Strange behavior of add_property in Boost.Python - c++

Question

I met a strange behavior when using add_property of Boost.Python.
Here is the example codes, it simply add two properties (read-only & read-write) to the wrapped class.
#include <boost/python.hpp>
using namespace boost::python;
struct X {
X( int value ) : val( value ) {}
int get_value() const
{ return val; }
void set_value(int value)
{ val = value; }
int val;
};
BOOST_PYTHON_MODULE(hello) {
class_<X>("X", init<int>() )
// NOTE the order
.add_property( "val_r", &X::get_value ) // read-only first
.add_property( "val_rw", &X::get_value, &X::set_value ) // read-write second
;
}
and the build command:
$ g++ -I/usr/include/python2.7 -shared -L/usr/local/lib -o bp.dll bp.cpp -lboost_python -lpython2.7
I'm working in Cygwin x86_64, so the file extension is .dll. As for Ubuntu just change the output extension to .so.
When importing the bp module, it crashes with a Segmentation fault. The core dump file doesn't contain any call stack information.
However, if I change the order of add_property (as below) to add the read-write property first, it works ok.
.add_property( "val_rw", &X::get_value, &X::set_value ) // read-write first
.add_property( "val_r", &X::get_value ) // read-only second
My environment:
Cygwin x86_64
python 2.7.10
gcc 5.4.0
boost: 1.60.0
BTW, there's no problem in Ubuntu 14.04 (64-bit) whatever the add_property order is.
Why would this happen?