[857] | 1 | //-----------------------------------------------------------------------------
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| 2 | // boost variant/detail/generic_result_type.hpp header file
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| 3 | // See http://www.boost.org for updates, documentation, and revision history.
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| 4 | //-----------------------------------------------------------------------------
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| 5 | //
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| 6 | // Copyright (c) 2003
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| 7 | // Eric Friedman
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| 8 | //
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| 9 | // Distributed under the Boost Software License, Version 1.0. (See
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| 10 | // accompanying file LICENSE_1_0.txt or copy at
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| 11 | // http://www.boost.org/LICENSE_1_0.txt)
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| 12 |
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| 13 | #ifndef BOOST_VARIANT_DETAIL_GENERIC_RESULT_TYPE_HPP
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| 14 | #define BOOST_VARIANT_DETAIL_GENERIC_RESULT_TYPE_HPP
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| 15 |
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| 16 | #include "boost/config.hpp"
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| 17 |
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| 18 | //////////////////////////////////////////////////////////////////////////
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| 19 | // (workaround) macro BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE
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| 20 | //
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| 21 | // On compilers with BOOST_NO_VOID_RETURNS, this macro provides a route
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| 22 | // to a single syntax for dealing with template functions that may (but
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| 23 | // not necessarily) return nothing (i.e. void).
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| 24 | //
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| 25 | // BOOST_VARIANT_AUX_RETURN_VOID provided for compilers w/ (erroneous?)
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| 26 | // warnings about non-void functions not returning a value.
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| 27 | //
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| 28 |
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| 29 | #if !defined(BOOST_NO_VOID_RETURNS)
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| 30 |
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| 31 | #define BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(T) \
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| 32 | T \
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| 33 | /**/
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| 34 |
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| 35 | #define BOOST_VARIANT_AUX_RETURN_VOID \
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| 36 | /**/
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| 37 |
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| 38 | #define BOOST_VARIANT_AUX_RETURN_VOID_TYPE \
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| 39 | void \
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| 40 | /**/
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| 41 |
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| 42 | #else // defined(BOOST_NO_VOID_RETURNS)
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| 43 |
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| 44 | namespace boost {
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| 45 | namespace detail { namespace variant {
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| 46 |
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| 47 | struct fake_return_void
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| 48 | {
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| 49 | fake_return_void()
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| 50 | {
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| 51 | }
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| 52 |
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| 53 | template <typename T>
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| 54 | fake_return_void(const T&)
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| 55 | {
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| 56 | }
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| 57 | };
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| 58 |
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| 59 | template <typename T>
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| 60 | struct no_void_returns_helper
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| 61 | {
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| 62 | typedef T type;
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| 63 | };
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| 64 |
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| 65 | template <>
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| 66 | struct no_void_returns_helper<void>
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| 67 | {
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| 68 | typedef fake_return_void type;
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| 69 | };
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| 70 |
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| 71 | }} // namespace detail::variant
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| 72 | } // namespace boost
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| 73 |
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| 74 | #define BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(T) \
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| 75 | BOOST_DEDUCED_TYPENAME \
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| 76 | ::boost::detail::variant::no_void_returns_helper< T >::type \
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| 77 | /**/
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| 78 |
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| 79 | #define BOOST_VARIANT_AUX_RETURN_VOID \
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| 80 | return ::boost::detail::variant::fake_return_void() \
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| 81 | /**/
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| 82 |
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| 83 | #define BOOST_VARIANT_AUX_RETURN_VOID_TYPE \
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| 84 | ::boost::detail::variant::fake_return_void
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| 85 |
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| 86 | #endif // BOOST_NO_VOID_RETURNS workaround
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| 87 |
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| 88 | #endif // BOOST_VARIANT_DETAIL_GENERIC_RESULT_TYPE_HPP
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