1
2// (C) Copyright Steve Cleary, Beman Dawes, Howard Hinnant & 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_IS_EMPTY_HPP_INCLUDED
10#define BOOST_TT_IS_EMPTY_HPP_INCLUDED
11
12#include <boost/type_traits/is_convertible.hpp>
13#include <boost/type_traits/detail/config.hpp>
14#include <boost/type_traits/intrinsics.hpp>
15
16#include <boost/type_traits/remove_cv.hpp>
17#include <boost/type_traits/is_class.hpp>
18#include <boost/type_traits/add_reference.hpp>
19
20#ifndef BOOST_INTERNAL_IS_EMPTY
21#define BOOST_INTERNAL_IS_EMPTY(T) false
22#else
23#define BOOST_INTERNAL_IS_EMPTY(T) BOOST_IS_EMPTY(T)
24#endif
25
26namespace boost {
27
28namespace detail {
29
30
31#ifdef BOOST_MSVC
32#pragma warning(push)
33#pragma warning(disable:4624) // destructor could not be generated
34#endif
35
36template <typename T>
37struct empty_helper_t1 : public T
38{
39 empty_helper_t1(); // hh compiler bug workaround
40 int i[256];
41private:
42 // suppress compiler warnings:
43 empty_helper_t1(const empty_helper_t1&);
44 empty_helper_t1& operator=(const empty_helper_t1&);
45};
46
47#ifdef BOOST_MSVC
48#pragma warning(pop)
49#endif
50
51struct empty_helper_t2 { int i[256]; };
52
53#if !BOOST_WORKAROUND(BOOST_BORLANDC, < 0x600)
54
55template <typename T, bool is_a_class = false>
56struct empty_helper
57{
58 BOOST_STATIC_CONSTANT(bool, value = false);
59};
60
61template <typename T>
62struct empty_helper<T, true>
63{
64 BOOST_STATIC_CONSTANT(
65 bool, value = (sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2))
66 );
67};
68
69template <typename T>
70struct is_empty_impl
71{
72 typedef typename remove_cv<T>::type cvt;
73 BOOST_STATIC_CONSTANT(
74 bool,
75 value = ( ::boost::detail::empty_helper<cvt,::boost::is_class<T>::value>::value || BOOST_INTERNAL_IS_EMPTY(cvt)));
76};
77
78#else // BOOST_BORLANDC
79
80template <typename T, bool is_a_class, bool convertible_to_int>
81struct empty_helper
82{
83 BOOST_STATIC_CONSTANT(bool, value = false);
84};
85
86template <typename T>
87struct empty_helper<T, true, false>
88{
89 BOOST_STATIC_CONSTANT(bool, value = (
90 sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2)
91 ));
92};
93
94template <typename T>
95struct is_empty_impl
96{
97 typedef typename remove_cv<T>::type cvt;
98 typedef typename add_reference<T>::type r_type;
99
100 BOOST_STATIC_CONSTANT(
101 bool, value = (
102 ::boost::detail::empty_helper<
103 cvt
104 , ::boost::is_class<T>::value
105 , ::boost::is_convertible< r_type,int>::value
106 >::value || BOOST_INTERNAL_IS_EMPTY(cvt));
107};
108
109#endif // BOOST_BORLANDC
110
111} // namespace detail
112
113template <class T> struct is_empty : integral_constant<bool, ::boost::detail::is_empty_impl<T>::value> {};
114
115} // namespace boost
116
117#undef BOOST_INTERNAL_IS_EMPTY
118
119#endif // BOOST_TT_IS_EMPTY_HPP_INCLUDED
120
121

source code of include/boost/type_traits/is_empty.hpp