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 // should be the last #include
  17 #include <boost/type_traits/detail/size_t_trait_def.hpp>
  18
  19 #ifdef BOOST_MSVC
  20 #   pragma warning(push)
  21 #   pragma warning(disable: 4121 4512) // alignment is sensitive to packing
  22 #endif
  23 #if defined(__BORLANDC__) && (__BORLANDC__ < 0x600)
  24 #pragma option push -Vx- -Ve-
  25 #endif
  26
  27 namespace boost {
  28
  29 template <typename T> struct alignment_of;
  30
  31 // get the alignment of some arbitrary type:
  32 namespace detail {
  33
  34 #ifdef BOOST_MSVC
  35 #pragma warning(push)
  36 #pragma warning(disable:4324) // structure was padded due to __declspec(align())
  37 #endif
  38 template <typename T>
  39 struct alignment_of_hack
  40 {
  41     char c;
  42     T t;
  43     alignment_of_hack();
  44 };
  45 #ifdef BOOST_MSVC
  46 #pragma warning(pop)
  47 #endif
  48
  49 template <unsigned A, unsigned S>
  50 struct alignment_logic
  51 {
  52     BOOST_STATIC_CONSTANT(std::size_t, value = A < S ? A : S);
  53 };
  54
  55
  56 template< typename T >
  57 struct alignment_of_impl
  58 {
  59 #if defined(BOOST_MSVC) && (BOOST_MSVC >= 1400)
  60         //
  61         // With MSVC both the native __alignof operator
  62         // and our own logic gets things wrong from time to time :-(
  63         // Using a combination of the two seems to make the most of a bad job:
  64         //
  65     BOOST_STATIC_CONSTANT(std::size_t, value =
  66         (::boost::detail::alignment_logic<
  67             sizeof(::boost::detail::alignment_of_hack<T>) - sizeof(T),
  68             __alignof(T)
  69         >::value));
  70 #elif !defined(BOOST_ALIGNMENT_OF)
  71     BOOST_STATIC_CONSTANT(std::size_t, value =
  72         (::boost::detail::alignment_logic<
  73             sizeof(::boost::detail::alignment_of_hack<T>) - sizeof(T),
  74             sizeof(T)
  75         >::value));
  76 #else
  77    //
  78    // We put this here, rather than in the definition of
  79    // alignment_of below, because MSVC's __alignof doesn't
  80    // always work in that context for some unexplained reason.
  81    // (See type_with_alignment tests for test cases).
  82    //
  83    BOOST_STATIC_CONSTANT(std::size_t, value = BOOST_ALIGNMENT_OF(T));
  84 #endif
  85 };
  86
  87 } // namespace detail
  88
  89 BOOST_TT_AUX_SIZE_T_TRAIT_DEF1(alignment_of,T,::boost::detail::alignment_of_impl<T>::value)
  90
  91 // references have to be treated specially, assume
  92 // that a reference is just a special pointer:
  93 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  94 template <typename T>
  95 struct alignment_of<T&>
  96     : alignment_of<T*>
  97 {
  98 };
  99 #endif
 100 #ifdef __BORLANDC__
 101 // long double gives an incorrect value of 10 (!)
 102 // unless we do this...
 103 struct long_double_wrapper{ long double ld; };
 104 template<> struct alignment_of<long double>
 105    : public alignment_of<long_double_wrapper>{};
 106 #endif
 107
 108 // void has to be treated specially:
 109 BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void,0)
 110 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
 111 BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void const,0)
 112 BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void volatile,0)
 113 BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void const volatile,0)
 114 #endif
 115
 116 } // namespace boost
 117
 118 #if defined(__BORLANDC__) && (__BORLANDC__ < 0x600)
 119 #pragma option pop
 120 #endif
 121 #ifdef BOOST_MSVC
 122 #   pragma warning(pop)
 123 #endif
 124
 125 #include <boost/type_traits/detail/size_t_trait_undef.hpp>
 126
 127 #endif // BOOST_TT_ALIGNMENT_OF_HPP_INCLUDED
 128