Streams causing heap crash using Python C-Extensions

Raj Batra batraraj at hotmail.com
Wed Sep 17 02:04:04 CEST 2003


Hi,

I've created a dll that you can import into python. The function
calls an ostringstream class. Calling this function repeatedly in python
will cause a Microsoft Visual C++ Debug Library error:

Debug Assertion Failed!
Program: C:\Program Files\Python22\python.exe
File: dbgheap.c
Line: 346

Expression: _CrtCheckMemory()

Here are snippets of the code:

// Method called by python via a PySwitchObject
static PyObject * pyCircuit(PySwitchObject * self, PyObject * args)
{
    int circuit;

    if (!PyArg_ParseTuple(args, "i", &circuit))
    {
       // Error handling... 
    }

    self->_switch->circuit((U8) circuit);
    Py_INCREF(Py_None);
    return(Py_None);
}

// Called by pyCircuit method above. Multiple calls to this method
// yield a heap assertion.
void Switch::circuit(U8 c)
{
    std::ostringstream close;

    close << "Some formating...";

    // Use the close method - doesn't really matter.
}


The error is always within the constructor or destructor of ostringstream and
in the file called xmutex.cpp (implements mutex lock for iostreams) which
calls the malloc/dealloc functions.

I have tried other streams such as fstream, and get similar behavior.
Switching to a char buffer[] and sprintf is my current work around the
ostringstream issue.

Any thoughts about what is going on?

I'm using Python2.2.2, with Visual C++ 7 (.NET). The error occurs using
both pythonwin and the standard command line python.

Thanks,

Raj




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