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From: dewar@cs.nyu.edu (Robert Dewar)
Subject: Re: C to Ada : a piece of code
Date: 1996/09/11
Message-ID: <dewar.842440450@schonberg>#1/1
X-Deja-AN: 179917298
references: <3231732C.2781@virgoa4.in2p3.fr>
 <JSA.96Sep7205717@alexandria><01bb9d61$537fe5e0$2b8371a5@dhoossr.iquest.com>
 <JSA.96Sep8202531@alexandria> <01bb9e40$d0312d80$348371a5@dhoossr.iquest.com>
 <dewar.842316873@schonberg> <514lpk$i0m@fozzie.sun3.iaf.nl>
organization: Courant Institute of Mathematical Sciences
newsgroups: comp.lang.ada
Date: 1996-09-11T00:00:00+00:00
List-Id: <comp.lang.ada>


iGeert said, regarding virtual origins

"Please, don't do this! It is possible, but certainly not perfect!  If
applications are long-lived and they dynamically allocate memory at a
certain rate, garbage collection is necessary for keeping the language
safe.

Since Ada-compilers do not provide garbage collection (sad, but still
true), users depend on being able to add a conservative garbage
collector.  Conservative garbage collectors depend on pointers to
objects be stored in a fixed format. Having virtual origins breaks all
conservative garbage collectors and makes it almost impossible for a
third party to add garbage collection to the compiler."

Nothing to worry about, obviously the use of virtual origins is only
possible with fat pointers. So just use thin pointers for your garbage
collected environment.