[lxml-dev] fix for another memory leak

[Stefan Behnel]

Narayan Desai wrote:
> In addition to the memory leak in the Element.get method, I have
> recently been seeing memory leaks in Element.Attrib.has_key. This
> results in the following trace from valgrind:
> ==12133== 8 bytes in 4 blocks are definitely lost in loss record 2 of 48
> ==12133==    at 0x401B422: malloc (vg_replace_malloc.c:149)
> ==12133==    by 0x453D8B5: xmlStrndup (in /usr/lib/libxml2.so.2.6.23)
> ==12133==    by 0x453D943: xmlStrdup (in /usr/lib/libxml2.so.2.6.23)
> ==12133==    by 0x453E0D1: xmlStrcat (in /usr/lib/libxml2.so.2.6.23)
> ==12133==    by 0x44E98A1: xmlNodeListGetString (in /usr/lib/libxml2.so.2.6.23)
> ==12133==    by 0x44EF6D2: xmlGetNoNsProp (in /usr/lib/libxml2.so.2.6.23)
> ==12133==    by 0x4462ED0: __pyx_f_5etree_7_Attrib_has_key (etree.c:5389)
> ==12133==    by 0x80B6BE3: (within /usr/bin/python2.3)
> ==12133==    by 0x80B8356: PyEval_EvalCodeEx (in /usr/bin/python2.3)
> ==12133==    by 0x80B85D4: PyEval_EvalCode (in /usr/bin/python2.3)
> ==12133==    by 0x80D8EFF: PyRun_InteractiveOneFlags (in /usr/bin/python2.3)
> ==12133==    by 0x80D9018: PyRun_InteractiveLoopFlags (in /usr/bin/python2.3)
> 
> The following patch appears to fix things for me. It is basically
> copied from the Element.get fix.

Hi,

sorry for the late reply.

Thank you for supplying the patch. I applied a slightly different patch to the
SVN trunk, also for the  __contains__ method, to keep them from using pointers
after calling free. Could you please check if the bug is gone? It would be
really nice if you could also test the __contains__ method with Valgrind.

Thanks again,
Stefan

Index: src/lxml/etree.pyx
===================================================================
--- src/lxml/etree.pyx  (Revision 23034)
+++ src/lxml/etree.pyx  (Arbeitskopie)
@@ -855,7 +855,11 @@
             result = tree.xmlGetNoNsProp(self._c_node, tag)
         else:
             result = tree.xmlGetNsProp(self._c_node, tag, ns)
-        return result is not NULL
+        if result is not NULL:
+            tree.xmlFree(result)
+            return True
+        else:
+            return False

     def __contains__(self, key):
         cdef xmlNs* c_ns
@@ -865,7 +869,11 @@
             result = tree.xmlGetNoNsProp(self._c_node, tag)
         else:
             result = tree.xmlGetNsProp(self._c_node, tag, ns)
-        return result is not NULL
+        if result is not NULL:
+            tree.xmlFree(result)
+            return True
+        else:
+            return False

 cdef _Attrib _attribFactory(_Document doc, xmlNode* c_node):
     cdef _Attrib result