Re: [boost] ScopeExit review

From: Alexander Nasonov (alnsn_at_[hidden])
Date: 2007-08-23 04:21:02

Maxim Yanchenko <maximyanchenko <at> yandex.ru> writes:

> I vote to accept the library into Boost.

Thanks.

> A couple of general comments after reading other reviews.
> 
> 1. The fact that the library takes all arguments by reference looks
> unavoidable.
> If it allowed passing by value (i.e. making copies) - the copy constructors
> can throw, and this exception will be thrown after you made the change to
> your container/whatever you'd like to rollback, and before you setup the
> rollback action.  So you can't guarantee that your rollback action will be
> executed.

Very good point.

It makes me think that ScopeExit and local functions have different defaults
for passing arguments.
Agruments should be passed by value to a local function to avoid
dangling references when the function outlives the scope.

So, my current favorite is BOOST_SCOPE_EXIT( cref(c) ref(r) val(v) ).
IMO, it looks more natural than (a)(b)(c). More verbose but this
verbosity has a purpose.

> So, in case you need a copy - it's much safer to create this copy before
> making the change to your container/whatever. It will also express your
> intention more clearly.

I should document it.

--
Alexander