ceph/src/boost/libs/variant/include/boost/variant/detail/generic_result_type.hpp

   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