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From: =?ISO-8859-1?Q?S=E9bastien?= <seb.morand@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Access procedure to pointer
Date: Wed, 28 May 2008 09:06:37 +0000
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Date: 2008-05-28T09:06:37+00:00
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> 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.

The point was I'm not using constant.

My code looks like this:


type Signal is (SIGHUP);
for Signal use (SIGHUP => 1);

type Signal_Callback is access procedure(sig: Signal);

procedure InterceptSignal(sig: in Signal; callback: in Signal_Callback);

procedure c_signal(sig: in Signal; callback: in System.Address);
pragma Import(C, c_signal, "signal");

procedure HelloFromSignal(sig: Signal) is
begin
	Put_Line("Hello from" & Signal'Image(sig));
end HelloFromSignal;

procedure Main is
begin
	InterceptSignal(SIGUP, HelloFromSignal'Access);
	delay 30;
end Main;

So I change the code following your instruction :
procedure c_signal(sig: in Signal; callback: in Signal_Callback);

And did add all the pragma Contention where you told me. It works fine 
and looks like more portable ;-) Thanks for all your answers and help.

Moreover, I discover that sigaction and other Signal function are 
implemented in Gnat 4.3 in the System.OS_Interface. Even if "signal" 
itself is missing, there is some ways to do it without any C interface 
in my code.

Really documentation is missing about what is available in GNAT and 
examples, too bad!

Sebastien