bpo-44881: Integrate GC untrack into trashcan begin. #27718
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For subtle reasons, PyObject_GC_UnTrack() function must be called before Py_TRASHCAN_BEGIN(). There have been a number of bugs over the years related to not doing this particular dance just right. Integrating the PyObject_GC_UnTrack() call makes it harder to do things incorrectly. That avoids some hard to find bugs (e.g. only triggered when object nesting gets deep enough). Extensions that still call PyObject_GC_UnTrack() explictly will still work correctly but the call is unneeded after this change. It would still be needed for the extension to work correctly with older versions of Python.
nascheme
requested review from
1st1,
markshannon,
methane and
rhettinger
as code owners
pablogsal
approved these changes
Aug 10, 2021
|
Let's land #27678 first to include that change in this PR |
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Just to be clear, I don't consider this PR a bugfix and it would not be appropriate to include in 3.10. |
Yep, we are on the same page :) |
It seems slightly cleaner to have the BEGIN/END macros at the start and end of the dealloc function body.
vstinner
reviewed
Aug 12, 2021
|
We won't be merging this as of yet because an alternative solution is evaluated in GH-27738. I added the assert Victor wanted so that the benchmarks are fairer between the two approaches. |
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This PR is stale because it has been open for 30 days with no activity. |
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For subtle reasons, PyObject_GC_UnTrack() function must be called before
Py_TRASHCAN_BEGIN(). There have been a number of bugs over the years
related to not doing this particular dance just right. Integrating
the PyObject_GC_UnTrack() call makes it harder to do things incorrectly.
That avoids some hard to find bugs (e.g. only triggered when object
nesting gets deep enough).
Extensions that still call PyObject_GC_UnTrack() explictly will
work correctly but the call is unneeded after this change. It would
still be needed for the extension to work correctly with older versions
of Python.
https://bugs.python.org/issue44881