Merge documentation fix from 'develop'

Conflicts:
	doc/html/index.html

doc/00_optional.qbk

@@ -83,7 +83,7 @@ This is how you solve it with `boost::optional`:
 [include 14_io.qbk]
 [include 15_optional_references.qbk]
 [include 16_in_place_factories.qbk]
-[include 17_optional_bool.qbk]
+[include 17_gotchas.qbk]
 [include 18_exception_safety.qbk]
 [include 19_type_requirements.qbk]
 [include 1A_on_performance.qbk]

doc/17_gotchas.qbk

@@ -0,0 +1,111 @@
+[section Gotchas]
+
+[section A note about optional<bool>]
+
+`optional<bool>` should be used with special caution and consideration.
+
+First, it is functionally similar to a tristate boolean (false, maybe, true)
+—such as __BOOST_TRIBOOL__— except that in a tristate boolean, the maybe state
+[_represents a valid value], unlike the corresponding state of an uninitialized
+`optional<bool>`.
+It should be carefully considered if an `optional<bool>` instead of a `tribool`
+is really needed.
+
+Second, although `optional<>` provides a contextual conversion to `bool` in C++11,
+ this falls back to an implicit conversion on older compilers. This conversion refers
+ to the initialization state and not to the contained value. Using `optional<bool>`
+ can lead to subtle errors due to the implicit `bool` conversion:
+
+    void foo ( bool v ) ;
+    void bar()
+    {
+        optional<bool> v = try();
+
+        // The following intended to pass the value of 'v' to foo():
+        foo(v);
+        // But instead, the initialization state is passed
+        // due to a typo: it should have been foo(*v).
+    }
+
+The only implicit conversion is to `bool`, and it is safe in the sense that
+typical integral promotions don't apply (i.e. if `foo()` takes an `int`
+instead, it won't compile).
+
+Third, mixed comparisons with `bool` work differently than similar mixed comparisons between pointers and `bool`, so the results might surprise you:
+
+    optional<bool> oEmpty(none), oTrue(true), oFalse(false);
+    
+    if (oEmpty == none);  // renders true
+    if (oEmpty == false); // renders false!
+    if (oEmpty == true);  // renders false!
+     
+    if (oFalse == none);  // renders false
+    if (oFalse == false); // renders true!
+    if (oFalse == true);  // renders false
+    
+    if (oTrue == none);   // renders false
+    if (oTrue == false);  // renders false
+    if (oTrue == true);   // renders true
+
+In other words, for `optional<>`, the following assertion does not hold:
+
+    assert((opt == false) == (!opt));
+[endsect]
+
+[section Moved-from `optional`]
+
+When an optional object that contains a value is moved from (is a source of move constructor or assignment) it still contains a value and its contained value is left in a moved-from state. This can be illustrated with the following example.
+
+    optional<std::unique_ptr<int>> opi {std::make_unique<int>(1)};
+    optional<std::unique_ptr<int>> opj = std::move(opi);
+    assert (opi);
+    assert (*opi == nullptr);
+
+Quite a lot of people expect that when an object that contains a value is moved from, its contained value should be destroyed. This is not so, for performance reasons. Current semantics allow the implementation of `boost::opiotnal<T>` to be trivially copyable when `T` is trivial.
+[endsect]
+
+[section Mixed relational comparisons]
+
+Because `T` is convertible to `optional<T>` and because `opiotnal<T>` is __SGI_LESS_THAN_COMPARABLE__ when `T` is __SGI_LESS_THAN_COMPARABLE__,
+you can sometimes get an unexpected runtime result where you would rather expect a compiler error:
+
+    optional<double> Flight_plan::weight(); // sometimes no weight can be returned
+
+    bool is_aircraft_too_heavy(Flight_plan const& p)
+    {
+       return p.weight() > p.aircraft().max_weight(); // compiles!
+    }                                                 // returns false when the optional contains no value 
+
+[endsect]
+
+[section False positive with -Wmaybe-uninitialized]
+
+Sometimes on GCC compilers below version 5.1 you may get an -Wmaybe-uninitialized warning when copiling with option -02 on a perfectly valid `boost::optional` usage. For instance in this program:
+
+    #include <boost/optional.hpp>
+
+    boost::optional<int> getitem();
+
+    int main(int argc, const char *[])
+    {
+      boost::optional<int> a = getitem();
+      boost::optional<int> b;
+
+      if (argc > 0)
+        b = argc;
+
+      if (a != b)
+        return 1;
+
+      return 0;
+    }
+    
+This is a bug in the compiler. As a workaround (provided in [@http://stackoverflow.com/questions/21755206/how-to-get-around-gcc-void-b-4-may-be-used-uninitialized-in-this-funct this Stack Overflow question]) use the following way of initializing an optional containing no value:
+
+    boost::optional<int> b = boost::make_optional(false, int());
+
+This is obviously redundant, but makes the warning disappear.
+
+[endsect]
+
+[endsect]

doc/17_optional_bool.qbk

@@ -1,52 +0,0 @@
-
-[section A note about optional<bool>]
-
-`optional<bool>` should be used with special caution and consideration.
-
-First, it is functionally similar to a tristate boolean (false, maybe, true)
-—such as __BOOST_TRIBOOL__— except that in a tristate boolean, the maybe state
-[_represents a valid value], unlike the corresponding state of an uninitialized
-`optional<bool>`.
-It should be carefully considered if an `optional<bool>` instead of a `tribool`
-is really needed.
-
-Second, although `optional<>` provides a contextual conversion to `bool` in C++11,
- this falls back to an implicit conversion on older compilers. This conversion refers
- to the initialization state and not to the contained value. Using `optional<bool>`
- can lead to subtle errors due to the implicit `bool` conversion:
-
-    void foo ( bool v ) ;
-    void bar()
-    {
-        optional<bool> v = try();
-
-        // The following intended to pass the value of 'v' to foo():
-        foo(v);
-        // But instead, the initialization state is passed
-        // due to a typo: it should have been foo(*v).
-    }
-
-The only implicit conversion is to `bool`, and it is safe in the sense that
-typical integral promotions don't apply (i.e. if `foo()` takes an `int`
-instead, it won't compile).
-
-Third, mixed comparisons with `bool` work differently than similar mixed comparisons between pointers and `bool`, so the results might surprise you:
-
-    optional<bool> oEmpty(none), oTrue(true), oFalse(false);
-    
-    if (oEmpty == none);  // renders true
-    if (oEmpty == false); // renders false!
-    if (oEmpty == true);  // renders false!
-     
-    if (oFalse == none);  // renders false
-    if (oFalse == false); // renders true!
-    if (oFalse == true);  // renders false
-    
-    if (oTrue == none);   // renders false
-    if (oTrue == false);  // renders false
-    if (oTrue == true);   // renders true
-
-In other words, for `optional<>`, the following assertion does not hold:
-
-    assert((opt == false) == (!opt));
-[endsect]

doc/1A_on_performance.qbk

@@ -23,7 +23,7 @@ Given type `optional<int>`, and assuming that `sizeof(int) == 4`, we will get `s
 
 [$images/opt_align1.png]
 
-This means you can fit twice as many `int`s as `optional<int>`s into the same space of memory. Therefore, if the size of the objects is critical for your application (e.g., because you want to utilize your CPU cache in order to gain performance) and you have determined you are willing to trade the code clarity, it is recommended that you simply go with type `int` and use some 'magic value' to represent ['not-an-int].
+This means you can fit twice as many `int`s as `optional<int>`s into the same space of memory. Therefore, if the size of the objects is critical for your application (e.g., because you want to utilize your CPU cache in order to gain performance) and you have determined you are willing to trade the code clarity, it is recommended that you simply go with type `int` and use some 'magic value' to represent ['not-an-int], or use something like [@https://github.com/akrzemi1/markable `markable`] library.
 
 Even if you cannot spare any value of `int` to represent ['not-an-int] (e.g., because every value is useful, or you do want to signal ['not-an-int] explicitly), at least for `Trivial` types you should consider storing the value and the `bool` flag representing the ['null-state] separately. Consider the following class:
 

doc/27_ref_optional_synopsis.qbk

@@ -15,6 +15,12 @@
 
     namespace boost {
 
+    class in_place_init_t { /* see below */ } ; ``[link reference_in_place_init __GO_TO__]``
+    const in_place_init_t in_place_init ( /* see below */ ) ;
+    
+    class in_place_init_if_t { /*see below*/ } ; ``[link reference_in_place_init_if __GO_TO__]``
+    const in_place_init_if_t in_place_init_if ( /*see below*/ ) ;
+    
     template <class T>
     class optional ; ``[link reference_operator_template __GO_TO__]``
     
@@ -67,6 +73,26 @@
 [endsect]
 
 
+[section:header_optional_in_place_init Initialization tags]
+
+[#reference_in_place_init]
+[#reference_in_place_init_if]
+
+    namespace boost {
+
+    class in_place_init_t { /* see below */ } ;
+    const in_place_init_t in_place_init ( /* see below */ ) ;
+    
+    class in_place_init_if_t { /*see below*/ } ;
+    const in_place_init_if_t in_place_init_if ( /*see below*/ ) ;
+    
+    }
+
+Classes `in_place_init_t` and `in_place_init_if_t` are empty clsses. Their purpose is to control overload resolution in the initialization of optional objects. 
+They are empty, trivially copyable classes with disabled default constructor.  
+
+[endsect]
+
 [section:header_optional_optional_values Optional Values]
 
 [#reference_operator_template]
@@ -91,7 +117,6 @@
         
         optional ( T&& v ) ; ``[link reference_optional_constructor_move_value __GO_TO__]``
 
-        // [new in 1.34]
         optional ( bool condition, T const& v ) ; ``[link reference_optional_constructor_bool_value __GO_TO__]`` 
 
         optional ( optional const& rhs ) ; ``[link reference_optional_constructor_optional __GO_TO__]``
@@ -101,6 +126,10 @@
         template<class U> explicit optional ( optional<U> const& rhs ) ; ``[link reference_optional_constructor_other_optional __GO_TO__]``
         
         template<class U> explicit optional ( optional<U>&& rhs ) ; ``[link reference_optional_move_constructor_other_optional __GO_TO__]``
+        
+        template<class... Args> explicit optional ( in_place_init_t, Args&&... args ) ; ``[link reference_optional_in_place_init __GO_TO__]``
+        
+        template<class... Args> explicit optional ( in_place_init_if_t, bool condition, Args&&... args ) ; ``[link reference_optional_in_place_init_if __GO_TO__]``
 
         template<class InPlaceFactory> explicit optional ( InPlaceFactory const& f ) ; ``[link reference_optional_constructor_factory __GO_TO__]``
 
@@ -120,7 +149,7 @@
         
         template<class U> optional& operator = ( optional<U>&& rhs ) ; ``[link reference_optional_operator_move_equal_other_optional __GO_TO__]``
         
-        template<class... Args> void emplace ( Args...&& args ) ; ``[link reference_optional_emplace __GO_TO__]``
+        template<class... Args> void emplace ( Args&&... args ) ; ``[link reference_optional_emplace __GO_TO__]``
 
         template<class InPlaceFactory> optional& operator = ( InPlaceFactory const& f ) ; ``[link reference_optional_operator_equal_factory __GO_TO__]``
 

doc/28_ref_optional_semantics.qbk

@@ -224,6 +224,53 @@ assert( *y == 123 ) ;
 
 __SPACE__
 
+[#reference_optional_in_place_init]
+
+[: `template<class... Args> explicit optional<T>::optional( in_place_init_t, Args&&... ars );`]
+
+* [*Requires:] `is_constructible_v<T, Args&&...>` is `true`.
+* [*Effect:] Initializes the contained value as if direct-non-list-initializing an object of type `T` with the
+arguments `std::forward<Args>(args)...`.
+* [*Postconditions:] `*this` is initialized.
+* [*Throws:] Any exception thrown by the selected constructor of `T`.
+* [*Notes: ] `T` need not be __MOVE_CONSTRUCTIBLE__. On compilers that do not suppor variadic templates or rvalue references, this constuctor is available in limited functionality. For details [link optional_emplace_workaround see here]. 
+
+* [*Example:]
+``
+// creates an std::mutex using its default constructor
+optional<std::mutex> om {in_place_init};
+assert (om);
+
+// creates a unique_lock by calling unique_lock(*om, std::defer_lock)
+optional<std::unique_lock<std::mutex>> ol {in_place_init, *om, std::defer_lock};
+assert (ol);
+assert (!ol->owns_lock());
+``
+
+__SPACE__
+
+[#reference_optional_in_place_init_if]
+
+[: `template<class... Args> explicit optional<T>::optional( in_place_init_if_t, bool condition, Args&&... ars );`]
+
+* [*Requires:] `is_constructible_v<T, Args&&...>` is `true`.
+* [*Effect:] If `condition` is `true`, initializes the contained value as if direct-non-list-initializing an object of type `T` with the arguments `std::forward<Args>(args)...`.
+* [*Postconditions:] `bool(*this) == condition`.
+* [*Throws:] Any exception thrown by the selected constructor of `T`.
+* [*Notes: ] `T` need not be __MOVE_CONSTRUCTIBLE__. On compilers that do not suppor variadic templates or rvalue references, this constuctor is available in limited functionality. For details [link optional_emplace_workaround see here]. 
+
+* [*Example:]
+``
+optional<std::vector<std::string>> ov1 {in_place_init_if, false, 3, "A"};
+assert (!ov1);
+
+optional<std::vector<std::string>> ov2 {in_place_init_if, true, 3, "A"};
+assert (ov2);
+assert (ov2->size() == 3);
+``
+
+__SPACE__
+
 [#reference_optional_constructor_factory]
 
