Re: Pointers in Ada

[Jeffrey Carter <spam@spam.com>]

Sebastian wrote:

> package Mdp_Lld;
>   type Message_Header is
>      record
>        Word_Count              : Byte;
>        Command_Id              : Byte;
>      end record;
> 
>      subtype Mdp_Message_Data is Byte(1..500);
> 
>      type A_Mdp_Message is
>         record
>           Header : aliased Message_Header;
>           Data   : aliased Mdp_Message_Data;
>         end record;
> 
>      type Driver_Msg_Ptr_Type is access all A_MDP_Message;
> 
>      procedure Put_Message
>         (Msg_Buffer_Ptr : in out Client_Msg_Ptr_Type;
> );

As you're no doubt aware, this won't compile. In addition to the syntax 
error in the declaration of Put_Message, Client_Msg_Ptr_Type has not 
been declared.

Before we can answer your questions, we need to know why you're using 
pointers. What wrong with

procedure Put_Message (Message : in An_Mdp_Message);

?

In Ada pointers are needed far more rarely than in some other languages. 
Since you're not building a dynamic data structure, it's likely that you 
don't need them. If you really do need them, it's probably a better 
design to hide them from the clients of the package. That way you can 
localize the memory management to your package.

-- 
Jeff Carter
"Saving keystrokes is the job of the text editor,
not the programming language."
Preben Randhol
64