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From: Michael Erdmann <michael.erdmann@snafu.de>
Newsgroups: comp.lang.ada
Subject: Re: How to get around "access type must not be outside generic unit"
Date: Sun, 17 Dec 2006 15:28:25 +0100
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Date: 2006-12-17T15:28:25+01:00
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Thanks; Solution 2 works, see below :-)

Pascal Obry wrote:
> Michael Erdmann a �crit :
>> gnade@hal:~/test> gnatmake -c usage.adb
>> gcc -c usage.adb
>> usage.adb:16:28: access type must not be outside generic unit
>> gnatmake: "usage.adb" compilation error
>>
>> What is the reason for this new compiler check and what can i do
>> about it?
> 
> Solution 1) Declare register using an anonymous access type :
> 
>    procedure Register
>      (Str : in String; A : access function return Boolean);
> 
Actually this does not work; compiler complains the anonymous types
are not allowed here.

> Solution 2) Move access to generic spec
> 
> with Base; use Base;
> 
> generic
>    type Data_Type is private;
> package Usage is
> 
>    function Install return Boolean ;
>    procedure Doit( X : in out Data_Type );
> 
>    Install_Access : P_Access := Install'Access;
> 
> end Usage;
> 
This works. In order to make Install_Access invisible to the rest of the
world i make it private.

with Base;   use Base;

generic
   type Data_Type is private;
package Usage is

   function Install return Boolean ;
   procedure Doit( X : in out Data_Type );

private
   Install_Access : constant Callback_Access := Install'Access;
end Usage;

But what is the gain of doing it like this. I don't see any
gain in security..?!


> ---- usage.adb
> with Base;   use Base;
> 
> package body Usage is
> 
>    function Install return Boolean is
>    begin
>       return True;
>    end Install;
> 
>    procedure Doit( X : in out Data_Type ) is
>    begin
>       null;
>    end Doit;
> 
> begin
>    Register ("Doit", Install_Access);
> end Usage;
> 
> package Base is
> 
>    type P_Access is access function return Boolean;
> 
>    procedure Register (Str : in String; A : P_Access);
> 
> end Base;
> 
> Pascal.
>