[Boost-bugs] [Boost C++ Libraries] #7080: make_constructor Does Not Initialize base_wrapper

Subject: [Boost-bugs] [Boost C++ Libraries] #7080: make_constructor Does Not Initialize base_wrapper
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-07-04 21:00:54

#7080: make_constructor Does Not Initialize base_wrapper
--------------------------------+-------------------------------------------
 Reporter:  team@…              |       Owner:  rwgk   
     Type:  Bugs                |      Status:  new    
Milestone:  To Be Determined    |   Component:  Python 
  Version:  Boost 1.51.0        |    Severity:  Problem
 Keywords:                      |  
--------------------------------+-------------------------------------------
 When binding a shared_ptr to Python, we're using a custom allocator
 defined using make_constructor:

 {{{
 class_< Controller, shared_ptr<Controller>, boost::noncopyable
 >("Controller", no_init)
             .def("__init__",
 boost::python::make_constructor(&Controller::make));
 }}}

 This works as expected except when classes are derived in Python.  In
 those cases, get_override does not work, since m_self is NULL.  If you use
 init<>() in the class_ constructor, instead of the make_constructor line,
 it works as expected.


 The bug is that make_constructor does not initialize the base_wrapper.
 I've tried a fix as follows, and it's now functional -- though I can't say
 if this is a good way to solve it.

 {{{
 +++ make_constructor.hpp
 @@ -59,6 +59,7 @@
            void* memory = holder::allocate(this->m_self,
 offsetof(instance_t, storage), sizeof(holder));
            try {
                (new (memory) holder(x))->install(this->m_self);
 +                         python::detail::initialize_wrapper(this->m_self,
 get_pointer(x));
            }
            catch(...) {
                holder::deallocate(this->m_self, memory);
 }}}

 It's also possible to fix this by partially specializing "template
 <typename T> struct install_holder;" before boost::python is included.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/7080>
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