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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Interfacing to C: big structures
Date: Mon, 25 Feb 2008 18:43:56 -0500
Organization: The World Public Access UNIX, Brookline, MA
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Date: 2008-02-25T18:43:56-05:00
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Maciej Sobczak <see.my.homepage@gmail.com> writes:

> Consider the C API that contains some structure S and a couple of
> functions that operate on the state that is stored in the Struct. A
> typical usage in C might be:
>
> struct S s;
>
> init(&s);
> foo(&s);
> bar(&s);
> baz(&s);
>
> Above, s is created with automatic storage duration.
>
> How to interface to this from Ada? I see two options:

Something like:

    type S is record ... end record;
    pragma Convention (C, S);
    
    X : aliased S;
    init (X'Access); -- or possibly 'Unchecked_Access
    foo (X'Access); -- or ...

Best to avoid heap management when you can.

- Bob