From 16e11da8449f7a40bd91b0ca57db8df7bd260571 Mon Sep 17 00:00:00 2001
From: badair <badair@harding.edu>
Date: Fri, 15 Apr 2016 21:57:44 -0500
Subject: [PATCH] working toward gcc 4.8 support

---
 .travis.yml                                        | 14 +++++++-------
 include/callable_traits/config.hpp                 |  6 ++++++
 include/callable_traits/detail/bind_expression.hpp |  5 +++--
 include/callable_traits/detail/can_invoke_impl.hpp |  2 +-
 test/bind_1.cpp                                    |  4 ++--
 test/bind_2.cpp                                    |  4 ++--
 6 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 8b8a371..a20ff0b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -85,13 +85,13 @@ matrix:
           sources: *sources
 
     # GCC 4.8
-    #- env: UNIT_TESTS=true CPP=1y COMPILER=g++-4.8 STDLIB=libstdc++
-    #  os: linux
-    #  compiler: g++
-    #  addons:
-    #    apt:
-    #      packages: ["g++-4.8"]
-    #      sources: *sources
+    - env: UNIT_TESTS=true CPP=1y COMPILER=g++-4.8 STDLIB=libstdc++
+      os: linux
+      compiler: g++
+      addons:
+        apt:
+          packages: ["g++-4.8"]
+          sources: *sources
 
 before_install:
 
diff --git a/include/callable_traits/config.hpp b/include/callable_traits/config.hpp
index 2e2324e..0a54601 100644
--- a/include/callable_traits/config.hpp
+++ b/include/callable_traits/config.hpp
@@ -14,6 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 #define CALLABLE_TRAITS_MAKE_IX_SEQ(...) ::std::make_index_sequence< __VA_ARGS__ >
 #define CALLABLE_TRAITS_DISJUNCTION(...) ::std::disjunction< __VA_ARGS__ >
 #define CALLABLE_TRAITS_CONJUNCTION(...) ::std::conjunction< __VA_ARGS__ >
+#define CALLALBLE_TRAITS_DECLTYPE_AUTO decltype(auto)
+
+#ifndef __cpp_decltype_auto
+#undef CALLALBLE_TRAITS_DECLTYPE_AUTO
+#define CALLALBLE_TRAITS_DECLTYPE_AUTO auto
+#endif
 
 #ifndef __cpp_lib_logical_traits
 #include <callable_traits/detail/polyfills/conjunction.hpp>
diff --git a/include/callable_traits/detail/bind_expression.hpp b/include/callable_traits/detail/bind_expression.hpp
index 0bdaeb2..ec92aa9 100644
--- a/include/callable_traits/detail/bind_expression.hpp
+++ b/include/callable_traits/detail/bind_expression.hpp
@@ -112,7 +112,8 @@ namespace callable_traits {
 
         template<typename T, typename std::enable_if<
             is_callable_traits_bind<shallow_decay<T>>::value, int>::type = 0>
-        inline constexpr decltype(auto) unwrap_std_bind(T&& t){
+        inline constexpr CALLALBLE_TRAITS_DECLTYPE_AUTO
+        unwrap_std_bind(T&& t){
             return t.get_std_bind();
         }
 
@@ -174,7 +175,7 @@ namespace callable_traits {
                         unwrap_std_bind(static_cast<Args>(args))...)) {}
 
             template<typename... Rgs>
-            inline decltype(auto)
+            inline CALLALBLE_TRAITS_DECLTYPE_AUTO
             operator()(Rgs&&... args) {
                 return std_bind(std::forward<Rgs>(args)...);
             }
diff --git a/include/callable_traits/detail/can_invoke_impl.hpp b/include/callable_traits/detail/can_invoke_impl.hpp
index facb538..8a37f76 100644
--- a/include/callable_traits/detail/can_invoke_impl.hpp
+++ b/include/callable_traits/detail/can_invoke_impl.hpp
@@ -11,7 +11,7 @@ namespace callable_traits {
     namespace detail {
 
         template<typename T, typename... Args>
-        inline constexpr decltype(auto)
+        inline constexpr auto
         can_invoke_impl(T&& t, Args&&... args) {
             using traits = detail::traits<T&&>;
             using test = detail::test_invoke<traits, Args&&...>;
diff --git a/test/bind_1.cpp b/test/bind_1.cpp
index c2c66fb..e56cad1 100644
--- a/test/bind_1.cpp
+++ b/test/bind_1.cpp
@@ -68,13 +68,13 @@ auto ordered_letters(A a, B b, C c, D d, E e, F f, G g) {
 }
 
 template <typename F, typename Tuple, std::size_t... I>
-constexpr decltype(auto)
+constexpr auto
 apply_helper(F&& f, Tuple&& t, CALLABLE_TRAITS_IX_SEQ(I...)) {
     return std::forward<F>(f)(std::get<I>(std::forward<Tuple>(t))...);
 }
 
 template <typename F, typename Tuple>
-constexpr decltype(auto)
+constexpr auto
 apply(F&& f, Tuple&& t) {
     return apply_helper(
         std::forward<F>(f),
diff --git a/test/bind_2.cpp b/test/bind_2.cpp
index 1e7f3d1..d962115 100644
--- a/test/bind_2.cpp
+++ b/test/bind_2.cpp
@@ -70,14 +70,14 @@ auto BEEF_returns_B(B, E, E, F) {
 }
 
 template <typename F, typename Tuple, std::size_t... I>
-constexpr decltype(auto)
+constexpr auto
 apply_helper(F&& f, Tuple&& t, CALLABLE_TRAITS_IX_SEQ(I...)) {
     return std::forward<F>(f)(std::get<I>(std::forward<Tuple>(t))...);
 }
 
 //used to apply the expected_args tuple to std::bind
 template <typename F, typename Tuple>
-constexpr decltype(auto)
+constexpr auto
 apply(F&& f, Tuple&& t) {
     return apply_helper(
         std::forward<F>(f),