Re: [boost] Need second opions from some threading / object creation experts...

Subject: Re: [boost] Need second opions from some threading / object creation experts...
From: Joel falcou (joel.falcou_at_[hidden])
Date: 2011-05-15 10:47:03

On 15/05/11 04:52, John Maddock wrote:
> Folks,
>
> I'm looking at the code for singleton_pool, and I can't *quite* convince
> myself that it's completely thread safe and guaranteed to do what it
> says, the code in question is in boost/pool/detail/singleton.hpp which
> is a deceptively clever/simple singleton implementation. I haven't been
> able to break it in practice, but would a sufficiently clever compiler
> be able to optimize away the call create_object.do_nothing(); and
> therefore not instantiate the object prior to main()?

No cause it's static and hence compiler wont remove it. I think it is 
suffisent, but I would worry of *other* static object in different TU 
calling singleton instance as the order of static initializer is random.

Thread safe singleton are huge beasts to get right, see 
http://stackoverflow.com/questions/6915/thread-safe-lazy-contruction-of-a-singleton-in-c

I think our best bet is having some atomic compare&swap in the singleton 
construction to be sure it is done properly.