 [: `template<InPlaceFactory> explicit optional<T>::optional( InPlaceFactory const& f );`]
@@ -446,7 +493,7 @@ __SPACE__
 
 [#reference_optional_emplace]
 
-[: `template<class... Args> void optional<T>::emplace( Args...&& args );`]
+[: `template<class... Args> void optional<T>::emplace( Args&&... args );`]
 
 * [*Requires:] The compiler supports rvalue references and variadic templates.
 * [*Effect:] If `*this` is initialized calls `*this = none`.
@@ -455,9 +502,7 @@ __SPACE__
 * [*Postconditions: ] `*this` is [_initialized].
 * [*Throws:] Whatever the selected `T`'s  constructor throws.
 * [*Exception Safety:] If an exception is thrown during the initialization of `T`, `*this` is ['uninitialized].
-* [*Notes:] `T` need not be __MOVE_CONSTRUCTIBLE__ or `MoveAssignable`. 
- On compilers that do not support variadic templates, the signature falls back to two overloads:`template<class Arg> void emplace(Arg&& arg)` and `void emplace()`. 
- On compilers that do not support rvalue references, the signature falls back to three overloads: taking `const` and non-`const` lvalue reference, and third with empty function argument list. 
+* [*Notes:] `T` need not be __MOVE_CONSTRUCTIBLE__ or `MoveAssignable`. On compilers that do not suppor variadic templates or rvalue references, this function is available in limited functionality. For details [link optional_emplace_workaround see here].  
 * [*Example:]
 ``
 T v;
@@ -770,6 +815,7 @@ __SPACE__
 [: `template<class R> optional<T&>::optional(R&& r) noexcept;`]
 * [*Postconditions:] `bool(*this) == true`; `addressof(**this) == addressof(r)`.
 * [*Remarks:] Unless `R` is an lvalue reference, the program is ill-formed. This constructor does not participate in overload resolution if `decay<R>` is an instance of `boost::optional`.
+* [*Notes:] This constructor is declared `explicit` on compilers that do not correctly suport binding to const lvalues of integral types. For more details [link optional_reference_binding see here]. 
 * [*Example:]
 ``
 T v;
@@ -1181,7 +1227,7 @@ __SPACE__
 [: `bool operator != ( optional<T> const& x, none_t ) noexcept;`]
 [: `bool operator != ( none_t, optional<T> const& x ) noexcept;`]
 
-* [*Returns: ] `!( x == y );`
+* [*Returns: ] `bool(x);`
 
 
 __SPACE__
@@ -1268,4 +1314,4 @@ assert ( !optX );
 assert (addressof(*opt0) == addressof(y));
 ``
 
-[endsect]
+[endsect]

doc/90_dependencies.qbk

@@ -27,8 +27,43 @@ The implementation uses the following other Boost modules:
 
 [endsect]
 
+[section Emplace operations in older compilers][#optional_emplace_workaround]
 
-[section Optional Reference Binding]
+Certain constructors and functions in the interface of `optional` perform a 'perfect forwarding' of arguments:
+
+    template<class... Args> optional(in_place_init_t, Args&&... args);
+    template<class... Args> optional(in_place_init_if_t, bool condition, Args&&... args);
+    template<class... Args> void emplace(Args&&... args);
+    
+On compilers that do not support variadic templates, each of these functions is substituted with two overloads, one forwarding a single argument, the other forwarding zero arguments. This forms the following set:
+
+    template<class Arg> optional(in_place_init_t, Arg&& arg);
+    optional(in_place_init_t);
+    
+    template<class Arg> optional(in_place_init_if_t, bool condition, Arg&& arg);
+    optional(in_place_init_if_t, bool condition);
+    
+    template<class Arg> void emplace(Arg&& arg);
+    void emplace();
+
+On compilers that do not support rvalue references, each of these functions is substituted with three overloadss: taking `const` and non-`const` lvalue reference, and third forwarding zero arguments. This forms the following set:
+
+    template<class Arg> optional(in_place_init_t, const Arg& arg);
+    template<class Arg> optional(in_place_init_t, Arg& arg);
+    optional(in_place_init_t);
+    
+    template<class Arg> optional(in_place_init_if_t, bool condition, const Arg& arg);
+    template<class Arg> optional(in_place_init_if_t, bool condition, Arg& arg);
+    optional(in_place_init_if_t, bool condition);
+    
+    template<class Arg> void emplace(const Arg& arg);
+    template<class Arg> void emplace(Arg& arg);
+    void emplace();
+
+This workaround addressess about 40% of all use cases. If this is insufficient, you need to resort to using [link boost_optional.tutorial.in_place_factories In-Place Factories].    
+[endsect]
+
+[section Optional Reference Binding][#optional_reference_binding]
 
 A number of compilers incorrectly treat const lvalues of integral type as rvalues, and create an illegal temporary when binding to an lvalue reference to const in some expressions. This could result in creating an optional lvalue reference that is in fact bound to an unexpected temporary rather than to the intended object. In order to prevent hard to find run-time bugs, this library performs compile-time checks to prevent expressions that would otherwise bind an optional reference to an unexpected temporary. As a consequence, on certain compilers certain pieces of functionality in optional references are missing. In order to maintain a portability of your code across diferent compilers, it is recommended that you only stick to the minimum portable interface of optional references: prefer direct-initialization and copy assignment of optional references to copy-initialization and assignment from `T&`:
 

doc/91_relnotes.qbk

@@ -11,6 +11,17 @@
 
 [section:relnotes Release Notes]
 
+[heading Boost Release 1.63]
+* Added two new in-place constructors. They work similarly to `emplace()` functions: they initialize the contained value by perfect-forwarding the obtained arguments. One constructor always initializes the contained value, the other based on a boolean condition.
+* Syntax `o = {}` now correctly un-initializes optional, just like in `std::optional`.
+* Fixed [@https://svn.boost.org/trac/boost/ticket/12203 Trac #12203].
+* Fixed [@https://svn.boost.org/trac/boost/ticket/12563 Trac #12563].
+
+
+[heading Boost Release 1.62]
+
+* Fixed [@https://svn.boost.org/trac/boost/ticket/12179 Trac #12179].
+
 
 [heading Boost Release 1.61]
 

doc/Jamfile.v2

@@ -46,4 +46,8 @@ boostbook standalone
         <format>docbook:<auto-index-internal>on
     ;
 
-
+###############################################################################
+alias boostdoc ;
+explicit boostdoc ;
+alias boostrelease : standalone ;
+explicit boostrelease ;

doc/html/boost_optional/dependencies_and_portability.html

@@ -7,7 +7,7 @@
 <link rel="home" href="../index.html" title="Boost.Optional">
 <link rel="up" href="../index.html" title="Boost.Optional">
 <link rel="prev" href="reference/header__boost_optional_hpp_.html" title="Header &lt;boost/optional.hpp&gt;">
-<link rel="next" href="dependencies_and_portability/optional_reference_binding.html" title="Optional Reference Binding">
+<link rel="next" href="dependencies_and_portability/emplace_operations_in_older_compilers.html" title="Emplace operations in older compilers">
 </head>
 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
 <table cellpadding="2" width="100%"><tr>
@@ -20,7 +20,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="reference/header__boost_optional_hpp_.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="dependencies_and_portability/optional_reference_binding.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="reference/header__boost_optional_hpp_.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="dependencies_and_portability/emplace_operations_in_older_compilers.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
@@ -29,6 +29,8 @@
 </h2></div></div></div>
 <div class="toc"><dl class="toc">
 <dt><span class="section"><a href="dependencies_and_portability.html#boost_optional.dependencies_and_portability.dependencies">Dependencies</a></span></dt>
+<dt><span class="section"><a href="dependencies_and_portability/emplace_operations_in_older_compilers.html">Emplace
+      operations in older compilers</a></span></dt>
 <dt><span class="section"><a href="dependencies_and_portability/optional_reference_binding.html">Optional
       Reference Binding</a></span></dt>
 </dl></div>
@@ -83,7 +85,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="reference/header__boost_optional_hpp_.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="dependencies_and_portability/optional_reference_binding.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="reference/header__boost_optional_hpp_.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="dependencies_and_portability/emplace_operations_in_older_compilers.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 </body>
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doc/html/boost_optional/dependencies_and_portability/emplace_operations_in_older_compilers.html

@@ -0,0 +1,90 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Emplace operations in older compilers</title>
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+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
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+<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td>
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+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
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+<a accesskey="p" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="optional_reference_binding.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.dependencies_and_portability.emplace_operations_in_older_compilers"></a><a class="link" href="emplace_operations_in_older_compilers.html" title="Emplace operations in older compilers">Emplace
+      operations in older compilers</a>
+</h3></div></div></div>
+<p>
+        <a name="optional_emplace_workaround"></a>Certain constructors and functions
+        in the interface of <code class="computeroutput"><span class="identifier">optional</span></code>
+        perform a 'perfect forwarding' of arguments:
+      </p>
+<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_t</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&amp;&amp;...</span> <span class="identifier">args</span><span class="special">);</span>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&amp;&amp;...</span> <span class="identifier">args</span><span class="special">);</span>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="identifier">Args</span><span class="special">&amp;&amp;...</span> <span class="identifier">args</span><span class="special">);</span>
+</pre>
+<p>
+        On compilers that do not support variadic templates, each of these functions
+        is substituted with two overloads, one forwarding a single argument, the
+        other forwarding zero arguments. This forms the following set:
+      </p>
+<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_t</span><span class="special">,</span> <span class="identifier">Arg</span><span class="special">&amp;&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_t</span><span class="special">);</span>
+
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">Arg</span><span class="special">&amp;&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">);</span>
+
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="identifier">Arg</span><span class="special">&amp;&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
+<span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">();</span>
+</pre>
+<p>
+        On compilers that do not support rvalue references, each of these functions
+        is substituted with three overloadss: taking <code class="computeroutput"><span class="keyword">const</span></code>
+        and non-<code class="computeroutput"><span class="keyword">const</span></code> lvalue reference,
+        and third forwarding zero arguments. This forms the following set:
+      </p>
+<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_t</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">Arg</span><span class="special">&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_t</span><span class="special">,</span> <span class="identifier">Arg</span><span class="special">&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_t</span><span class="special">);</span>
+
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">Arg</span><span class="special">&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">Arg</span><span class="special">&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special">(</span><span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">);</span>
+
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Arg</span><span class="special">&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
+<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Arg</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="identifier">Arg</span><span class="special">&amp;</span> <span class="identifier">arg</span><span class="special">);</span>
+<span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">();</span>
+</pre>
+<p>
+        This workaround addressess about 40% of all use cases. If this is insufficient,
+        you need to resort to using <a class="link" href="../tutorial/in_place_factories.html" title="In-Place Factories">In-Place
+        Factories</a>.
+      </p>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="optional_reference_binding.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/dependencies_and_portability/optional_reference_binding.html

