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From: Robert Dewar <robert_dewar@my-deja.com>
Subject: Re: Ammo-zilla
Date: 1999/10/31
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In article <7vb3c4$8a21@news.cis.okstate.edu>,
  dvdeug@x8b4e53cd. (David Starner) wrote:
> As a side question: Ada 95's designers must have been familiar
> with Modula 3's support of garbage collection while letting
> real time stuff keep track of its own memory. What stopped
> them from adopting something like that for Ada 95?


By the way, speaking as someone quite familiar with garbage
collection (remember I chaired WG2.1 for many years, and
was responsible for the SPITBOL compilers -- see for example
the 1977 paper in SP&E that discusses a new GC algorithm used
very successfully in SPITBOL), I find the mixture of low level
system facilities, including those that let you break the type
model, and GC to be very worrisome, sounds like it can easily
create a debugging nightmare. Note that one of the reasons that
GC can succeed in Java is the extremely limited nature of the
language. GC is more practical in Ada if you severely restrict
the subset of Ada you support, and eliminate for instance
stuff like Unchecked_Conversion and address overlays.

What for instance does it mean to do address overlays that
reference the address of some object if the address of that
object changes due to GC? I have no idea what a sensible answer
to this question might be!


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