On 13/05/2007 12.41, Phil Thompson wrote:
Hi Phil,
I've got another bug with object lifetimes:
=========================================
from qt import *
import weakref
app = QApplication([])
ql = QListView(None)
viewport = ql.viewport()
o = QObject(viewport)
o.xxx = viewport # bug-trigger!
destroyed = []
def cb(wr):
destroyed.append(1)
wr = weakref.ref(o, cb)
del o
del viewport
assert not destroyed, "object destroyed too early #1!"
import gc
gc.collect()
assert not destroyed, "object destroyed too early #2!"
del ql
import gc
gc.collect()
assert destroyed, "object never destroyed!"
=========================================
Traceback (most recent call last):
File "pyqtbug19.py", line 25, in ?
assert not destroyed, "object destroyed too early #2!"
AssertionError: object destroyed too early #2!
This happens with latest PyQt and SIP official releases (3.17.1 and
4.6). The line that seems to trigger the bug is the one marked with a
comment.
This behaves as I would expect - ie. it's a missing feature rather than a bug.
Although ql is the parent of viewport, Python doesn't know that and there is
no hidden extra reference to viewport to keep it alive when collect() is run.
But the problem here is that "o" is collected. o is a QObject whose lifetime
should be transferred to C++ (given that it has a non-NULL parent, right?).
And why is this behaviour triggered *only* when I add the "xxx" attribute to
o? If I don't do that, everything looks right.
--
Giovanni Bajo
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