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From: "Alex R. Mosteo" <devnull@mailinator.com>
Newsgroups: comp.lang.ada
Subject: Re: Type safety on wikipedia
Date: Thu, 26 Jan 2006 16:18:52 +0100
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Date: 2006-01-26T16:18:52+01:00
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jimmaureenrogers@worldnet.att.net wrote:

> I do not see how Unchecked_Deallocation interferes with type safety.
> Ada access types are typed. There is no Ada equivalent to a C void*. An
> Ada access type cannot be made to point to an object of some foreign
> type. For instance,
> 
>     type Integer_Access is access Integer;
> 
> An instance of Integer_Access cannot reference a task, or a real
> number, or some record type. Garbage collection cannot improve type
> safety in Ada or any other language. It can only automate the process
> of deallocating dynamically allocated objects.

Well, the argument given in the discussion is like this: you allocate a 
pointer, make some aliases and free one of them. Further allocations 
(presumibly unrelated) reuse the same heap area. You can now use a 
dangling pointer not correctly deallocated pointing to a valid memory 
area within the program, but holding completely unrelated data (from 
other types, probably).

Obviously, in a GCed language, no memory area can be reallocated as long 
as any reference to it is still alive.

There's a glaring affirmation in the article (not discussion) saying 
that Ada is type safe, with ML. So I wonder.