From 24b7d226d3316d36711c40b7ca854c2b2d4565be Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Sat, 16 May 2015 18:39:49 +0100
Subject: [PATCH] Add fix for false positives in is_virtual_base_of See
 https://svn.boost.org/trac/boost/ticket/11309

---
 include/boost/type_traits/is_virtual_base_of.hpp | 15 +++++++++++++++
 test/is_virtual_base_of_test.cpp                 | 13 +++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/include/boost/type_traits/is_virtual_base_of.hpp b/include/boost/type_traits/is_virtual_base_of.hpp
index 33db914..3daad1b 100644
--- a/include/boost/type_traits/is_virtual_base_of.hpp
+++ b/include/boost/type_traits/is_virtual_base_of.hpp
@@ -36,6 +36,17 @@ struct is_virtual_base_of_impl
 template<typename Base, typename Derived>
 struct is_virtual_base_of_impl<Base, Derived, mpl::true_>
 {
+   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 
     {
@@ -43,6 +54,7 @@ struct is_virtual_base_of_impl<Base, Derived, mpl::true_>
        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 
     {
@@ -50,6 +62,7 @@ struct is_virtual_base_of_impl<Base, Derived, mpl::true_>
        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 
@@ -58,6 +71,7 @@ struct is_virtual_base_of_impl<Base, Derived, mpl::true_>
        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 
     {
@@ -65,6 +79,7 @@ struct is_virtual_base_of_impl<Base, Derived, mpl::true_>
        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)));
diff --git a/test/is_virtual_base_of_test.cpp b/test/is_virtual_base_of_test.cpp
index 2877b4a..256e67c 100644
--- a/test/is_virtual_base_of_test.cpp
+++ b/test/is_virtual_base_of_test.cpp
@@ -38,6 +38,13 @@ public:
    virtual int X();
 };
 
+//
+// These are from https://svn.boost.org/trac/boost/ticket/11309
+//
+struct bug11309_A { int a; };
+struct bug11309_B : public virtual bug11309_A {};
+struct bug11309_C : public bug11309_A { virtual ~bug11309_C() {} };
+
 TT_TEST_BEGIN(is_virtual_base_of)
 
 BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_virtual_base_of<Derived,Base>::value), false);
@@ -75,6 +82,12 @@ BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_virtual_base_of<Base,virtual_inherit6>::
 BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_virtual_base_of<virtual_inherit6,Base>::value), false);
 BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_virtual_base_of<B,D>::value), false);
 BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_virtual_base_of<non_virtual_base,non_virtual_derived>::value), false);
+//
+// Bug cases:
+//
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_virtual_base_of<bug11309_A, bug11309_C>::value), false);
+BOOST_CHECK_INTEGRAL_CONSTANT((::tt::is_virtual_base_of<bug11309_A, bug11309_B>::value), true);
+
 
 TT_TEST_END