ceph/src/boost/libs/type_traits/doc/is_pod.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_pod is_pod]
   9    template <class T>
  10    struct is_pod : public __tof {};
  11
  12 __inherit If T is a (possibly cv-qualified) POD type then inherits from __true_type,
  13 otherwise inherits from __false_type.
  14
  15 POD stands for "Plain old data".
  16 Arithmetic types, and enumeration types,
  17 a pointers and pointer to members are all PODs.  Classes and unions can also
  18 be POD's if they have no non-static data members that are of reference or
  19 non-POD type, no user defined constructors, no user defined assignment
  20 operators, no private or protected non-static data members,
  21 no virtual functions and no base classes.  Finally, a cv-qualified POD is
  22 still a POD, as is an array of PODs.
  23
  24 __std_ref 3.9p10 and 9p4 (Note that POD's are also aggregates, see 8.5.1).
  25
  26 __compat Without some (as yet unspecified) help from the compiler, is_pod will
  27 never report that a class or struct is a POD; this is always safe,
  28 if possibly sub-optimal.
  29 Currently (June 2015) compilers more recent than Visual C++ 8, Clang-3, GCC-4.3, Greenhills 6.0,
  30 Intel-11.0, and Codegear have the necessary compiler __intrinsics to ensure that this
  31 trait "just works".  You may also test to see if the necessary __intrinsics are available
  32 by checking to see if the macro `BOOST_IS_POD` is defined.
  33
  34
  35 __header ` #include <boost/type_traits/is_pod.hpp>` or ` #include <boost/type_traits.hpp>`
  36
  37 __examples
  38
  39 [:`is_pod<int>` inherits from `__true_type`.]
  40
  41 [:`is_pod<char*>::type` is the type `__true_type`.]
  42
  43 [:`is_pod<int (*)(long)>::value` is an integral constant
  44 expression that evaluates to /true/.]
  45
  46 [:`is_pod<MyClass>::value` is an integral constant
  47 expression that evaluates to /false/.]
  48
  49 [:`is_pod<T>::value_type` is the type `bool`.]
  50
  51 [endsect]
  52