[fpc-devel] Can someone confirm if this is a bug? (ancestor in TWRiter.WriteProperty)

[Paul Ishenin]

Michael Van Canneyt wrote:
>>
>> when you get to write TPersistenChild  you enter the following code
>>
>>   tkClass:
>>     begin
>>       ObjValue := TObject(GetObjectProp(Instance, PropInfo));
>>       if HasAncestor then
>>       begin
>>         AncestorObj := TObject(GetObjectProp(Ancestor, PropInfo));
>>         if Assigned(AncestorObj) then
>>           if Assigned(ObjValue) and
>>             (TComponent(AncestorObj).Owner = FRootAncestor) and
>>             (TComponent(ObjValue).Owner = Root) and
>>             (UpperCase(TComponent(AncestorObj).Name) = 
>> UpperCase(TComponent(ObjValue).Name)) then
>>             AncestorObj := ObjValue
>> //            else
>> //              AncestorObj := nil;
>>       end else
>>         AncestorObj := nil;
>> --------------
>>
>> TObject(GetObjectProp(Ancestor, PropInfo));  returns the TpersistentChil
>> as well as ObjValue being TPersistent
>>
>>
>> both get casted to TComponent with no check?
> I may have mis-judged t, but the problem is still the same:
>
> Ancestors can only be a TComponent.
Ancestor (in this report http://bugs.freepascal.org/view.php?id=14364) 
is TLabel, HasAncestor = True (since Ancestor is TLabel and 
Instance.ClassType = Ancestor.ClassType) and both ObjValue and 
AncestorObj are TAnchorSide (descendant of TPersistent and not 
TComponent). Therefore it accessing TAnchorSide property (TPersistent) 
as TComponent and we have a crash.

But maybe the problem is somewhere else. For example can Ancestor be 
TLabel or it is usually some form, frame or datamodule?

Best regards,
Paul Ishenin.