Re: [boost] Re: Singleton

From: Jeff Garland (jeff_at_[hidden])
Date: 2005-01-05 22:15:43

On Wed, 5 Jan 2005 19:02:44 -0000, Dave Handley wrote
>
> > Is there any other functionality that should be added?  Specifically,
> > is it sufficient to enforce that singletons are created in a specific
> > order before main and destroyed in the reverse order after main (using
> > dependency instances), or should I provide some way to support
> > alternate lifetimes (ex: create on first reference to instance)?
> 
> Ordering of Singletons is, in my opinion, one of the most important 
> issues with Singletons.  It is almost certainly insufficient in most 
> applications to create in a specific order, and delete in reverse 
> order.  

Yep -- I've spent way to much time fighting the 'crash on exit' problems
associated with unordered singleton destruction at program shutdown (not my
code, of course :-)

> > Is there any interest in adding this library to Boost?
> 
> I would love to see a robust implementation of a Singleton in Boost. 

Yep, we should have one.  However, I agree, something more along the lines of
the Loki singleton would be better than the proposal from 'Mr. Chaos'....

> Whenever I start a software project, almost without exception I tend 
> to add both Boost and Loki to the project - it would be great if I 
> could add only Boost.  I have to say however, that a more general 
> library which implemented a variety of design patterns (like Loki) 
> would be even better.  For example:
> 
> 1)    Singleton
> 2)    Visitor - like Loki implementing both a conventional cyclic 
> visitor, and an acyclic visitor. 
>3)    Composite 
>4)    Abstract Factory
> 5)    etc. etc.

Agree, agree,....

Jeff