PyObject_CallFunction Access violation writing location 0x0000000c.

Question

I am trying to wrap a c communication library in python and am having some trouble when I attempt to handle large amounts of data. The following code will work for smaller messages but when the message is larger than 400MB I get the following error from the PyObject_CallFunction call:

Unhandled exception at 0x1e00d65f in python.exe: 0xC0000005: Access violation writing location 0x0000000c.

int request_callback(c_request* req, c_msg* msg, void* client)
{
 PyGILState_STATE gstate;
 PyObject* callback;
 PyObject* result;
 unsigned int request_addr;
 PyObject* py_request_addr;
 PyObject* message;

 gstate = PyGILState_Ensure();

 request_addr = (unsigned int)req;
 py_request_addr = PyInt_FromLong(request_addr);

 if (PyDict_Contains(request_callback_dict, py_request_addr) == 1)
 {
  callback = PyDict_GetItem(request_callback_dict, py_request_addr);
  message = PyString_FromStringAndSize(msg->data, msg->len);  

  result = PyObject_CallFunction(callback, "O", message);
 }

 PyGILState_Release(gstate);

 return 0;
}

Any thoughts as to what could cause this. Thanks.

Answer 1

After debugging the code further it is actually a problem with the the python code that uses the string. The string is a google protocol buffer and when the data is written from a file and the bytes are parsed I can catch a python exception thrown by the library.