[pywin32-bugs] [ pywin32-Bugs-723837 ] PyHANDLE destructor triggers a SystemError

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Bugs item #723837, was opened at 2003-04-18 19:03
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Jason Orendorff (jorend)
Assigned to: Nobody/Anonymous (nobody)
Summary: PyHANDLE destructor triggers a SystemError

Initial Comment:
This code is in PyHANDLE.cpp:

/*static*/ void PyHANDLE::deallocFunc(PyObject *ob)
{
	// Call virtual method Close
	((PyHANDLE *)ob)->Close();
    PyErr_Clear(); // can not leave pending exceptions
in destructors.
	delete (PyHANDLE *)ob;
}

If this is called because an unrelated exception
occurred, it incorrectly clears the exception.

For example, suppose I have Python code that calls a
Python function f1().  This function successfully
creates a PyHANDLE, stores it in a local varaible, and
then raises an unrelated exception.  The caller, f2(),
catches the exception.  At this point, the PyHANDLE
still exists because the traceback object has a
reference to it (indirectly).  Now suppose f2() throws
an exception.  The previous traceback object is now
released (replaced by the new traceback).  The PyHANDLE
object is decref'd and freed.  PyHANDLE::deallocFunc()
is called.  The exception that f2() threw is now cleared.

This results in a SystemError.  The attached test case
reproduces it.

I think it should be

    if (!((PyHANDLE *)ob)->Close())
        PyErr_Clear();

but I'm not sure.

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