[with patch, needs review] recursion stack overflow in control flow analysis

[scoder]

Here is an example for a program that Cython currently cannot compile as the control flow analysis reaches the maximum recursion limit. The problem appears to be the long sequence of simple "if" statements.

[scoder]

As a 'quick' fix, it might work to materialise the control flow state at branching/merge points. That would speed up the lookups and prevent deep recursion.

[scoder]

Here is a patch that reimplements the control flow traversal with a loop instead of recursion. I can't easily check if I broke anything (which I likely did), so I don't push it directly. Robert, do you have a way to check if this still works as expected?

[scoder]

use a loop instead of recursion

[scoder]

Cythonized version of Sieves.py (uses C ints and basically runs in no-time)

[robertwb]

Looks fine to me, though I can't think of how to add a good automated test. I see you've pushed.