[857] | 1 | //-----------------------------------------------------------------------------
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| 2 | // boost variant/detail/forced_return.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_FORCED_RETURN_HPP
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| 14 | #define BOOST_VARIANT_DETAIL_FORCED_RETURN_HPP
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| 15 |
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| 16 | #include "boost/config.hpp"
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| 17 | #include "boost/variant/detail/generic_result_type.hpp"
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| 18 | #include "boost/assert.hpp"
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| 19 |
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| 20 | #if !defined(BOOST_MSVC) && !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
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| 21 | # include "boost/type_traits/remove_reference.hpp"
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| 22 | #endif
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| 23 |
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| 24 | namespace boost {
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| 25 | namespace detail { namespace variant {
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| 26 |
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| 27 | ///////////////////////////////////////////////////////////////////////////////
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| 28 | // (detail) function template forced_return
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| 29 | //
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| 30 | // Logical error to permit invocation at runtime, but (artificially) satisfies
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| 31 | // compile-time requirement of returning a result value.
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| 32 | //
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| 33 |
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| 34 | #if !defined(BOOST_MSVC) \
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| 35 | && !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) \
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| 36 | && !defined(BOOST_NO_VOID_RETURNS)
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| 37 |
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| 38 | // "standard" implementation:
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| 39 |
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| 40 | template <typename T>
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| 41 | inline T forced_return( BOOST_EXPLICIT_TEMPLATE_TYPE(T) )
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| 42 | {
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| 43 | // logical error: should never be here! (see above)
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| 44 | BOOST_ASSERT(false);
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| 45 |
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| 46 | typedef typename boost::remove_reference<T>::type basic_type;
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| 47 | basic_type* dummy = 0;
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| 48 | return *static_cast< basic_type* >(dummy);
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| 49 | }
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| 50 |
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| 51 | template <>
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| 52 | inline void forced_return<void>( BOOST_EXPLICIT_TEMPLATE_TYPE_SPEC(void) )
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| 53 | {
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| 54 | // logical error: should never be here! (see above)
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| 55 | BOOST_ASSERT(false);
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| 56 | }
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| 57 |
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| 58 | #elif !defined(BOOST_MSVC)
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| 59 |
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| 60 | // workaround implementation
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| 61 | //
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| 62 | // TODO: Determine the most efficient way to handle this -- as below? by
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| 63 | // throwing? by recursive call to forced_return itself? etc.
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| 64 | //
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| 65 |
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| 66 | template <typename T>
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| 67 | inline
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| 68 | BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(T)
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| 69 | forced_return( BOOST_EXPLICIT_TEMPLATE_TYPE(T) )
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| 70 | {
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| 71 | // logical error: should never be here! (see above)
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| 72 | BOOST_ASSERT(false);
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| 73 |
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| 74 | BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(T) (*dummy)() = 0;
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| 75 | return dummy();
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| 76 | }
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| 77 |
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| 78 | #else // defined(BOOST_MSVC)
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| 79 |
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| 80 | // msvc-specific implementation
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| 81 | //
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| 82 | // Leverages __declspec(noreturn) for optimized implementation.
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| 83 | //
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| 84 |
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| 85 | __declspec(noreturn)
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| 86 | inline void forced_return_no_return() {};
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| 87 |
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| 88 | template <typename T>
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| 89 | inline
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| 90 | BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(T)
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| 91 | forced_return( BOOST_EXPLICIT_TEMPLATE_TYPE(T) )
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| 92 | {
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| 93 | // logical error: should never be here! (see above)
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| 94 | BOOST_ASSERT(false);
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| 95 |
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| 96 | forced_return_no_return();
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| 97 | }
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| 98 |
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| 99 | #endif // BOOST_MSVC optimization
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| 100 |
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| 101 | }} // namespace detail::variant
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| 102 | } // namespace boost
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| 103 |
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| 104 | #endif // BOOST_VARIANT_DETAIL_FORCED_RETURN_HPP
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