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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