Re: The D Programming Language
Andrei Alexandrescu (See Website For Email) wrote:
David Abrahams wrote:
Of course, this means that other threads can see pointers to
objects which aren't yet constructed. But that's generally true
in Java, even without threads; just call a virtual function from
a base class constructor. Worse, other threads can see pointers
to objects which haven't yet been zero initialized (or
initialized at all). That is, of course, the undefined behavior
that Java supposedly doesn't have. (I'm rather surprised that
Andrei doesn't recognize this. IIRC, he's written on the
problems of double checked locking in the past, and this problem
is related.)
Wow. I'm out of my element here, but it does sound sticky.
It does sound sticky, indeed. As I discussed in my reply to that post,
it also turns out to be incorrect. I'd insert some more sarcastic
remarks to James about not dispensing information that one is not sure
about, unless I wasn't guilty of the same myself... quite a few times :o).
It's the medium:-). The worst part of it is that I knew that
there was ongoing work concerning the Java memory model, and
that it had changed since I'd used Java. But finding the most
recent version of the specification and verifying the current
status would have taken too much time, and broken the momentum
of the interaction.
Of course, the formal change is fairly recent (Sept., 2004).
And I'm still curious as to how one implements it without
unacceptable run-time overhead. (Off hand, I'd guess that the
least expensive strategy would be for the garbage collector to
zero out all memory it makes available to the allocator. But I
think that even that would have unacceptable cost for some types
of applications.)
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James Kanze (GABI Software) email:james.kanze@gmail.com
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