Re: [boost] [scope_exit] D-style scope(failure) and scope(success) in C++

Subject: Re: [boost] [scope_exit] D-style scope(failure) and scope(success) in C++
From: Evgeny Panasyuk (evgeny.panasyuk_at_[hidden])
Date: 2013-09-30 07:09:26

30.09.2013 8:55, Emil Dotchevski:
>> Writing throwing destructors is discouraged, everyone knows that. But
>> sometimes you just need it because it offers benefits compared to other
>> approaches.
>
> It also has drawbacks. :)
>
> Perhaps "need" is an overstatement here, I'm sure there are other ways
> to do this even if we insist on using the same syntax.

If that is possible then scope(failure/success) also can be implemented 
in that way (without unwinding_indicator). Many have tried to do that in 
portable C++ with no success.

> I didn't intend to create an argument, but I think that it is a
> mistake to open this Pandora's box, so I don't want to provide support
> for it in the exception library.

1. Throwing destructors is just one use case for scope(success)-like 
objects. But there are other use cases with scope(failure)-like objects 
which do not throw anything from destructor.

2. There is ISO proposal by Herb Sutter - 
http://isocpp.org/files/papers/N3614.pdf - for adding similar 
functionality: std::unwinding_exception().

3. There is article by Jon Kalb and Dave Abrahams regarding throwing 
destructors: "Evil, or Just Misunderstood?" 
http://cpp-next.com/archive/2012/08/evil-or-just-misunderstood/

-- 
Evgeny Panasyuk