Access to subprogram

Access to subprogram

[Sebastian]

What is the meaning of this
" subprogram must not be deeper than access type"

Re: Access to subprogram

[Grein, Christoph]

> 
> What is the meaning of this
> " subprogram must not be deeper than access type"

package Pak is

  type Access_P is access procedure;
  Global: Access_P;

end Pak;

with Pak;
procedure Proc is

  procedure Local is separate;
  LA: Pak.Access_P := Local'Access;

begin
  Global := LA;
end Proc;

Here Local has a deeper level than Access_P, i.e. a shorter lifetime. The 
aforementioned rule forbids such a use as LA, since Global will point to a 
non-existing item after Porc has finished.

Re: Access to subprogram

[David C. Hoos]

----- Original Message ----- 
From: "Sebastian" <sebastian.madunic@avionics.saab.se>
Newsgroups: comp.lang.ada
To: <comp.lang.ada@ada.eu.org>
Sent: Tuesday, May 07, 2002 7:47 AM
Subject: Access to subprogram


> What is the meaning of this
> " subprogram must not be deeper than access type"
It means exactly what it says.  You're trying to take the access
value of a subprogram that is nested more deeply than is the
place where the access type is declared.

To remedy this, you need to do one of two things, viz.:

   1.  Declare the subprogram at library level -- i.e., not in
        a package or nested within another subprogram

   2.  Use 'Unrestricted_Access instead of 'Access, if you're
        using GNAT, and if your are certain that the lifetime of
        the subprogram is at least as long as the lifetime of the
        access type.


    

Re: Access to subprogram

[Stephen Leake]

"David C. Hoos" <david.c.hoos.sr@ada95.com> writes:

> From: "Sebastian" <sebastian.madunic@avionics.saab.se>
> > What is the meaning of this
> > " subprogram must not be deeper than access type"
> It means exactly what it says.  You're trying to take the access
> value of a subprogram that is nested more deeply than is the
> place where the access type is declared.
> 
> To remedy this, you need to do one of two things, viz.:
> 
>    1.  Declare the subprogram at library level -- i.e., not in
>         a package or nested within another subprogram
> 
>    2.  Use 'Unrestricted_Access instead of 'Access, if you're
>         using GNAT, and if your are certain that the lifetime of
>         the subprogram is at least as long as the lifetime of the
>         access type.

Rule 2 is actually too restrictive. You can use Unrestricted_Access if
you are sure that the lifetime of the program is at least as long as
that of all copies of the access value. The compiler assumes copies of
the access value can last as long as the access type, but you don't
have to.

-- 
-- Stephe

Re: Access to subprogram

[Sebastian]

Wow,
It works!

Thanks


"David C. Hoos" <david.c.hoos.sr@ada95.com> wrote in message
news:mailman.1020776522.17239.comp.lang.ada@ada.eu.org...
>
> ----- Original Message -----
> From: "Sebastian" <sebastian.madunic@avionics.saab.se>
> Newsgroups: comp.lang.ada
> To: <comp.lang.ada@ada.eu.org>
> Sent: Tuesday, May 07, 2002 7:47 AM
> Subject: Access to subprogram
>
>
> > What is the meaning of this
> > " subprogram must not be deeper than access type"
> It means exactly what it says.  You're trying to take the access
> value of a subprogram that is nested more deeply than is the
> place where the access type is declared.
>
> To remedy this, you need to do one of two things, viz.:
>
>    1.  Declare the subprogram at library level -- i.e., not in
>         a package or nested within another subprogram
>
>    2.  Use 'Unrestricted_Access instead of 'Access, if you're
>         using GNAT, and if your are certain that the lifetime of
>         the subprogram is at least as long as the lifetime of the
>         access type.
>
>
>
>