On Tue, Sep 17, 2013 at 2:14 PM, <exarkun@twistedmatrix.com> wrote:

I think there are still many unported dependencies of `twistd` to port first.

Sure, but every little bit helps, right? :)

Can someone comment as to why this was put there in the first place, and,
specifically, why it can't just be "pass"? Is there some logging system
that looks at the current exception or something when twistd (or some other
script) starts?

Both `log.err()´ and `Failure()´ look at the current exception. If we don't `sys.clear_exc()´ here then the first piece of code that tries to use either of those may get a surprising result. The current exception state can last a long time so this surprise can hide for a remarkably long time before showing up.

Okay, cool. From what I understand:

1. _preamble is just a hack to get bin/whatever to work right without installing (i.e. from a checkout)

2. (not too sure about this) in py3k, except statements do the clearing bit already: www.python.org/dev/peps/pep-3110/#semantic-changes

So, does that mean we can do a try: ... ; except AttributeError and be done with it?

The exception state also holds references to lots of extra things on the stack which is undesirable even if there are no other side-effects.

Jean-Paul

lvh