@@ -6,7 +6,7 @@
 <meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../dependencies_and_portability.html" title="Dependencies and Portability">
-<link rel="prev" href="../dependencies_and_portability.html" title="Dependencies and Portability">
+<link rel="prev" href="emplace_operations_in_older_compilers.html" title="Emplace operations in older compilers">
 <link rel="next" href="../relnotes.html" title="Release Notes">
 </head>
 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
@@ -20,7 +20,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../relnotes.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="emplace_operations_in_older_compilers.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../relnotes.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h3 class="title">
@@ -28,18 +28,19 @@
       Reference Binding</a>
 </h3></div></div></div>
 <p>
-        A number of compilers incorrectly treat const lvalues of integral type as
-        rvalues, and create an illegal temporary when binding to an lvalue reference
-        to const in some expressions. This could result in creating an optional lvalue
-        reference that is in fact bound to an unexpected temporary rather than to
-        the intended object. In order to prevent hard to find run-time bugs, this
-        library performs compile-time checks to prevent expressions that would otherwise
-        bind an optional reference to an unexpected temporary. As a consequence,
-        on certain compilers certain pieces of functionality in optional references
-        are missing. In order to maintain a portability of your code across diferent
-        compilers, it is recommended that you only stick to the minimum portable
-        interface of optional references: prefer direct-initialization and copy assignment
-        of optional references to copy-initialization and assignment from <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span></code>:
+        <a name="optional_reference_binding"></a>A number of compilers incorrectly
+        treat const lvalues of integral type as rvalues, and create an illegal temporary
+        when binding to an lvalue reference to const in some expressions. This could
+        result in creating an optional lvalue reference that is in fact bound to
+        an unexpected temporary rather than to the intended object. In order to prevent
+        hard to find run-time bugs, this library performs compile-time checks to
+        prevent expressions that would otherwise bind an optional reference to an
+        unexpected temporary. As a consequence, on certain compilers certain pieces
+        of functionality in optional references are missing. In order to maintain
+        a portability of your code across diferent compilers, it is recommended that
+        you only stick to the minimum portable interface of optional references:
+        prefer direct-initialization and copy assignment of optional references to
+        copy-initialization and assignment from <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span></code>:
       </p>
 <pre class="programlisting"><span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
 <span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">or1</span><span class="special">;</span>
@@ -100,7 +101,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../relnotes.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="emplace_operations_in_older_compilers.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../relnotes.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 </body>
 </html>

doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html

@@ -268,9 +268,7 @@
             <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
           </p></blockquote></div>
 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
-              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
-              <span class="identifier">x</span> <span class="special">==</span>
-              <span class="identifier">y</span> <span class="special">);</span></code>
+              <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span></code>
             </li></ul></div>
 <p>
           <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>

doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_references.html

@@ -55,6 +55,12 @@
               is an lvalue reference, the program is ill-formed. This constructor
               does not participate in overload resolution if <code class="computeroutput"><span class="identifier">decay</span><span class="special">&lt;</span><span class="identifier">R</span><span class="special">&gt;</span></code> is an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code>.
             </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes:</strong></span> This constructor is declared
+              <code class="computeroutput"><span class="keyword">explicit</span></code> on compilers
+              that do not correctly suport binding to const lvalues of integral types.
+              For more details <a class="link" href="../../dependencies_and_portability/optional_reference_binding.html#optional_reference_binding">see here</a>.
+            </li>
 <li class="listitem">
               <span class="bold"><strong>Example:</strong></span>
 <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>

doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_values.html

@@ -403,6 +403,94 @@
 </pre>
             </li>
 </ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_in_place_init"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span>
+            <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">in_place_init_t</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&amp;&amp;...</span> <span class="identifier">ars</span>
+            <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_constructible_v</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&amp;&amp;...&gt;</span></code> is <code class="computeroutput"><span class="keyword">true</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Effect:</strong></span> Initializes the contained
+              value as if direct-non-list-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code> with the arguments <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special">&lt;</span><span class="identifier">Args</span><span class="special">&gt;(</span><span class="identifier">args</span><span class="special">)...</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Throws:</strong></span> Any exception thrown by the
+              selected constructor of <code class="computeroutput"><span class="identifier">T</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+              need not be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>.
+              On compilers that do not suppor variadic templates or rvalue references,
+              this constuctor is available in limited functionality. For details
+              <a class="link" href="../../dependencies_and_portability/emplace_operations_in_older_compilers.html#optional_emplace_workaround">see here</a>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="comment">// creates an std::mutex using its default constructor</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">mutex</span><span class="special">&gt;</span> <span class="identifier">om</span> <span class="special">{</span><span class="identifier">in_place_init</span><span class="special">};</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">om</span><span class="special">);</span>
+
+<span class="comment">// creates a unique_lock by calling unique_lock(*om, std::defer_lock)</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_lock</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">mutex</span><span class="special">&gt;&gt;</span> <span class="identifier">ol</span> <span class="special">{</span><span class="identifier">in_place_init</span><span class="special">,</span> <span class="special">*</span><span class="identifier">om</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">defer_lock</span><span class="special">};</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">ol</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">ol</span><span class="special">-&gt;</span><span class="identifier">owns_lock</span><span class="special">());</span>
+</pre>
+            </li>
+</ul></div>
+<p>
+          <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+        </p>
+<a name="reference_optional_in_place_init_if"></a><div class="blockquote"><blockquote class="blockquote"><p>
+            <code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span>
+            <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span>
+            <span class="identifier">Args</span><span class="special">&amp;&amp;...</span>
+            <span class="identifier">ars</span> <span class="special">);</span></code>
+          </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+              <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_constructible_v</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&amp;&amp;...&gt;</span></code> is <code class="computeroutput"><span class="keyword">true</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="identifier">condition</span></code>
+              is <code class="computeroutput"><span class="keyword">true</span></code>, initializes the
+              contained value as if direct-non-list-initializing an object of type
+              <code class="computeroutput"><span class="identifier">T</span></code> with the arguments
+              <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special">&lt;</span><span class="identifier">Args</span><span class="special">&gt;(</span><span class="identifier">args</span><span class="special">)...</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">condition</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Throws:</strong></span> Any exception thrown by the
+              selected constructor of <code class="computeroutput"><span class="identifier">T</span></code>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+              need not be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>.
+              On compilers that do not suppor variadic templates or rvalue references,
+              this constuctor is available in limited functionality. For details
+              <a class="link" href="../../dependencies_and_portability/emplace_operations_in_older_compilers.html#optional_emplace_workaround">see here</a>.
+            </li>
+<li class="listitem">
+              <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;&gt;</span> <span class="identifier">ov1</span> <span class="special">{</span><span class="identifier">in_place_init_if</span><span class="special">,</span> <span class="keyword">false</span><span class="special">,</span> <span class="number">3</span><span class="special">,</span> <span class="string">"A"</span><span class="special">};</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">ov1</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;&gt;</span> <span class="identifier">ov2</span> <span class="special">{</span><span class="identifier">in_place_init_if</span><span class="special">,</span> <span class="keyword">true</span><span class="special">,</span> <span class="number">3</span><span class="special">,</span> <span class="string">"A"</span><span class="special">};</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">ov2</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">ov2</span><span class="special">-&gt;</span><span class="identifier">size</span><span class="special">()</span> <span class="special">==</span> <span class="number">3</span><span class="special">);</span>
+</pre>
+            </li>
+</ul></div>
 <p>
           <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
         </p>
@@ -1007,7 +1095,7 @@
         </p>
 <a name="reference_optional_emplace"></a><div class="blockquote"><blockquote class="blockquote"><p>
             <code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span>
-            <span class="keyword">void</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">emplace</span><span class="special">(</span> <span class="identifier">Args</span><span class="special">...&amp;&amp;</span> <span class="identifier">args</span>
+            <span class="keyword">void</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">emplace</span><span class="special">(</span> <span class="identifier">Args</span><span class="special">&amp;&amp;...</span> <span class="identifier">args</span>
             <span class="special">);</span></code>
           </p></blockquote></div>
 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
@@ -1037,15 +1125,8 @@
               <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
               need not be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
               or <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>.
-              On compilers that do not support variadic templates, the signature
-              falls back to two overloads:<code class="computeroutput"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span>
-              <span class="identifier">Arg</span><span class="special">&gt;</span>
-              <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="identifier">Arg</span><span class="special">&amp;&amp;</span> <span class="identifier">arg</span><span class="special">)</span></code> and <code class="computeroutput"><span class="keyword">void</span>
-              <span class="identifier">emplace</span><span class="special">()</span></code>.
-              On compilers that do not support rvalue references, the signature falls
-              back to three overloads: taking <code class="computeroutput"><span class="keyword">const</span></code>
-              and non-<code class="computeroutput"><span class="keyword">const</span></code> lvalue reference,
-              and third with empty function argument list.
+              On compilers that do not suppor variadic templates or rvalue references,
+              this function is available in limited functionality. For details <a class="link" href="../../dependencies_and_portability/emplace_operations_in_older_compilers.html#optional_emplace_workaround">see here</a>.
             </li>
 <li class="listitem">
               <span class="bold"><strong>Example:</strong></span>

doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_in_place_init.html

@@ -0,0 +1,61 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Initialization tags</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header &lt;boost/optional/optional.hpp&gt;">
+<link rel="prev" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header &lt;boost/optional/optional.hpp&gt;">
+<link rel="next" href="header_optional_optional_values.html" title="Optional Values">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header_optional_optional_values.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.header_optional_in_place_init"></a><a class="link" href="header_optional_in_place_init.html" title="Initialization tags">Initialization
+        tags</a>
+</h4></div></div></div>
+<a name="reference_in_place_init"></a><a name="reference_in_place_init_if"></a><pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span>
+
+<span class="keyword">class</span> <span class="identifier">in_place_init_t</span> <span class="special">{</span> <span class="comment">/* see below */</span> <span class="special">}</span> <span class="special">;</span>
+<span class="keyword">const</span> <span class="identifier">in_place_init_t</span> <span class="identifier">in_place_init</span> <span class="special">(</span> <span class="comment">/* see below */</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="keyword">class</span> <span class="identifier">in_place_init_if_t</span> <span class="special">{</span> <span class="comment">/*see below*/</span> <span class="special">}</span> <span class="special">;</span>
+<span class="keyword">const</span> <span class="identifier">in_place_init_if_t</span> <span class="identifier">in_place_init_if</span> <span class="special">(</span> <span class="comment">/*see below*/</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="special">}</span>
+</pre>
+<p>
+          Classes <code class="computeroutput"><span class="identifier">in_place_init_t</span></code>
+          and <code class="computeroutput"><span class="identifier">in_place_init_if_t</span></code>
+          are empty clsses. Their purpose is to control overload resolution in the
+          initialization of optional objects. They are empty, trivially copyable
+          classes with disabled default constructor.
+        </p>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header_optional_optional_values.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html

@@ -6,7 +6,7 @@
 <meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
 <link rel="home" href="../../../index.html" title="Boost.Optional">
 <link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header &lt;boost/optional/optional.hpp&gt;">
-<link rel="prev" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header &lt;boost/optional/optional.hpp&gt;">
+<link rel="prev" href="header_optional_in_place_init.html" title="Initialization tags">
 <link rel="next" href="header_optional_optional_refs.html" title="Optional References">
 </head>
 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
@@ -20,7 +20,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="header_optional_in_place_init.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h4 class="title">
@@ -47,7 +47,6 @@
 
     <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&amp;&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_move_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="comment">// [new in 1.34]</span>
     <span class="identifier">optional</span> <span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_bool_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
 
     <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
@@ -58,6 +57,10 @@
 
     <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;&amp;&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_move_constructor_other_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
 
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">in_place_init_t</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&amp;&amp;...</span> <span class="identifier">args</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_in_place_init"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&amp;&amp;...</span> <span class="identifier">args</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_in_place_init_if"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
     <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">InPlaceFactory</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_factory"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
 
     <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">TypedInPlaceFactory</span><span class="special">&gt;</span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_factory"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
@@ -76,7 +79,7 @@
 
     <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;&amp;&amp;</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_move_equal_other_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
 
-    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span> <span class="special">(</span> <span class="identifier">Args</span><span class="special">...&amp;&amp;</span> <span class="identifier">args</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_emplace"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span> <span class="keyword">void</span> <span class="identifier">emplace</span> <span class="special">(</span> <span class="identifier">Args</span><span class="special">&amp;&amp;...</span> <span class="identifier">args</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_emplace"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
 
     <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">InPlaceFactory</span><span class="special">&gt;</span> <span class="identifier">optional</span><span class="special">&amp;</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_factory"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
 
