I'm getting a weird segfault from a tiny function (SSCCE) using cython with python 2.7. I'm seeing something similar with cython and python 3.5, though I did not create an SSCCE for 3.5. This same code used to work with slightly older cythons and pythons, and a slightly older version of Linux Mint. The code is at http://stromberg.dnsalias.org/svn/why-is-python-slow/trunk (more specifically at http://stromberg.dnsalias.org/svn/why-is-python-slow/trunk/tst.pyx ) In short, cdef'ing a list of doubles with about a million elements, and using only the 0th element once, segfaults - but cdef'ing a slightly smaller array does not segfault under otherwise identical conditions. Any suggestions? Does Cython have a limit on the max size of a stack frame? Thanks! I quite like cython.