[Cython] Hash-based vtables

[Stefan Behnel]

Dag Sverre Seljebotn, 04.06.2012 21:44:
>    This can cause crashes/stack smashes
>    etc. if there's lower-64bit-of-md5 collisions, but a) the
>    probability is incredibly small, b) it would only matter in
>    situations that should cause an AttributeError anyway, c) if we
>    really care, we can always use an interning-like mechanism to
>    validate on module loading that its hashes doesn't collide with
>    other hashes (and raise an exception "Congratulations, you've
>    discovered a phenomenal md5 collision, get in touch with cython
>    devs and we'll work around it right away").

I'm not a big fan of such an attitude. If this happens at runtime, it can
induce any cost from cheap-at-test-time to hugely-expensive-in-production.
Thinking with my evil hat on, this can potentially be data triggered from
the outside (e.g. if a JIT compiler is involved at one end), thus possibly
even leading to a security hole.

We should try to produce software that others can build a business on.

Stefan