Re: [Boost-bugs] [Boost C++ Libraries] #11229: vector incorrectly copies move-only objects using memcpy

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #11229: vector incorrectly copies move-only objects using memcpy
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-04-28 21:28:58

#11229: vector incorrectly copies move-only objects using memcpy
-------------------------------+------------------------
  Reporter:  joseph.thomson@…  |      Owner:  igaztanaga
      Type:  Bugs              |     Status:  new
 Milestone:  To Be Determined  |  Component:  move
   Version:  Boost 1.58.0      |   Severity:  Problem
Resolution:                    |   Keywords:
-------------------------------+------------------------

Comment (by joseph.thomson@…):

 Sorry, I incorrectly assumed that trunk would contain the latest version
 of the source code (I was using 1.57.0, tested 1.58.0 briefly, and then
 looked to fix the change in trunk).

 I have just tested your update, and it seems conceptually fine.  However,
 it fails to compile on MSVC because `yes_type` and `no_type` are
 undefined.  Copy-paste error I think.  Here is the test program I used:

 {{{
 #include <boost/container/vector.hpp>

 #include <iostream>
 #include <memory>

 int main() {
     auto deleter = [](int*) {
         std::cout << "delete\n";
     };

     using T = std::unique_ptr<int, decltype(deleter)>;

     std::cout << std::boolalpha;
     std::cout << "is_copy_constructible: " <<
 boost::move_detail::is_copy_constructible<T>::value << "\n";
     std::cout << "is_copy_assignable: " <<
 boost::move_detail::is_copy_assignable<T>::value << "\n";
     std::cout << "is_trivially_copy_constructible: " <<
 boost::move_detail::is_trivially_copy_constructible<T>::value << "\n";
     std::cout << "is_trivially_copy_assignable: " <<
 boost::move_detail::is_trivially_copy_assignable<T>::value << "\n";

     boost::container::vector<T> values;

     values.push_back(T(new int(), deleter));
     values.push_back(T(new int(), deleter));
 }
 }}}

 You assessment about the MSVC behaviour agrees with mine.  Boost.Container
 should still work thanks to the interaction of those two bugs :)  I have
 looked at the 2015 preview, and it seems that they have fixed
 `std::is_copy_constructible` and `std::is_copy_assignable`, but not
 `__has_trivial_copy`, `__has_trivial_assign` and
 `std::is_trivially_copyable`.  I have filed a bug about the latter, but
 whether or not it is fixed should not affect Boost.Container, as the
 `std::is_copy_constructible` and `std::is_copy_assignable` not correctly
 return false in this case.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11229#comment:5>
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