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From: Stephen Leake <Stephen.Leake@gsfc.nasa.gov>
Subject: Re: Program error from assignment??
Date: 1998/07/22
Message-ID: <u7m15dbki.fsf@gsfc.nasa.gov>#1/1
X-Deja-AN: 373888634
References: <6p3070$bvn$1@nnrp1.dejanews.com>
 <6p4skk$j73$1@nnrp1.dejanews.com>
Organization: NASA Goddard Space Flight Center -- Greenbelt, Maryland USA
Newsgroups: comp.lang.ada
Date: 1998-07-22T00:00:00+00:00
List-Id: <comp.lang.ada>

dennison@telepath.com writes:

> Program_Error can happen on this assignment when the accessability level of
> the source pointer's object is deeper than that of the target object's type.
> That's so I can't keep around a pointer to an object after it goes away. Fair
> enough.
> 
> So now this turns into an "accessability level" question. The object that is
> pointed to is declared in the declaration section of the main routine. It
> exists the entire program. I don't understand the exact rules on accessability
> levels, but in my book I should *never* fail an accessability check with this
> object. The access type is declared in a package spec.
> 
> T.E.D.

The compiler doesn't know that this routine is your main routine, so
it assumes it could be called from some other routine; then the
accessibility check makes sense. (uh oh; is this an advantage for C
"main"? :). 

You have two options:

1) Declare the object in a library level package (I usually call such
a package main_aux.ads or some such).

2) Use 'Unchecked_Access. This situation is pretty much what
Unchecked_Access is for; you are telling the compiler that you are
smarter than it is (well, at least you promise not to use the pointer
after the object goes out of scope :).

-- Stephe