@@ -135,7 +138,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="header_optional_in_place_init.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 </body>
 </html>

doc/html/boost_optional/relnotes.html

@@ -28,6 +28,38 @@
 </h2></div></div></div>
 <h4>
 <a name="boost_optional.relnotes.h0"></a>
+      <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_63"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_63">Boost
+      Release 1.63</a>
+    </h4>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+          Added two new in-place constructors. They work similarly to <code class="computeroutput"><span class="identifier">emplace</span><span class="special">()</span></code>
+          functions: they initialize the contained value by perfect-forwarding the
+          obtained arguments. One constructor always initializes the contained value,
+          the other based on a boolean condition.
+        </li>
+<li class="listitem">
+          Syntax <code class="computeroutput"><span class="identifier">o</span> <span class="special">=</span>
+          <span class="special">{}</span></code> now correctly un-initializes
+          optional, just like in <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">optional</span></code>.
+        </li>
+<li class="listitem">
+          Fixed <a href="https://svn.boost.org/trac/boost/ticket/12203" target="_top">Trac #12203</a>.
+        </li>
+<li class="listitem">
+          Fixed <a href="https://svn.boost.org/trac/boost/ticket/12563" target="_top">Trac #12563</a>.
+        </li>
+</ul></div>
+<h4>
+<a name="boost_optional.relnotes.h1"></a>
+      <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_62"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_62">Boost
+      Release 1.62</a>
+    </h4>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+          Fixed <a href="https://svn.boost.org/trac/boost/ticket/12179" target="_top">Trac #12179</a>.
+        </li></ul></div>
+<h4>
+<a name="boost_optional.relnotes.h2"></a>
       <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_61"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_61">Boost
       Release 1.61</a>
     </h4>
@@ -70,7 +102,7 @@
         </li>
 </ul></div>
 <h4>
-<a name="boost_optional.relnotes.h1"></a>
+<a name="boost_optional.relnotes.h3"></a>
       <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_60"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_60">Boost
       Release 1.60</a>
     </h4>
@@ -81,7 +113,7 @@
           #11203</a>.
         </li></ul></div>
 <h4>
-<a name="boost_optional.relnotes.h2"></a>
+<a name="boost_optional.relnotes.h4"></a>
       <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_59"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_59">Boost
       Release 1.59</a>
     </h4>
@@ -95,7 +127,7 @@
         </li>
 </ul></div>
 <h4>
-<a name="boost_optional.relnotes.h3"></a>
+<a name="boost_optional.relnotes.h5"></a>
       <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_58"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_58">Boost
       Release 1.58</a>
     </h4>
@@ -131,7 +163,7 @@
         </li>
 </ul></div>
 <h4>
-<a name="boost_optional.relnotes.h4"></a>
+<a name="boost_optional.relnotes.h6"></a>
       <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_57"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_57">Boost
       Release 1.57</a>
     </h4>
@@ -141,7 +173,7 @@
           to fix C++03 compile error on <code class="computeroutput"><span class="identifier">logic_error</span><span class="special">(</span><span class="string">"..."</span><span class="special">)</span></code>"</em></span>.
         </li></ul></div>
 <h4>
-<a name="boost_optional.relnotes.h5"></a>
+<a name="boost_optional.relnotes.h7"></a>
       <span class="phrase"><a name="boost_optional.relnotes.boost_release_1_56"></a></span><a class="link" href="relnotes.html#boost_optional.relnotes.boost_release_1_56">Boost
       Release 1.56</a>
     </h4>

doc/html/boost_optional/tutorial/exception_safety_guarantees.html

@@ -6,7 +6,7 @@
 <meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../../optional/tutorial.html" title="Tutorial">
-<link rel="prev" href="a_note_about_optional_bool_.html" title="A note about optional&lt;bool&gt;">
+<link rel="prev" href="gotchas/false_positive_with__wmaybe_uninitialized.html" title="False positive with -Wmaybe-uninitialized">
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@@ -20,7 +20,7 @@
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+<a accesskey="p" href="gotchas/false_positive_with__wmaybe_uninitialized.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="type_requirements.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
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@@ -169,7 +169,7 @@
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+<a accesskey="p" href="gotchas/false_positive_with__wmaybe_uninitialized.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="type_requirements.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
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doc/html/boost_optional/tutorial/gotchas.html

@@ -0,0 +1,112 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Gotchas</title>
+<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../index.html" title="Boost.Optional">
+<link rel="up" href="../../optional/tutorial.html" title="Tutorial">
+<link rel="prev" href="in_place_factories.html" title="In-Place Factories">
+<link rel="next" href="gotchas/moved_from__optional_.html" title="Moved-from optional">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="in_place_factories.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="gotchas/moved_from__optional_.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.tutorial.gotchas"></a><a class="link" href="gotchas.html" title="Gotchas">Gotchas</a>
+</h3></div></div></div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.tutorial.gotchas.a_note_about_optional_bool_"></a><a class="link" href="gotchas.html#boost_optional.tutorial.gotchas.a_note_about_optional_bool_" title="A note about optional&lt;bool&gt;">A
+        note about optional&lt;bool&gt;</a>
+</h4></div></div></div>
+<p>
+          <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span></code>
+          should be used with special caution and consideration.
+        </p>
+<p>
+          First, it is functionally similar to a tristate boolean (false, maybe,
+          true) &#8212;such as <a href="../../../../../../doc/html/tribool.html" target="_top">boost::tribool</a>&#8212;
+          except that in a tristate boolean, the maybe state <span class="underline">represents
+          a valid value</span>, unlike the corresponding state of an uninitialized
+          <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span></code>.
+          It should be carefully considered if an <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span></code> instead of a <code class="computeroutput"><span class="identifier">tribool</span></code>
+          is really needed.
+        </p>
+<p>
+          Second, although <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;&gt;</span></code> provides a contextual conversion
+          to <code class="computeroutput"><span class="keyword">bool</span></code> in C++11, this falls
+          back to an implicit conversion on older compilers. This conversion refers
+          to the initialization state and not to the contained value. Using <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span></code>
+          can lead to subtle errors due to the implicit <code class="computeroutput"><span class="keyword">bool</span></code>
+          conversion:
+        </p>
+<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">foo</span> <span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="keyword">void</span> <span class="identifier">bar</span><span class="special">()</span>
+<span class="special">{</span>
+    <span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span> <span class="identifier">v</span> <span class="special">=</span> <span class="keyword">try</span><span class="special">();</span>
+
+    <span class="comment">// The following intended to pass the value of 'v' to foo():</span>
+    <span class="identifier">foo</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+    <span class="comment">// But instead, the initialization state is passed</span>
+    <span class="comment">// due to a typo: it should have been foo(*v).</span>
+<span class="special">}</span>
+</pre>
+<p>
+          The only implicit conversion is to <code class="computeroutput"><span class="keyword">bool</span></code>,
+          and it is safe in the sense that typical integral promotions don't apply
+          (i.e. if <code class="computeroutput"><span class="identifier">foo</span><span class="special">()</span></code>
+          takes an <code class="computeroutput"><span class="keyword">int</span></code> instead, it won't
+          compile).
+        </p>
+<p>
+          Third, mixed comparisons with <code class="computeroutput"><span class="keyword">bool</span></code>
+          work differently than similar mixed comparisons between pointers and <code class="computeroutput"><span class="keyword">bool</span></code>, so the results might surprise you:
+        </p>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">&gt;</span> <span class="identifier">oEmpty</span><span class="special">(</span><span class="identifier">none</span><span class="special">),</span> <span class="identifier">oTrue</span><span class="special">(</span><span class="keyword">true</span><span class="special">),</span> <span class="identifier">oFalse</span><span class="special">(</span><span class="keyword">false</span><span class="special">);</span>
+
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oEmpty</span> <span class="special">==</span> <span class="identifier">none</span><span class="special">);</span>  <span class="comment">// renders true</span>
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oEmpty</span> <span class="special">==</span> <span class="keyword">false</span><span class="special">);</span> <span class="comment">// renders false!</span>
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oEmpty</span> <span class="special">==</span> <span class="keyword">true</span><span class="special">);</span>  <span class="comment">// renders false!</span>
+
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oFalse</span> <span class="special">==</span> <span class="identifier">none</span><span class="special">);</span>  <span class="comment">// renders false</span>
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oFalse</span> <span class="special">==</span> <span class="keyword">false</span><span class="special">);</span> <span class="comment">// renders true!</span>
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oFalse</span> <span class="special">==</span> <span class="keyword">true</span><span class="special">);</span>  <span class="comment">// renders false</span>
+
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oTrue</span> <span class="special">==</span> <span class="identifier">none</span><span class="special">);</span>   <span class="comment">// renders false</span>
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oTrue</span> <span class="special">==</span> <span class="keyword">false</span><span class="special">);</span>  <span class="comment">// renders false</span>
+<span class="keyword">if</span> <span class="special">(</span><span class="identifier">oTrue</span> <span class="special">==</span> <span class="keyword">true</span><span class="special">);</span>   <span class="comment">// renders true</span>
+</pre>
+<p>
+          In other words, for <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;&gt;</span></code>, the following assertion does not
+          hold:
+        </p>
+<pre class="programlisting"><span class="identifier">assert</span><span class="special">((</span><span class="identifier">opt</span> <span class="special">==</span> <span class="keyword">false</span><span class="special">)</span> <span class="special">==</span> <span class="special">(!</span><span class="identifier">opt</span><span class="special">));</span>
+</pre>
+</div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="in_place_factories.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="gotchas/moved_from__optional_.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/tutorial/gotchas/false_positive_with__wmaybe_uninitialized.html

@@ -0,0 +1,77 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>False positive with -Wmaybe-uninitialized</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../gotchas.html" title="Gotchas">
+<link rel="prev" href="mixed_relational_comparisons.html" title="Mixed relational comparisons">
+<link rel="next" href="../exception_safety_guarantees.html" title="Exception Safety Guarantees">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="mixed_relational_comparisons.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../gotchas.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../exception_safety_guarantees.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.tutorial.gotchas.false_positive_with__wmaybe_uninitialized"></a><a class="link" href="false_positive_with__wmaybe_uninitialized.html" title="False positive with -Wmaybe-uninitialized">False
+        positive with -Wmaybe-uninitialized</a>
+</h4></div></div></div>
+<p>
+          Sometimes on GCC compilers below version 5.1 you may get an -Wmaybe-uninitialized
+          warning when copiling with option -02 on a perfectly valid <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code> usage. For instance in this
+          program:
+        </p>
+<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">optional</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">getitem</span><span class="special">();</span>
+
+<span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">argc</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*[])</span>
+<span class="special">{</span>
+  <span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">a</span> <span class="special">=</span> <span class="identifier">getitem</span><span class="special">();</span>
+  <span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">b</span><span class="special">;</span>
+
+  <span class="keyword">if</span> <span class="special">(</span><span class="identifier">argc</span> <span class="special">&gt;</span> <span class="number">0</span><span class="special">)</span>
+    <span class="identifier">b</span> <span class="special">=</span> <span class="identifier">argc</span><span class="special">;</span>
+
+  <span class="keyword">if</span> <span class="special">(</span><span class="identifier">a</span> <span class="special">!=</span> <span class="identifier">b</span><span class="special">)</span>
+    <span class="keyword">return</span> <span class="number">1</span><span class="special">;</span>
+
+  <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
+<span class="special">}</span>
+</pre>
+<p>
+          This is a bug in the compiler. As a workaround (provided in <a href="http://stackoverflow.com/questions/21755206/how-to-get-around-gcc-void-b-4-may-be-used-uninitialized-in-this-funct" target="_top">this
+          Stack Overflow question</a>) use the following way of initializing
+          an optional containing no value:
+        </p>
+<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">b</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">make_optional</span><span class="special">(</span><span class="keyword">false</span><span class="special">,</span> <span class="keyword">int</span><span class="special">());</span>
+</pre>
+<p>
+          This is obviously redundant, but makes the warning disappear.
+        </p>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="mixed_relational_comparisons.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../gotchas.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../exception_safety_guarantees.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/tutorial/gotchas/mixed_relational_comparisons.html

@@ -0,0 +1,59 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Mixed relational comparisons</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../gotchas.html" title="Gotchas">
+<link rel="prev" href="moved_from__optional_.html" title="Moved-from optional">
+<link rel="next" href="false_positive_with__wmaybe_uninitialized.html" title="False positive with -Wmaybe-uninitialized">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="moved_from__optional_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../gotchas.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="false_positive_with__wmaybe_uninitialized.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.tutorial.gotchas.mixed_relational_comparisons"></a><a class="link" href="mixed_relational_comparisons.html" title="Mixed relational comparisons">Mixed
+        relational comparisons</a>
+</h4></div></div></div>
+<p>
+          Because <code class="computeroutput"><span class="identifier">T</span></code> is convertible
+          to <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
+          and because <code class="computeroutput"><span class="identifier">opiotnal</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
+          is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a> when <code class="computeroutput"><span class="identifier">T</span></code> is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>, you can sometimes
+          get an unexpected runtime result where you would rather expect a compiler
+          error:
+        </p>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;</span> <span class="identifier">Flight_plan</span><span class="special">::</span><span class="identifier">weight</span><span class="special">();</span> <span class="comment">// sometimes no weight can be returned</span>
+
+<span class="keyword">bool</span> <span class="identifier">is_aircraft_too_heavy</span><span class="special">(</span><span class="identifier">Flight_plan</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">p</span><span class="special">)</span>
+<span class="special">{</span>
+   <span class="keyword">return</span> <span class="identifier">p</span><span class="special">.</span><span class="identifier">weight</span><span class="special">()</span> <span class="special">&gt;</span> <span class="identifier">p</span><span class="special">.</span><span class="identifier">aircraft</span><span class="special">().</span><span class="identifier">max_weight</span><span class="special">();</span> <span class="comment">// compiles!</span>
+<span class="special">}</span>                                                 <span class="comment">// returns false when the optional contains no value </span>
+</pre>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="moved_from__optional_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../gotchas.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="false_positive_with__wmaybe_uninitialized.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/tutorial/gotchas/moved_from__optional_.html

