[libvirt] [PATCH] python: Avoid memory leaks on libvirt_virNodeGetMemoryStats
eblake at redhat.com
Tue Feb 14 13:11:47 UTC 2012
On 02/14/2012 03:08 AM, Peter Krempa wrote:
> On 02/14/2012 09:31 AM, ajia at redhat.com wrote:
>> From: Alex Jia<ajia at 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 at 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.
I'd actually initialize to NULL, not VIR_PY_NONE. Use of VIR_PY_NONE
increments the reference count on the Python None object; and if you
then later return anything else, you would also have to reduce that
reference count to avoid a resource leak in the form of an un-freeable
> 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)
And I think that's actually correct! Returning VIR_PY_NONE is a _valid_
python object, and library code interprets it as "I successfully called
your function, but had no object to return; now you can check for the
libvirt error class to see why, but there is no python exception".
Returning NULL means "I encountered a python exception; you can now
catch that exception". They are handled quite differently in the
calling code. Returning VIR_PY_NONE should be reserved for the case
where we called a libvirt API that failed (then libvirt did indeed
populate a libvirt error, and there is no python exception); while
returning NULL should be reserved for the case where a python glue code
failed (such as inability to create a new python dictionary) or where we
explicitly raised a python exception (such as when we detect an OOM
situation and call PyErr_NoMemory()).
Eric Blake eblake at redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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