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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Access procedure to pointer
Newsgroups: comp.lang.ada
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Date: Tue, 27 May 2008 20:26:58 +0200
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Date: 2008-05-27T20:27:00+02:00
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On Tue, 27 May 2008 17:45:25 +0000, in comp.lang.ada you wrote:

> Ludovic Brenta a �crit :
>> procedure Foo;
>> 
>> Access_Foo : constant access procedure := Foo'Access;
>> 
>> Foo_Address : constant System.Address := Foo'Address;
>> Foo_Address : constant System.Address := Access_Foo.all'Address;
>> 
> 
> It was refused by the compiler, "subtype mark is required here".

Egh? It the following should work:

   procedure Foo;
   pragma Convention (C, Foo); -- You deal with C, right?
   Ptr : constant Address := Foo'Address;

> I succeed using an unchecked conversion, looks like access to a 
> procedure has the same size than System.address since I didn't get any 
> warning.

I would suggest a cleaner:

   type Callback is access procedure;
   pragma Convention (C, Callback);
   
   procedure Foo;
   pragma Convention (C, Foo);
   
   Ptr : constant Callback := Foo'Access;

Callback is an equivalent to C pointer to a function.

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