Re: [Boost-users] seeking comments on 'weak_key_map' experiments

Subject: Re: [Boost-users] seeking comments on 'weak_key_map' experiments
From: Nicolas Lelong (rotoglup_at_[hidden])
Date: 2008-12-13 06:56:01

> Accessing unrelated objects on destruction/deletion does not quite fit the
> shared_ptr/weak_ptr philosophy.

I take for granted that you're right about this ! I was more thinking about
the 'instantness' and not about the 'implicit coupling / lifetime
dependency' :)

> This introduces data races and coupling and locking issues in the presence
> of multiple threads.

You have a very good point here. I'm far from being proficient when comes
threading issues and lock free programming.

In fact, my current usage pattern of this construct is quite similar to A.
Alexandrescu's WRRM map (Write Rarely Read Many) in this
article<http://erdani.org/publications/cuj-2004-10.pdf>.
So, it is perhaps possible to have a similar contruct, with a minimalist
interface (say only query / update), and only returning copies of stored
objects.

This way, the client have, when queried, a full copy of the value - that
won't be deleted under its feet. That could come in complement to the fact
that, for querying you need to hold a shared_ptr on the key, which should
prevent another thread to delete the key instance during the query.