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
27namespace boost {
28
29template <typename T> struct alignment_of;
30
31// get the alignment of some arbitrary type:
32namespace detail {
33
34#ifdef BOOST_MSVC
35#pragma warning(push)
36#pragma warning(disable:4324) // structure was padded due to __declspec(align())
37#endif
38template <typename T>
39struct 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
49template <unsigned A, unsigned S>
50struct alignment_logic
51{
52 BOOST_STATIC_CONSTANT(std::size_t, value = A < S ? A : S);
53};
54
55
56template< typename T >
57struct 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
89BOOST_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:
93template <typename T>
94struct alignment_of<T&>
95 : public alignment_of<T*>
96{
97};
98#ifdef __BORLANDC__
99// long double gives an incorrect value of 10 (!)
100// unless we do this...
101struct long_double_wrapper{ long double ld; };
102template<> struct alignment_of<long double>
103 : public alignment_of<long_double_wrapper>{};
104#endif
105
106// void has to be treated specially:
107BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void,0)
108#ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
109BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void const,0)
110BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void volatile,0)
111BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void const volatile,0)
112#endif
113
114} // namespace boost
115
116#if defined(__BORLANDC__) && (__BORLANDC__ < 0x600)
117#pragma option pop
118#endif
119#ifdef BOOST_MSVC
120# pragma warning(pop)
121#endif
122
123#include <boost/type_traits/detail/size_t_trait_undef.hpp>
124
125#endif // BOOST_TT_ALIGNMENT_OF_HPP_INCLUDED
126
127