@@ -0,0 +1,63 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Moved-from optional</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../gotchas.html" title="Gotchas">
+<link rel="prev" href="../gotchas.html" title="Gotchas">
+<link rel="next" href="mixed_relational_comparisons.html" title="Mixed relational comparisons">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../gotchas.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../gotchas.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="mixed_relational_comparisons.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.tutorial.gotchas.moved_from__optional_"></a><a class="link" href="moved_from__optional_.html" title="Moved-from optional">Moved-from
+        <code class="computeroutput"><span class="identifier">optional</span></code></a>
+</h4></div></div></div>
+<p>
+          When an optional object that contains a value is moved from (is a source
+          of move constructor or assignment) it still contains a value and its contained
+          value is left in a moved-from state. This can be illustrated with the following
+          example.
+        </p>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;&gt;</span> <span class="identifier">opi</span> <span class="special">{</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">make_unique</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;(</span><span class="number">1</span><span class="special">)};</span>
+<span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;&gt;</span> <span class="identifier">opj</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">opi</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">opi</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(*</span><span class="identifier">opi</span> <span class="special">==</span> <span class="keyword">nullptr</span><span class="special">);</span>
+</pre>
+<p>
+          Quite a lot of people expect that when an object that contains a value
+          is moved from, its contained value should be destroyed. This is not so,
+          for performance reasons. Current semantics allow the implementation of
+          <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">opiotnal</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
+          to be trivially copyable when <code class="computeroutput"><span class="identifier">T</span></code>
+          is trivial.
+        </p>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright &#169; 2014-2016 Andrzej Krzemie&#324;ski<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../gotchas.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../gotchas.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="mixed_relational_comparisons.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>

doc/html/boost_optional/tutorial/in_place_factories.html

@@ -7,7 +7,7 @@
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../../optional/tutorial.html" title="Tutorial">
 <link rel="prev" href="optional_references/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">
-<link rel="next" href="a_note_about_optional_bool_.html" title="A note about optional&lt;bool&gt;">
+<link rel="next" href="gotchas.html" title="Gotchas">
 </head>
 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
 <table cellpadding="2" width="100%"><tr>
@@ -20,7 +20,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="optional_references/rebinding_semantics_for_assignment_of_optional_references.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="a_note_about_optional_bool_.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="optional_references/rebinding_semantics_for_assignment_of_optional_references.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="gotchas.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h3 class="title">
@@ -191,7 +191,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="optional_references/rebinding_semantics_for_assignment_of_optional_references.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="a_note_about_optional_bool_.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="optional_references/rebinding_semantics_for_assignment_of_optional_references.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/tutorial.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="gotchas.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 </body>
 </html>

doc/html/boost_optional/tutorial/performance_considerations.html

@@ -67,7 +67,7 @@
         for your application (e.g., because you want to utilize your CPU cache in
         order to gain performance) and you have determined you are willing to trade
         the code clarity, it is recommended that you simply go with type <code class="computeroutput"><span class="keyword">int</span></code> and use some 'magic value' to represent
-        <span class="emphasis"><em>not-an-int</em></span>.
+        <span class="emphasis"><em>not-an-int</em></span>, or use something like <a href="https://github.com/akrzemi1/markable" target="_top"><code class="computeroutput"><span class="identifier">markable</span></code></a> library.
       </p>
 <p>
         Even if you cannot spare any value of <code class="computeroutput"><span class="keyword">int</span></code>

doc/html/index.html

@@ -64,8 +64,7 @@
       references</a></span></dt>
 <dt><span class="section"><a href="boost_optional/tutorial/in_place_factories.html">In-Place
       Factories</a></span></dt>
-<dt><span class="section"><a href="boost_optional/tutorial/a_note_about_optional_bool_.html">A
-      note about optional&lt;bool&gt;</a></span></dt>
+<dt><span class="section"><a href="boost_optional/tutorial/gotchas.html">Gotchas</a></span></dt>
 <dt><span class="section"><a href="boost_optional/tutorial/exception_safety_guarantees.html">Exception
       Safety Guarantees</a></span></dt>
 <dt><span class="section"><a href="boost_optional/tutorial/type_requirements.html">Type requirements</a></span></dt>
@@ -90,6 +89,8 @@
     and Portability</a></span></dt>
 <dd><dl>
 <dt><span class="section"><a href="boost_optional/dependencies_and_portability.html#boost_optional.dependencies_and_portability.dependencies">Dependencies</a></span></dt>
+<dt><span class="section"><a href="boost_optional/dependencies_and_portability/emplace_operations_in_older_compilers.html">Emplace
+      operations in older compilers</a></span></dt>
 <dt><span class="section"><a href="boost_optional/dependencies_and_portability/optional_reference_binding.html">Optional
       Reference Binding</a></span></dt>
 </dl></dd>
@@ -144,7 +145,7 @@
 </div>
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
-<td align="left"><p><small>Last revised: March 06, 2016 at 18:30:08 GMT</small></p></td>
+<td align="left"><p><small>Last revised: March 22, 2017 at 21:55:47 GMT</small></p></td>
 <td align="right"><div class="copyright-footer"></div></td>
 </tr></table>
 <hr>

doc/html/optional/reference/header__boost_optional_optional_hpp_.html

@@ -7,7 +7,7 @@
 <link rel="home" href="../../index.html" title="Boost.Optional">
 <link rel="up" href="../reference.html" title="Reference">
 <link rel="prev" href="../../boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html" title="Header &lt;boost/optional/optional_fwd.hpp&gt;">
-<link rel="next" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html" title="Optional Values">
+<link rel="next" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_in_place_init.html" title="Initialization tags">
 </head>
 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
 <table cellpadding="2" width="100%"><tr>
@@ -20,7 +20,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="../../boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="../../boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_in_place_init.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 <div class="section">
 <div class="titlepage"><div><div><h3 class="title">
@@ -35,6 +35,12 @@
 
 <span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span>
 
+<span class="keyword">class</span> <span class="identifier">in_place_init_t</span> <span class="special">{</span> <span class="comment">/* see below */</span> <span class="special">}</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_in_place_init.html#reference_in_place_init"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">const</span> <span class="identifier">in_place_init_t</span> <span class="identifier">in_place_init</span> <span class="special">(</span> <span class="comment">/* see below */</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="keyword">class</span> <span class="identifier">in_place_init_if_t</span> <span class="special">{</span> <span class="comment">/*see below*/</span> <span class="special">}</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_in_place_init.html#reference_in_place_init_if"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="keyword">const</span> <span class="identifier">in_place_init_if_t</span> <span class="identifier">in_place_init_if</span> <span class="special">(</span> <span class="comment">/*see below*/</span> <span class="special">)</span> <span class="special">;</span>
+
 <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span>
 <span class="keyword">class</span> <span class="identifier">optional</span> <span class="special">;</span> <a class="link" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html#reference_operator_template"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
 
@@ -95,7 +101,7 @@
 </tr></table>
 <hr>
 <div class="spirit-nav">
-<a accesskey="p" href="../../boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+<a accesskey="p" href="../../boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../../boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_in_place_init.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
 </div>
 </body>
 </html>

doc/html/optional/tutorial.html

@@ -38,8 +38,7 @@
       references</a></span></dt>
 <dt><span class="section"><a href="../boost_optional/tutorial/in_place_factories.html">In-Place
       Factories</a></span></dt>
-<dt><span class="section"><a href="../boost_optional/tutorial/a_note_about_optional_bool_.html">A
-      note about optional&lt;bool&gt;</a></span></dt>
+<dt><span class="section"><a href="../boost_optional/tutorial/gotchas.html">Gotchas</a></span></dt>
 <dt><span class="section"><a href="../boost_optional/tutorial/exception_safety_guarantees.html">Exception
       Safety Guarantees</a></span></dt>
 <dt><span class="section"><a href="../boost_optional/tutorial/type_requirements.html">Type requirements</a></span></dt>

include/boost/optional/detail/optional_config.hpp

@@ -96,4 +96,21 @@
 
 #endif // defined(__GNUC__)
 
+#if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && !defined(BOOST_NO_CXX11_DECLTYPE) && !BOOST_WORKAROUND(BOOST_MSVC, < 1800) && !BOOST_WORKAROUND(BOOST_GCC_VERSION, < 40500) && !defined(__SUNPRO_CC)
+  // this condition is a copy paste from is_constructible.hpp
+  // I also disable SUNPRO, as it seems not to support type_traits correctly
+#else
+# define BOOST_OPTIONAL_DETAIL_NO_IS_CONSTRUCTIBLE_TRAIT
+#endif
+
+#if defined __SUNPRO_CC
+# define BOOST_OPTIONAL_DETAIL_NO_SFINAE_FRIENDLY_CONSTRUCTORS
+#elif (defined _MSC_FULL_VER) && (_MSC_FULL_VER < 190023026)
+# define BOOST_OPTIONAL_DETAIL_NO_SFINAE_FRIENDLY_CONSTRUCTORS
+#elif defined BOOST_GCC && !defined BOOST_GCC_CXX11
+# define BOOST_OPTIONAL_DETAIL_NO_SFINAE_FRIENDLY_CONSTRUCTORS
+#elif defined BOOST_GCC_VERSION && BOOST_GCC_VERSION < 40800
+# define BOOST_OPTIONAL_DETAIL_NO_SFINAE_FRIENDLY_CONSTRUCTORS
+#endif
+
 #endif // header guard

include/boost/optional/detail/optional_reference_spec.hpp

@@ -44,6 +44,23 @@ BOOST_DEDUCED_TYPENAME boost::remove_reference<T>::type& forward_reference(T&& r
 
 #endif // BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 
+
+template <class T>
+struct is_const_integral
+{
+  static const bool value = boost::is_const<T>::value && boost::is_integral<T>::value;
+};
+
+template <class T>
+struct is_const_integral_bad_for_conversion
+{
+#if (!defined BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES) && (defined BOOST_OPTIONAL_CONFIG_NO_PROPER_CONVERT_FROM_CONST_INT)
+  static const bool value = boost::is_const<T>::value && boost::is_integral<T>::value;
+#else
+  static const bool value = false;
+#endif
+};
+
 template <class From>
 void prevent_assignment_from_false_const_integral()
 {
@@ -51,12 +68,13 @@ void prevent_assignment_from_false_const_integral()
 #ifdef BOOST_OPTIONAL_CONFIG_NO_PROPER_ASSIGN_FROM_CONST_INT
     // MSVC compiler without rvalue refernces: we need to disable the asignment from
     // const integral lvalue reference, as it may be an invalid temporary
-    BOOST_STATIC_ASSERT_MSG(!(boost::is_const<From>::value && boost::is_integral<From>::value), 
+    BOOST_STATIC_ASSERT_MSG(!is_const_integral<From>::value, 
                             "binding const lvalue references to integral types is disabled in this compiler");
 #endif
 #endif   
 }
 
+
 template <class T>
 struct is_optional_
 {
@@ -75,6 +93,21 @@ struct is_no_optional
   static const bool value = !is_optional_<BOOST_DEDUCED_TYPENAME boost::decay<T>::type>::value;
 };
 
+
+template <class T, class U>
+  struct is_same_decayed
+  {
+    static const bool value = ::boost::is_same<T, BOOST_DEDUCED_TYPENAME ::boost::remove_reference<U>::type>::value
+                           || ::boost::is_same<T, const BOOST_DEDUCED_TYPENAME ::boost::remove_reference<U>::type>::value;
+  };
+
+template <class T, class U>
+struct no_unboxing_cond
+{
+  static const bool value = is_no_optional<U>::value && !is_same_decayed<T, U>::value;
+};
+
+
 } // namespace detail
 
 template <class T>
@@ -94,13 +127,21 @@ public:
     optional(none_t) BOOST_NOEXCEPT : ptr_() {}  
 
     template <class U>
-        explicit optional(const optional<U&>& rhs) BOOST_NOEXCEPT : ptr_(rhs.ptr_) {}
-    optional(const optional& rhs) BOOST_NOEXCEPT : ptr_(rhs.ptr_) {}
+        explicit optional(const optional<U&>& rhs) BOOST_NOEXCEPT : ptr_(rhs.get_ptr()) {}
+    optional(const optional& rhs) BOOST_NOEXCEPT : ptr_(rhs.get_ptr()) {}
     
-
-    optional& operator=(const optional& rhs) BOOST_NOEXCEPT { ptr_ = rhs.ptr_; return *this; }
+    // the following two implement a 'conditionally explicit' constructor: condition is a hack for buggy compilers with srewed conversion construction from const int
     template <class U>
-        optional& operator=(const optional<U&>& rhs) BOOST_NOEXCEPT { ptr_ = rhs.ptr_; return *this; }
+      explicit optional(U& rhs, BOOST_DEDUCED_TYPENAME boost::enable_if_c<detail::is_same_decayed<T, U>::value && detail::is_const_integral_bad_for_conversion<U>::value>::type* = 0) BOOST_NOEXCEPT
+      : ptr_(boost::addressof(rhs)) {}
+      
+    template <class U>
+      optional(U& rhs, BOOST_DEDUCED_TYPENAME boost::enable_if_c<detail::is_same_decayed<T, U>::value && !detail::is_const_integral_bad_for_conversion<U>::value>::type* = 0) BOOST_NOEXCEPT
+      : ptr_(boost::addressof(rhs)) {}
+
+    optional& operator=(const optional& rhs) BOOST_NOEXCEPT { ptr_ = rhs.get_ptr(); return *this; }
+    template <class U>
+        optional& operator=(const optional<U&>& rhs) BOOST_NOEXCEPT { ptr_ = rhs.get_ptr(); return *this; }
     optional& operator=(none_t) BOOST_NOEXCEPT { ptr_ = 0; return *this; }
     
