[boost] Re: thread_specific_ptr suggestion

From: Michael Glassford (glassfordm_at_[hidden])
Date: 2004-05-15 20:44:21

Howard Hinnant wrote:

> thread_specific_ptr<T> is the thread local data storage mechanism of the 
> excellent (thanks William!) boost threads library.  
> thread_specific_ptr<T> isn't capable of supporting custom deleters for 
> good reason.  

Actually, the version of thread_specific_ptr<T> that is currently in CVS 
(recently moved from the thread_dev branch) does support custom cleanup 
functions.

> The deleter function must be a real function (not a 
> functor) so as to work well with various OS level threading api's (like 
> Posix threads).  So the pointer passed into a thread_specific_ptr<T> 
> (via reset) must be free-able with delete.

> thread_specific_ptr<T> could offer a custom deleter constrained to be a 
> function pointer instead of a more general deleter policy (functor), but 
> that seems like it would be of limited functionality and frankly just 
> not much fun in a C++ environment.

It does have the limitation of using a real function pointer that takes 
a T* and returns nothing.

> However, there is one case where another deleter policy is common enough 
> to warrant special attention:  delete [].
> 
> So I suggest a partial specialization for thread_specific_ptr:

I suppose there could still be a partial specialization such as you 
describe that supplies a default deleter that calls delete[] if the user 
doesn't supply a custom deleter.

[snip code]

Mike