I am not very familiar with the code, so before reporting, I'd like to ask:

trunc\rtl\objpas\classes\writer.inc
procedure TWriter.WriteProperty(Instance: TPersistent; PropInfo: Pointer);

Imagine you a writing an Component, that does have an ancestor. The same component should have

   property Foo: TPersistentChild read FFoo write FFoo;

You should end up in the following code: (line 1091 in recent (a few
weeks) trunc )
// this is the last else, it's not a component, and it is not a collection
          else
            begin
            SavedAncestor := Ancestor;
            SavedPropPath := FPropPath;
            try
              FPropPath := FPropPath + PPropInfo(PropInfo)^.Name + '.';
              if HasAncestor then
                Ancestor := TPersistent(GetObjectProp(Ancestor,
PropInfo));
              WriteProperties(TPersistent(ObjValue));
            finally
              Ancestor := SavedAncestor;
              FPropPath := SavedPropPath;
            end;
            end;
--------------------------------------
              if HasAncestor then
                Ancestor := TPersistent(GetObjectProp(Ancestor,
PropInfo));

sets the ancestor to a persitent object

Now if TPersistentChild  itself has
  property Some: TComponent

then you end up again in TWriter.WriteProperty writing a tclass property

    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;

and this code assumes that the ancestor is a TComponent, but as seen before, the ancestor is not.

Shall I report a bug, or do I miss understand something? (is there a workaround?)

Martin

I may have mis-judged t, but the problem is still the same:

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?

Ancestors can only be a TComponent.

Michael.

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.

and on top of that, Ancestor can be a TPersitent:
because if the AnchorSide writes it's properties, the following code, sts ancestor to anchorside:

      begin
            SavedAncestor := Ancestor;
            SavedPropPath := FPropPath;
            try
              FPropPath := FPropPath + PPropInfo(PropInfo)^.Name + '.';
              if HasAncestor then
                Ancestor := TPersistent(GetObjectProp(Ancestor,
PropInfo));  // <<<<<
              WriteProperties(TPersistent(ObjValue));
            finally
              Ancestor := SavedAncestor;
              FPropPath := SavedPropPath;
            end;