More fixed links.

[SVN r43279]

base_from_member.html

@@ -334,7 +334,7 @@ with the exact pointer type used in <code>switcher</code>'s constructor.</p>
 <h3><a name="contributors">Contributors</a></h3>
 
 <dl>
-	<dt><a href="../../people/ed_brey.htm">Ed Brey</a>
+	<dt><a href="http://www.boost.org/people/ed_brey.htm">Ed Brey</a>
 	<dd>Suggested some interface changes.
 
 	<dt><a href="http://www.moocat.org">R. Samuel Klatchko</a> (<a
@@ -343,7 +343,7 @@ with the exact pointer type used in <code>switcher</code>'s constructor.</p>
 	<dd>Invented the idiom of how to use a class member for initializing
 		a base class.
 
-	<dt><a href="../../people/dietmar_kuehl.htm">Dietmar Kuehl</a>
+	<dt><a href="http://www.boost.org/people/dietmar_kuehl.htm">Dietmar Kuehl</a>
 	<dd>Popularized the base-from-member idiom in his
 		<a href="http://www.informatik.uni-konstanz.de/~kuehl/c++/iostream/">IOStream
 		example classes</a>.
@@ -353,7 +353,7 @@ with the exact pointer type used in <code>switcher</code>'s constructor.</p>
 		can be controlled and automated with macros.  The implementation uses
 		the <a href="../preprocessor/index.html">Preprocessor library</a>.
 
-	<dt><a href="../../people/daryle_walker.html">Daryle Walker</a>
+	<dt><a href="http://www.boost.org/people/daryle_walker.html">Daryle Walker</a>
 	<dd>Started the library.  Contributed the test file <cite><a
 		href="base_from_member_test.cpp">base_from_member_test.cpp</a></cite>.
 </dl>

generator_iterator.htm

@@ -153,7 +153,7 @@ int main()
   <!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan -->05 December, 2006<!--webbot bot="Timestamp" endspan i-checksum="38516" --></p>
 
   <p><i>Copyright &copy; 2001 <a href=
-  "../../people/jens_maurer.htm">Jens Maurer</a></i></p>
+  "http://www.boost.org/people/jens_maurer.htm">Jens Maurer</a></i></p>
 
   <p><i>Distributed under the Boost Software License, Version 1.0. (See
   accompanying file <a href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or

include/boost/utility/result_of.hpp

@@ -10,9 +10,10 @@
 #define BOOST_RESULT_OF_HPP
 
 #include <boost/config.hpp>
-#include <boost/type_traits/ice.hpp>
-#include <boost/type.hpp>
-#include <boost/preprocessor.hpp>
+#include <boost/preprocessor/iteration/iterate.hpp> 
+#include <boost/preprocessor/punctuation/comma_if.hpp> 
+#include <boost/preprocessor/repetition/enum_params.hpp> 
+#include <boost/preprocessor/repetition/enum_shifted_params.hpp> 
 #include <boost/detail/workaround.hpp>
 #include <boost/mpl/has_xxx.hpp>
 #include <boost/mpl/if.hpp>

include/boost/utility/value_init.hpp

@@ -1,109 +1,98 @@
-// (C) Copyright 2002-2007, Fernando Luis Cacciola Carballal.
+// (C) Copyright 2002-2008, 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
-// 16 Nov 2007 (Refactoring: removed private base classes) Fernando Cacciola, Niels Dekker
+// 30 Jan 2008 (Worked around compiler bugs, added initialized_value) Fernando Cacciola, Niels Dekker
 //
 #ifndef BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP
 #define BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP
 
-#include <boost/detail/select_type.hpp>
-#include <boost/type_traits/cv_traits.hpp>
-#include <boost/detail/workaround.hpp>
-
-// 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:
-#if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1500))
-#  define BOOST_UTILITY_VALUE_INIT_WORKAROUND
-#endif
-
-#ifdef BOOST_UTILITY_VALUE_INIT_WORKAROUND
+// Note: The implementation of boost::value_initialized had to deal with the
+// fact that various compilers haven't fully implemented value-initialization.
+// The constructor of boost::value_initialized<T> works around these compiler
+// issues, by clearing the bytes of T, before constructing the T object it
+// contains. More details on these issues are at libs/utility/value_init.htm
 
