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Subject: Re: [boost] [core] [noncopyable] Add nonmoveable?
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2017-04-26 08:53:45

On 04/26/17 03:00, Gavin Lambert via Boost wrote:
> On 25/04/2017 22:23, Andrey Semashev via Boost wrote:
>> I think in C++11 noncopyable should be considered deprecated and
>> generally avoided. It affects class hierarchy, adds an extra namespace
>> to ADL and may not be optimized away with EBO. I would even avoid it in
>> C++03 as well. It follows that nonmoveable makes no sense in C++11. Just
>> use the language features you have.
> boost::noncopyable has protection so it won't ADL to the boost:: namespace.

Yes, but it doesn't remove the dummy namespace from ADL.

> Also, since it does not explicitly declare move constructors either way,
> anything that inherits from boost::noncopyable is also non-moveable by
> default, which is usually what you want.

Deleted copy constructor/assignment have the same property.

> The C++11 way, however, would be to use a std::unique_ptr as a private
> member of your class (eg. for PIMPL), which automatically makes your
> class moveable but not copyable via Rule of Zero.
> Or use shared_ptr if you want your class to be copyable but have all
> copies point to a shared implementation (handle-body or reference idiom).

That's fine if your design already employs pimpl (or you're willing to
change it that way). But otherwise why would you want to add a data
member to implement movability?

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