Hello,
sorry if this question is too trivial, but I've got some rather strange problem
with using the boost::python type wrapper for the python list.
It goes as follows: I've got a very small demo program (say main.cpp).
Running it causes a segfault. (The actual project is much larger, of course.)
The system I use is a Linux OpenSuse 11.1, with the distribution package
python-2.6.0-2.23.1
installed. I manually installed boost 1.44 (because the newer versions didn't
quite work with the
boost-log package, which is needed for the actual project). Which other
information might be helpful?
This is the program:
*******************************************
#include <iostream>
#include <boost/python.hpp>
using namespace std;
int main() {
boost::python::list myList;
myList.append("foo");
myList.append("fork");
cerr << "Printing length of list." << endl;
cerr << "Length of myList: " << boost::python::len(myList) << endl;
// the above line causes a segfault!
cerr << "TheList: " << boost::python::extract<string>(myList[0])() << ","
<< boost::python::extract<string>(myList[1])() << endl;
cerr << "Finished" << endl;
}
*******************************************
which I compile by the two commands:
/usr/bin/c++ -O0 -Wall -g -I. -I/usr/include/python2.6 -I/usr/local/include
-o main.o -c main.cpp
/usr/bin/c++ -O0 -Wall -g main.o -o boost_list_test -rdynamic
-L/usr/local/lib /usr/local/lib/libboost_python.so -lpython2.6
-Wl,-rpath,/usr/local/lib
The segfault occurs at the call to boost::python::len(myList). I debugged
the program with gdb, but the backtrace
#0 0xb7ec6027 in PyErr_Occurred () from /usr/lib/libpython2.6.so.1.0
#1 0x0804b0b1 in main () at main.cpp:15
doesn't really tell me anything. Interestingly, removing the offending line
causes a segfault at the *next* line, with a more verbose backtrace:
#0 0xb7e529d7 in PyInt_FromLong () from /usr/lib/libpython2.6.so.1.0
#1 0x0804ba33 in arg_to_python (this=0xbfffee70, x=@0xbfffef48) at
/usr/local/include/boost/python/converter/builtin_converters.hpp:122
#2 0x0804ba5d in boost::python::api::object_initializer_impl<false,
false>::get<int> (x=@0xbfffef48) at
/usr/local/include/boost/python/object_core.hpp:393
#3 0x0804ba9e in boost::python::api::object_base_initializer<int>
(x=@0xbfffef48) at /usr/local/include/boost/python/object_core.hpp:315
#4 0x0804bab1 in object<int> (this=0xbfffeedc, x=@0xbfffef48) at
/usr/local/include/boost/python/object_core.hpp:334
#5 0x0804bae1 in
boost::python::api::object_operators<boost::python::api::object>::operator[]<int>
(this=0xbfffef28, key=@0xbfffef48)
at /usr/local/include/boost/python/object_items.hpp:61
#6 0x0804af46 in main () at main.cpp:17
I really don't understand what I'm doing wrong. Do I need to resize the list
before using append? The documentation
(http://www.boost.org/doc/libs/1_44_0/libs/python/doc/v2/list.html) doesn't say
anything about this.
Any tips or hints are greatly appreciated!
Thankyou,
- Michael Wand
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