Re: [xml] using "raise" in Python error handler callbacks

On 31 Mar 2005, at 22:43, Daniel Veillard wrote:

On Thu, Mar 31, 2005 at 10:25:41PM +0100, Andrew McDermott wrote:
Whilst experimenting with the Python bindings I noticed that exceptions
are not propagated when using registerErrorHandler().  If I run the
following I get the error message:

        /etc/passwd : failed to parse.

However, there is no Traceback for the "raise".  Is this correct?

import libxml2
import sys

  You have
    Python calling C calling Python.
the internal exception in the callback does not cross the C boundary
I don't see how this could work without disastrous side effects like
memory leaks or general instability in the program.

I was reading a section from the link below which gave me the impression this was possible.

The return value of PyEval_CallObject() is ``new'': either it is a brand new object, or it is an existing object whose reference count has been incremented. So, unless you want to save it in a global variable, you should somehow Py_DECREF() the result, even (especially!) if you are not interested in its value.

Before you do this, however, it is important to check that the return value isn't NULL. If it is, the Python function terminated by raising an exception. If the C code that called PyEval_CallObject() is called from Python, it should now return an error indication to its Python caller, so the interpreter can print a stack trace, or the calling Python code can handle the exception. If this is not possible or desirable, the exception should be cleared by calling PyErr_Clear(). For example:

Isn't it the case that the calling sequence starts within Python so it should be possible to return an error indication?


Daniel Veillard      | Red Hat Desktop team
veillard redhat com | libxml GNOME XML XSLT toolkit | Rpmfind RPM search engine

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