Re: Do garbage collected languages need destructors?

From: Dave Harris (brangdon_at_cix.co.uk)
Date: 10/29/03 

Date: Wed, 29 Oct 2003 20:18 +0000 (GMT Standard Time)

ulf.wendel@phpdoc.de (Ulf Wendel) wrote (abridged):
> Do garbage collected languages need destructors?

Depends on what you mean by that. Generally we all need to model object
lifetimes and we all need deterministic release of resources. Destructors
are a C++ mechanism for dealing with that. If you solve the problem a
different way, for example by using block closures or "around methods",
then you don't need destructors.

In practice few GCed languages have them. I gather .NET is getting
destructors, but that's the exception rather than the rule. Note that
finalisers play a different role, because they are not executed
deterministically and because they can't really release resources. (That
is, an object may become reachable after its finaliser has been run, so a
finaliser ought to preserve its class invariant, and in general the class
invariant may require resources.)

Java is unusual in having neither block closures nor destructors. This
makes object lifetimes difficult to model in that language. It certainly
"needs" something.

-- Dave Harris, Nottingham, UK

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