Hello, FPC developers' list.
We are preparing a next lazarus version and our users are heavily
testing thing. One bug report let me found one error which is not a
lazarus error, but fpc. This error happen because we used TObjectList to
store bitmaps in a list.
TObjectList is a useful thing - we dont need to think about object
destroying. They will be destroyed on deleting from the list. And
everyting works except next call: AList[AIndex] := NewObject
I attached a test projects which shows a bug.
But in few words this bug happen due to double object destroying:
1. In TObjectList.SetItem (this is *not correct* place to destroy)
2. In TObjectList.Notify (this is *correct* place to destroy)
A solution is simple: remove everything from TObjectList.SetItem except
Put call.
--
Best regards,
Paul Ishenin.
program fpc_object_list_bug;
{$mode objfpc}{$H+}
uses
Contnrs;
var
List: TObjectList;
begin
List := TObjectList.Create(True);
List.Add(TObject.Create);
List[0] := TObject.Create; // crash here :)
List.Free;
end.
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