Re: [xml] segmentation fault

[Daniel Veillard <veillard redhat com>]

On Thu, Apr 01, 2010 at 10:23:57AM -0400, Oswalt, Ed (GE Healthcare) wrote:
> Hi,
> I am tracing the cause of a segmentation fault, apparently in the
> libxml2 module.
> My application is purely python and uses the libxml2 library for simple
> data file look-up.
>  
> The core file is useless as it just indicates the main module name and a
> physical memory address that has not meaning to me.
>  
> The python trace module produces the following:
>  
>
>       ErrCode.py(43):                 _doc = libxml2.parseFile(
> self.__dataFile )
>       
>       ErrCode.py(47):             _ctxt = _doc.xpathNewContext()
>       ErrCode.py(51):             _xpath =
> "/ERROR_TABLE/ROW[ code=\"%s\"]/@msg" % code
>       ErrCode.py(53):             _parms = _ctxt.xpathEval( _xpath )
>       
>       ErrCode.py(56):             _doc.freeDoc()
>        --- modulename: libxml2, funcname: freeDoc

here you are freeing the document  ...

>       libxml2.py(4079):         libxml2mod.xmlFreeDoc(self._o)
>       ErrCode.py(57):             _ctxt.xpathFreeContext()
>        --- modulename: libxml2, funcname: xpathFreeContext
>       libxml2.py(6849):
> libxml2mod.xmlXPathFreeContext(self._o)
>       
>       ErrCode.py(64):             for _pm in _parms:
>       ErrCode.py(65):                 return (code,_pm.content)
>        --- modulename: libxml2, funcname: get_content
>       libxml2.py(267):         return
> libxml2mod.xmlNodeGetContent(self._o)
>       Segmentation fault

  holding the content you are trying to manipulate at this point.

XPath queries return pointers into the document tree. Don't free the
tree until you are still accessing it.

Daniel

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