 #include <boost/aligned_storage.hpp>
+#include <boost/detail/workaround.hpp>
+#include <boost/type_traits/cv_traits.hpp>
 #include <boost/type_traits/alignment_of.hpp>
 #include <cstring>
 #include <new>
 
-#ifdef BOOST_MSVC
-#pragma warning(push)
-#if _MSC_VER >= 1310
-// When using MSVC 7.1 or higher, placement new, "new (&x) T()", may trigger warning C4345:
-// "behavior change: an object of POD type constructed with an initializer of the form ()
-// will be default-initialized".  There is no need to worry about this, though.
-#pragma warning(disable: 4345)
-#endif
-#endif
-
 namespace boost {
 
 template<class T>
 class value_initialized
 {
   private :
-    mutable typename ::boost::aligned_storage<sizeof(T), ::boost::alignment_of<T>::value>::type x;
+    struct wrapper
+    {
+#if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x592))
+      typename
+#endif 
+      remove_const<T>::type data;
+    };
+
+    mutable
+#if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x592))
+      typename
+#endif 
+      aligned_storage<sizeof(wrapper), alignment_of<wrapper>::value>::type x;
+
+    wrapper * wrapper_address() const
+    {
+      return static_cast<wrapper *>( static_cast<void*>(&x));
+    }
 
   public :
 
     value_initialized()
     {
       std::memset(&x, 0, sizeof(x));
-      new (&x) T();
+#ifdef BOOST_MSVC
+#pragma warning(push)
+#if _MSC_VER >= 1310
+// When using MSVC 7.1 or higher, the following placement new expression may trigger warning C4345:
+// "behavior change: an object of POD type constructed with an initializer of the form ()
+// will be default-initialized".  It is safe to ignore this warning when using value_initialized.
+#pragma warning(disable: 4345)
+#endif
+#endif
+      new (wrapper_address()) wrapper();
+#ifdef BOOST_MSVC
+#pragma warning(pop)
+#endif
+    }
+
+    value_initialized(value_initialized const & arg)
+    {
+      new (wrapper_address()) wrapper( static_cast<wrapper const &>(*(arg.wrapper_address())));
+    }
+
+    value_initialized & operator=(value_initialized const & arg)
+    {
+      this->data() = static_cast<T const &>( arg.data() );
+      return *this;
     }
 
     ~value_initialized()
     {
-      void * ptr = &x; 
-      static_cast<T*>(ptr)->T::~T(); 
+      wrapper_address()->wrapper::~wrapper();
     }
 
     T& data() const
     {
-      void * ptr = &x;
-      return *static_cast<T*>(ptr);
+      return wrapper_address()->data;
     }
 
     operator T&() const { return this->data(); }
 
 } ;
 
-#ifdef BOOST_MSVC
-// Restores the state of warning C4345.
-#pragma warning(pop)
-#endif
-
-#else
-
-namespace boost {
-
-template<class T>
-class value_initialized
-{
-  public :
-
-    value_initialized() : x() {}
-
-    T& data() const { return x; }
-
-    operator T&() const { return this->data(); }
-
-    mutable
-#if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
-    typename 
-#endif
-    ::boost::remove_const<T>::type x ;
-
-} ;
-#endif
-
 
 
 template<class T>
@@ -117,6 +106,18 @@ T& get ( value_initialized<T>& x )
   return x.data() ;
 }
 
+
+class initialized_value
+{
+  public :
+    
+    template <class T> operator T() const
+    {
+      return get( value_initialized<T>() );
+    }
+};
+
+
 } // namespace boost
 
 

operators.htm

@@ -2029,13 +2029,13 @@ public:
     <h2><a name="contributors">Contributors</a></h2>
 
     <dl>
-      <dt><a href="../../people/dave_abrahams.htm">Dave Abrahams</a></dt>
+      <dt><a href="http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a></dt>
 
       <dd>Started the library and contributed the arithmetic operators in
       <cite><a href=
       "../../boost/operators.hpp">boost/operators.hpp</a></cite>.</dd>
 
-      <dt><a href="../../people/jeremy_siek.htm">Jeremy Siek</a></dt>
+      <dt><a href="http://www.boost.org/people/jeremy_siek.htm">Jeremy Siek</a></dt>
 
