Re: GCC 4.0 Ada.Containers Cursor danger.

[Matthew Heaney <matthewjheaney@earthlink.net>]

"Dmitriy Anisimkov" <anisimkov@yahoo.com> writes:

> <<
> >No, this checking is too much overhead.
> Too much overhead, compared to what?
> >>
> 
> Ok. I thought that you told about checking in
>    pragma Assert (not Has_Element (C2));
>    pragma Assert (not M.Contains ("two"));

No, I was referring to the checking in the implementation of the map
container itself.  The checks above are part of the example, and exist
for informational purposes only.


> if you told about new checking inside of
> 
>    Replace_Element (C, -2);  -- dangling cursor
> 
> it is not "too much".

Yes, that's the checking to which I was referring.  I'm glad to hear you
don't think it's too much.  (However, to check for dangling cursors,
you'll have to enable assertion checks when you compile.)

Did you try compiling your original example with assertions enabled?
What happens when you do?  (I have been modifying the GCC sources to be
more thorough in my use of assertion checks and cursor vetting, but you
still have an older version.  If you're having an emergency, I can
update the sources at tigris too, so you can have the improved checking
right away.)


> << This is a false analogy, since the name of the operations are
> To_Pointer
> and To_Address.  Nary an "unchecked" in site... >>
> 
> Isn't To_Pointer equivalent to Unchecked_Conversion from Address to
> Access ?

Yes, but since these conversions are provided by the language, they're
not outside the type system anymore, and hence don't require any scary
"unchecked" names.  "Unchecked" conversions imply that you're leaving
the type system, and that's never the case for the containers.