Re: [Boost-bugs] [Boost C++ Libraries] #2049: extracting c++ pointer from python object with multiple parents

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #2049: extracting c++ pointer from python object with multiple parents
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2008-06-26 14:27:59

#2049: extracting c++ pointer from python object with multiple parents
-----------------------------------+----------------------------------------
  Reporter:  bloodyfanatic_at_[hidden]  |       Owner:  dave   
      Type:  Bugs                  |      Status:  closed 
 Milestone:  Boost 1.35.1          |   Component:  Python 
   Version:  Boost 1.35.0          |    Severity:  Problem
Resolution:  invalid               |    Keywords:         
-----------------------------------+----------------------------------------
Changes (by dave):

 * cc: stefan (added)
  * status:  new => closed
  * resolution:  => invalid

Comment:

 Replying to [comment:2 bloodyfanatic_at_[hidden]]:
 > Replying to [comment:1 dave]:
 > > Does this fail even when the dtors are non-virtual?
 >
 > yes it does, with the same error as always:

 In that case, please post the ''fully reduced'' test case

 Also, you need an __init__ method in both1 and both2 that initializes
 *both* bases or this can never work, because a wrapped class' __init__
 function is what actually constructs the C++ base object.  Without it,
 there is no base object to which a pointer can be returned from
 {{{extract}}}:
 {{{
   def __init__(self):
      Base1.__init__(self)
      Base2.__init__(self)
 }}}
 I don't know how to do this properly with super (the technique Stefan was
 suggesting), but his suggestion as written didn't take care of both bases,
 as the following demonstrates:

 {{{
 #!python
 >>> class X(object):
 ...    def __init__(self):
 ...        print 'X'
 ...
 >>> class Y(object):
 ...     def __init__(self):
 ...         print 'Y'
 ...
 >>> class Z(X,Y): pass  # essentially what you posted
 ...
 >>> z = Z()
 X
 >>> class Z(X,Y):
 ...     def __init__(self):
 ...         super(Z,self).__init__()  # Stefan's suggestion
 ...
 >>> z = Z()
 X
 >>> class Z(X,Y):
 ...     def __init__(self):
 ...         X.__init__(self)
 ...         Y.__init__(self)
 ...
 >>> z = Z()
 X
 Y
 >>>
 }}}

 I'm pretty sure this solves your problem so I'm closing the ticket, but if
 it doesn't, please re-open it.

-- 
Ticket URL: <http://svn.boost.org/trac/boost/ticket/2049#comment:3>
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