[Cython] memoryview refcount error

[Syam Gadde]

Hi again,

I'm exploring the typed memoryview feature with numpy and encountered a 
refcount error.  It seems to happen when I create a slice of a 
memoryview, and transpose it.  If I don't do both, I don't get the 
refcount error.  It happens in the error cleanup code.  I suspect that 
any error that causes the function to jump to the error cleanup code 
will do the same thing as the Exception below -- but that seemed the 
easiest way to demonstrate the problem. However, if there truly is an 
error in my code, please let me know! Thanks,

-syam

# BEGIN CODE
import numpy
cimport numpy

class MyException(Exception):
     def __init__(self):
         Exception.__init__(self)

def testfunc():
    a = numpy.arange(12).reshape([3,4])

    cdef numpy.int_t[:,:] a_view = a

    ## here is a slice followed by a transpose
    cdef numpy.int_t[:,:] b = a_view[:,:].T
    ## same thing happens with a more realistic slicing:
    #cdef numpy.int_t[:,:] b = a_view[1:2,:].T
    ## however, there is no error if I do this instead:
    #cdef numpy.int_t[:,:] b = a_view.T
    ## also no error if I do this instead:
    #cdef numpy.int_t[:,:] b = a_view[:,:]

    # The exception below is just to force the function to abort
    # and run the extraneous __PYX_XDEC_MEMVIEW in the error
    # cleanup code:
    #   Fatal Python error: Acquisition count is 0 (line XXXX)
    # Comment out this exception and we don't get the error
    raise MyException()

try:
     testfunc()
except MyException:
     pass
# END CODE