ceph/src/boost/libs/flyweight/include/boost/flyweight/detail/perfect_fwd.hpp

   1 /* Copyright 2006-2014 Joaquin M Lopez Munoz.
   2  * Distributed under the Boost Software License, Version 1.0.
   3  * (See accompanying file LICENSE_1_0.txt or copy at
   4  * http://www.boost.org/LICENSE_1_0.txt)
   5  *
   6  * See http://www.boost.org/libs/flyweight for library home page.
   7  */
   8
   9 #ifndef BOOST_FLYWEIGHT_DETAIL_PERFECT_FWD_HPP
  10 #define BOOST_FLYWEIGHT_DETAIL_PERFECT_FWD_HPP
  11
  12 #if defined(_MSC_VER)
  13 #pragma once
  14 #endif
  15
  16 /* C++03-compatible implementation of perfect forwarding.
  17  * Usage:
  18  *
  19  *  # define NAME ...
  20  *  # define BODY(args) {...BOOST_FLYWEIGHT_FORWARD(args)...}
  21  *  BOOST_FLYWEIGHT_PERFECT_FWD(name,body)
  22  *
  23  * where NAME includes the return type and qualifiers (if any) and BODY(args)
  24  * is expected to fo the forwarding through BOOST_FLYWEIGHT_FORWARD(args).
  25  *
  26  * In compilers capable of perfect forwarding, the real thing is provided
  27  * (just one variadic args overload is generated). Otherwise the machinery
  28  * generates n+1 overloads, if rvalue refs are supported, or else 2^(n+1)-1
  29  * overloads accepting any combination of lvalue refs and const lvalue refs,
  30  * up to BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS args.
  31  *
  32  * BOOST_FLYWEIGHT_PERFECT_FWD_WITH_ARGS(name,body) is a variation omitting the
  33  * overloads with zero args --when perfect forwarding is available, this second
  34  * macro is exactly the same as the original.
  35  */
  36
  37 #include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
  38 #include <boost/preprocessor/cat.hpp>
  39 #include <boost/preprocessor/repetition/enum.hpp>
  40 #include <boost/preprocessor/repetition/enum_params.hpp>
  41 #include <boost/preprocessor/seq/seq.hpp>
  42
  43 #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
  44 #include <utility>
  45 #endif
  46
  47 #define BOOST_FLYWEIGHT_FORWARD_FORWARD_AUX(z,n,_) \
  48 std::forward<BOOST_PP_CAT(T,n)>(BOOST_PP_CAT(t,n))
  49
  50 #define BOOST_FLYWEIGHT_FORWARD_FORWARD(n) \
  51 BOOST_PP_ENUM(n,BOOST_FLYWEIGHT_FORWARD_FORWARD_AUX,~)
  52
  53 #define BOOST_FLYWEIGHT_FORWARD_ENUM(n) BOOST_PP_ENUM_PARAMS(n,t)
  54
  55 #define BOOST_FLYWEIGHT_FORWARD_PASS(arg) arg
  56
  57 #define BOOST_FLYWEIGHT_FORWARD(args)\
  58 BOOST_PP_CAT(BOOST_FLYWEIGHT_FORWARD_,BOOST_PP_SEQ_HEAD(args))( \
  59 BOOST_PP_SEQ_HEAD(BOOST_PP_SEQ_TAIL(args)))
  60
  61 #if defined(BOOST_NO_CXX11_RVALUE_REFERENCES)||\
  62     defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
  63
  64 #if !defined(BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS)
  65 #define BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS 5
  66 #endif
  67
  68 #if BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS<0
  69 #error BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS must be >=0
  70 #endif
  71
  72 #if BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS<=5
  73 #include <boost/flyweight/detail/pp_perfect_fwd.hpp>
  74 #else
  75 #include <boost/flyweight/detail/dyn_perfect_fwd.hpp>
  76 #endif
  77
  78 #else
  79
  80 /* real perfect forwarding */
  81
  82 #define BOOST_FLYWEIGHT_PERFECT_FWD(name,body) \
  83 template<typename... Args>name(Args&&... args) \
  84 body((PASS)(std::forward<Args>(args)...))
  85
  86 #define BOOST_FLYWEIGHT_PERFECT_FWD_WITH_ARGS  \
  87 BOOST_FLYWEIGHT_PERFECT_FWD
  88
  89 #endif
  90 #endif