     
@@ -121,8 +162,10 @@ public:
     
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES   
  
+    optional(T&& /* rhs */) BOOST_NOEXCEPT { detail::prevent_binding_rvalue<T&&>(); }
+    
     template <class R>
-        optional(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<R> >::type* = 0) BOOST_NOEXCEPT
+        optional(R&& r, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::no_unboxing_cond<T, R> >::type* = 0) BOOST_NOEXCEPT
         : ptr_(boost::addressof(r)) { detail::prevent_binding_rvalue<R>(); }
         
     template <class R>
@@ -154,19 +197,26 @@ public:
       
 #else  // BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 
+    
+    // the following two implement a 'conditionally explicit' constructor
     template <class U>
-        optional(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) BOOST_NOEXCEPT : ptr_(boost::addressof(v)) { }
+      explicit optional(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if_c<detail::no_unboxing_cond<T, U>::value && detail::is_const_integral_bad_for_conversion<U>::value >::type* = 0) BOOST_NOEXCEPT
+      : ptr_(boost::addressof(v)) { }
+      
+    template <class U>
+      optional(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if_c<detail::no_unboxing_cond<T, U>::value && !detail::is_const_integral_bad_for_conversion<U>::value >::type* = 0) BOOST_NOEXCEPT
+      : ptr_(boost::addressof(v)) { }
         
     template <class U>
-        optional(bool cond, U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) BOOST_NOEXCEPT : ptr_(cond ? boost::addressof(v) : 0) {}
+      optional(bool cond, U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) BOOST_NOEXCEPT : ptr_(cond ? boost::addressof(v) : 0) {}
 
     template <class U>
-        BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U>, optional<T&>&>::type
-        operator=(U& v) BOOST_NOEXCEPT
-        {
-            detail::prevent_assignment_from_false_const_integral<U>();
-            ptr_ = boost::addressof(v); return *this;
-        }
+      BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U>, optional<T&>&>::type
+      operator=(U& v) BOOST_NOEXCEPT
+      {
+        detail::prevent_assignment_from_false_const_integral<U>();
+        ptr_ = boost::addressof(v); return *this;
+      }
 
     template <class U>
         void emplace(U& v, BOOST_DEDUCED_TYPENAME boost::enable_if<detail::is_no_optional<U> >::type* = 0) BOOST_NOEXCEPT

include/boost/optional/optional.hpp

@@ -1,5 +1,5 @@
 // Copyright (C) 2003, 2008 Fernando Luis Cacciola Carballal.
-// Copyright (C) 2014, 2015 Andrzej Krzemienski.
+// Copyright (C) 2014 - 2016 Andrzej Krzemienski.
 //
 // Use, modification, and distribution is subject to the Boost Software
 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
@@ -56,6 +56,31 @@
 #include <boost/optional/detail/old_optional_implementation.hpp>
 #else
 namespace boost {
+  
+namespace optional_ns {
+  
+// a tag for in-place initialization of contained value
+struct in_place_init_t
+{
+  struct init_tag{};
+  explicit in_place_init_t(init_tag){}
+};            
+const in_place_init_t in_place_init ((in_place_init_t::init_tag()));
+
+// a tag for conditional in-place initialization of contained value	
+struct in_place_init_if_t
+{
+  struct init_tag{};
+  explicit in_place_init_if_t(init_tag){}
+};
+const in_place_init_if_t in_place_init_if ((in_place_init_if_t::init_tag()));
+  
+} // namespace optional_ns
+
+using optional_ns::in_place_init_t;
+using optional_ns::in_place_init;
+using optional_ns::in_place_init_if_t;
+using optional_ns::in_place_init_if;
 
 namespace optional_detail {
 
@@ -338,51 +363,179 @@ class optional_base : public optional_tag
 #if (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) && (!defined BOOST_NO_CXX11_VARIADIC_TEMPLATES)
     // Constructs in-place
     // upon exception *this is always uninitialized
+    template<class... Args>
+    void construct ( in_place_init_t, Args&&... args )
+    {
+      ::new (m_storage.address()) value_type( boost::forward<Args>(args)... ) ;
+      m_initialized = true ;
+    }
+
     template<class... Args>
     void emplace_assign ( Args&&... args )
-     {
-       destroy();
-       ::new (m_storage.address()) value_type( boost::forward<Args>(args)... );
-       m_initialized = true ;
-     }
+    {
+      destroy();
+      construct(in_place_init, boost::forward<Args>(args)...);
+    }
+     
+    template<class... Args>
+    explicit optional_base ( in_place_init_t, Args&&... args )
+      :
+      m_initialized(false)
+    {
+      construct(in_place_init, boost::forward<Args>(args)...);
+    }
+    
+    template<class... Args>
+    explicit optional_base ( in_place_init_if_t, bool cond, Args&&... args )
+      :
+      m_initialized(false)
+    {
+      if ( cond )
+        construct(in_place_init, boost::forward<Args>(args)...);
+    }
 #elif (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
     template<class Arg>
-    void emplace_assign ( Arg&& arg )
+    void construct ( in_place_init_t, Arg&& arg )
      {
-       destroy();
        ::new (m_storage.address()) value_type( boost::forward<Arg>(arg) );
        m_initialized = true ;
      }
      
-    void emplace_assign ()
+    void construct ( in_place_init_t )
      {
-       destroy();
        ::new (m_storage.address()) value_type();
        m_initialized = true ;
      }
-#else
+     
     template<class Arg>
-    void emplace_assign ( const Arg& arg )
+    void emplace_assign ( Arg&& arg )
      {
        destroy();
+       construct(in_place_init, boost::forward<Arg>(arg)) ;
+     }
+     
+    void emplace_assign ()
+     {
+       destroy();
+       construct(in_place_init) ;
+     }
+     
+    template<class Arg>
+    explicit optional_base ( in_place_init_t, Arg&& arg )
+      :
+      m_initialized(false)
+    {
+      construct(in_place_init, boost::forward<Arg>(arg));
+    }
+    
+    explicit optional_base ( in_place_init_t )
+      :
+      m_initialized(false)
+    {
+      construct(in_place_init);
+    }
+    
+    template<class Arg>
+    explicit optional_base ( in_place_init_if_t, bool cond, Arg&& arg )
+      :
+      m_initialized(false)
+    {
+      if ( cond )
+        construct(in_place_init, boost::forward<Arg>(arg));
+    }
+    
+    explicit optional_base ( in_place_init_if_t, bool cond )
+      :
+      m_initialized(false)
+    {
+      if ( cond )
+        construct(in_place_init);
+    }
+
+#else
+     
+    template<class Arg>
+    void construct ( in_place_init_t, const Arg& arg )
+     {
        ::new (m_storage.address()) value_type( arg );
        m_initialized = true ;
      }
      
+    template<class Arg>
+    void construct ( in_place_init_t, Arg& arg )
+     {
+       ::new (m_storage.address()) value_type( arg );
+       m_initialized = true ;
+     }
+     
+    void construct ( in_place_init_t )
+     {
+       ::new (m_storage.address()) value_type();
+       m_initialized = true ;
+     }
+
+    template<class Arg>
+    void emplace_assign ( const Arg& arg )
+    {
+      destroy();
+      construct(in_place_init, arg);
+    }
+     
     template<class Arg>
     void emplace_assign ( Arg& arg )
-     {
-       destroy();
-       ::new (m_storage.address()) value_type( arg );
-       m_initialized = true ;
-     }
+    {
+      destroy();
+      construct(in_place_init, arg);
+    }
      
     void emplace_assign ()
-     {
-       destroy();
-       ::new (m_storage.address()) value_type();
-       m_initialized = true ;
-     }
+    {
+      destroy();
+      construct(in_place_init);
+    }
+    
+    template<class Arg>
+    explicit optional_base ( in_place_init_t, const Arg& arg )
+      : m_initialized(false)
+    {
+      construct(in_place_init, arg);
+    }
+
+    template<class Arg>
+    explicit optional_base ( in_place_init_t, Arg& arg )
+      : m_initialized(false)
+    {
+      construct(in_place_init, arg);
+    }
+    
+    explicit optional_base ( in_place_init_t )
+      : m_initialized(false)
+    {
+      construct(in_place_init);
+    }
+    
+    template<class Arg>
+    explicit optional_base ( in_place_init_if_t, bool cond, const Arg& arg )
+      : m_initialized(false)
+    {
+      if ( cond )
+        construct(in_place_init, arg);
+    }
+    
+    template<class Arg>
+    explicit optional_base ( in_place_init_if_t, bool cond, Arg& arg )
+      : m_initialized(false)
+    {
+      if ( cond )
+        construct(in_place_init, arg);
+    } 
+    
+    explicit optional_base ( in_place_init_if_t, bool cond )
+      : m_initialized(false)
+    {
+      if ( cond )
+        construct(in_place_init);
+    }
 #endif
 
 #ifndef BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
@@ -574,30 +727,36 @@ class optional_base : public optional_tag
 template <typename U>
 struct is_optional_related
   : boost::conditional< boost::is_base_of<optional_detail::optional_tag, BOOST_DEDUCED_TYPENAME boost::decay<U>::type>::value
-                     || boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<U>::type, none_t>::value,
+                     || boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<U>::type, none_t>::value
+                     || boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<U>::type, in_place_init_t>::value
+                     || boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<U>::type, in_place_init_if_t>::value,
     boost::true_type, boost::false_type>::type
 {};
 
-#if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && !defined(BOOST_NO_CXX11_DECLTYPE) && !BOOST_WORKAROUND(BOOST_MSVC, < 1800) && !BOOST_WORKAROUND(BOOST_GCC_VERSION, < 40500) && !defined(__SUNPRO_CC)
-  // this condition is a copy paste from is_constructible.hpp
-  // I also disable SUNPRO, as it seems not to support type_traits correctly
+#if !defined(BOOST_OPTIONAL_DETAIL_NO_IS_CONSTRUCTIBLE_TRAIT)
   
 template <typename T, typename U>
 struct is_convertible_to_T_or_factory
   : boost::conditional< boost::is_base_of<boost::in_place_factory_base, BOOST_DEDUCED_TYPENAME boost::decay<U>::type>::value
                      || boost::is_base_of<boost::typed_in_place_factory_base, BOOST_DEDUCED_TYPENAME boost::decay<U>::type>::value
-                     || boost::is_constructible<T, U&&>::value
+                     || (boost::is_constructible<T, U&&>::value && !boost::is_same<T, BOOST_DEDUCED_TYPENAME boost::decay<U>::type>::value)
                       , boost::true_type, boost::false_type>::type
 {};
 
+template <typename T, typename U>
+struct is_optional_constructible : boost::is_constructible<T, U>
+{};
+
 #else
 
-#define BOOST_OPTIONAL_DETAIL_NO_IS_CONSTRUCTIBLE_TRAIT
-
 template <typename, typename>
 struct is_convertible_to_T_or_factory : boost::true_type
 {};
 
+template <typename T, typename U>
+struct is_optional_constructible : boost::true_type
+{};
+
 #endif // is_convertible condition
 
 template <typename T, typename U>
@@ -657,7 +816,11 @@ class optional : public optional_detail::optional_base<T>
     // Requires a valid conversion from U to T.
     // Can throw if T::T(U const&) does
     template<class U>
-    explicit optional ( optional<U> const& rhs )
+    explicit optional ( optional<U> const& rhs
+#ifndef BOOST_OPTIONAL_DETAIL_NO_SFINAE_FRIENDLY_CONSTRUCTORS
+                        ,typename boost::enable_if< optional_detail::is_optional_constructible<T, U const&> >::type* = 0
+#endif
+                      )
       :
       base()
     {
@@ -670,7 +833,11 @@ class optional : public optional_detail::optional_base<T>
     // Requires a valid conversion from U to T.
     // Can throw if T::T(U&&) does
     template<class U>
-    explicit optional ( optional<U> && rhs )
+    explicit optional ( optional<U> && rhs
+#ifndef BOOST_OPTIONAL_DETAIL_NO_SFINAE_FRIENDLY_CONSTRUCTORS
+                        ,typename boost::enable_if< optional_detail::is_optional_constructible<T, U> >::type* = 0
+#endif
+                      )
       :
       base()
     {
@@ -789,6 +956,19 @@ class optional : public optional_detail::optional_base<T>
       }
 #endif
 
