Re: GCC 4.0 Ada.Containers Cursor danger.

["Matthew Heaney" <mheaney@on2.com>]

Pascal Obry wrote:
>
> That such problem could occur again. We must ensure that at least the
> documentation is clear (very clear) about the semantics here.

Cursors confer no greater safety than you get with named access types.
If this isn't clear, then yes, we need to better job of advertising
this feature.

In general, don't keep cursors around unless you have a good reason.
And if you have a key (this is a map, say), then you can always use
key-based operations instead of cursor-based ones.  (In Dmitriy's case,
he should have been using Include or Replace, not Replace_Element.)


> I'm not saying that Ada.Containers or Cursor are bad, I already like this
> library much (this is not the case for Dmitriy :), what I'm saying is that
> this problem could happen to others and it is dangerous enough for us to take
> great care about it :)

I took Dmitriy's complaint seriously enough that I've been adding
assertion checks that can detect dangling cursors.  (When you build his
original example with assertions enabled, the program now fails with a
nice error message.)