[Lazarus] App crash at TScreen.GetCustomFormsZOrdered

[Mattias Gaertner]

On Fri, 27 Jun 2014 11:33:53 +0200
Petr Hlozek <petr at ok2cqr.com> wrote:

> Hi,
> 
> I have an Linux app, it has over 76k lines of code, 78 Forms and uses threads.
> After I close the app, it always crashes in
> 
> function TScreen.GetCustomFormsZOrdered(Index: Integer): TCustomForm;
> begin
>   Result := TCustomForm(FCustomFormsZOrdered[Index]);
> end;
> 
> The index variable value is something like 42325 or so.
>
> I tried to debug and here is what I found out:
> 
> It goes through all FormCloseQuesry, FormDestroy and
> DatamoduleDestory, then it goes to
> TApplication.DoBeforeFinalization and then into
> TScreen..GetCustomFormsZOrdered where it fails.
> I spent days trying to find out where could be the problem but didn't
> find anything. I'm lost. Do you have any idea where could be a
> problem, please? Thanks a lot!

Maybe some event uses an already freed object.
Set all references to nil, when freeing objects. For example in
TForm1.FormDestroy add Form1:=nil;

And compile with -gh.

Then you can run your program with environment variable
HEAPTRC=keepreleased


Mattias