Re: Allocators and exceptions

[Maciej Sobczak <see.my.homepage@gmail.com>]

On 10 Wrz, 14:42, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
wrote:

> The question is not only about deallocation, it is also about finalization
> of the components initialized before the initialization raised an
> exception.

Right.

> Components are initialized in an arbitrary order.

Oops.

> I cannot tell for sure, but I guess that your example is a bounded error.

> But you should really ask a language lawyer.

I hoped that c.l.a. is a good place for this.

> > P.S. Exceptions in constructors is a bad idea.

No, it's a very good idea. Otherwise you have to deal with half-baked
objects, which is Even Bigger Mess (tm).

> Consider this:
>
>    type T (Init : Integer) is record
>       B : access Positive := new Positive;
>       C : Positive := Positive (Init);
>    end record;
>
>    Ptr := new T (-5);
>
> Now you might really want the compiler not to deallocate Ptr, so that you
> were able to free Ptr.B before. But where do you know that B was
> initialized?

It's not my business. The compiler knows for sure what what already
initialized and can therefore take the informed decision on what to
roll back.

I'm surprised by this issue. Really.

--
Maciej Sobczak
http://www.msobczak.com/