Re: Type safety on wikipedia

[Martin Krischik <krischik@users.sourceforge.net>]

Alex R. Mosteo wrote:

> 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.

It's a Wiki and there is a dispute warning on top of it. I wonder if the Ada
link need to be removed! And perhaps a chapter on almost type save
languages could be added where Ada would more better placed.

But then Ada is supposed to me GC - only the vendors are to lazy to add an
collector.

As said: It made me think.

Martin

-- 
mailto://krischik@users.sourceforge.net
Ada programming at: http://ada.krischik.com