[MAL, on Py_AtExit()]
> PyObject_Del() [must be avoided] as well ?
I don't think that one's a problem. The Py{Object,Mem}_{Del,DEL,Free,FREE}
spellings have resolved to plain free(). Under pymalloc that's different,
but pymalloc never tears itself down so it's safe there too.
>> We have two sets of exit-function gimmicks, one that runs at
>> the very start of Py_Finalize(), and the other at the very end.
>> If you need to clean up Python objects, you have to get into
>> the first group.
> I suppose the first one is what the atexit module exposes
> in Python 2.0+, right ?
Yes, but do read Skip's message too. atexit.py wraps a primitive gimmick
that was also in 1.5.2. See the docs for sys.exitfunc at
http://www.python.org/doc/1.5.2p2/lib/module-sys.html
The docs are pretty much the same now, except atexit.py provides a rational
way to register multiple exit functions now. Hmm! The logic in atexit.py
looks wrong if sys.exitfunc already exists: then atexit appends it to the
module's own list of exit functions, but then forgets to do anything to
ensure that its own list gets run at the end. I conclude that nobody has
tried mixing these gimmicks.
In any case, you can do something safe across all versions via:
import sys
try:
inherited = sys.exitfunc
except AttributeError:
def inherited():
pass
def myexitfunc():
clean_up_my_stuff()
inherited()
sys.exitfunc = myexitfunc
del sys
You can get screwed then if somebody else sets sys.exitfunc later without
being as considerate of your hook as the code above is of a pre-existing
hook, but then that's why atexit.py was created and you should move to a
later Python if you want saner behavior <wink>.
> The problem with that approach is that there may still be some
> references to objects left in lists and dicts which are cleaned
> up after having called the atexit functions. This is not so
> much a problem in my cases, but something to watch out in other
> applications which use C level Python objects as globals.
I don't know specifically what you have in mind there, but I expect that it
would kick off another round of the every-18-months discussion of what kind
of module finalization protocol Python should start to support. A PEP for
that is long overdue.
>>> Also, atexit.py is not present in Python 1.5.2.
>> What's that <wink>?
> That's the Python version which was brand new just 3 years
> ago. I know... in US terms that's for history books ;-)
Oh, 3 years ago is sooooo 20th century! Goodness, they didn't even have
cellophane sleeping tubes back then. May as well go back to worshipping
cats while you're at it.
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