[Cython] gcc error when compiling cython

[Thomas Holenstein]

Hey all,

recently, I had a gcc compile time error with cython. The work around
is obvious, as the problem happens when a cdef-ed numpy array in a
function is unused. Nevertheless, I feel it's useful to report the
problem I had.

The following is a test case
---------------------------------------- test.pyx
import numpy as np
cimport numpy as np

def f(np.ndarray[dtype=np.int_t, ndim=2] arg1):
    cdef np.ndarray[dtype=np.int_t, ndim=2] arr
    return 3
----------------------------------------- setup.py
from distutils.core import setup
from Cython.Build import cythonize

setup(
    ext_modules = cythonize("test.pyx"),
)
----------------------------------------------------------
This gives me the error

error: ‘__pyx_pybuffernd_arr’ undeclared

Full shell output:
 ~/tmp/ctest > python setup.py build_ext --inplace
running build_ext
building 'test' extension
x86_64-linux-gnu-gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv
-O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include/python2.7 -c test.c
-o build/temp.linux-x86_64-2.7/test.o
In file included from /usr/include/python2.7/numpy/ndarraytypes.h:1761:0,
                 from /usr/include/python2.7/numpy/ndarrayobject.h:17,
                 from /usr/include/python2.7/numpy/arrayobject.h:4,
                 from test.c:250:
/usr/include/python2.7/numpy/npy_1_7_deprecated_api.h:15:2: warning:
#warning "Using deprecated NumPy API, disable it by " "#defining
NPY_NO_DEPRECATED_API NPY_1_7_API_VERSION" [-Wcpp]
 #warning "Using deprecated NumPy API, disable it by " \
  ^
test.c: In function ‘__pyx_pf_4test_f’:
test.c:1240:30: error: ‘__pyx_pybuffernd_arr’ undeclared (first use in
this function)
     __Pyx_SafeReleaseBuffer(&__pyx_pybuffernd_arr.rcbuffer->pybuffer);
                              ^
test.c:1240:30: note: each undeclared identifier is reported only once
for each function it appears in
In file included from /usr/include/python2.7/numpy/ndarrayobject.h:26:0,
                 from /usr/include/python2.7/numpy/arrayobject.h:4,
                 from test.c:250:
test.c: At top level:
/usr/include/python2.7/numpy/__multiarray_api.h:1629:1: warning:
‘_import_array’ defined but not used [-Wunused-function]
 _import_array(void)
 ^
In file included from /usr/include/python2.7/numpy/ufuncobject.h:327:0,
                 from test.c:251:
/usr/include/python2.7/numpy/__ufunc_api.h:241:1: warning:
‘_import_umath’ defined but not used [-Wunused-function]
 _import_umath(void)
 ^
error: command 'x86_64-linux-gnu-gcc' failed with exit status 1