Author terry.reedy
Recipients Arfrever, chortos, gvanrossum, petri.lehtinen, pitrou, python-dev, r.david.murray, serhiy.storchaka, terry.reedy, vstinner
Date 2013-09-21.23:02:07
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Message-id <1379804527.99.0.805331581279.issue12085@psf.upfronthosting.co.za>
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The message problem can arise during exit if __del__ depends an any attribute of any object. It is hard to imagine a __del__ method that does not. Any __del__ method, including that of Popen, could handle AttributeErrors by wrapping the whole body in

try:
  <body>
except AttributeError:
  pass

The is essentially what is done by the code that calls __del__, except that 'pass' is replaced by "print(message, file=sys.stderr)".

If we patch Popen at all, I think this try:except should be the fix, not a class attribute.

To explain what I meant by the class attribute hack being tricky, consider the original version of Popen.__del__, minus the comments. 

    def __del__(self, _maxsize=sys.maxsize, _active=_active):
        if not self._child_created:
            return
        self._internal_poll(_deadstate=_maxsize)
        if self.returncode is None and _active is not None:
            _active.append(self)

Since self._internal_poll is an instance method, it is not a problem. But what about the self.returncode data attribute? Should we also add a class 'returncode' attribute? If so, what should be its value? None? or object()? Or is it guaranteed that when _child_created is set true, returncode will be defined, so that a class attribute is not needed?

I don't know the answers to these questions. Popen.__init__ is about 130 lines and self._child_created is set to True in two other methods. I did not look where returncode is set, but it is not near the spots where _child_created is set True.
History
Date User Action Args
2013-09-21 23:02:08terry.reedysetrecipients: + terry.reedy, gvanrossum, pitrou, vstinner, Arfrever, r.david.murray, chortos, python-dev, petri.lehtinen, serhiy.storchaka
2013-09-21 23:02:07terry.reedysetmessageid: <1379804527.99.0.805331581279.issue12085@psf.upfronthosting.co.za>
2013-09-21 23:02:07terry.reedylinkissue12085 messages
2013-09-21 23:02:07terry.reedycreate