       <dd>Contributed the <a href="#deref">dereference operators and iterator
       helpers</a> in <cite><a href=
@@ -2043,19 +2043,19 @@ public:
       contributed <cite><a href=
       "iterators_test.cpp">iterators_test.cpp</a></cite>.</dd>
 
-      <dt><a href="../../people/aleksey_gurtovoy.htm">Aleksey
+      <dt><a href="http://www.boost.org/people/aleksey_gurtovoy.htm">Aleksey
       Gurtovoy</a></dt>
 
       <dd>Contributed the code to support <a href="#chaining">base class
       chaining</a> while remaining backward-compatible with old versions of
       the library.</dd>
 
-      <dt><a href="../../people/beman_dawes.html">Beman Dawes</a></dt>
+      <dt><a href="http://www.boost.org/people/beman_dawes.html">Beman Dawes</a></dt>
 
       <dd>Contributed <cite><a href=
       "operators_test.cpp">operators_test.cpp</a></cite>.</dd>
 
-      <dt><a href="../../people/daryle_walker.html">Daryle Walker</a></dt>
+      <dt><a href="http://www.boost.org/people/daryle_walker.html">Daryle Walker</a></dt>
 
       <dd>Contributed classes for the shift operators, equivalence, partial
       ordering, and arithmetic conversions. Added the grouped operator

shared_container_iterator.html

@@ -315,7 +315,7 @@ Last modified: Mon Aug 11 11:27:03 EST 2003
 <p><EFBFBD> Copyright 2003 The Trustees of Indiana University.
  Use, modification and distribution is subject to 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)</p>
+ http://www.boost.org/LICENSE_1_0.txt)</p>
 
 </body>
 

utility.htm

@@ -68,7 +68,7 @@ const std::list&lt;T&gt;::iterator next = boost::next(prev, 2);</pre>
                 <p>The distance from the given iterator should be supplied as an absolute value. For
 			example, the iterator four iterators prior to the given iterator <code>p</code>
 			may be obtained by <code>prior(p, 4)</code>.</p>
-		<p>Contributed by <a href="../../people/dave_abrahams.htm">Dave Abrahams</a>.  Two-argument versions by Daniel Walker.</p>
+		<p>Contributed by <a href="http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a>.  Two-argument versions by Daniel Walker.</p>
 		<h2><a name="Class_noncopyable">Class noncopyable</a></h2>
 		<p>Class <strong>noncopyable</strong> is a base class.&nbsp; Derive your own class 
 			from <strong>noncopyable</strong> when you want to prohibit copy construction 
@@ -89,7 +89,7 @@ const std::list&lt;T&gt;::iterator next = boost::next(prev, 2);</pre>
 			to verify class <b>noncopyable</b> works as expected. It has have been run 
 			successfully under GCC 2.95, Metrowerks CodeWarrior 5.0, and Microsoft Visual 
 			C++ 6.0 sp 3.</p>
-		<p>Contributed by <a href="../../people/dave_abrahams.htm">Dave Abrahams</a>.</p>
+		<p>Contributed by <a href="http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a>.</p>
 		<h3>Example</h3>
 		<blockquote>
 			<pre>// inside one of your own headers ...

value_init.htm

@@ -17,11 +17,13 @@
 <dl>
   <dt><a href="#rationale">Rationale</a></dt>
   <dt><a href="#intro">Introduction</a></dt>
+  <dt><a href="#details">Details</a></dt>
 </dl>
                    
 <ul>
           <li><a href="#valueinit">value-initialization</a></li>
           <li><a href="#valueinitsyn">value-initialization syntax</a></li>
+          <li><a href="#compiler_issues">compiler issues</a></li>
                    
 </ul>
                    
@@ -30,7 +32,8 @@
 </dl>
                    
 <ul>
-          <li><a href="#val_init"><code>value_initialized&lt;&gt;</code></a></li>
+          <li><a href="#val_init"><code>template class value_initialized&lt;T&gt;</code></a></li>
+          <li><a href="#initialized_value"><code>class initialized_value</code></a></li>
                    
