Do not set TStringList.sorted:=True with default comparison

Now, this is a nasty bug, especially for Delphi 2009, reported by an anonymous user in my other blog post here:

The Windows API CompareStr() in Windows XP SP3, using Danish locale (and probably most others), thinks that 59A < 59-A < -59-A < 5-9A < 59-A.

TStringList.Find uses binary lookups on a sorted list of strings, which means that for 1024 items in a TStringList, it does not need to make more than 10 string comparisons in order to find the index of a specific string. This is fast, but it requires the list to be sorted in a deterministic way, and it requires CompareStr() to be able to tell, what direction to go to find the string. On a Danish Windows XP SP3, this code will trigger error #1 and error #3:

var
  list1: TStringList;
  idx1:Integer;
begin
  list1 := TStringList.create;
  try
    list1.Sorted := True;
    list1.Add('59A');
    list1.Add('-59-A');
    list1.Add('5-9A');
    list1.Add('59-A');
    if list1.IndexOf('5-9A')=-1 then
      ShowMessage ('Error #1: IndexOf does not work.');
    if list1.Find('5-9A',idx1) then begin
      if list1[idx1]<>'5-9A' then
        ShowMessage ('Error #2: Find failed and found the wrong string.');
    end else
      ShowMessage ('Error #3: Find failed because it did not find the string which is present.');
  finally
    FreeAndNil (list1);
  end;
end;

Error #1 is triggered, because .IndexOf uses .Find on sorted lists in Delphi 2009. CodeGear cannot fix this problem easily, because it's actually a bug in Windows. This bug is worse for Delphi 2009, because it optimizes the .IndexOf function by using .Find, for sorted strings.

You can make Windows Explorer demonstrate the same problem. Create 4 files like this:

Date             Size  Name  
14-06-2009 09:00   54  -59-A
14-06-2009 08:58    0  5-9A
14-06-2009 09:01    4  59-A
14-06-2009 09:02  168  59A

Then, show the folder using Windows explorer in Detailed view, and do this:

* Click the column Size, to sort by size
* Click the column Name, to sort by name.
* You can now see that the order is 5-9A, 59A, 59-A, -59-A
* Click the change date column, to sort by change date
* Click the column Name, to sort by name
* The order is now 59A, 59-A, -59-A, 5-9A

I didn't try this on 32-bit Vista or 64-Vista, yet.