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1 | //----------------------------------------------------------------------------- |
2 | // boost variant/detail/generic_result_type.hpp header file | |
3 | // See http://www.boost.org for updates, documentation, and revision history. | |
4 | //----------------------------------------------------------------------------- | |
5 | // | |
6 | // Copyright (c) 2003 | |
7 | // Eric Friedman | |
8 | // | |
9 | // Distributed under the Boost Software License, Version 1.0. (See | |
10 | // accompanying file LICENSE_1_0.txt or copy at | |
11 | // http://www.boost.org/LICENSE_1_0.txt) | |
12 | ||
13 | #ifndef BOOST_VARIANT_DETAIL_GENERIC_RESULT_TYPE_HPP | |
14 | #define BOOST_VARIANT_DETAIL_GENERIC_RESULT_TYPE_HPP | |
15 | ||
16 | #include <boost/config.hpp> | |
17 | ||
18 | ////////////////////////////////////////////////////////////////////////// | |
19 | // (workaround) macro BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE | |
20 | // | |
21 | // On compilers with BOOST_NO_VOID_RETURNS, this macro provides a route | |
22 | // to a single syntax for dealing with template functions that may (but | |
23 | // not necessarily) return nothing (i.e. void). | |
24 | // | |
25 | // BOOST_VARIANT_AUX_RETURN_VOID provided for compilers w/ (erroneous?) | |
26 | // warnings about non-void functions not returning a value. | |
27 | // | |
28 | ||
29 | #if !defined(BOOST_NO_VOID_RETURNS) | |
30 | ||
31 | #define BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(T) \ | |
32 | T \ | |
33 | /**/ | |
34 | ||
35 | #define BOOST_VARIANT_AUX_RETURN_VOID \ | |
36 | /**/ | |
37 | ||
38 | #define BOOST_VARIANT_AUX_RETURN_VOID_TYPE \ | |
39 | void \ | |
40 | /**/ | |
41 | ||
42 | #else // defined(BOOST_NO_VOID_RETURNS) | |
43 | ||
44 | namespace boost { | |
45 | namespace detail { namespace variant { | |
46 | ||
47 | struct fake_return_void | |
48 | { | |
49 | fake_return_void() | |
50 | { | |
51 | } | |
52 | ||
53 | template <typename T> | |
54 | fake_return_void(const T&) | |
55 | { | |
56 | } | |
57 | }; | |
58 | ||
59 | template <typename T> | |
60 | struct no_void_returns_helper | |
61 | { | |
62 | typedef T type; | |
63 | }; | |
64 | ||
65 | template <> | |
66 | struct no_void_returns_helper<void> | |
67 | { | |
68 | typedef fake_return_void type; | |
69 | }; | |
70 | ||
71 | }} // namespace detail::variant | |
72 | } // namespace boost | |
73 | ||
74 | #define BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(T) \ | |
75 | BOOST_DEDUCED_TYPENAME \ | |
76 | ::boost::detail::variant::no_void_returns_helper< T >::type \ | |
77 | /**/ | |
78 | ||
79 | #define BOOST_VARIANT_AUX_RETURN_VOID \ | |
80 | return ::boost::detail::variant::fake_return_void() \ | |
81 | /**/ | |
82 | ||
83 | #define BOOST_VARIANT_AUX_RETURN_VOID_TYPE \ | |
84 | ::boost::detail::variant::fake_return_void | |
85 | ||
86 | #endif // BOOST_NO_VOID_RETURNS workaround | |
87 | ||
88 | #endif // BOOST_VARIANT_DETAIL_GENERIC_RESULT_TYPE_HPP |