 </ul>
               <a href="#acknowledgements">Acknowledgements</a><br>
@@ -44,24 +47,104 @@
 for    initialization. Depending on the type, the value of a newly constructed
   object  can be zero-initialized (logically 0), default-constructed (using
   the default constructor), or indeterminate. When writing generic code,
-this   problem must be addressed. <code>value_initialized</code> provides
+this  problem must be addressed. The template <code>value_initialized</code> provides
 a solution   with consistent syntax for value   initialization of scalar,
-union and class   types. <br>
+union and class   types.
+Moreover, <code>value_initialized</code> offers a workaround to various
+compiler issues regarding value-initialization.
+
+Furthermore a convenience class, <code>initialized_value</code> is provided,
+to avoid repeating the type name when retrieving the value from a
+<code>value_initialized&lt;T&gt;</code> object.
+<br>
   </p>
         
 <h2><a name="intro"></a>Introduction</h2>
      
-<p>The C++ standard [<a href="#references">1</a>] contains the definitions 
+<p>
+There are various ways to initialize a variable, in C++. The following
+declarations all <em>may</em> have a local variable initialized to its default
+value:
+<pre>
+  T1 var1;
+  T2 var2 = 0;
+  T3 var3 = {};
+  T4 var4 = T4();
+</pre> 
+Unfortunately, whether or not any of those declarations correctly
+initialize the variable very much depends on its type. The first
+declaration is valid for any <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html">
+DefaultConstructible</a> type (by definition).
+However, it does not always do an initialization!
+It correctly initializes the variable when it's an instance of a
+class, and the author of the class has provided a proper default
+constructor. On the other hand, the value of <code>var1</code> is <em>indeterminate</em> when
+its type is an arithmetic type, like <code>int</code>, <code>float</code>, or <code>char</code>.
+An arithmetic variable
+is of course initialized properly by the second declaration, <code>T2
+var2 = 0</code>. But this initialization form usually won't work for a
+class type (unless the class was especially written to support being
+initialized that way). The third form,  <code>T3 var3 = {}</code>
+initializes an aggregate, typically a "C-style" <code>struct</code> or a "C-style" array.
+However, the syntax is not allowed for a class that has an explicitly declared
+constructor.  (But watch out for an upcoming C++ language change, 
+by Bjarne Stroustrup et al [<a href="#references">1</a>]!)
+The fourth form is the most generic form of them, as it
+can be used to initialize arithmetic types, class types, aggregates, pointers, and
+other types. The declaration,  <code>T4 var4 = T4()</code>, should be read
+as follows: First a temporary object is created, by <code>T4()</code>.
+This object is <a href="#valueinit">value-initialized</a>. Next the temporary
+object is copied to the named variable, <code>var4</code>. Afterwards, the temporary
+is destroyed. While the copying and the destruction are likely to
+be optimized away, C++ still requires the type <code>T4</code> to be
+<a href="CopyConstructible.html">CopyConstructible</a>.
+(So <code>T4</code> needs to be <em>both</em> DefaultConstructible <em>and</em> CopyConstructible.) 
+A class may not be CopyConstructible, for example because it may have a
+private and undefined copy constructor,
+or because it may be derived from <a href="utility.htm#Class_noncopyable">boost::noncopyable</a>.
+Scott Meyers [<a href="#references">2</a>] explains why a class would be defined like that.
+</p>
+<p>
+There is another, less obvious disadvantage to the fourth form, <code>T4 var4 = T4()</code>:
+It suffers from various  <a href="#compiler_issues">compiler issues</a>, causing
+a variable to be left uninitialized in some compiler specific cases.
+</p>
+<p>
+The template <a href="#val_init"><code>value_initialized</code></a>
+offers a generic way to initialize
+an object, like <code>T4 var4 = T4()</code>, but without requiring its type
+to be CopyConstructible. And it offers a workaround to those compiler issues
+regarding value-initialization as well! It allows getting an initialized
+variable of any type; it <em>only</em> requires the type to be DefaultConstructible.
+A properly <em>value-initialized</em> object of type <code>T</code> is
+constructed by the following declaration:
+<pre>
+  value_initialized&lt;T&gt; var;
+</pre>
+</p>
+<p>
+The convenience class <a href="#initialized_value"><code>initialized_value</code></a>
+allows value-initializing a variable as follows:
+<pre>
+  T var = initialized_value();
+</pre>
+This form of initialization is also very similar to <code>T4 var4 = T4()</code>,
+but robust against the aforementioned compiler issues.
+
+</p>
+
+<h2><a name="details"></a>Details</h2>
+<p>The C++ standard [<a href="#references">3</a>] contains the definitions 
     of <code>zero-initialization</code> and <code>default-initialization</code>.
      Informally, zero-initialization means that the object is given the initial
      value 0 (converted to the type) and default-initialization means that
- POD   [<a href="#references">2</a>] types are zero-initialized, while class
+ POD   [<a href="#references">4</a>] types are zero-initialized, while non-POD class
  types   are initialized with their corresponding default constructors. A
 <i>declaration</i>   can contain an <i>initializer</i>, which specifies the
 object's initial value.  The initializer can be just '()', which states that
-the object shall be default-initialized  (but see below). However, if a <i>declaration</i> 
+the object shall be value-initialized  (but see below). However, if a <i>declaration</i> 
   has no <i>initializer</i>  and it is of a non-<code>const</code>, non-<code>static</code> 
-   POD type, the initial value is indeterminate:<cite>(see &sect;8.5 for the
+   POD type, the initial value is indeterminate: <cite>(see &sect;8.5, [dcl.init], for the
    accurate definitions).</cite></p>
                    
