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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: What exactly is the licensing situation with GNAT?
Date: Fri, 14 Nov 2014 09:36:10 +0100
Organization: cbb software GmbH
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Xref: news.eternal-september.org comp.lang.ada:23272
Date: 2014-11-14T09:36:10+01:00
List-Id: <comp.lang.ada>

On Thu, 13 Nov 2014 15:51:54 -0600, Randy Brukardt wrote:

> I recall Adam suggesting that some special sort of named 
> access-to-subprogram type be defined with similar characteristics to the 
> anonymous access-to-subprogram. Such a thing could be made to work, while 
> the bare pointer used for normal access-to-subprogram types would not work. 
> But of course it would be susceptible to dangling pointers, and won't 
> (usually) be compatible with C.

I was always wondering why it was not a plain subprogram type. That would
solve a lot of problem, interfacing C included. E.g.

   type procedure Callback;
   pragma Convention (C, Callback);

   procedure Foo (F : Callback);
   pragma Import (C, Foo);

   procedure Bar is
      X : Callback :=
      begin
          ...
      end;
   begin
      Foo (X); -- I know what I am doing
   end Bar;

Certainly there is a danger that C would copy the pointer and use it after
leaving Bar, but that is not Ada's concern. Because it is equally apply to
*any* non-scalar arguments passed to C.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de