From 55f3c351a388a1bc2c38cb06d4e6a324faaaa66e Mon Sep 17 00:00:00 2001
From: Niels Dekker <nielsdekker@xs4all.nl>
Date: Fri, 7 Sep 2007 17:17:09 +0000
Subject: [PATCH] Added MSVC workaround to value_initialized, as described by
 ticket #1217, proposed at the Boost Developers mailing list, and discussed
 with Fernando Cacciola.

[SVN r39157]
---
 include/boost/utility/value_init.hpp | 84 ++++++++++++++++++++++++++--
 1 file changed, 80 insertions(+), 4 deletions(-)

diff --git a/include/boost/utility/value_init.hpp b/include/boost/utility/value_init.hpp
index 65600e5..a564658 100644
--- a/include/boost/utility/value_init.hpp
+++ b/include/boost/utility/value_init.hpp
@@ -1,10 +1,11 @@
-// (C) 2002, Fernando Luis Cacciola Carballal.
+// (C) Copyright 2002-2007, Fernando Luis Cacciola Carballal.
 //
 // 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)
 //
 // 21 Ago 2002 (Created) Fernando Cacciola
+// 07 Set 2007 (Worked around MSVC++ bug) Fernando Cacciola, Niels Dekker
 //
 #ifndef BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP
 #define BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP
@@ -13,6 +14,75 @@
 #include <boost/type_traits/cv_traits.hpp>
 #include <boost/detail/workaround.hpp>
 
+#if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1500) )
+// Microsoft Visual C++ does not correctly support value initialization, as reported by
+// Pavel Kuznetsov (MetaCommunications Engineering), 7/28/2005, Feedback ID 100744,
+// Feedback Title: Value-initialization in new-expression
+// https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=100744
+// The report was closed at 11/14/2006, and its status was set to "Closed (Won't Fix)".
+// Luckily, even in the presence of this compiler bug, boost::value_initialized will still
+// do its job correctly, when using the following workaround:
+#define BOOST_UTILITY_VALUE_INIT_WORKAROUND
+#endif
+
+#ifdef BOOST_UTILITY_VALUE_INIT_WORKAROUND
+#include <boost/aligned_storage.hpp>
+#include <boost/type_traits/alignment_of.hpp>
+#include <cstring>
+#include <new>
+
+namespace boost {
+
+namespace vinit_detail {
+
+template<class T>
+class const_T_base
+{
+  protected :
+
+    const_T_base()
+    {
+      std::memset(&x, 0, sizeof(x));
+      new (&x) T();
+    }
+
+    ~const_T_base() { get().T::~T(); }
+
+    T & get() const
+    {
+      void const * ptr = &x;
+      return *static_cast<T*>(ptr);
+    }
+
+  private :
+    typename ::boost::aligned_storage<sizeof(T), ::boost::alignment_of<T>::value>::type x;
+} ;
+
+template<class T>
+class non_const_T_base
+{
+  protected :
+
+    non_const_T_base()
+    {
+      std::memset(&x, 0, sizeof(x));
+      new (&x) T();
+    }
+
+    ~non_const_T_base() { get().T::~T(); }
+
+    T & get() const
+    { 
+      void * ptr = &x;
+      return *static_cast<T*>(ptr);
+    }
+
+  private :
+    mutable typename ::boost::aligned_storage<sizeof(T), ::boost::alignment_of<T>::value>::type x;
+} ;
+
+#else
+
 namespace boost {
 
 namespace vinit_detail {
@@ -23,20 +93,26 @@ class const_T_base
   protected :
 
    const_T_base() : x() {}
+   T & get() const { return x; }
 
+  private :
    T x ;
 } ;
 
 template<class T>
-struct non_const_T_base
+class non_const_T_base
 {
   protected :
 
    non_const_T_base() : x() {}
+   T & get() const { return x; }
 
+  private :
    mutable T x ;
 } ;
 
+#endif
+
 template<class T>
 struct select_base
 {
@@ -57,9 +133,9 @@ class value_initialized : private vinit_detail::select_base<T>::type
 
     value_initialized() {}
 
-    operator T&() const { return this->x ; }
+    operator T&() const { return this->get(); }
 
-    T& data() const { return this->x ; }
+    T& data() const { return this->get(); }
 
 } ;