Re: [Boost-users] How can I have an object-specific and thread-specific pointer?

Subject: Re: [Boost-users] How can I have an object-specific and thread-specific pointer?
From: Peter Dimov (pdimov_at_[hidden])
Date: 2011-11-18 04:04:55

Phillip Hellewell wrote:
> Glad to know I'm not the only one who sees this "feature" as a bug :)
> I wonder how hard it would be to at least provide an option to clean
> up all the TLS data when it is destroyed?

Very. By specification, TLS cleanup occurs in the same thread that allocated 
the data (because the data may have been allocated by a thread-specific 
allocator). When thread_specific_ptr is destroyed, it obviously can't do 
that.

> The only way I could use a static/global thread_specific_ptr is if it
> pointed to a map of object (its address) to its buffer.

Either map< weak_ptr<Object>, buffer > or set< weak_ptr<Object> > with map< 
thread_id, buffer > in the object, as I see it.

> But that puts me back in the same boat as I started in, with the same same 
> problems as trying to use a thread_specific_ptr as a member var.

I'm not sure about that. Let's take the first option. What's the problem 
with it? No locks are needed, and in the function that creates a new map 
entry for the current object you can purge the expired weak_ptr entries in 
order to not let the map grow out of hand.