Re: [boost] Re: Basic guarantee and synchronized multiple updates.

From: David Abrahams (dave_at_[hidden])
Date: 2002-09-27 11:17:06

From: "Fredrik Blomqvist" <f_blq_at_[hidden]>

> Fernando Cacciola (hotmail) wrote:
> > Consider this example of "synchronized multiple
> > updates"
> [...]
> > The goal is to achieve the basic guarantee for the
> > synchronized push_back.
> >
> > How would you do this?
> > (Without copying the whole thing just to move the
> > final state at the end, of course)
>
> David Abrahams wrote:
> [...]
> >     {
> >         vector1.push_back(e1);
> >         try {
> >             vector2.push_back(e2):
> >         }
> >         catch(...) {
> >             vector1.pop_back();
> >             throw;
> >         }
>
> Isn't this a good example of something scopeguard +
> bind/lambda would be well suited to handle?

I don't really like scopeguard-like things for such jobs, since the danger
of the above is that you have to remember to throw;, while you need to
remember to cancel the scopeguard. It's an even trade. Of course if you
factor in Mr. Terekhov's favorite issue (weird entaglements with
not-really-C++ platform "exceptions"), the scopeguard might be a better
solution.

-----------------------------------------------------------
           David Abrahams * Boost Consulting
dave_at_[hidden] * http://www.boost-consulting.com