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From: Laurent.Guerby@enst-bretagne.fr (Laurent Guerby)
Subject: Re: Free'ing extended types
Date: 1996/04/29
Message-ID: <4xpw8qvlau.fsf@lagrange.enst-bretagne.fr>#1/1
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sender: guerby@lagrange.enst-bretagne.fr
references: <3183AC75.335C@ehs.ericsson.se> <dewar.830716817@schonberg>
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organization: Telecom Bretagne
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Date: 1996-04-29T00:00:00+00:00
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Jonas Nygren writes
[deleted complete Bob's crystal-clear explanations ;-]
: Yes, I think it would be nice. Every now and then I start thinking
: of defining my own language and implement it always with GC as a 
: basic feature. But then it always stops at the thought because
: of the sheer complexity of the task.
[deleted]

   Note that the impact of a  GC on the  "erronenousness" of a program
is    interesting.  An   Ada run-time  with   GC    can  simply ignore
Unchecked_Dealocation calls, or do smart thing and raise Program_Error
when an access to a previously deallocated object is performed. In the
first case (do  nothing on deallocation)  I think the execution is not
erroneous because RM95-13.11.2(16) says :

"Evaluating  a  name that denotes a  nonexistent  object is erroneous.
The execution  of a call to  an  instance of Unchecked_Deallocation is
erroneous if the object was created other than by  an allocator for an
access type whose pool is Name'Storage_Pool."

   On  a garbage collected implementation,  the object is likely to be
"existant" or your GC is wrong ;-).

: /jonas

-- 
--  Laurent Guerby, student at Telecom Bretagne (France), Team Ada.
--  "Use the Source, Luke. The Source will be with you, always (GPL)."
--  http://www-eleves.enst-bretagne.fr/~guerby/ (GATO Project).
--  Try GNAT, the GNU Ada 95 compiler (ftp://cs.nyu.edu/pub/gnat).