 <pre>int x ; // no initializer. x value is indeterminate.<br>std::string s ; // no initializer, s is default-constructed.<br><br>int y = int() ; <br>// y is initialized using copy-initialization<br>// but the temporary uses an empty set of parentheses as the initializer,<br>// so it is default-constructed.<br>// A default constructed POD type is zero-initialized,<br>// therefore, y == 0.<br><br>void foo ( std::string ) ;<br>foo ( std::string() ) ; <br>// the temporary string is default constructed <br>// as indicated by the initializer ()  </pre>
@@ -87,14 +170,11 @@ the object shall be default-initialized  (but see below). However, if a <i>decla
 <p>In order to specify value-initialization of an object we need to use the
      empty-set initializer: (). </p>
                    
-<p><i>(but recall that the current C++ Standard states that '()' invokes default-initialization,
-not value-initialization)</i></p>
-                   
 <p>As before, a declaration with no intializer specifies default-initialization, 
     and a declaration with a non-empty initializer specifies copy (=xxx) or
   direct  (xxx) initialization. </p>
                    
-<pre>template&lt;class T&gt; void eat(T);<br>int x ; // indeterminate initial value.<br>std::string s; // default-initialized.<br>eat ( int() ) ; // value-initialized<br>eat ( std::string() ) ; // value-initialied</pre>
+<pre>template&lt;class T&gt; void eat(T);<br>int x ; // indeterminate initial value.<br>std::string s; // default-initialized.<br>eat ( int() ) ; // value-initialized<br>eat ( std::string() ) ; // value-initialized</pre>
                     
 <h4><a name="valueinitsyn">value-initialization</a> syntax</h4>
                    
@@ -102,7 +182,7 @@ not value-initialization)</i></p>
 parentheses is not permitted by the syntax of initializers because it is
 parsed as the declaration of a function taking no arguments: </p>
                    
-<pre>int x() ; // declares function int(*)()<br>int y ( int() ) ; // decalares function int(*)( int(*)() )</pre>
+<pre>int x() ; // declares function int(*)()</pre>
                     
 <p>Thus, the empty () must be put in some other initialization context.</p>
                    
@@ -124,8 +204,50 @@ data member:</p>
                    
 <pre>template&lt;class T&gt; <br>struct W <br>{<br>  // value-initialization of 'data' here.<br>  W() : data() {}<br>  T data ;<br>} ;<br>W&lt;int&gt; w ;<br>// w.data is value-initialized for any type. </pre>
                     
