Re: [PATCH libgpiod] bindings: python: fix Line.request() crashing

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Tue, Oct 6, 2020 at 7:26 PM Jiri Benc <jbenc@xxxxxxx> wrote:
>
> On an attempt to call the 'request' method of a Line object, the program
> crashes with this exception:
>
> > SystemError: ../Objects/dictobject.c:2606: bad argument to internal function
> >
> > The above exception was the direct cause of the following exception:
> >
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in <module>
> > SystemError: <class 'gpiod.LineBulk'> returned a result with an error set
>
> The problem is that keyword args are NULL (rather than an empty dict) if
> they are not present. However, PyDict_Size sets an exception if it gets
> NULL.
>
> Fixes: 02a3d0a2ab5e ("bindings: python: fix segfault when calling Line.request()")
> Signed-off-by: Jiri Benc <jbenc@xxxxxxx>
> ---
>  bindings/python/gpiodmodule.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/bindings/python/gpiodmodule.c b/bindings/python/gpiodmodule.c
> index b3ae2bfebb8a..fee4c32406fa 100644
> --- a/bindings/python/gpiodmodule.c
> +++ b/bindings/python/gpiodmodule.c
> @@ -472,7 +472,7 @@ static PyObject *gpiod_Line_request(gpiod_LineObject *self,
>         gpiod_LineBulkObject *bulk_obj;
>         int rv;
>
> -       if (PyDict_Size(kwds) > 0) {
> +       if (kwds && PyDict_Size(kwds) > 0) {
>                 def_val = PyDict_GetItemString(kwds, "default_val");
>                 def_vals = PyDict_GetItemString(kwds, "default_vals");
>         } else {
> --
> 2.18.1
>

Hi Jiri!

Thanks for the fixes. Could you send me a chunk of code that triggers
this error so I can make a test-case for it?

Bartosz