[boost] Re: bald singleton pointers

From: Pavel Vozenilek (pavel_vozenilek_at_[hidden])
Date: 2005-02-13 15:31:43

"Dave Handley" wrote:

[bald pointer out of singleton]
>
> The only instance that I can think of where you may want to do this is in 
> a multi-threaded environment.  And even then only in a very specific set 
> of circumstances.  Specifically, you may want to do this when you don't 
> want the overhead of a lock, but, for some other reason, you can 
> absolutely guarantee that concurrent access to the object (or parts of the 
> object you are accessing) is valid.  If I'm honest though, I'm having some 
> difficulty convincing myself that something like this would actually 
> genuinely be useful.  Perhaps if you could get a "bald pointer" through a 
> protected member, that was therefore only accessible to derived classes 
> (hence the singletons themselves).  This could be useful to build into a 
> static access function that provided a safe pointer, but perhaps without 
> the overhead of a lock?
>
The use case is a legacy code that accepts only bald pointer.

A singleton may have function unsafe_get().  The object would be
instantiated if not already.

Code using its result will promise not to destroy given object.

/Pavel