Re: strange cursor in nested containers

["Randy Brukardt" <randy@rrsoftware.com>]

It's not required to detect such cursors because it is expensive to do so 
perfectly (essentially, each cursor has to be controlled and one has to keep 
a list of them associated with the container). There are imperfect solutions 
which are likely to be "good enough" in practice, but they still have a 
(small) cost which may be an issue for some uses. Thus, most implementers 
don't use them. I know the original GNAT containers had a debugging version 
that included such checks, but I don't know if they still exist or how one 
would enable them if they do.

            Randy.

"Mario Blunk" <mario.blunk.gplus@gmail.com> wrote in message 
news:9a1c3ba5-d5ae-41d3-9eab-2b8cd941bc66n@googlegroups.com...
>> > How could I solve the problem ? Not using "rename" ? Using an aliased 
>> > access type as John Barnes suggests in Ada2005 on page 275 ?
>> You have to avoid calling Element. Since you have a cursor, you can call
>> Query_Element, which should pass the actual element to the procedure you 
>> supply.
>
> Right, that solves the problem. For those interested please find a 
> comparison here:
>
> 1. The demo with a dangling (dangerous) cursor:
> https://github.com/Blunk-electronic/ada_training/blob/master/src/containers/demo/nested/nest_1.adb
>
> And the demo with the issue solved properly:
> https://github.com/Blunk-electronic/ada_training/blob/master/src/containers/demo/nested/nest_2.adb
>
> Still the question remains, why such a dangling cursor is not detected at 
> runtime.