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Re: [libvirt] [PATCH] python: Avoid memory leaks on libvirt_virNodeGetMemoryStats



On 02/14/2012 06:08 PM, Peter Krempa wrote:
On 02/14/2012 09:31 AM, ajia redhat com wrote:
From: Alex Jia<ajia redhat com>

Detected by valgrind. Leaks are introduced in commit 17c7795.

* python/libvirt-override.c (libvirt_virNodeGetMemoryStats): fix memory leaks
and improve codes return value.

For details, please see the following link:
RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=770944

Signed-off-by: Alex Jia<ajia redhat com>
---
python/libvirt-override.c | 41 ++++++++++++++++++++++++++++++-----------
  1 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/python/libvirt-override.c b/python/libvirt-override.c
index 4e8a97e..ecb11ea 100644
--- a/python/libvirt-override.c
+++ b/python/libvirt-override.c
@@ -2426,7 +2426,9 @@ libvirt_virNodeGetCPUStats(PyObject *self ATTRIBUTE_UNUSED, PyObject *args)
  static PyObject *
libvirt_virNodeGetMemoryStats(PyObject *self ATTRIBUTE_UNUSED, PyObject *args)
  {
-    PyObject *ret;
+    PyObject *info, *ret;

I'd initialize ret to VIR_PY_NONE here instead of doing it multiple times later on.

+    PyObject *key = NULL;
+    PyObject *val = NULL;
      PyObject *pyobj_conn;
      virConnectPtr conn;
      unsigned int flags;
@@ -2446,28 +2448,45 @@ libvirt_virNodeGetMemoryStats(PyObject *self ATTRIBUTE_UNUSED, PyObject *args)

      if (nparams) {
          if (VIR_ALLOC_N(stats, nparams)<  0)
-            return VIR_PY_NONE;
+            return PyErr_NoMemory();

          LIBVIRT_BEGIN_ALLOW_THREADS;
c_retval = virNodeGetMemoryStats(conn, cellNum, stats,&nparams, flags);
          LIBVIRT_END_ALLOW_THREADS;
          if (c_retval<  0) {
-            VIR_FREE(stats);
-            return VIR_PY_NONE;
+            ret = VIR_PY_NONE;

Like here.

+            goto cleanup;
          }
      }
-    if (!(ret = PyDict_New())) {
-        VIR_FREE(stats);
-        return VIR_PY_NONE;
+    if (!(info = PyDict_New())) {
+        ret = VIR_PY_NONE;

And here

+        goto cleanup;
      }
+
      for (i = 0; i<  nparams; i++) {
-        PyDict_SetItem(ret,
-                       libvirt_constcharPtrWrap(stats[i].field),
-                       libvirt_ulonglongWrap(stats[i].value));
+        key = libvirt_constcharPtrWrap(stats[i].field);
+        val = libvirt_ulonglongWrap(stats[i].value);
+
+        if (!key || !val)
+            goto cleanup;
+
+        if (PyDict_SetItem(info, key, val)<  0) {
+            Py_DECREF(info);
+            goto cleanup;
+        }
+
+        Py_DECREF(key);
+        Py_DECREF(val);
      }

      VIR_FREE(stats);
-    return ret;
+    return info;
+
+cleanup:

This label gets called only on a error path, so I'd call it "error" instead of cleanup.

+    VIR_FREE(stats);
+    Py_XDECREF(key);
+    Py_XDECREF(val);
+    return NULL;

You're returning NULL instead of VIR_PY_NONE. (or the variable err)

  }

  static PyObject *

With code like this, the variable err isn't used anywhere.

Introduction of the new variable "info" is probably not needed, and you may use "ret" for this purpose.
If so, the 'ret' will have 2 different function, the one is return value, the other is dictionary object, I'm not sure it's a good idea to override previous variable 'ret', although the codes are quite simple.

Thanks for your comment,
Alex

It should be possible to rewrite the code (especialy the cleanup section) so that also the success path may pass that way. That would simplify the code.

Peter


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