Odtnhj

Using SWIG to generate a wrapper around a C++ class is causing a strange assertion at run-time:

Assertion failed!

Program: C:Python37python37_d.dll
File: c:_work4sobjectstypeobject.c
Line: 3634

Expression: PyTuple_Check(args)

For information on how your program can cause an assertion
failure, see the Visual C++ documentation on asserts

(Press Retry to debug the application - JIT must be enabled)

If ignore is clicked on the dialogue that pops up, everything seems to work fine.

I've created an example program to try replicate the problem and have experienced the same issue:

main.cpp

#include "testwrapper.h"

#pragma push_macro("slots")
#undef slots
#include "Python.h"
#pragma pop_macro("slots")

#include "SwigModules/generated/swig_runtime.h"

PyObject * ConvertToWrapper(SwigInterface * instance)

 swig_type_info * pTypeInfo = SWIG_TypeQuery("SwigInterface *");
 PyObject* obj = SWIG_NewPointerObj(instance, pTypeInfo, 0); <- issue occurs here
 return obj;


TestWrapper * wrapper = new TestWrapper();

void TestSwig()

 Py_Initialize();
 PyRun_SimpleString("import test_module");
 ConvertToWrapper(wrapper);
 Py_Finalize();


int main(int argc, char *argv)

 TestSwig();
 return 0;

testwrapper.h

#pragma once
#include "swiginterface.h"

class TestWrapper : public SwigInterface

public:
 TestWrapper()
 virtual ~TestWrapper()
 virtual void Test();
;

swiginterface.h

#pragma once

class SwigInterface

public:
 virtual ~SwigInterface()
 virtual void Test() = 0;
;

test_module.i (swig interface file)

%module test_module

%
#include "../swiginterface.h"
%

%include "../SwigInterface.h"

%inline %
 SwigInterface * test;
%

setup_function (python)

from distutils.core import setup, Extension
setup(name="test_module",
 py_modules=['test_module'],
 ext_modules=[Extension("_test_module",
 ["test_module.i"],
 extra_compile_args=["-DSWIG_TYPE_TABLE=test_module"],
 swig_opts=["-c++", "-py3"],
 )])

Function in swig_runtime.h where issue occurs:

SWIGRUNTIME PyObject* 
SWIG_Python_NewShadowInstance(SwigPyClientData *data, PyObject *swig_this)
{
#if (PY_VERSION_HEX >= 0x02020000)
 PyObject *inst = 0;
 PyObject *newraw = data->newraw;
 if (newraw) 
 inst = PyObject_Call(newraw, data->newargs, NULL);
 if (inst) 
#if !defined(SWIG_PYTHON_SLOW_GETSET_THIS)
 PyObject **dictptr = _PyObject_GetDictPtr(inst);
 if (dictptr != NULL) 
 PyObject *dict = *dictptr;
 if (dict == NULL) 
 dict = PyDict_New();
 *dictptr = dict;
 PyDict_SetItem(dict, SWIG_This(), swig_this);
 
 
#else
 PyObject *key = SWIG_This();
 PyObject_SetAttr(inst, key, swig_this);
#endif
 
 else 
#if PY_VERSION_HEX >= 0x03000000
 inst = ((PyTypeObject*) data->newargs)->tp_new((PyTypeObject*) data->newargs, Py_None, Py_None); //<----- HERE
 if (inst) 
 PyObject_SetAttr(inst, SWIG_This(), swig_this);
 Py_TYPE(inst)->tp_flags &= ~Py_TPFLAGS_VALID_VERSION_TAG;
 
#else
 PyObject *dict = PyDict_New();
 if (dict) 
 PyDict_SetItem(dict, SWIG_This(), swig_this);
 inst = PyInstance_NewRaw(data->newargs, dict);
 Py_DECREF(dict);
 
#endif
 
 return inst;

I've tried this with multiple versions of SWIG and all result the same. It loads the module no problem, both into the C++ code and into an external python interpreter. How do I go about debugging / fixing this issue?

To resolve this issue, I needed to downgrade from Python3.7 to Python3.6