Re: Issue with GNAT GPL 2009 and GtkAda

[Adam Beneschan <adam@irvine.com>]

On Jun 26, 2:03 pm, Damien Carbonne <damien.carbo...@free.fr> wrote:
> If what you say is true, why does the following example work fine (using
> GNAT), without any compiler warning or execution error ?

Because you're not trying to store the 'Access anywhere.

The problem in your original example is with the line

   BB := B.all'Access;

where BB is a variable of type Base_Ref.  Since the type Base_Ref is
global (i.e. has library-level accessibility), since it's defined in a
library package, any value of type Base_Ref also has to be global (if
you never use 'Unchecked_Access).  It can't be the 'Access of a local
variable.  Otherwise, you could work things out (by assigning
something else to BB) so that you have a global variable of type
Base_Ref that points to a local variable that no longer exists.

But in the second example, when you take the 'Access of a parameter,
you never try to convert it to a global type.  You're converting it to
an "anonymous access parameter" type when, say, you call P1A
(X'Access...), but that's OK, since anonymous access parameters take
on the accessibility level of whatever you pass them.  (Very roughly
speaking.)

It has nothing to do with "aliased".  Stephe was a tad confused.
Omitting "aliased" can make a program illegal but I do not believe
there is any way that it can cause a Program_Error at runtime.

                            -- Adam