Re: [libvirt] [PATCH 2/2] python: return error if PyObject obj is NULL for unwrapper helper functions
On 04/17/2012 11:49 AM, Eric Blake wrote:
On 04/17/2012 11:45 AM, Guannan Ren wrote:
> The result is indeterminate for NULL argument to python
> functions as follows. It's better to return negative value in
> these situations.
>
> PyObject_IsTrue will segfault if the argument is NULL
> PyFloat_AsDouble(NULL) is -1.000000
> PyLong_AsUnsignedLongLong(NULL) is 0.000000
> ---
> python/typewrappers.c | 26 +++++++++++++++++++++++---
> 1 files changed, 23 insertions(+), 3 deletions(-)
ACK.
I spoke too soon. On looking at it more, I'm wondering if all callers
do the right thing in this case. It would probably be better if we
explicitly raised a python exception before returning -1, so that
callers can blindly assume that a return of -1 means that the correct
python error is already present.
That is, instead of:
if (!obj)
return -1;
should we instead be doing something like:
if (!obj) {
PyErr_SetString(PyExc_TypeError, "unexpected type");
return -1;
}
Or are we guaranteed that the only way obj is NULL is if the caller
already encountered an error, so there is already a python error set?
--
Eric Blake eblake(a)redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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