Re: Eyeballs needed on new reference counted pointer template

Jonathan Wakely wrote:
>
> Users sharing Rows between threads already have to ensure
> the Result object doesn't go out of scope in another thread,

Well, funny you should bring give that example. The template we are discussing in this thread was created to solve the single-threaded version of the same problem.

This comes up when someone runs a query, gets some Rows, then wants to get a new result set without copying the Row data to a new data structure just to work around the existing dependency of Row on the Result that created it. This is a common need when details of the second query depend on the results of the first. This problem is now solved; Rows no longer require their creator to outlive them.

The atomic inc/dec issue brought up by Joseph Artsimovich is all that prevents the problem in your example from being solved, too. The question is, does it *need* to be solved? Obviously I think the singlethread  variant of this problem does need to be solved. But in light of the bottleneck argument I gave in my response to Joseph, you can guess that I'm not seeing the value in solving the multi-thread variant.

So, tell me why I'm wrong. Why is it helpful to send off Rows to a second thread while the first reuses the Result object for a new query?

> http://www.artima.com/cppsource/safebool.html

Thanks for the link, this was most helpful.

> I think the latest Boost.SharedPtr actually uses a pointer to member
> data, not member function.

Do you need help?

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Are you endorsing this difference, or just pointing it out?

> With a safe bool there's no need for operator!

Actually, I don't see why it was needed with the existing scheme, but it was necessary to make something compile. I don't remember the details.

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