Re: [libvirt] [PATCH] python: Avoid memory leaks on libvirt_virNodeGetMemoryStats
On 02/14/2012 03:08 AM, Peter Krempa wrote:
On 02/14/2012 09:31 AM, ajia(a)redhat.com wrote:
> From: Alex Jia<ajia(a)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(a)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
python object.
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(a)redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
Attachments:
- signature.asc (application/pgp-signature — 620 bytes)