ceph/src/boost/boost/type_traits/alignment_of.hpp

   1
   2 //  (C) Copyright John Maddock 2000.
   3 //  Use, modification and distribution are subject to the Boost Software License,
   4 //  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   5 //  http://www.boost.org/LICENSE_1_0.txt).
   6 //
   7 //  See http://www.boost.org/libs/type_traits for most recent version including documentation.
   8
   9 #ifndef BOOST_TT_ALIGNMENT_OF_HPP_INCLUDED
  10 #define BOOST_TT_ALIGNMENT_OF_HPP_INCLUDED
  11
  12 #include <boost/config.hpp>
  13 #include <cstddef>
  14
  15 #include <boost/type_traits/intrinsics.hpp>
  16 #include <boost/type_traits/integral_constant.hpp>
  17
  18 #ifdef BOOST_MSVC
  19 #   pragma warning(push)
  20 #   pragma warning(disable: 4121 4512) // alignment is sensitive to packing
  21 #endif
  22 #if defined(__BORLANDC__) && (__BORLANDC__ < 0x600)
  23 #pragma option push -Vx- -Ve-
  24 #endif
  25
  26 namespace boost {
  27
  28 template <typename T> struct alignment_of;
  29
  30 // get the alignment of some arbitrary type:
  31 namespace detail {
  32
  33 #ifdef BOOST_MSVC
  34 #pragma warning(push)
  35 #pragma warning(disable:4324) // structure was padded due to __declspec(align())
  36 #endif
  37 template <typename T>
  38 struct alignment_of_hack
  39 {
  40     char c;
  41     T t;
  42     alignment_of_hack();
  43 };
  44 #ifdef BOOST_MSVC
  45 #pragma warning(pop)
  46 #endif
  47
  48 template <unsigned A, unsigned S>
  49 struct alignment_logic
  50 {
  51     BOOST_STATIC_CONSTANT(std::size_t, value = A < S ? A : S);
  52 };
  53
  54
  55 template< typename T >
  56 struct alignment_of_impl
  57 {
  58 #if defined(BOOST_MSVC) && (BOOST_MSVC >= 1400)
  59     //
  60     // With MSVC both the native __alignof operator
  61     // and our own logic gets things wrong from time to time :-(
  62     // Using a combination of the two seems to make the most of a bad job:
  63     //
  64     BOOST_STATIC_CONSTANT(std::size_t, value =
  65         (::boost::detail::alignment_logic<
  66             sizeof(::boost::detail::alignment_of_hack<T>) - sizeof(T),
  67             __alignof(T)
  68         >::value));
  69 #elif !defined(BOOST_ALIGNMENT_OF)
  70     BOOST_STATIC_CONSTANT(std::size_t, value =
  71         (::boost::detail::alignment_logic<
  72             sizeof(::boost::detail::alignment_of_hack<T>) - sizeof(T),
  73             sizeof(T)
  74         >::value));
  75 #else
  76    //
  77    // We put this here, rather than in the definition of
  78    // alignment_of below, because MSVC's __alignof doesn't
  79    // always work in that context for some unexplained reason.
  80    // (See type_with_alignment tests for test cases).
  81    //
  82    BOOST_STATIC_CONSTANT(std::size_t, value = BOOST_ALIGNMENT_OF(T));
  83 #endif
  84 };
  85
  86 } // namespace detail
  87
  88 template <class T> struct alignment_of : public integral_constant<std::size_t, ::boost::detail::alignment_of_impl<T>::value>{};
  89
  90 // references have to be treated specially, assume
  91 // that a reference is just a special pointer:
  92 template <typename T> struct alignment_of<T&> : public alignment_of<T*>{};
  93
  94 #ifdef __BORLANDC__
  95 // long double gives an incorrect value of 10 (!)
  96 // unless we do this...
  97 struct long_double_wrapper{ long double ld; };
  98 template<> struct alignment_of<long double> : public alignment_of<long_double_wrapper>{};
  99 #endif
 100
 101 // void has to be treated specially:
 102 template<> struct alignment_of<void> : integral_constant<std::size_t, 0>{};
 103 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
 104 template<> struct alignment_of<void const> : integral_constant<std::size_t, 0>{};
 105 template<> struct alignment_of<void const volatile> : integral_constant<std::size_t, 0>{};
 106 template<> struct alignment_of<void volatile> : integral_constant<std::size_t, 0>{};
 107 #endif
 108
 109 } // namespace boost
 110
 111 #if defined(__BORLANDC__) && (__BORLANDC__ < 0x600)
 112 #pragma option pop
 113 #endif
 114 #ifdef BOOST_MSVC
 115 #   pragma warning(pop)
 116 #endif
 117
 118 #endif // BOOST_TT_ALIGNMENT_OF_HPP_INCLUDED
 119