Re: [Boost-bugs] [Boost C++ Libraries] #11132: Boost.Variant's boost::recursive_wrapper missing noexcept specifier on move constructor

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #11132: Boost.Variant's boost::recursive_wrapper missing noexcept specifier on move constructor
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-06-22 19:59:39

#11132: Boost.Variant's boost::recursive_wrapper missing noexcept specifier on move
constructor
-------------------------------+-----------------------
  Reporter:  peterhuene@…      |      Owner:  apolukhin
      Type:  Bugs              |     Status:  assigned
 Milestone:  To Be Determined  |  Component:  variant
   Version:  Boost 1.57.0      |   Severity:  Problem
Resolution:                    |   Keywords:
-------------------------------+-----------------------
Changes (by apolukhin):

 * owner:  ebf => apolukhin
 * status:  new => assigned

Comment:

 This issue has been discussed a lot. After a very long discussion it was
 decided to leave `recursive_wrapper` as is.

 Personaly I dislike the existing approach, but agree that it must stay as
 is.

 The only way that I could help you, is to show some possible workarounds.
 Here's a workaround for std::vectors that support incomplete/forward
 declared types (fastest possible solution):
 {{{
 #include <boost/variant.hpp>
 #include <vector>

 using namespace std;
 using namespace boost;

 struct foo
 {
         foo() = default;
         foo(foo&&) noexcept = default;
         foo(foo const&) = delete;
 };

 struct variant_type: boost::variant<foo, vector<variant_type> > {
     typedef boost::variant<foo, vector<variant_type> > base_t;

     variant_type() = default;

     template <class T>
     variant_type(T&& v)
         : base_t(std::forward<T>(v))
     {}

 };


 int main() {
         vector<variant_type> value;
         value.emplace_back();
         variant_type other = std::move(value);
 }
 }}}

 This example must work on popular STL implementations.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11132#comment:5>
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