[xml] memory leak while parsing from memory buffer

[Petr Pajas <pajas ufal ms mff cuni cz>]

Hi Daniel, All,

in our Perl bindings, we have something similar to this (we keep
compatibility with older releases, that's why we still use the old
parser API):


xmlParserCtxtPtr ctxt = xmlCreateMemoryParserCtxt((const char*)ptr, len);

/* leak here - comment out to get rid of it */
if ( ctxt->input != NULL ) {
   ctxt->input->filename = xmlStrdup((const xmlChar *) "");
} 

xmlParseDocument(ctxt);

real_doc = ctxt->myDoc;
ctxt->myDoc = NULL;

xmlFreeParserCtxt(ctxt);

return real_doc;


Now, the reason we set ctxt->input->filename to "" is that otherwise
libxml2 (since 2.6) doesn't return line-numbers on error - we want
something like

:3: element bar: validity error : No declaration for element bar
<bar/>
      ^

but if we leave filename == NULL, we only get 

element bar: validity error : No declaration for element bar
<bar/>
      ^

(No problem with this.)

But, although ctxt->input->filename _does_ get freed with
xmlFreeParserCtxt, the above code leaks. If the line with xmlStrdup is
removed, the leak disappears. I suspect, that somewhere, during
xmlParseDocument some copies of filename are made but never freed or
something similar. Otherwise I don't know why this line would make any
difference. BTW, it's the same if I set

ctxt->input->filename = "";

and put 

ctxt->input->filename = NULL;

just before xmlFreeParserCtxt(ctxt).

Any hints?

Thanks,

-- Petr

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