It worked! That problem had been driving me crazy for the past 2 days. I don't know why I couldn't find the answer via Google. Perhaps its because of all the brain damage from my Java programming. Thank you so much. - John 2008/2/10 Chad Austin <chad@imvu.com>:

Hi all,

A month ago or so we discovered a bug in Boost.Python that manifests when using enable_shared_from_this. Here is a test case that demonstrates the bug:

#include <boost/python.hpp> #include <boost/enable_shared_from_this.hpp>

using namespace boost; using namespace boost::python;

class Test; typedef shared_ptr<Test> TestPtr;

class Test : public enable_shared_from_this<Test> { public: static TestPtr construct() { return TestPtr(new Test); }

void act() { TestPtr kungFuDeathGrip(shared_from_this()); }

void take(TestPtr t) { } };

void Export_test() { class_<Test, TestPtr, noncopyable>("Test") .def("construct", &Test::construct) .staticmethod("construct")

.def("act", &Test::act) .def("take", &Test::take) ; }

And here is the Python:

x = Test.construct() x.take(x) x.act()

The bug (as I understand it) is that the shared_ptr_from_python converter creates a new shared_ptr for the Test instance to pass it into C++. This new shared_ptr has a nop deleter, except that it keeps the Python object alive as long as the new shared_ptr is alive. The problem here is that creating a shared_ptr to an object of type T when T is enable_shared_from_this<T> resets the weak pointer inside of enable_shared_from_this<T>. (See shared_ptr's constructors for the details of the implementation.) A fix that passes the test above and has worked for us is to change shared_ptr's constructor to accept a dont_enable_shared_from_this argument and pass that in from the shared_ptr_from_python converter. The patch is attached (against boost 1.33, but the bug didn't look fixed in 1.34 either).

Cheers, Chad

p.s. I have seen other people with this problem as well. Googling for bad_weak_ptr turns up several results.

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