-<p><code>This is the solution supplied by the value_initialized&lt;&gt; template
-     class.</code></p>
+<p>This is the solution as it was supplied by earlier versions of the
+<code>value_initialized&lt;T&gt;</code> template
+     class. Unfortunately this approach suffered from various compiler issues.</p>
+		 
+<h4><a name="compiler_issues">compiler issues</a> </h4>
+
+Various compilers haven't yet fully implemented value-initialization.
+So when an object should be <em>value-initialized</em> (according to the C++ Standard),
+it <em>may</em> in practice still be left uninitialized, because of those
+compiler issues! It's hard to make a general statement on what those issues
+are like, because they depend on the compiler you are using, its version number,
+and the type of object you would like to have value-initialized.
+Compilers usually support value-initialization for built-in types properly.
+But objects of user-defined types that involve <em>aggregates</em> may <em>in some cases</em>
+be partially, or even entirely left uninitialized, when they should be value-initialized.
+</p>
+<p>
+We have encountered issues regarding value-initialization on compilers by
+Microsoft, Sun, Borland, and GNU. Here is a list of bug reports on those issues:
+<table summary="Compiler bug reports regarding value-initialization" border="0" cellpadding="7" cellspacing="1" >
+<tr><td>
+<a href="https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=100744">
+Microsoft Feedback ID 100744 - Value-initialization in new-expression</a>
+<br>Reported by Pavel Kuznetsov (MetaCommunications Engineering), 2005-07-28
+<br>
+<a href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30111">
+GCC Bug 30111 - Value-initialization of POD base class doesn't initialize members</a>
+<br>Reported by Jonathan Wakely, 2006-12-07 
+<br>
+<a href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33916">
+GCC Bug 33916 - Default constructor fails to initialize array members</a>
+<br>Reported by Michael Elizabeth Chastain, 2007-10-26
+<br>
+<a href="http://qc.codegear.com/wc/qcmain.aspx?d=51854">
+Borland Report 51854 - Value-initialization: POD struct should be zero-initialized</a>
+<br>Reported by Niels Dekker (LKEB, Leiden University Medical Center), 2007-09-11
+<br>
+</td></tr></table>
+</p><p>
+New versions of <code>value_initialized</code>
+(Boost release version 1.35 or higher)
+offer a workaround to these issues: <code>value_initialized</code> will now clear
+its internal data, prior to constructing the object that it contains.
+</p>
                    
 <h2><a name="types"></a>Types</h2>
                    
@@ -189,25 +311,72 @@ wrapped object from within a constant wrapper can be avoided if access to
 the wrapped object is always performed with the <code>get()</code> idiom:</p>
                    
 <pre>value_initialized&lt;int&gt; x ;<br>get(x) = 1 ; // OK<br><br>value_initialized&lt;int const&gt; cx ;<br>get(x) = 1 ; // ERROR: Cannot modify a const object<br><br>value_initialized&lt;int&gt; const x_c ;<br>get(x_c) = 1 ; // ERROR: Cannot modify a const object<br><br>value_initialized&lt;int const&gt; const cx_c ;<br>get(cx_c) = 1 ; // ERROR: Cannot modify a const object<br></pre>
+
+<h2><a name="initialized_value"><code>class initialized_value</code></a></h2>
+
+<pre>
+namespace boost {
+class initialized_value
+{
+  public :
+    template &lt;class T&gt; operator T() const ;
+};
+} // namespace boost
+</pre>
+
+The class <code>initialized_value</code> provides a convenient way to get
+an initialized value: its conversion operator provides an appropriate
+<em>value-initialized</em> object for any CopyConstructible type.
+
+Suppose you need to have an initialized variable of type <code>T</code>.
+You could do it as follows:
+<pre>
+  T var = T();
+</pre>
+But as mentioned before, this form suffers from various compiler issues.
+The template <code>value_initialized</code> offers a workaround:
+<pre>
+  T var = get( value_initialized&lt;T&gt;() );
+</pre>
+Unfortunately both forms repeat the type name, which
+is rather short now (<code>T</code>), but could of course be 
+more like <code>Namespace::Template&lt;Arg&gt;::Type</code>.
+Instead, one could use <code>initialized_value</code> as follows:
+<pre>
+  T var = initialized_value();
+</pre>
                     
