added in_place constructors

include/boost/optional/optional.hpp

@@ -56,6 +56,21 @@
 #include <boost/optional/detail/old_optional_implementation.hpp>
 #else
 namespace boost {
+  
+namespace optional_ns {
+  
+class in_place_init_t {};            // a tag for in-place initialization
+const in_place_init_t in_place_init; // of contained value
+
+class in_place_init_if_t {};               // a tag for conditional in-place
+const in_place_init_if_t in_place_init_if; // init of contained value
+  
+} // 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 +353,177 @@ 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();
+      destroy();
-       ::new (m_storage.address()) value_type( boost::forward<Args>(args)... );
+      construct(in_place_init, boost::forward<Args>(args)...);
-       m_initialized = true ;
+    }
-     }
+     
+    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) ;
+     }
+     
+    explicit optional_base ( in_place_init_t, Arg&& args )
+      :
+      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);
+    }
+    
+    explicit optional_base ( in_place_init_if_t, bool cond, Arg&& args )
+      :
+      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();
+      destroy();
-       ::new (m_storage.address()) value_type( arg );
+      construct(in_place_init, arg);
-       m_initialized = true ;
+    }
-     }
      
     void emplace_assign ()
-     {
+    {
-       destroy();
+      destroy();
-       ::new (m_storage.address()) value_type();
+      construct(in_place_init);
-       m_initialized = true ;
+    }
-     }
+    
+    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
@@ -820,9 +961,20 @@ 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 +986,24 @@ 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 +1021,34 @@ 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 )

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();
 }