[saywhat] The operation static_cast<std::string>(boost::python::extract<std::string>(...)) crashes Python. Seems to create reference counting problem.

[Konstantin Aslanidi <konstantin.aslanidi@…>]

I submit boost::python based python extension code that crashes Python interpreter when used as described below. I attach Visual Studio .NET project files.

C:\KDocuments\Variance Swap Validation 2\VarSw2\Debug>python ActivePython 2.5.2.2 (ActiveState Software Inc.) based on Python 2.5.2 (r252:60911, Mar 27 2008, 17:57:18) [MSC v.1310 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information.

import vrsw2 p=vrsw2.VarSwapTest() p.set(((1,2),(3,4)))

<crash here>

The C++ extension code: #include <string> #include <fstream> #include <boost/python.hpp> #include <boost/shared_ptr.hpp> using namespace boost::python;

class VarSwapTest { private:

class Impl { private:

std::ofstream theFile;

public:

Impl()

: theFile("VarSwapTestEcho.txt") {}

void set( object& input ) {

object o=input.attr("str")(); extract<std::string> ex(o); if( ex.check() )

theFile<<(static_cast<std::string>(ex()))<<std::endl;

else

theFile<<"failed to extract string"<<std::endl;

}

};

private:

boost::shared_ptr<Impl> theImpl;

public:

VarSwapTest() : theImpl(new Impl()) {} void set( object input ) {

theImpl->set(input);

}

};

BOOST_PYTHON_MODULE(vrsw2) {

class_<VarSwapTest>("VarSwapTest")

.def("set",&VarSwapTest::set)

;

}

[Konstantin Aslanidi <konstantin.aslanidi@…>]

Less complicated inputs do not create immediate problem: p.set((1,2)) p.set('d')

are fine.

[Dave Abrahams]

suppose you replace

static_cast<std::string>(boost::python::extract<std::string>(...))

with

boost::python::extract<std::string>(...)() // note extra parens

If the static_cast fails but my replacement works, I think you need to file a bug report with your compiler vendor.

[Konstantin Aslanidi <konstantin.aslanidi@…>]

Dave,

I tried all combinations, I do use extra perens in the submitted code. The code compiles, links, runs. It succeds for list,dicts,strings etc. It fails for embedded structures such as tuple of tuples.

For example: import vrsw2 p=vrsw2.VarSwapTest() p.set((1,2)) p.set('d')

are successful.

However, p.set(((1,2),(3,4))) crashes. I did some debugging, it appears that the crash occurs during heap deallocation. I was unable to find any version of the submitted code that would pass the tuple of tuples.

K.

[Konstantin Aslanidi <konstantin.aslanidi@…>]

Please, see the newly submitted correction.

Replying to dave:

suppose you replace

static_cast<std::string>(boost::python::extract<std::string>(...))

with

boost::python::extract<std::string>(...)() // note extra parens

If the static_cast fails but my replacement works, I think you need to file a bug report with your compiler vendor.

[Konstantin Aslanidi <konstantin.aslanidi@…>]

... in addition to previous comments, I verified the below suggestion. It does not work.

Replying to dave:

suppose you replace

static_cast<std::string>(boost::python::extract<std::string>(...))

with

boost::python::extract<std::string>(...)() // note extra parens

If the static_cast fails but my replacement works, I think you need to file a bug report with your compiler vendor.

[troy d. straszheim]

unable to reproduce with recent gcc. Test case simplified and added to my branch in git, will test on vc9, if it doesn't pass there i'll reopen.

the test:

​http://gitorious.org/~straszheim/boost/straszheim/commit/43829f0e3290b74aa88907a25698e30c573b1012