 <h3><a name="references">References</a></h3>
-          [1] The C++ Standard, ISO/IEC 14882:98 <br>
-          [2] Plain Old Data           
+          [1] Bjarne Stroustrup, Gabriel Dos Reis, and J. Stephen Adamczyk wrote
+          various papers, proposing to extend the support for brace-enclosed <em>initializer lists</em>
+          in the next version of C++.
+          This would allow a variable <code>var</code> of any DefaultConstructible type
+          <code>T</code> to be <em>value-initialized</em> by doing <code>T var = {}</code>.
+          The papers are listed at Bjarne's web page,
+          <a href="http://www.research.att.com/~bs/WG21.html">My C++ Standards committee papers</a>  <br> 
+          [2] Scott Meyers, Effective C++, Third Edition, item 6,
+          <em>Explicitly disallow the use of compiler-generated functions you do not want</em>, 
+          <a href="http://www.aristeia.com/books.html">Scott Meyers: Books and CDs</a>  <br>
+          [3] The C++ Standard, Second edition (2003), ISO/IEC 14882:2003 <br>
+          [4] POD stands for "Plain Old Data"
+
 <h3><a name="acknowledgements"></a>Acknowledgements</h3>
      value_initialized was developed by Fernando Cacciola, with help and
 suggestions from David Abrahams and Darin Adler.<br>
-Special thanks to Bj<EFBFBD>rn Karlsson who carefully edited and completed this documentation.
-                   
+Special thanks to Bj&ouml;rn Karlsson who carefully edited and completed this documentation.
+                 
+<p>value_initialized was reimplemented by Fernando Cacciola and Niels Dekker
+for Boost release version 1.35 (2008), offering a workaround to various compiler issues.
+     </p>
 <p>Developed by <a href="mailto:fernando_cacciola@hotmail.com">Fernando Cacciola</a>,
      the latest version of this file can be found at <a
- href="http://www.boost.org">www.boost.org</a>, and the boost discussion list
-at <a href="http://www.yahoogroups.com/list/boost">www.yahoogroups.com/list/boost</a>.
+ href="http://www.boost.org">www.boost.org</a>.
      </p>
                     
 <hr>          
-<p>Revised 19 September 2002</p>
+<p>Revised 16 January 2008</p>
                    
-<p>&copy; Copyright Fernando Cacciola, 2002.</p>
+<p>&copy; Copyright Fernando Cacciola, 2002, 2008.</p>
                    
 <p>Distributed under the Boost Software License, Version 1.0. See
 <a href="http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a></p>

value_init_test.cpp

@@ -1,4 +1,4 @@
-// Copyright 2002, Fernando Luis Cacciola Carballal.
+// Copyright 2002-2008, Fernando Luis Cacciola Carballal.
 //
 // Distributed under the Boost Software License, Version 1.0. (See
 // accompanying file LICENSE_1_0.txt or copy at
@@ -6,12 +6,15 @@
 //
 // Test program for "boost/utility/value_init.hpp"
 //
-// Initial: 21 Agu 2002
+// 21 Ago 2002 (Created) Fernando Cacciola
+// 19 Jan 2008 (Added tests regarding compiler issues and initialized_value) Fernando Cacciola, Niels Dekker
 
+#include <cstring>  // For memcmp.
 #include <iostream>
 #include <string>
 
 #include "boost/utility/value_init.hpp"
+#include <boost/shared_ptr.hpp>
 
 #ifdef __BORLANDC__
 #pragma hdrstop
@@ -49,7 +52,7 @@ struct NonPODBase
 struct NonPOD : NonPODBase
 {
   NonPOD () : id() {}
-  NonPOD ( std::string const& id_) : id(id_) {}
+  explicit NonPOD ( std::string const& id_) : id(id_) {}
 
   friend std::ostream& operator << ( std::ostream& os, NonPOD const& npod )
     { return os << '(' << npod.id << ')' ; }
@@ -152,6 +155,57 @@ struct AggregatePODStructWrapper
 bool operator == ( AggregatePODStructWrapper const& lhs, AggregatePODStructWrapper const& rhs )
 { return lhs.dataMember == rhs.dataMember ; }
 
