crash in Py3 with non-sliceable slices

[robertwb]

I believe

range(10)[1:2]

is enough to trigger it.

[scoder]

I tried cythonising

range(10)[1:2]
1[2:3]

which generates a C file without crashing the compiler. However, when I run it, I get a crash in PySequence_GetSlice() on the following code:

    mp = s->ob_type->tp_as_mapping;
    if (mp->mp_subscript) {

The mp pointer is NULL. Clearly a bug in CPython, introduced in the Py3 series.

 http://bugs.python.org/issue9834

[scoder]

As a workaround, we could replace the calls to PySequence_GetSlice by a macro call that expands to an additional s->ob_type->tp_as_mapping check before the call for the affected CPython versions. Let's expect this to be fixed in the next official releases.

[scoder]

Bug will be fixed in releases after CPython 3.1.2, Cython work-around is implemented here:

 http://hg.cython.org/cython-devel/rev/142faf1058ff