ceph/src/boost/libs/type_traits/doc/has_trivial_move_assign.qbk

   1 [/
   2   Copyright 2007 John Maddock.
   3   Copyright 2013 Antony Polukhin.
   4   Distributed under the Boost Software License, Version 1.0.
   5   (See accompanying file LICENSE_1_0.txt or copy at
   6   http://www.boost.org/LICENSE_1_0.txt).
   7 ]
   8
   9 [section:has_trivial_move_assign has_trivial_move_assign]
  10    template <class T>
  11    struct has_trivial_move_assign : public __tof {};
  12
  13 __inherit If T is a (possibly cv-qualified) type with a trivial move assignment-operator
  14 then inherits from __true_type, otherwise inherits from __false_type.
  15
  16 If a type has a trivial move assignment-operator then the operator has the same effect
  17 as copying the bits of one object to the other:
  18 calls to the operator can be safely replaced with a call to `memcpy`.
  19
  20 __compat Without some (as yet unspecified) help from the compiler,
  21 has_trivial_move_assign will never report that a user-defined class or struct has a
  22 trivial move assign; this is always safe, if possibly sub-optimal.
  23 In addition, in order to correctly handle private or deleted move assignment
  24 operators then c++11's `decltype` is required.
  25 Currently (June 2015) compilers that have the necessary __intrinsics to ensure that this
  26 trait "just works" include Clang, GCC-5.1 and MSVC-12.0.
  27 You may also test to see if the necessary __intrinsics are available
  28 by checking to see if the macro `BOOST_HAS_TRIVIAL_MOVE_ASSIGN` is defined.
  29
  30
  31 __header ` #include <boost/type_traits/has_trivial_move_assign.hpp>` or ` #include <boost/type_traits.hpp>`
  32
  33 __examples
  34
  35 [:`has_trivial_move_assign<int>` inherits from `__true_type`.]
  36
  37 [:`has_trivial_move_assign<char*>::type` is the type `__true_type`.]
  38
  39 [:`has_trivial_move_assign<int (*)(long)>::value` is an integral constant
  40 expression that evaluates to /true/.]
  41
  42 [:`has_trivial_move_assign<MyClass>::value` is an integral constant
  43 expression that evaluates to /false/.]
  44
  45 [:`has_trivial_move_assign<T>::value_type` is the type `bool`.]
  46
  47 [endsect]
  48