ceph/src/boost/libs/type_traits/doc/has_trivial_destructor.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_destructor has_trivial_destructor]
   9    template <class T>
  10    struct has_trivial_destructor : public __tof {};
  11
  12 __inherit If T is a (possibly cv-qualified) type with a trivial destructor
  13 then inherits from __true_type, otherwise inherits from __false_type.
  14
  15 If a type has a trivial destructor then the destructor has no effect:
  16 calls to the destructor can be safely omitted.  Note that using meta-programming
  17 to omit a call to a single trivial-constructor call is of no benefit whatsoever.
  18 However, if loops and/or exception handling code can also be omitted, then some
  19 benefit in terms of code size and speed can be obtained.
  20
  21 __compat Without some (as yet unspecified) help from the compiler,
  22 has_trivial_destructor will never report that a user-defined class or struct has a
  23 trivial destructor; this is always safe, if possibly sub-optimal.
  24 In addition, in order to correctly handle deleted or private destructors then
  25 support for C++11's `decltype` is required.
  26 Currently (June 2015) compilers more recent than Visual C++ 8, GCC-4.3, Greenhills 6.0,
  27 Intel-11.0, and Codegear have the necessary compiler __intrinsics to ensure that this
  28 trait "just works".  You may also test to see if the necessary __intrinsics are available
  29 by checking to see if the macro `BOOST_HAS_TRIVIAL_DESTRUCTOR` is defined.
  30
  31
  32 __std_ref 12.4p3.
  33
  34 __header ` #include <boost/type_traits/has_trivial_destructor.hpp>` or ` #include <boost/type_traits.hpp>`
  35
  36 __examples
  37
  38 [:`has_trivial_destructor<int>` inherits from `__true_type`.]
  39
  40 [:`has_trivial_destructor<char*>::type` is the type `__true_type`.]
  41
  42 [:`has_trivial_destructor<int (*)(long)>::value` is an integral constant
  43 expression that evaluates to /true/.]
  44
  45 [:`has_trivial_destructor<MyClass>::value` is an integral constant
  46 expression that evaluates to /false/.]
  47
  48 [:`has_trivial_destructor<T>::value_type` is the type `bool`.]
  49
  50 [endsect]
  51