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From: Matthew Heaney <matthew_heaney@acm.org>
Subject: Re: Why a PROGRAM ERROR?
Date: 1998/12/11
Message-ID: <m3yaofmpon.fsf@mheaney.ni.net>#1/1
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Sender: matt@mheaney.ni.net
References: <3670178F.8751F9B9@nowhere.com>
NNTP-Posting-Date: Thu, 10 Dec 1998 17:28:38 PDT
Newsgroups: comp.lang.ada
Date: 1998-12-11T00:00:00+00:00
List-Id: <comp.lang.ada>

Rusnak <bogus@nowhere.com> writes:

> I have the following code  in a generic package (or code similar to it
> anyway):
> 
> 
>       Given a tagged type "My_Instance" and a type defined as
> 
>           type My_Class_Object_Type is access all My_Instance'Class;
> 
>     I have a function in the spec/body, defined in the body as
> 
>           function Unpack(The_Object : access My_Instance'Class)
>                                       Core_Text : String)
>          return Command_Object
>          is
>             Return_Value :  Command_Object;
>         begin
>             . . .
>                Command_Object.The_Object :=
> My_Class_Object_Type(The_Object);
>            . . .
>          end Unpack;
> 
> 
>         Any time I try to cast the anonymous access type to
> My_Instance'Class to the type My_Class_Object_Type,
>         a program error is raised.  Why is this the case, why is the
> error not caught at compile time, and how can I resolve
>        the error?  It seems to only occur  when a cast like this one is
> made inside an instantiation of a generic package.
> 
>        Any help is greatly appreciated.


Is it possible that you're following a path that doesn't include a
return statement (because of an internal exception, perhaps)?  If you're
getting Program_Error when you execute a function, that's usually the
reason.