[Lazarus] GDB - cannot perform pointer math on incomplete types

[David Emerson]

> Still if you can get me the log + unit source ?
> 
> because the IDE in many cases tries to work those out. So I wonder what 
> happens behind the curtains...

I just constructed this program, which allows me to reproduce the issue. I 
put a breakpoint on the writeln.
Watch List items:
tsrl_ag_cp(cf.f_ag).f_curve.f_cps.f_list[0] -- gives GDB error
^tsrl_ag_cp(tsrl_ag_cp(cf.f_ag).f_curve.f_cps.f_list)[0] -- succeeds

I'll see how much of this I can cut out and still reproduce :)

program dumdum;

{$mode objfpc}

uses classes;

type
  ptr_array = array of pointer;
  tsrl_ag = class (tobject);

  t_list_frame = class (tobject)
    f_list : ptr_array;
    end;

  t_unsorted_pointer_list = class (t_list_frame)
    procedure add (p : pointer);
    end;

  generic gt_unsorted_pointer_list <_class> = class 
(t_unsorted_pointer_list)
    end;

  t_ordered_ag_list = specialize gt_unsorted_pointer_list <tsrl_ag>;

  tsrl_ag_cp_list = class (t_ordered_ag_list);

  tsrl_shape = class
    f_ag : tsrl_ag;
    end;

  tsrl_crowsfoot_icon = tsrl_shape;

  tsrl_curve = class (tsrl_shape)
    f_cps : tsrl_ag_cp_list;
    end;

  tsrl_ag_cp = class (tsrl_ag)
    f_curve : tsrl_curve;
    end;

procedure t_unsorted_pointer_list.add (p : pointer);
  var l : longint;
  begin
    l := length(f_list);
    setlength (f_list, l+1);
    f_list[l] := p;
  end;

var
  cf : tsrl_crowsfoot_icon;
  cf_ag, other_cp : tsrl_ag_cp;
  curve : tsrl_curve;

begin
  cf_ag := tsrl_ag_cp.create;
  other_cp := tsrl_ag_cp.create;
  curve := tsrl_curve.create;
  curve.f_cps := tsrl_ag_cp_list.create;
  curve.f_cps.add(other_cp);
  curve.f_cps.add(cf_ag);
  cf_ag.f_curve := curve;
  cf := tsrl_crowsfoot_icon.create;
  cf.f_ag := cf_ag;
  writeln ('hi');
end.