ctypes problem

Can anyone tell me why the Python code below is not equivalent to the C code? The Python code fails (returning None), where the C code correctly returns a pointer. As far as I can see, they should be identical.

Many thanks,

Ben

----------------------------- python version

import ctypes
from numpy import ctypeslib
import numpy as np

f = ctypes.cdll.LoadLibrary('/usr/local/lib/libfftw3.3.dylib')

rank = 2
n = np.array([5,5])
howmany = 1
inp = np.random.rand(10,10)+0.j
inembed = n
istride = 1
idist = 0
out = np.random.rand(10,10)+0.j
onembed = n
ostride = 1
odist = 0
sign = -1
flags = 0

##
f.fftw_plan_many_dft.argtypes = [ctypes.c_int, # rank
                   ctypeslib.ndpointer(dtype=int, ndim=1, # n
                                       flags='contiguous,aligned'),
                    ctypes.c_int, # howmany
                    ctypeslib.ndpointer(dtype='complex128', # in
                                        flags='aligned,writeable'),
                    ctypeslib.ndpointer(dtype=int, ndim=1, # inembed
                                        flags='contiguous,aligned'),
                    ctypes.c_int, # istride
                    ctypes.c_int, # idist
                    ctypeslib.ndpointer(dtype='complex128', # out
                                        flags='aligned,writeable'),
                    ctypeslib.ndpointer(dtype=int, ndim=1, # onembed
                                        flags='contiguous,aligned'),
                    ctypes.c_int, # ostride
                    ctypes.c_int, # odist
                    ctypes.c_int, # sign
                    ctypes.c_uint] # flags

f.fftw_plan_many_dft.restype = ctypes.c_void_p

##
p = f.fftw_plan_many_dft(rank, n, howmany, inp, inembed, istride, idist,
                         out, onembed, ostride, odist, sign, flags)

print p

--------------------------- C version

#include <fftw3.h>
#include <stdio.h>

main()
{
     int rank = 2;
     int n[2] = {5, 5};
     int howmany = 1;
     fftw_complex in[100];
     int *inembed = n;
     int istride = 1;
     int idist = 0;
     fftw_complex out[100];
     int *onembed = n;
     int ostride = 1;
     int odist = 0;
     int sign = -1;
     unsigned flags = 0;
     fftw_plan p;
          
     p = fftw_plan_many_dft(rank, n, howmany, in, inembed, istride, idist,
                            out, onembed, ostride, odist, sign, flags);
     
     printf("%p\n", p); 
}


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