+#ifndef BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX
+
+    // Assigns from a T (deep-moves/copies the rhs value)
+    template <typename T_>
+    BOOST_DEDUCED_TYPENAME boost::enable_if<boost::is_same<T, BOOST_DEDUCED_TYPENAME boost::decay<T_>::type>, optional&>::type
+    operator= ( T_&& val )
+      {
+        this->assign( boost::forward<T_>(val) ) ;
+        return *this ;
+      }
+      
+#else
+
     // Assigns from a T (deep-copies the rhs value)
     // Basic Guarantee: If T::( T const& ) throws, this is left UNINITIALIZED
     optional& operator= ( argument_type val )
@@ -796,7 +976,7 @@ class optional : public optional_detail::optional_base<T>
         this->assign( val ) ;
         return *this ;
       }
-
+      
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Assigns from a T (deep-moves the rhs value)
     optional& operator= ( rval_reference_type val )
@@ -805,7 +985,9 @@ class optional : public optional_detail::optional_base<T>
         return *this ;
       }
 #endif
-
+      
+#endif // BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX
+      
     // Assigns from a "none"
     // Which destroys the current value, if any, leaving this UNINITIALIZED
     // No-throw (assuming T::~T() doesn't)
@@ -820,9 +1002,20 @@ class optional : public optional_detail::optional_base<T>
     // upon exception *this is always uninitialized
     template<class... Args>
     void emplace ( Args&&... args )
-     {
-       this->emplace_assign( boost::forward<Args>(args)... );
-     }
+    {
+      this->emplace_assign( boost::forward<Args>(args)... );
+    }
+     
+    template<class... Args>
+    explicit optional ( in_place_init_t, Args&&... args )
+    : base( in_place_init, boost::forward<Args>(args)... )
+    {}
+    
+    template<class... Args>
+    explicit optional ( in_place_init_if_t, bool cond, Args&&... args )
+    : base( in_place_init_if, cond, boost::forward<Args>(args)... )
+    {}
+    
 #elif (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
     template<class Arg>
     void emplace ( Arg&& arg )
@@ -834,6 +1027,24 @@ class optional : public optional_detail::optional_base<T>
      {
        this->emplace_assign();
      }
+     
+    template<class Args>
+    explicit optional ( in_place_init_t, Args&& args )
+    : base( in_place_init, boost::forward<Args>(args) )
+    {}
+
+    explicit optional ( in_place_init_t )
+    : base( in_place_init )
+    {}
+    
+    template<class Args>
+    explicit optional ( in_place_init_if_t, bool cond, Args&& args )
+    : base( in_place_init_if, cond, boost::forward<Args>(args) )
+    {}
+    
+    explicit optional ( in_place_init_if_t, bool cond )
+    : base( in_place_init_if, cond )
+    {}
 #else
     template<class Arg>
     void emplace ( const Arg& arg )
@@ -851,6 +1062,34 @@ class optional : public optional_detail::optional_base<T>
      {
        this->emplace_assign();
      }
+     
+    template<class Arg>
+    explicit optional ( in_place_init_t, const Arg& arg )
+    : base( in_place_init, arg )
+    {}
+    
+    template<class Arg>
+    explicit optional ( in_place_init_t, Arg& arg )
+    : base( in_place_init, arg )
+    {}
+
+    explicit optional ( in_place_init_t )
+    : base( in_place_init )
+    {}
+    
+    template<class Arg>
+    explicit optional ( in_place_init_if_t, bool cond, const Arg& arg )
+    : base( in_place_init_if, cond, arg )
+    {}
+    
+    template<class Arg>
+    explicit optional ( in_place_init_if_t, bool cond, Arg& arg )
+    : base( in_place_init_if, cond, arg )
+    {} 
+    
+    explicit optional ( in_place_init_if_t, bool cond )
+    : base( in_place_init_if, cond )
+    {}
 #endif
 
     void swap( optional & arg )

include/boost/optional/optional_fwd.hpp

@@ -16,7 +16,7 @@
 #ifndef BOOST_OPTIONAL_OPTIONAL_FWD_FLC_19NOV2002_HPP
 #define BOOST_OPTIONAL_OPTIONAL_FWD_FLC_19NOV2002_HPP
 
-#include <boost/config/suffix.hpp>
+#include <boost/config.hpp>
 
 namespace boost {
 

test/Jamfile.v2

@@ -1,7 +1,7 @@
 # Boost.Optional Library test Jamfile
 #
 # Copyright (C) 2003, Fernando Luis Cacciola Carballal.
-# Copyright (C) 2014, 2015 Andrzej Krzemienski
+# Copyright (C) 2014 - 2016 Andrzej Krzemienski
 #
 # Use, modification, and distribution is subject to the Boost Software
 # License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
@@ -20,6 +20,8 @@ import testing ;
     [ run optional_test.cpp ]
     [ run optional_test_swap.cpp ]
     [ run optional_test_conversions_from_U.cpp ]
+    [ run optional_test_convert_from_T.cpp ]
+    [ run optional_test_empty_braces.cpp ]
     [ run optional_test_tie.cpp ]
     [ run optional_test_ref_assign_portable_minimum.cpp ]
     [ run optional_test_ref_assign_mutable_int.cpp ]
@@ -40,7 +42,7 @@ import testing ;
     [ run optional_test_emplace.cpp ]
     [ run optional_test_minimum_requirements.cpp ]
     [ run optional_test_msvc_bug_workaround.cpp ]
-    [ compile optional_test_sfinae_friendly_value_ctor.cpp ]
+    [ compile optional_test_sfinae_friendly_ctor.cpp ]
     [ compile-fail optional_test_ref_convert_assign_const_int_prevented.cpp ]
     [ compile-fail optional_test_fail1.cpp ]
     [ compile-fail optional_test_fail3a.cpp ]

test/optional_test_common.cpp

@@ -152,21 +152,21 @@ bool X::pending_assign  = false ;
 bool X::throw_on_copy   = false ;
 bool X::throw_on_assign = false ;
 
-inline void set_pending_copy           ( X const* x ) { X::pending_copy  = true  ; }
-inline void set_pending_dtor           ( X const* x ) { X::pending_dtor  = true  ; }
-inline void set_pending_assign         ( X const* x ) { X::pending_assign = true  ; }
-inline void set_throw_on_copy          ( X const* x ) { X::throw_on_copy = true  ; }
-inline void set_throw_on_assign        ( X const* x ) { X::throw_on_assign = true  ; }
-inline void reset_throw_on_copy        ( X const* x ) { X::throw_on_copy = false ; }
-inline void reset_throw_on_assign      ( X const* x ) { X::throw_on_assign = false ; }
-inline void check_is_pending_copy      ( X const* x ) { BOOST_TEST( X::pending_copy ) ; }
-inline void check_is_pending_dtor      ( X const* x ) { BOOST_TEST( X::pending_dtor ) ; }
-inline void check_is_pending_assign    ( X const* x ) { BOOST_TEST( X::pending_assign ) ; }
-inline void check_is_not_pending_copy  ( X const* x ) { BOOST_TEST( !X::pending_copy ) ; }
-inline void check_is_not_pending_dtor  ( X const* x ) { BOOST_TEST( !X::pending_dtor ) ; }
-inline void check_is_not_pending_assign( X const* x ) { BOOST_TEST( !X::pending_assign ) ; }
-inline void check_instance_count       ( int c, X const* x ) { BOOST_TEST( X::count == c ) ; }
-inline int  get_instance_count         ( X const* x ) { return X::count ; }
+inline void set_pending_copy           ( X const* ) { X::pending_copy  = true  ; }
+inline void set_pending_dtor           ( X const* ) { X::pending_dtor  = true  ; }
+inline void set_pending_assign         ( X const* ) { X::pending_assign = true  ; }
+inline void set_throw_on_copy          ( X const* ) { X::throw_on_copy = true  ; }
+inline void set_throw_on_assign        ( X const* ) { X::throw_on_assign = true  ; }
+inline void reset_throw_on_copy        ( X const* ) { X::throw_on_copy = false ; }
+inline void reset_throw_on_assign      ( X const* ) { X::throw_on_assign = false ; }
+inline void check_is_pending_copy      ( X const* ) { BOOST_TEST( X::pending_copy ) ; }
+inline void check_is_pending_dtor      ( X const* ) { BOOST_TEST( X::pending_dtor ) ; }
+inline void check_is_pending_assign    ( X const* ) { BOOST_TEST( X::pending_assign ) ; }
+inline void check_is_not_pending_copy  ( X const* ) { BOOST_TEST( !X::pending_copy ) ; }
+inline void check_is_not_pending_dtor  ( X const* ) { BOOST_TEST( !X::pending_dtor ) ; }
+inline void check_is_not_pending_assign( X const* ) { BOOST_TEST( !X::pending_assign ) ; }
+inline void check_instance_count       ( int c, X const* ) { BOOST_TEST( X::count == c ) ; }
+inline int  get_instance_count         ( X const* ) { return X::count ; }
 
 inline void set_pending_copy           (...) {}
 inline void set_pending_dtor           (...) {}

test/optional_test_convert_from_T.cpp

@@ -0,0 +1,70 @@
+// Copyright (C) 2014 Andrzej Krzemienski.
+//
+// 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)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include "boost/optional/optional.hpp"
+
+#ifdef __BORLANDC__
+#pragma hdrstop
+#endif
+
+#include "boost/core/lightweight_test.hpp"
+#include "boost/none.hpp"
+
+//#ifndef BOOST_OPTIONAL_NO_CONVERTING_COPY_CTOR
+
+using boost::optional;
+using boost::none;
+
+template <typename U>
+struct superconv
+{
+  #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
+  template <typename T>
+    superconv(T&&) { BOOST_STATIC_ASSERT(sizeof(T) == 0); }
+  #else
+  template <typename T>
+    superconv(const T&) { BOOST_STATIC_ASSERT(sizeof(T) == 0); }
+  template <typename T>
+    superconv(      T&) { BOOST_STATIC_ASSERT(sizeof(T) == 0); }
+  #endif
+  
+  superconv() {}
+};
+
+void test_optional_of_superconverting_T() // compile-time test
+{
+#ifndef BOOST_OPTIONAL_DETAIL_NO_IS_CONSTRUCTIBLE_TRAIT
+  superconv<optional<int> > s;
+   superconv<optional<int> > & rs = s;
+  optional<superconv<optional<int> > > os = rs;
+#endif
+}
+
+void test_optional_optional_T()
+{
+  optional<int> oi1 (1), oiN;
+  optional< optional<int> > ooi1 (oi1), ooiN(oiN);
+  
+  BOOST_TEST(ooi1);
+  BOOST_TEST(*ooi1);
+  BOOST_TEST_EQ(**ooi1, 1);
+  
+  BOOST_TEST(ooiN);
+  BOOST_TEST(!*ooiN);
+}  
+
+int main()
+{
+    test_optional_optional_T();
+    test_optional_of_superconverting_T();
+    
+    return boost::report_errors();
+}

test/optional_test_emplace.cpp

@@ -23,6 +23,8 @@
 
 using boost::optional;
 using boost::none;
+using boost::in_place_init;
+using boost::in_place_init_if;
 
 #if (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) && (!defined BOOST_NO_CXX11_VARIADIC_TEMPLATES)
 
@@ -87,6 +89,109 @@ void test_emplace()
     BOOST_TEST(7 == o->which_ctor);
 }
 
+void test_in_place_ctor()
+{
+    int i = 0;
+    double d = 0.0;
+    const std::string cs;
+    std::string ms;
+        
+  {
+    optional<Guard> o (in_place_init);
+    BOOST_TEST(o);
+    BOOST_TEST(0 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init, i, 2.0);
+    BOOST_TEST(o);
+    BOOST_TEST(1 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init, 1, d);
+    BOOST_TEST(o);
+    BOOST_TEST(2 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init, 1, 2.0);
+    BOOST_TEST(o);
+    BOOST_TEST(3 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init, i, d);
+    BOOST_TEST(o);
+    BOOST_TEST(4 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init, cs);
+    BOOST_TEST(o);
+    BOOST_TEST(5 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init, ms);
+    BOOST_TEST(o);
+    BOOST_TEST(6 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init, std::string());
+    BOOST_TEST(o);
+    BOOST_TEST(7 == o->which_ctor);
+  }
+}
+
+void test_in_place_if_ctor()
+{
+    int i = 0;
+    double d = 0.0;
+    const std::string cs;
+    std::string ms;
+        
+  {
+    optional<Guard> o (in_place_init_if, true);
+    BOOST_TEST(o);
+    BOOST_TEST(0 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init_if, true, i, 2.0);
+    BOOST_TEST(o);
+    BOOST_TEST(1 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init_if, true, 1, d);
+    BOOST_TEST(o);
+    BOOST_TEST(2 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init_if, true, 1, 2.0);
+    BOOST_TEST(o);
+    BOOST_TEST(3 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init_if, true, i, d);
+    BOOST_TEST(o);
+    BOOST_TEST(4 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init_if, true, cs);
+    BOOST_TEST(o);
+    BOOST_TEST(5 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init_if, true, ms);
+    BOOST_TEST(o);
+    BOOST_TEST(6 == o->which_ctor);
+  }
+  {  
+    optional<Guard> o (in_place_init_if, true, std::string());
+    BOOST_TEST(o);
+    BOOST_TEST(7 == o->which_ctor);
+  }
+  
+  {
+    optional<Guard> o (in_place_init_if, false, 1, 2.0);
+    BOOST_TEST(!o);
+  }
+}
+
 
