From fc135e0d72610e13c6dac0aa11e09f710526f022 Mon Sep 17 00:00:00 2001
From: Glen Fernandes <glen.fernandes@gmail.com>
Date: Sun, 9 Sep 2018 15:00:49 -0400
Subject: [PATCH] Avoid inheritance for final types in compressed_pair

---
 include/boost/detail/compressed_pair.hpp | 25 +++++++----
 test/Jamfile.v2                          |  1 +
 test/compressed_pair_final_test.cpp      | 55 ++++++++++++++++++++++++
 3 files changed, 73 insertions(+), 8 deletions(-)
 create mode 100644 test/compressed_pair_final_test.cpp

diff --git a/include/boost/detail/compressed_pair.hpp b/include/boost/detail/compressed_pair.hpp
index 5dc21e2..b090a72 100644
--- a/include/boost/detail/compressed_pair.hpp
+++ b/include/boost/detail/compressed_pair.hpp
@@ -24,6 +24,7 @@
 
 #include <boost/type_traits/remove_cv.hpp>
 #include <boost/type_traits/is_empty.hpp>
+#include <boost/type_traits/is_final.hpp>
 #include <boost/type_traits/is_same.hpp>
 #include <boost/call_traits.hpp>
 
@@ -42,6 +43,14 @@ class compressed_pair;
 
 namespace details
 {
+   template<class T, bool E = boost::is_final<T>::value>
+   struct compressed_pair_empty
+      : ::boost::false_type { };
+
+   template<class T>
+   struct compressed_pair_empty<T, false>
+      : ::boost::is_empty<T> { };
+
    // JM altered 26 Jan 2000:
    template <class T1, class T2, bool IsSame, bool FirstEmpty, bool SecondEmpty>
    struct compressed_pair_switch;
@@ -343,8 +352,8 @@ class compressed_pair
                     T1,
                     T2,
                     ::boost::is_same<typename remove_cv<T1>::type, typename remove_cv<T2>::type>::value,
-                    ::boost::is_empty<T1>::value,
-                    ::boost::is_empty<T2>::value>::value>
+                    ::boost::details::compressed_pair_empty<T1>::value,
+                    ::boost::details::compressed_pair_empty<T2>::value>::value>
 {
 private:
    typedef details::compressed_pair_imp<T1, T2,
@@ -352,8 +361,8 @@ private:
                     T1,
                     T2,
                     ::boost::is_same<typename remove_cv<T1>::type, typename remove_cv<T2>::type>::value,
-                    ::boost::is_empty<T1>::value,
-                    ::boost::is_empty<T2>::value>::value> base;
+                    ::boost::details::compressed_pair_empty<T1>::value,
+                    ::boost::details::compressed_pair_empty<T2>::value>::value> base;
 public:
    typedef T1                                                 first_type;
    typedef T2                                                 second_type;
@@ -388,8 +397,8 @@ class compressed_pair<T, T>
                     T,
                     T,
                     ::boost::is_same<typename remove_cv<T>::type, typename remove_cv<T>::type>::value,
-                    ::boost::is_empty<T>::value,
-                    ::boost::is_empty<T>::value>::value>
+                    ::boost::details::compressed_pair_empty<T>::value,
+                    ::boost::details::compressed_pair_empty<T>::value>::value>
 {
 private:
    typedef details::compressed_pair_imp<T, T,
@@ -397,8 +406,8 @@ private:
                     T,
                     T,
                     ::boost::is_same<typename remove_cv<T>::type, typename remove_cv<T>::type>::value,
-                    ::boost::is_empty<T>::value,
-                    ::boost::is_empty<T>::value>::value> base;
+                    ::boost::details::compressed_pair_empty<T>::value,
+                    ::boost::details::compressed_pair_empty<T>::value>::value> base;
 public:
    typedef T                                                  first_type;
    typedef T                                                  second_type;
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 7fd5b2f..739edc0 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -16,6 +16,7 @@ run binary_test.cpp ;
 run call_traits_test.cpp : -u ;
 
 run compressed_pair_test.cpp ;
+run compressed_pair_final_test.cpp ;
 
 run iterators_test.cpp ;
 
diff --git a/test/compressed_pair_final_test.cpp b/test/compressed_pair_final_test.cpp
new file mode 100644
index 0000000..247f3fc
--- /dev/null
+++ b/test/compressed_pair_final_test.cpp
@@ -0,0 +1,55 @@
+/*
+Copyright 2018 Glen Joseph Fernandes
+(glenjofe@gmail.com)
+
+Distributed under the Boost Software License, Version 1.0.
+(http://www.boost.org/LICENSE_1_0.txt)
+*/
+#include <boost/config.hpp>
+#if !defined(BOOST_NO_CXX11_FINAL)
+#include <boost/compressed_pair.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+struct type1 {
+    operator bool() const {
+        return false;
+    }
+};
+
+struct type2 final {
+    operator bool() const {
+        return false;
+    }
+};
+
+#if !defined(BOOST_IS_FINAL)
+namespace boost {
+
+template<>
+struct is_final<type2>
+    : true_type { };
+
+} /* boost*/
+#endif
+
+template<class T1, class T2>
+void test()
+{
+    boost::compressed_pair<T1, T2> p;
+    BOOST_TEST(!p.first());
+    BOOST_TEST(!p.second());
+}
+
+int main()
+{
+    test<type1, type2>();
+    test<type2, type1>();
+    test<type2, type2>();
+    return boost::report_errors();
+}
+#else
+int main()
+{
+    return 0;
+}
+#endif