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Diffstat (limited to 'boost/flyweight/detail/perfect_fwd.hpp')
| -rw-r--r-- | boost/flyweight/detail/perfect_fwd.hpp | 80 |
1 files changed, 71 insertions, 9 deletions
diff --git a/boost/flyweight/detail/perfect_fwd.hpp b/boost/flyweight/detail/perfect_fwd.hpp index 05d670c69f..18c9e0aeee 100644 --- a/boost/flyweight/detail/perfect_fwd.hpp +++ b/boost/flyweight/detail/perfect_fwd.hpp @@ -1,4 +1,4 @@ -/* Copyright 2006-2008 Joaquin M Lopez Munoz. +/* Copyright 2006-2014 Joaquin M Lopez Munoz. * Distributed under the Boost Software License, Version 1.0. * (See accompanying file LICENSE_1_0.txt or copy at * http://www.boost.org/LICENSE_1_0.txt) @@ -6,23 +6,85 @@ * See http://www.boost.org/libs/flyweight for library home page. */ -/* Brute force implementation of perfect forwarding overloads. - * Usage: include after having defined the argument macros: - * BOOST_FLYWEIGHT_PERFECT_FWD_NAME - * BOOST_FLYWEIGHT_PERFECT_FWD_BODY - */ +#ifndef BOOST_FLYWEIGHT_DETAIL_PERFECT_FWD_HPP +#define BOOST_FLYWEIGHT_DETAIL_PERFECT_FWD_HPP + +#if defined(_MSC_VER) +#pragma once +#endif -/* This user_definable macro limits the maximum number of arguments to - * be perfect forwarded. Beware combinatorial explosion: manual perfect - * forwarding for n arguments produces 2^n distinct overloads. +/* C++03-compatible implementation of perfect forwarding. + * Usage: + * + * # define NAME ... + * # define BODY(args) {...BOOST_FLYWEIGHT_FORWARD(args)...} + * BOOST_FLYWEIGHT_PERFECT_FWD(name,body) + * + * where NAME includes the return type and qualifiers (if any) and BODY(args) + * is expected to fo the forwarding through BOOST_FLYWEIGHT_FORWARD(args). + * + * In compilers capable of perfect forwarding, the real thing is provided + * (just one variadic args overload is generated). Otherwise the machinery + * generates n+1 overloads, if rvalue refs are supported, or else 2^(n+1)-1 + * overloads accepting any combination of lvalue refs and const lvalue refs, + * up to BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS args. + * + * BOOST_FLYWEIGHT_PERFECT_FWD_WITH_ARGS(name,body) is a variation omitting the + * overloads with zero args --when perfect forwarding is available, this second + * macro is exactly the same as the original. */ +#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */ +#include <boost/preprocessor/cat.hpp> +#include <boost/preprocessor/repetition/enum.hpp> +#include <boost/preprocessor/repetition/enum_params.hpp> +#include <boost/preprocessor/seq/seq.hpp> + +#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES) +#include <utility> +#endif + +#define BOOST_FLYWEIGHT_FORWARD_FORWARD_AUX(z,n,_) \ +std::forward<BOOST_PP_CAT(T,n)>(BOOST_PP_CAT(t,n)) + +#define BOOST_FLYWEIGHT_FORWARD_FORWARD(n) \ +BOOST_PP_ENUM(n,BOOST_FLYWEIGHT_FORWARD_FORWARD_AUX,~) + +#define BOOST_FLYWEIGHT_FORWARD_ENUM(n) BOOST_PP_ENUM_PARAMS(n,t) + +#define BOOST_FLYWEIGHT_FORWARD_PASS(arg) arg + +#define BOOST_FLYWEIGHT_FORWARD(args)\ +BOOST_PP_CAT(BOOST_FLYWEIGHT_FORWARD_,BOOST_PP_SEQ_HEAD(args))( \ +BOOST_PP_SEQ_HEAD(BOOST_PP_SEQ_TAIL(args))) + +#if defined(BOOST_NO_CXX11_RVALUE_REFERENCES)||\ + defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) + #if !defined(BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS) #define BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS 5 #endif +#if BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS<0 +#error BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS must be >=0 +#endif + #if BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS<=5 #include <boost/flyweight/detail/pp_perfect_fwd.hpp> #else #include <boost/flyweight/detail/dyn_perfect_fwd.hpp> #endif + +#else + +/* real perfect forwarding */ + +#define BOOST_FLYWEIGHT_PERFECT_FWD(name,body) \ +template<typename... Args>name(Args&&... args) \ +body((PASS)(std::forward<Args>(args)...)) + +#define BOOST_FLYWEIGHT_PERFECT_FWD_WITH_ARGS \ +BOOST_FLYWEIGHT_PERFECT_FWD + +#endif +#endif |