Re: Threadsafe singletons

From:

"kanze" <kanze@gabi-soft.fr>

Newsgroups:

comp.lang.c++.moderated,comp.programming.threads

Date:

1 Aug 2006 08:56:51 -0400

Message-ID:

<1154432457.984287.121900@m79g2000cwm.googlegroups.com>

David Barrett-Lennard wrote:

Chris Thomasson wrote:

"David Barrett-Lennard" <davidbl@iinet.net.au> wrote in message
news:1154313829.569314.297530@p79g2000cwp.googlegroups.com...

There have been extensive discussions on
comp.lang.c++.moderated and comp.programming.threads about
the problem of writing a threadsafe singleton. Most of
this centers around the double checked idiom, known to be
broken.

I assume you actually mean that there are a lot of existing
implementations' out there that happen to be "completely"
broken... Correct?

Yes, and also AFAIK there doesn't exist a platform independent
implementation.

Given that anything concerning threads is platform dependant:-).

The problem is that there isn't a portable solution even accross
e.g. Posix conformant systems.

The actual pattern itself it perfectly fine IMO, and can be
successfully implemented with assembly language and
externally assembled into a library with a coherent ABI and
portable C interface; no doubt about it... IMHO, most of the
problems that are generally associated with double checked
locking seem to be related to compiler reordering, and of
course, the "apparent" widespread lack of knowledge wrt
memory barrier functionality...

My solution is *much* simpler and it's platform independent.

It's also faster:-). On the other hand, it introduces a certain
number of other constraints.

--
James Kanze GABI Software
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