Re: [boost] Interest in breakable labeled scope emulation?

Subject: Re: [boost] Interest in breakable labeled scope emulation?
From: TONGARI (tongari95_at_[hidden])
Date: 2013-01-14 07:13:03

2013/1/14 Rob Stewart <robertstewart_at_[hidden]>

> On Jan 13, 2013, at 7:30 AM, TONGARI <tongari95_at_[hidden]> wrote:
>
> > One of the few things I appreciate in Java is the labeled-break feature.
> > I think C++ would provide it as well in future standard but it seems
> that there's no even such a proposal.
> >
> > In lack of the language feature, a simple emulation can be used:
> >
> > ---------------------------------------------------
> > #define BOOST_SCOPE(name) \
> > if (const bool LABELED_SCOPE_##name = false){break(name); name:;} else
> >
> >
> > #define break(name) \
> > (void)LABELED_SCOPE_##name; goto name;
> > ---------------------------------------------------
> > Now we can write:
> >
> > BOOST_SCOPE(a)
> > {
> >    break(a);
> >    cout << "123\n";
> > }
> >
> > The real world usage would reside in nested loop&switch where
> labeled-break
> > really shines.
>
> While I understand the value of being able to exit such compound scopes
> cleanly, goto is a poor solution as it bypasses destructors, which makes
> this idea error prone.
>

No. At least for g++ & clang that I tested the stack is correctly unwound and
the dtors are called.