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

   1 [/
   2   Copyright 2007 John Maddock.
   3   Distributed under the Boost Software License, Version 1.0.
   4   (See accompanying file LICENSE_1_0.txt or copy at
   5   http://www.boost.org/LICENSE_1_0.txt).
   6 ]
   7
   8 [section:has_trivial_copy has_trivial_copy]
   9
  10    template <class T>
  11    struct has_trivial_copy : public __tof {};
  12
  13    template <class T>
  14    struct has_trivial_copy_constructor : public __tof {};
  15
  16 __inherit If T is a (possibly cv-qualified) type with a trivial copy-constructor
  17 then inherits from __true_type, otherwise inherits from __false_type.
  18
  19 These two traits are synonyms for each other.
  20
  21 If a type has a trivial copy-constructor then the constructor has the same effect
  22 as copying the bits of one object to the other:
  23 calls to the constructor can be safely replaced with a call to `memcpy`.
  24
  25 __compat Without some (as yet unspecified) help from the compiler,
  26 has_trivial_copy will never report that a user-defined class or struct has a
  27 trivial constructor; this is always safe, if possibly sub-optimal.
  28 In addition, in order to correctly handle deleted or private copy-constructors
  29 then C++11's `dectype` is required.
  30 Currently (May 2015) compilers more recent than Visual C++ 8, GCC-4.3, Greenhills 6.0,
  31 Intel-11.0, and Codegear have the necessary compiler __intrinsics to ensure that this
  32 trait "just works".  You may also test to see if the necessary __intrinsics are available
  33 by checking to see if the macro `BOOST_HAS_TRIVIAL_COPY` is defined.
  34
  35
  36 __std_ref 12.8p6.
  37
  38 __header ` #include <boost/type_traits/has_trivial_copy.hpp>` or ` #include <boost/type_traits.hpp>`
  39
  40 __examples
  41
  42 [:`has_trivial_copy<int>` inherits from `__true_type`.]
  43
  44 [:`has_trivial_copy<char*>::type` is the type `__true_type`.]
  45
  46 [:`has_trivial_copy<int (*)(long)>::value` is an integral constant
  47 expression that evaluates to /true/.]
  48
  49 [:`has_trivial_copy<MyClass>::value` is an integral constant
  50 expression that evaluates to /false/.]
  51
  52 [:`has_trivial_copy<T>::value_type` is the type `bool`.]
  53
  54 [endsect]
  55