+typedef unsigned char ArrayOfBytes[256];
+
+
+//
+// A struct that allows testing whether the appropriate copy functions are called.
+//
+struct CopyFunctionCallTester
+{
+  bool is_copy_constructed;
+  bool is_assignment_called;
+
+  CopyFunctionCallTester()
+  : is_copy_constructed(false), is_assignment_called(false) {}
+
+  CopyFunctionCallTester(const CopyFunctionCallTester & )
+  : is_copy_constructed(true), is_assignment_called(false) {}
+
+  CopyFunctionCallTester & operator=(const CopyFunctionCallTester & )
+  {
+    is_assignment_called = true ;
+    return *this ;
+  }
+};
+
+
+template<class T>
+void check_initialized_value ( T const& y )
+{
+  T initializedValue = boost::initialized_value() ;
+  BOOST_CHECK ( y == initializedValue ) ;
+}
+
+#ifdef  __BORLANDC__
+#if __BORLANDC__ == 0x582
+void check_initialized_value( NonPOD const& )
+{
+  // The initialized_value check is skipped for Borland 5.82
+  // and this type (NonPOD), because the following statement
+  // won't compile on this particular compiler version:
+  //   NonPOD initializedValue = boost::initialized_value() ;
+  //
+  // This is caused by a compiler bug, that is fixed with a newer version
+  // of the Borland compiler.  The Release Notes for Delphi(R) 2007 for
+  // Win32(R) and C++Builder(R) 2007 (http://dn.codegear.com/article/36575)
+  // say about similar statements:
+  //   both of these statements now compile but under 5.82 got the error:
+  //   Error E2015: Ambiguity between 'V::V(const A &)' and 'V::V(const V &)'
+}
+#endif
+#endif
+
 //
 // This test function tests boost::value_initialized<T> for a specific type T.
 // The first argument (y) is assumed have the value of a value-initialized object.
@@ -161,9 +215,13 @@ template<class T>
 bool test ( T const& y, T const& z )
 {
   const boost::unit_test::counter_t counter_before_test = boost::minimal_test::errors_counter();
+
+  check_initialized_value(y);
+
   boost::value_initialized<T> x ;
   BOOST_CHECK ( y == x ) ;
   BOOST_CHECK ( y == boost::get(x) ) ;
+
   static_cast<T&>(x) = z ;
   boost::get(x) = z ;
   BOOST_CHECK ( x == z ) ;
@@ -175,6 +233,16 @@ bool test ( T const& y, T const& z )
   x_c_ref = z ;
   BOOST_CHECK ( x_c == z ) ;
 
+  boost::value_initialized<T> const copy1 = x;
+  BOOST_CHECK ( boost::get(copy1) == boost::get(x) ) ;
+
+  boost::value_initialized<T> copy2;
+  copy2 = x;
+  BOOST_CHECK ( boost::get(copy2) == boost::get(x) ) ;
+  
+  boost::shared_ptr<boost::value_initialized<T> > ptr( new boost::value_initialized<T> );
+  BOOST_CHECK ( y == *ptr ) ;
+
 #if !BOOST_WORKAROUND(BOOST_MSVC, < 1300)
   boost::value_initialized<T const> cx ;
   BOOST_CHECK ( y == cx ) ;
@@ -184,6 +252,7 @@ bool test ( T const& y, T const& z )
   BOOST_CHECK ( y == cx_c ) ;
   BOOST_CHECK ( y == boost::get(cx_c) ) ;
 #endif
+
   return boost::minimal_test::errors_counter() == counter_before_test ;
 }
 
@@ -232,8 +301,26 @@ int test_main(int, char **)
   aggregatePODStructWrapper1.dataMember = nonZeroInitializedAggregatePODStruct;
   BOOST_CHECK ( test(aggregatePODStructWrapper0, aggregatePODStructWrapper1) );
 
+  ArrayOfBytes zeroInitializedArrayOfBytes = { 0 };
+  boost::value_initialized<ArrayOfBytes> valueInitializedArrayOfBytes;
+  BOOST_CHECK (std::memcmp(get(valueInitializedArrayOfBytes), zeroInitializedArrayOfBytes, sizeof(ArrayOfBytes)) == 0);
+
+  boost::value_initialized<CopyFunctionCallTester> copyFunctionCallTester1;
+  BOOST_CHECK ( ! get(copyFunctionCallTester1).is_copy_constructed);
+  BOOST_CHECK ( ! get(copyFunctionCallTester1).is_assignment_called);
+
+  boost::value_initialized<CopyFunctionCallTester> copyFunctionCallTester2 = boost::value_initialized<CopyFunctionCallTester>(copyFunctionCallTester1);
+  BOOST_CHECK ( get(copyFunctionCallTester2).is_copy_constructed);
+  BOOST_CHECK ( ! get(copyFunctionCallTester2).is_assignment_called);
+
+  boost::value_initialized<CopyFunctionCallTester> copyFunctionCallTester3;
+  copyFunctionCallTester3 = boost::value_initialized<CopyFunctionCallTester>(copyFunctionCallTester1);
+  BOOST_CHECK ( ! get(copyFunctionCallTester3).is_copy_constructed);
+  BOOST_CHECK ( get(copyFunctionCallTester3).is_assignment_called);
+
   return 0;
 }
 
 
 unsigned int expected_failures = 0;
+