[Boost-bugs] [Boost C++ Libraries] #7330: Patch adding move constructors and move assignments

Subject: [Boost-bugs] [Boost C++ Libraries] #7330: Patch adding move constructors and move assignments
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-09-05 18:29:57

#7330: Patch adding move constructors and move assignments
-------------------------------------+--------------------------------------
 Reporter:  apolukhin                |       Owner:  dgregor     
     Type:  Patches                  |      Status:  new         
Milestone:  To Be Determined         |   Component:  function    
  Version:  Boost Development Trunk  |    Severity:  Optimization
 Keywords:                           |  
-------------------------------------+--------------------------------------
 Use of move constructor and move assignment reduce memory
 allocation/deallocations count and do not call functor copy operator for
 big functors.
 Example:
 {{{
 struct big_aggregating_structure {
     int disable_small_objects_optimizations[32];

     void operator()() {}
 };

 ...

 function<void()> f1 = big_aggregating_structure();
 function<void()> f2 = f1; // will call new, copy()
 function<void()> f3 = std::move(f1); // Just swaps pointers, leaves f1
 empty
 f3 = f2; // Will call new, copy(), destory(), delete
 f3 = std::move(f2); // Just swaps pointers, leaves f2 empty (calls
 destory(), delete for f3)

 {
     function<void()> f_new1 = big_aggregating_structure();
     function<void()> f_new2 = std::move(f_new1);
     // Without move constructor, there will be additional new, copy(),
 destroy(), delete calls
 }

 }}}

 This patch could be very usefull for boost::asio, boost::thread and
 anyone, who uses boost::function in STL containers on C++11 compilers.
 Patch was tested on MSVC2010, GCC-4.6

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/7330>
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