id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
2049	extracting c++ pointer from python object with multiple parents	bloodyfanatic@…	Dave Abrahams	"Extracting a C++ pointer from a python object which inherited two base classes form C++ doesn't work correctly.
Only the first base can be extracted, the second cannot be extracted under all circumstances.
The script runs within an embedded python interpreter.

CPP code:

{{{
#define BOOST_PYTHON_STATIC_LIB
#include <boost/python.hpp>

using namespace boost::python;

class Base1
{
public:
	virtual ~Base1() {}
};

class Base2
{
public:
	virtual ~Base2() {}
};


void extractBase1( boost::python::object& obj)
{
	Base1* ex1 = extract<Base1*>(obj) BOOST_EXTRACT_WORKAROUND;
	Base1& ex2 = extract<Base1&>(obj) BOOST_EXTRACT_WORKAROUND;
}

void extractBase2( boost::python::object& obj)
{
	Base2* ex1 = extract<Base2*>(obj) BOOST_EXTRACT_WORKAROUND;
	Base2& ex2 = extract<Base2&>(obj) BOOST_EXTRACT_WORKAROUND;
}


BOOST_PYTHON_MODULE(Test_ext)
{
	class_<Base1, boost::noncopyable>(""Base1"");
	class_<Base2, boost::noncopyable>(""Base2"");

	def(""extractBase1"", extractBase1);
	def(""extractBase2"", extractBase2);
}


int main(int, char **) 
{
	try
	{
		Py_Initialize();	  
		initTest_ext();

		object main = import(""__main__"");
		object dictionary(main.attr(""__dict__""));
		object result = exec_file(""test.py"", dictionary, dictionary );
	}
	catch (error_already_set)
	{
		PyErr_Print();
	}

	return 0;
}
}}}

test.py:

{{{

from Test_ext import *

class both1(Base1, Base2):
	def foo(self):
		print ""foo!""

class both2(Base2, Base1):
	def foo(self):
		print ""foo2!""

obj1 = both1()

extractBase1(obj1)
extractBase2(obj1)	# doesn't work

obj2 = both()

extractBase1(obj2)	# doesn't work
extractBase2(obj2)
}}}
"	Bugs	closed		python USE GITHUB	Boost 1.35.0	Problem	invalid		Stefan Seefeld