Possible bug in Cython generated C++ code

I'm trying to create a Cython wrapper for the __gnu_parallel::sort in the same way as they do in this thread Parallel in-place sort for numpy arrays.

This is my simplified code for wrapparallel.pyx:

import cython
cimport cython 

cdef extern from "<parallel/algorithm>" namespace "__gnu_parallel":
    cdef void sort[T](T first, T last) nogil 

def parallel_sort(double[::1] a):
    sort(&a[0], &a[a.shape[0] - 1])

I generate c++ code with:

cython --cplus wrapparallel.pyx

Compile and link with:

g++ -g -march=native -Ofast -fpic -c wrapparallel.cpp -o wrapparallel.o -fopenmp -I/usr/include/python2.7 -I/usr/include/x86_64-linux-gnu/python2.7
g++ -g -march=native -Ofast -shared -o wrapparallel.so wrapparallel.o -lpthread -ldl  -lutil -lm  -lpython2.7 -lgomp 

Now to test it:

In [1]: import numpy as np
        from wrapparallel import parallel_sort

        a = np.random.randn(10)
        parallel_sort(a)
        a

Out[1]: array([-1.23569683, -1.05639448, -0.76990205, -0.2512839 , -0.25022328,
                0.12711458,  0.81659571,  0.92205287,  2.15019125, -0.45902146])

As pointed out in the comment in the original thread this code does not sort the last element and the commentator suggests that the " - 1" be removed in the call to sort in the pyx-file. However this change would not solve anything since a[a.shape[0]] would be out of bounds.

This made me suspect that there might be an issue in the c++ code. The snippet where the actual call to __gnu_parallel::sort happens looks like this:

static PyObject *__pyx_pf_12wrapparallel_parallel_sort(CYTHON_UNUSED PyObject *__pyx_self, __Pyx_memviewslice __pyx_v_a) {
  PyObject *__pyx_r = NULL;
  __Pyx_RefNannyDeclarations
  Py_ssize_t __pyx_t_1;
  int __pyx_t_2;
  Py_ssize_t __pyx_t_3;
  int __pyx_lineno = 0;
  const char *__pyx_filename = NULL;
  int __pyx_clineno = 0;
  __Pyx_RefNannySetupContext("parallel_sort", 0);

  __pyx_t_1 = 0;
  __pyx_t_2 = -1;
  if (__pyx_t_1 < 0) {
    __pyx_t_1 += __pyx_v_a.shape[0];
    if (unlikely(__pyx_t_1 < 0)) __pyx_t_2 = 0;
  } else if (unlikely(__pyx_t_1 >= __pyx_v_a.shape[0])) __pyx_t_2 = 0;
  if (unlikely(__pyx_t_2 != -1)) {
    __Pyx_RaiseBufferIndexError(__pyx_t_2);
    {__pyx_filename = __pyx_f[0]; __pyx_lineno = 31; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
  }
  __pyx_t_3 = ((__pyx_v_a.shape[0]) - 1);
  __pyx_t_2 = -1;
  if (__pyx_t_3 < 0) {
    __pyx_t_3 += __pyx_v_a.shape[0];
    if (unlikely(__pyx_t_3 < 0)) __pyx_t_2 = 0;
  } else if (unlikely(__pyx_t_3 >= __pyx_v_a.shape[0])) __pyx_t_2 = 0;
  if (unlikely(__pyx_t_2 != -1)) {
    __Pyx_RaiseBufferIndexError(__pyx_t_2);
    {__pyx_filename = __pyx_f[0]; __pyx_lineno = 31; __pyx_clineno = __LINE__; goto __pyx_L1_error;}
  }
  __gnu_parallel::sort<double *>((&(*((double *) ( /* dim=0 */ ((char *) (((double *) __pyx_v_a.data) + __pyx_t_1)) )))), (&(*((double *) ( /* dim=0 */ ((char *) (((double *) __pyx_v_a.data) + __pyx_t_3)) )))));


  /* function exit code */
  __pyx_r = Py_None; __Pyx_INCREF(Py_None);
  goto __pyx_L0;
  __pyx_L1_error:;
  __Pyx_AddTraceback("wrapparallel.parallel_sort", __pyx_clineno, __pyx_lineno, __pyx_filename);
  __pyx_r = NULL;
  __pyx_L0:;
  __PYX_XDEC_MEMVIEW(&__pyx_v_a, 1);
  __Pyx_XGIVEREF(__pyx_r);
  __Pyx_RefNannyFinishContext();
  return __pyx_r;
}

My knowledge of c++ is not enough to grasp whats going on here so my question is: Is there something wrong with call to __gnu_parallel::sort and how might I change it to also include the last element in the memoryview?