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From:Warren Young Date:August 16 2007 9:23am
Subject:Re: Eyeballs needed on new reference counted pointer template
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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 single-
thread 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. 

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.
Thread
Eyeballs needed on new reference counted pointer templateWarren Young15 Aug
  • Re: Eyeballs needed on new reference counted pointer templateChris Frey15 Aug
    • Re: Eyeballs needed on new reference counted pointer templateWarren Young16 Aug
  • Re: Eyeballs needed on new reference counted pointer templateAlex Burton15 Aug
    • Re: Eyeballs needed on new reference counted pointer templateWarren Young16 Aug
  • Re: Eyeballs needed on new reference counted pointer templateJoseph Artsimovich15 Aug
    • Re: Eyeballs needed on new reference counted pointer templateJonathan Wakely16 Aug
      • Re: Eyeballs needed on new reference counted pointer templateWarren Young16 Aug
        • Re: Eyeballs needed on new reference counted pointer templateJonathan Wakely18 Aug
          • Re: Eyeballs needed on new reference counted pointer templateJonathan Wakely18 Aug
          • Re: Eyeballs needed on new reference counted pointer templateWarren Young20 Aug
    • Re: Eyeballs needed on new reference counted pointer templateWarren Young16 Aug
  • RE: Eyeballs needed on new reference counted pointer templateJoel Fielder15 Aug
    • Re: Eyeballs needed on new reference counted pointer templateWarren Young16 Aug
  • Re: Eyeballs needed on new reference counted pointer templateRobert Mecklenburg15 Aug
    • Re: Eyeballs needed on new reference counted pointer templateGraham Reitz15 Aug
    • Re: Eyeballs needed on new reference counted pointer templateGraham Reitz15 Aug
    • Re: Eyeballs needed on new reference counted pointer templateWarren Young16 Aug
  • Re: Eyeballs needed on new reference counted pointer templateGraham Reitz15 Aug