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

From: Peter Dimov (pdimov_at_[hidden])
Date: 2002-09-30 09:47:49

From: "Hillel Y. Sims" <hsims_at_[hidden]>
>
> {
>      vector1.push_back(e1);
>      try {
>          vector2.push_back(e2):
>      }
>      catch(...) {
>          vector1.pop_back();
>          throw;
>     }
> }
>
> vs.
>
> {
>     vector1.push_back(e1);
>     ScopeGuard guard =
> MakeObjScopeGuard(vector1,{typeof(vector1)}::pop_back);
>     vector2.push_back(e2);
>     guard.Dismiss();
> }

vs.

{
    transaction t1 = do_push_back(vector1, e1);
    transaction t2 = do_push_back(vector2, e2);
    transaction t3 = do_push_back(vector3, e3);
// ...
    t1.commit();
    t2.commit();
    t3.commit();
// ...
}

> The ScopeGuard version is 1) fewer lines of code, 2) easier to test -- if
> you forget to Dismiss(), you'll find out immediately during ordinary
> testing, vs. missing the throw; in more difficult to test (possibly even
> untested?) exception-handling code, 3) scales better (what if you have
> three/four/etc. updates to synchronize?),

... but at some point the overhead of writing do_push_back is amortized and
do_push_back wins against "raw" ScopeGuard.