ceph/src/boost/libs/type_traits/doc/is_stateless.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:is_stateless is_stateless]
   9    template <class T>
  10    struct is_stateless : public __tof {};
  11
  12 __inherit If T is a stateless type then inherits from __true_type, otherwise
  13 from __false_type.
  14
  15 Type T must be a complete type.
  16
  17 A stateless type is a type that has no storage and whose constructors and
  18 destructors are trivial. That means that `is_stateless` only inherits from
  19 __true_type if the following expression is `true`:
  20
  21    ::boost::has_trivial_constructor<T>::value
  22    && ::boost::has_trivial_copy<T>::value
  23    && ::boost::has_trivial_destructor<T>::value
  24    && ::boost::is_class<T>::value
  25    && ::boost::is_empty<T>::value
  26
  27 __std_ref 3.9p10.
  28
  29 __header ` #include <boost/type_traits/is_stateless.hpp>` or ` #include <boost/type_traits.hpp>`
  30
  31 __compat Without some (as yet unspecified) help from the compiler, is_stateless will never
  32 report that a class or struct is stateless; this is always safe,
  33 if possibly sub-optimal.
  34 Currently (June 2015) compilers more recent than Visual C++ 8, Clang, GCC-4.3, Greenhills 6.0,
  35 Intel-11.0, and Codegear have the necessary compiler __intrinsics to ensure that this
  36 trait "just works".
  37
  38 [endsect]
  39