Documented limitations reported in Trac #12194 and Trac #12307

example/doc_template_assign.cpp

@@ -0,0 +1,98 @@
+//////////////////////////////////////////////////////////////////////////////
+//
+// (C) Copyright Ion Gaztanaga 2014-2014.
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/libs/move for documentation.
+//
+//////////////////////////////////////////////////////////////////////////////
+
+#include <boost/move/detail/config_begin.hpp>
+#include <boost/move/detail/meta_utils_core.hpp>
+
+#include <boost/move/move.hpp>
+
+//[template_assign_example_foo_bar
+
+class Foo
+{
+   BOOST_COPYABLE_AND_MOVABLE(Foo)
+
+   public:
+   int i;
+   explicit Foo(int val)      : i(val)   {}
+
+   Foo(BOOST_RV_REF(Foo) obj) : i(obj.i) {}
+
+   Foo& operator=(BOOST_RV_REF(Foo) rhs)
+   {  i = rhs.i; rhs.i = 0; return *this; }
+
+   Foo& operator=(BOOST_COPY_ASSIGN_REF(Foo) rhs)
+   {  i = rhs.i; return *this;   } //(1)
+
+   template<class U> //(*) TEMPLATED ASSIGNMENT, potential problem
+   //<-
+   #if 1
+   typename ::boost::move_detail::disable_if_same<U, Foo, Foo&>::type
+   operator=(const U& rhs)
+   #else
+   //->
+   Foo& operator=(const U& rhs)
+   //<-
+   #endif
+   //->
+   {  i = -rhs.i; return *this;  } //(2)
+};
+//]
+
+struct Bar
+{
+   int i;
+   explicit Bar(int val) : i(val) {}
+};
+
+
+//<-
+#ifdef NDEBUG
+#undef NDEBUG
+#endif
+//->
+#include <cassert>
+
+int main()
+{
+//[template_assign_example_main
+   Foo foo1(1);
+   //<-
+   assert(foo1.i == 1);
+   //->
+   Foo foo2(2);
+   //<-
+   assert(foo2.i == 2);
+   Bar bar(3);
+   assert(bar.i == 3);
+   //->
+   foo2 = foo1; // Calls (1) in C++11 but (2) in C++98
+   //<-
+   assert(foo2.i == 1);
+   assert(foo1.i == 1); //Fails in C++98 unless workaround is applied
+   foo1 = bar;
+   assert(foo1.i == -3);
+   foo2 = boost::move(foo1);
+   assert(foo1.i == 0);
+   assert(foo2.i == -3);
+   //->
+   const Foo foo5(5);
+   foo2 = foo5; // Calls (1) in C++11 but (2) in C++98
+   //<-
+   assert(foo2.i == 5); //Fails in C++98 unless workaround is applied
+   assert(foo5.i == 5);
+   //->
+//]
+   return 0;
+}
+
+
+#include <boost/move/detail/config_end.hpp>