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Date: Mon, 08 Mar 2004 15:03:20 -0500
From: Hyman Rosen <hyrosen@mail.com>
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Subject: Re: abstract sub programs overriding
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Date: 2004-03-08T15:03:20-05:00
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Adam Beneschan wrote:
 > whenever you call a subprogram (either directly or via dispatching),
 > that subprogram will be concrete (as opposed to C++, which I believe
 > does not guarantee this).

This can happen in C++ only during object constructors or destructors
which Ada does not have (at least not in the same sense). C++ does not
allow objects of abstract type to be created, but during the execution
of a constructor or destructor, the type of the object is the type of
the class whose *tor is running, and that may be an abstract class. It
is undefined behavior to make a dispatching call which resolves to an
abstract method. Most implementations make such a call execute a stub
function which prints an error message and aborts the program.