Re: The D Programming Language

From:

"Andrei Alexandrescu (See Website For Email)" <SeeWebsiteForEmail@erdani.org>

Newsgroups:

comp.lang.c++.moderated

Date:

27 Nov 2006 06:41:58 -0500

Message-ID:

<J9DD1t.9p7@beaver.cs.washington.edu>

Peter Dimov wrote:

Andrei Alexandrescu (See Website For Email) wrote:

Peter Dimov wrote:

Andrei Alexandrescu (See Website For Email) wrote:

That's simply wrong. Java does not check thread safety statically, yet
is able to define behavior of even incorrect multithreaded code.

It does on a physical level (long and double aside), but not on a
logical level. An object invariant can easily be broken by a data race.
The behavior from this point onwards is defined but makes no sense.
This decision is correct for safety reasons, but doesn't offer many
other benefits.

And that contradicts my statement how?

Your statement is completely correct if we stick to the formal
definitions of "undefined behavior" as in the C++ standard and
"incorrect MT code" as in the Java memory model. So it doesn't. I was
just pointing out that programs with defined behavior that don't work
aren't necessarily better than programs without defined behavior that
don't work.

But remarking that well-defined programs could behave erratically is
trite with or without threads out of the picture. The sky is blue,
motherhood is good, and defined well-programs fail to keep their
higher-level invariants in ways that make them practically impossible to
track.

Anyhow, on to a more interesting point - what happens to long and double
when there are races on them? I thought the worst that could happen is
that you have an unpredictable value stored in them. Right?

Andrei

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