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 91