 #endif
 
@@ -112,6 +217,24 @@ void test_no_moves_on_emplacement()
         BOOST_TEST(false);
     }
 }
+
+void test_no_moves_on_in_place_ctor()
+{
+    try {
+        optional<ThrowOnMove> o (in_place_init, 1);
+        BOOST_TEST(o);
+        
+        optional<ThrowOnMove> p (in_place_init_if, true, 1);
+        BOOST_TEST(p);
+        
+        optional<ThrowOnMove> q (in_place_init_if, false, 1);
+        BOOST_TEST(!q);
+    } 
+    catch (...) {
+        BOOST_TEST(false);
+    }
+}
+
 #endif
 
 struct Thrower
@@ -158,6 +281,7 @@ void test_no_assignment_on_emplacement()
 }
 
 namespace no_rvalue_refs {
+
 class Guard
 {
 public:
@@ -188,19 +312,78 @@ void test_emplace()
     BOOST_TEST(o);
     BOOST_TEST(6 == o->which_ctor);
 }
-} 
+
+void test_in_place_ctor()
+{
+  const std::string cs;
+  std::string ms;
+  
+  {
+    optional<Guard> o (in_place_init);
+    BOOST_TEST(o);
+    BOOST_TEST(0 == o->which_ctor);
+  }
+  {
+    optional<Guard> o (in_place_init, cs);
+    BOOST_TEST(o);
+    BOOST_TEST(5 == o->which_ctor);
+  }
+  {
+    optional<Guard> o (in_place_init, ms);
+    BOOST_TEST(o);
+    BOOST_TEST(6 == o->which_ctor);
+  }
+}
+
+void test_in_place_if_ctor()
+{
+  const std::string cs;
+  std::string ms;
+  
+  {
+    optional<Guard> n (in_place_init_if, false);
+    BOOST_TEST(!n);
+    
+    optional<Guard> o (in_place_init_if, true);
+    BOOST_TEST(o);
+    BOOST_TEST(0 == o->which_ctor);
+  }
+  {
+    optional<Guard> n (in_place_init_if, false, cs);
+    BOOST_TEST(!n);
+    
+    optional<Guard> o (in_place_init_if, true, cs);
+    BOOST_TEST(o);
+    BOOST_TEST(5 == o->which_ctor);
+  }
+  {
+    optional<Guard> n (in_place_init_if, false, ms);
+    BOOST_TEST(!n);
+    
+    optional<Guard> o (in_place_init_if, true, ms);
+    BOOST_TEST(o);
+    BOOST_TEST(6 == o->which_ctor);
+  }
+}
+
+} // namespace no_rvalue_ref
 
 int main()
 {
 #if (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) && (!defined BOOST_NO_CXX11_VARIADIC_TEMPLATES)
     test_emplace();
+    test_in_place_ctor();
+    test_in_place_if_ctor();
 #endif
 #if (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
     test_no_moves_on_emplacement();
+    test_no_moves_on_in_place_ctor();
 #endif
     test_clear_on_throw();
     test_no_assignment_on_emplacement();
     no_rvalue_refs::test_emplace();
+    no_rvalue_refs::test_in_place_ctor();
+    no_rvalue_refs::test_in_place_if_ctor();
   
     return boost::report_errors();
 }

test/optional_test_empty_braces.cpp

@@ -0,0 +1,57 @@
+// Copyright (C) 2016 Andrzej Krzemienski.
+//
+// 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)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include "boost/optional/optional.hpp"
+
+#ifdef __BORLANDC__
+#pragma hdrstop
+#endif
+
+#include "boost/core/lightweight_test.hpp"
+
+//#ifndef BOOST_OPTIONAL_NO_CONVERTING_ASSIGNMENT
+//#ifndef BOOST_OPTIONAL_NO_CONVERTING_COPY_CTOR
+
+using boost::optional;
+
+struct Value
+{
+  explicit Value(int) {}
+};
+
+#ifndef BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX
+template <typename T>
+void test_brace_init()
+{
+  optional<T> o = {};
+  BOOST_TEST(!o);
+}
+
+template <typename T>
+void test_brace_assign()
+{
+  optional<T> o;
+  o = {};
+  BOOST_TEST(!o);
+} 
+#endif
+
+int main()
+{
+#ifndef BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX
+  test_brace_init<int>();
+  test_brace_init<Value>();
+  test_brace_assign<int>();
+  test_brace_assign<Value>();
+#endif
+
+  return boost::report_errors();
+}

test/optional_test_ref_assign_portable_minimum.cpp

@@ -39,6 +39,7 @@ int main()
 {
   test_optional_ref_assignment<ScopeGuard>();
   test_optional_ref_assignment<Abstract>();
+  test_optional_ref_assignment< optional<int> >();
   
   return boost::report_errors();
 }

test/optional_test_ref_converting_ctor.cpp

@@ -102,6 +102,7 @@ int main()
   test_all_const_cases<int>();
   test_all_const_cases<ScopeGuard>();
   test_all_const_cases<Abstract>();
+  test_all_const_cases< optional<int> >();
   
   return boost::report_errors();
 }

test/optional_test_ref_fail_init_from_Trefref.cpp

@@ -10,6 +10,7 @@
 //  akrzemi1@gmail.com
 //
 #include "boost/optional.hpp"
+#include "boost/core/ignore_unused.hpp"
 
 #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
 //
@@ -18,6 +19,7 @@
 void optional_reference__test_no_init_from_Trefref()
 {
   boost::optional<const int&> opt = int(3);
+  boost::ignore_unused(opt);
 }
 
 #else

test/optional_test_ref_fail_init_from_Urefref.cpp

@@ -1,4 +1,4 @@
-// Copyright (C) 2014, andrzej Krzemienski.
+// Copyright (C) 2014, 2016 andrzej Krzemienski.
 //
 // Use, modification, and distribution is subject to the Boost Software
 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
@@ -10,6 +10,7 @@
 //  akrzemi1@gmail.com
 //
 #include "boost/optional.hpp"
+#include "boost/core/ignore_unused.hpp"
 
 #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
 //
@@ -18,6 +19,7 @@
 void optional_reference__test_no_init_from_Urefref()
 {
   boost::optional<const int&> opt = long(3);
+  boost::ignore_unused(opt);
 }
 
 #else

test/optional_test_ref_portable_minimum.cpp

@@ -430,6 +430,23 @@ void test_swap()
   BOOST_TEST(boost::addressof(*o2_) == boost::addressof(v1));
 }
 
+template <typename T, typename U>
+void test_convertability_of_compatible_reference_types()
+{
+  typename concrete_type_of<T>::type v1(1);
+  optional<T&> oN, o1(v1);
+  optional<U&> uN(oN), u1(o1);
+  BOOST_TEST(!uN);
+  BOOST_TEST(u1);
+  BOOST_TEST(boost::addressof(*u1) == boost::addressof(*o1));
+  
+  uN = o1;
+  u1 = oN;
+  BOOST_TEST(!u1);
+  BOOST_TEST(uN);
+  BOOST_TEST(boost::addressof(*uN) == boost::addressof(*o1));
+}
+
 template <typename T>
 void test_optional_ref()
 {
@@ -465,10 +482,18 @@ int main()
   test_optional_ref<int>();
   test_optional_ref<ScopeGuard>();
   test_optional_ref<Abstract>();
+  test_optional_ref< optional<int> >();
   
   test_optional_const_ref<int>();
   test_optional_const_ref<ScopeGuard>();
   test_optional_const_ref<Abstract>();
+  test_optional_const_ref< optional<int> >();
+  
+  test_convertability_of_compatible_reference_types<int, const int>();
+  test_convertability_of_compatible_reference_types<Impl, Abstract>();
+  test_convertability_of_compatible_reference_types<Impl, const Abstract>();
+  test_convertability_of_compatible_reference_types<const Impl, const Abstract>();
+  test_convertability_of_compatible_reference_types<optional<int>, const optional<int> >();
   
   return boost::report_errors();
 }

test/optional_test_sfinae_friendly_ctor.cpp

@@ -0,0 +1,49 @@
+// Copyright (C) 2014 Andrzej Krzemienski.
+//
+// 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)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  akrzemi1@gmail.com
+
+#include "boost/optional/optional.hpp"
+
+#ifdef __BORLANDC__
+#pragma hdrstop
+#endif
+
+using boost::optional;
+
+#if (!defined BOOST_OPTIONAL_DETAIL_NO_IS_CONSTRUCTIBLE_TRAIT)
+
+struct X {};
+struct Y {};
+  
+struct Resource
+{
+  explicit Resource(const X&) {}
+};
+
+BOOST_STATIC_ASSERT((  boost::is_constructible<Resource, const X&>::value ));
+BOOST_STATIC_ASSERT(( !boost::is_constructible<Resource, const Y&>::value ));
+
+BOOST_STATIC_ASSERT((  boost::is_constructible<optional<Resource>, const X&>::value ));
+BOOST_STATIC_ASSERT(( !boost::is_constructible<optional<Resource>, const Y&>::value ));
+
+#ifndef BOOST_OPTIONAL_DETAIL_NO_SFINAE_FRIENDLY_CONSTRUCTORS
+BOOST_STATIC_ASSERT((  boost::is_constructible< optional< optional<int> >, optional<int> >::value ));
+BOOST_STATIC_ASSERT(( !boost::is_constructible< optional<int>, optional< optional<int> > >::value ));
+
+BOOST_STATIC_ASSERT((  boost::is_constructible< optional< optional<int> >, const optional<int>& >::value ));
+BOOST_STATIC_ASSERT(( !boost::is_constructible< optional<int>, const optional< optional<int> >& >::value ));
+
+BOOST_STATIC_ASSERT((  boost::is_constructible<optional<Resource>, const optional<X>&>::value ));
+BOOST_STATIC_ASSERT(( !boost::is_constructible<optional<Resource>, const optional<Y>&>::value ));
+#endif
+  
+#endif
+
+int main() { }

test/optional_test_sfinae_friendly_value_ctor.cpp

@@ -1,38 +0,0 @@
-// Copyright (C) 2014 Andrzej Krzemienski.
-//
-// 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)
-//
-// See http://www.boost.org/lib/optional for documentation.
-//
-// You are welcome to contact the author at:
-//  akrzemi1@gmail.com
-
-#include "boost/optional/optional.hpp"
-
-#ifdef __BORLANDC__
-#pragma hdrstop
-#endif
-
-using boost::optional;
-
-#if (!defined BOOST_OPTIONAL_DETAIL_NO_IS_CONSTRUCTIBLE_TRAIT)
-
-struct X {};
-struct Y {};
-  
-struct Resource
-{
-  explicit Resource(const X&) {}
-};
-
-BOOST_STATIC_ASSERT(( boost::is_constructible<Resource, const X&>::value));
-BOOST_STATIC_ASSERT((!boost::is_constructible<Resource, const Y&>::value));
-
-BOOST_STATIC_ASSERT(( boost::is_constructible<optional<Resource>, const X&>::value));
-BOOST_STATIC_ASSERT((!boost::is_constructible<optional<Resource>, const Y&>::value));
-  
-#endif
-
-int main() { }

test/optional_xconfig_NO_LEGAL_CONVERT_FROM_REF_fail.cpp

@@ -15,7 +15,7 @@
 
 #if (defined BOOST_NO_CXX11_RVALUE_REFERENCES) || (!defined BOOST_OPTIONAL_CONFIG_NO_LEGAL_CONVERT_FROM_REF)
 
-static_assert(false, "failed as requested");
+# error "failed as requested"
 
 #else
 

test/testable_classes.hpp

@@ -12,6 +12,8 @@
 #ifndef BOOST_OPTIONAL_TEST_TESTABKE_CLASSES_AK_07JAN2015_HPP
 #define BOOST_OPTIONAL_TEST_TESTABKE_CLASSES_AK_07JAN2015_HPP
 
+#include "boost/optional/optional.hpp"
+
 struct ScopeGuard // no copy/move ctor/assign
 {
   int val_;
@@ -74,13 +76,23 @@ struct has_arrow<int>
   static const bool value = false;
 };
 
+template <>
+struct has_arrow< boost::optional<int> >
+{
+  static const bool value = false;
+};
+
 int& val(int& i) { return i; }
 int& val(Abstract& a) { return a.val(); }
+int& val(Impl& a) { return a.val(); }
 int& val(ScopeGuard& g) { return g.val(); }
+template <typename T> int& val(T& o) { return *o; }
 
 const int& val(const int& i) { return i; }
 const int& val(const Abstract& a) { return a.val(); }
+const int& val(const Impl& a) { return a.val(); }
 const int& val(const ScopeGuard& g) { return g.val(); }
+template <typename T> const int& val(const T& o) { return *o; }
 
 bool operator==(const Abstract& l, const Abstract& r) { return l.val() == r.val(); }
 bool operator==(const ScopeGuard& l, const ScopeGuard& r) { return l.val() == r.val(); }