  List := TList.Create;
  for p in List do
    ShowMessage(IntToStr(Integer(P)));
  List.Free;
end;