[PATCH] Fix memory leaks in libxc python bindings

[PATCH] Fix memory leaks in libxc python bindings

[Jiri Denemark]

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Hi,

Reference counters are not correctly decreased for python object in several
places in python bindings for libxc. Most of them are around PyList_Append(),
which unlike PyList_SetItem() does increment reference counter of the object
being added to a list.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>


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diff -r bd376919f03a tools/python/xen/lowlevel/xc/xc.c
--- a/tools/python/xen/lowlevel/xc/xc.c	Tue Sep 29 11:28:33 2009 +0100
+++ b/tools/python/xen/lowlevel/xc/xc.c	Tue Sep 29 18:45:33 2009 +0200
@@ -387,8 +387,11 @@
     cpulist = PyList_New(0);
     for ( i = 0; cpumap != 0; i++ )
     {
-        if ( cpumap & 1 )
-            PyList_Append(cpulist, PyInt_FromLong(i));
+        if ( cpumap & 1 ) {
+            PyObject *pyint = PyInt_FromLong(i);
+            PyList_Append(cpulist, pyint);
+            Py_DECREF(pyint);
+        }
         cpumap >>= 1;
     }
     PyDict_SetItemString(info_dict, "cpumap", cpulist);
@@ -1104,22 +1107,31 @@
     {
         PyObject *cpus = PyList_New(0);
         for ( j = 0; j <= max_cpu_id; j++ )
-            if ( i == map[j])
-                PyList_Append(cpus, PyInt_FromLong(j));
+            if ( i == map[j]) {
+                PyObject *pyint = PyInt_FromLong(j);
+                PyList_Append(cpus, pyint);
+                Py_DECREF(pyint);
+            }
         PyList_Append(node_to_cpu_obj, cpus); 
+        Py_DECREF(cpus);
     }
 
     node_to_memory_obj = PyList_New(0);
 
     for ( i = 0; i < info.nr_nodes; i++ )
     {
+        PyObject *pyint;
+
         xc_availheap(self->xc_handle, 0, 0, i, &free_heap);
-        PyList_Append(node_to_memory_obj,
-                      PyInt_FromLong(free_heap / 1024));
+        pyint = PyInt_FromLong(free_heap / 1024);
+        PyList_Append(node_to_memory_obj, pyint);
+        Py_DECREF(pyint);
     }
 
     PyDict_SetItemString(ret_obj, "node_to_cpu", node_to_cpu_obj);
+    Py_DECREF(node_to_cpu_obj);
     PyDict_SetItemString(ret_obj, "node_to_memory", node_to_memory_obj);
+    Py_DECREF(node_to_memory_obj);
  
     return ret_obj;
 #undef MAX_CPU_ID

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Re: [PATCH] Fix memory leaks in libxc python bindings

[Konrad Rzeszutek Wilk]

On Tue, Sep 29, 2009 at 06:54:09PM +0200, Jiri Denemark wrote:
> Hi,
> 
> Reference counters are not correctly decreased for python object in several

I am curious how did you find this? Is there a python 'valgrind' that
can help track this? Or is there a python flag to be report such abnormalities?

Re: [PATCH] Fix memory leaks in libxc python bindings

[Jiri Denemark]

> > Reference counters are not correctly decreased for python object in several
> 
> I am curious how did you find this? Is there a python 'valgrind' that
> can help track this? Or is there a python flag to be report such abnormalities?

None that I know of. I just used the source code. I found it because long
running xend managed by libvirt was consuming increasing amount of memory.
From the only repeatedly executed command virsh list I got to xm info and
xc_physinfo(). And then I just looked for all other calls to PyDict_* and
PyList_Append and fixed them.

Jirka