Re: Pass a serial port as user data in a GTK callback handler?

[adambeneschan@gmail.com]

On Saturday, February 15, 2014 3:32:58 PM UTC-8, hreba wrote:
> Hi,
> 
> I am new to Ada and still overwhelmed by the complexity of the language.
> 
> My actual programming exercise has a GTK GUI, and I want a callback 
> handler to communicate through a serial port, so I need to pass the port 
> in my user data, which must be of
> 
>     type User_Type (<>) is private;
> 
> which means it must be nonlimited.
> 
> But GNAT.Serial_Communications.Serial_Port is limited:
> 
>     type Serial_Port is new Ada.Streams.Root_Stream_Type with private;
>     type Root_Stream_Type is abstract tagged limited private;
> 
> I tried to pass a reference to the port, and it must be an "access all" 
> (because it is not allocated by my, but a preexisting variable (hardware 
> resource), as I understand it):
> 
>     port: access all GNAT.Serial_Communications.Serial_Port;
> 
> But then I get an error message
> 
>     "all" is not permitted for anonymous access types.
> 
> Is there a solution?

I agree with everyone else that anonymous access types aren't needed in this case, and you're better off using a named access type or something else.  Having said that, I just wanted to point out something about Ada: all anonymous access types are automatically "access all", i.e. they can refer to aliased variables.  So you could have solved the problem by just removing the "all" keyword.

                                 -- Adam