From 63dea93d99a5157cfde519a6e845ff340942c43d Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Wed, 9 May 2018 19:14:50 +0100
Subject: [PATCH] is_virtual_base_of.hpp: Reinstate old version for old broken
 compilers.

---
 .../boost/type_traits/is_virtual_base_of.hpp  | 81 +++++++++++++++++++
 1 file changed, 81 insertions(+)

diff --git a/include/boost/type_traits/is_virtual_base_of.hpp b/include/boost/type_traits/is_virtual_base_of.hpp
index 1321f22..d2efebb 100644
--- a/include/boost/type_traits/is_virtual_base_of.hpp
+++ b/include/boost/type_traits/is_virtual_base_of.hpp
@@ -10,6 +10,7 @@
 #define BOOST_TT_IS_VIRTUAL_BASE_OF_HPP_INCLUDED
 
 #include <boost/type_traits/is_base_of.hpp>
+#include <boost/type_traits/is_same.hpp>
 
 namespace boost {
 namespace detail {
@@ -22,6 +23,8 @@ namespace detail {
 #pragma GCC system_header
 #endif
 
+#if !defined(BOOST_NO_SFINAE_EXPR) && !defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS) && !defined(BOOST_NO_CXX11_NULLPTR)
+
 template<class Base, class Derived>
 struct is_virtual_base_of_impl
 {
@@ -60,6 +63,84 @@ struct is_virtual_base_of_impl
 
 template <class Base, class Derived> struct is_virtual_base_of : public integral_constant<bool, (::boost::detail::is_virtual_base_of_impl<Base, Derived>::value)>{};
 
+#else
+
+   template<typename Base, typename Derived, typename tag>
+   struct is_virtual_base_of_impl
+   {
+      BOOST_STATIC_CONSTANT(bool, value = false);
+   };
+
+   template<typename Base, typename Derived>
+   struct is_virtual_base_of_impl<Base, Derived, true_type>
+   {
+      union max_align
+      {
+         unsigned u;
+         unsigned long ul;
+         void* v;
+         double d;
+         long double ld;
+#ifndef BOOST_NO_LONG_LONG
+         long long ll;
+#endif
+      };
+#ifdef __BORLANDC__
+      struct boost_type_traits_internal_struct_X : public virtual Derived, public virtual Base
+      {
+         boost_type_traits_internal_struct_X();
+         boost_type_traits_internal_struct_X(const boost_type_traits_internal_struct_X&);
+         boost_type_traits_internal_struct_X& operator=(const boost_type_traits_internal_struct_X&);
+         ~boost_type_traits_internal_struct_X()throw();
+         max_align data[4];
+      };
+      struct boost_type_traits_internal_struct_Y : public virtual Derived
+      {
+         boost_type_traits_internal_struct_Y();
+         boost_type_traits_internal_struct_Y(const boost_type_traits_internal_struct_Y&);
+         boost_type_traits_internal_struct_Y& operator=(const boost_type_traits_internal_struct_Y&);
+         ~boost_type_traits_internal_struct_Y()throw();
+         max_align data[4];
+      };
+#else
+      struct boost_type_traits_internal_struct_X : public Derived, virtual Base
+      {
+         boost_type_traits_internal_struct_X();
+         boost_type_traits_internal_struct_X(const boost_type_traits_internal_struct_X&);
+         boost_type_traits_internal_struct_X& operator=(const boost_type_traits_internal_struct_X&);
+         ~boost_type_traits_internal_struct_X()throw();
+         max_align data[16];
+      };
+      struct boost_type_traits_internal_struct_Y : public Derived
+      {
+         boost_type_traits_internal_struct_Y();
+         boost_type_traits_internal_struct_Y(const boost_type_traits_internal_struct_Y&);
+         boost_type_traits_internal_struct_Y& operator=(const boost_type_traits_internal_struct_Y&);
+         ~boost_type_traits_internal_struct_Y()throw();
+         max_align data[16];
+      };
+#endif
+      BOOST_STATIC_CONSTANT(bool, value = (sizeof(boost_type_traits_internal_struct_X) == sizeof(boost_type_traits_internal_struct_Y)));
+   };
+
+   template<typename Base, typename Derived>
+   struct is_virtual_base_of_impl2
+   {
+      typedef boost::integral_constant<bool, (boost::is_base_of<Base, Derived>::value && !boost::is_same<Base, Derived>::value)> tag_type;
+      typedef is_virtual_base_of_impl<Base, Derived, tag_type> imp;
+      BOOST_STATIC_CONSTANT(bool, value = imp::value);
+   };
+
+#ifdef BOOST_MSVC
+#pragma warning( pop )
+#endif
+
+} // namespace detail
+
+template <class Base, class Derived> struct is_virtual_base_of : public integral_constant<bool, (::boost::detail::is_virtual_base_of_impl2<Base, Derived>::value)> {};
+
+#endif
+
 template <class Base, class Derived> struct is_virtual_base_of<Base&, Derived> : public false_type{};
 template <class Base, class Derived> struct is_virtual_base_of<Base, Derived&> : public false_type{};
 template <class Base, class Derived> struct is_virtual_base_of<Base&, Derived&> : public false_type{};