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: 2015-12-02 13:57:59

#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 anonymous):

 Replying to [comment:8 joseph.thomson@…]:
 > A trivially copyable class must have:
 >
 > * No non-trivial copy constructors
 > * No non-trivial copy assignment operators
 > * No non-trivial move constructors
 > * No non-trivial move assignment operators
 > * A trivial destructor
 >
 > `__has_trivial_copy` simply reports whether the class has a trivial copy
 constructor.

 I get that, and I see that for clang there's a workaround so that
 boost::has_trivial_copy *also* checks whether it is copy constructible
 (boost/type_traits/has_trivial_copy.hpp )
 {{{
 template <typename T>
 struct has_trivial_copy_impl
 {
 #ifdef BOOST_HAS_TRIVIAL_COPY
 #  ifdef __clang__ // Why not do this for GCC 4.9 too?
    BOOST_STATIC_CONSTANT(bool, value = BOOST_HAS_TRIVIAL_COPY(T) &&
 boost::is_copy_constructible<T>::value);
 #  else
    BOOST_STATIC_CONSTANT(bool, value = BOOST_HAS_TRIVIAL_COPY(T));
 #  endif
 #else
    BOOST_STATIC_CONSTANT(bool, value =
       (::boost::type_traits::ice_and<
          ::boost::is_pod<T>::value,
          ::boost::type_traits::ice_not< ::boost::is_volatile<T>::value
 >::value
       >::value));
 #endif

 }}}
  but this is only the case for Clang, not for GCC 4.9 and up; even though
 the semantics of the intrinsic for Clang and GCC are the same; so that's
 the problem I think needs addressing (and was the original intend of the
 ticket).

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11229#comment:9>
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