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GeezerVison is showing github.com — gh-117139: Fix a few wrong steals in bytecodes.c by Fidget-Spinner · Pull Request #121127 · python/cpython

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Fidget-Spinner commented Jun 28, 2024 •

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I actually caught these using a tool I built following the stackref semantics here https://github.com/faster-cpython/ideas/blob/kenjin/stackref-semantics/3.14/stackref_semantics.md.

I'll send the PR for the tool in a separate PR.

These bugs were quite hard to notice, I will explain each one in comments below.

Issue: Set up tagged pointers in the evaluation stack #117139

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          Fix a few wrong steals in bytecodes.c

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Fidget-Spinner requested a review from markshannon as a code owner

June 28, 2024 14:23

bedevere-app Bot mentioned this pull request

Jun 28, 2024

Set up tagged pointers in the evaluation stack #117139

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Jun 28, 2024

Fidget-Spinner added the skip news label

Jun 28, 2024

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Jun 28, 2024

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Python/bytecodes.c

		}
		else {
		err = PyObject_SetItem(PyStackRef_AsPyObjectBorrow(container), slice, PyStackRef_AsPyObjectSteal(v));
		err = PyObject_SetItem(PyStackRef_AsPyObjectBorrow(container), slice, PyStackRef_AsPyObjectBorrow(v));

Fidget-Spinner Jun 28, 2024

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PyObject_SetItem and the entire family actually takes borrowed references to the container and item. So this steal is wrong, it should be borrow.

This was caught when the PyStackRef_CLOSE(v) below tried to close an already invalid stackref (it was made invalid by the steal).

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Python/bytecodes.c

		inst(SET_ADD, (set, unused[oparg-1], v -- set, unused[oparg-1])) {
		int err = PySet_Add(PyStackRef_AsPyObjectBorrow(set),
		PyStackRef_AsPyObjectSteal(v));
		PyStackRef_AsPyObjectBorrow(v));

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Same for PySet_Add

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Python/bytecodes.c

		PyObject *name = GETITEM(FRAME_CO_NAMES, oparg);
		int err = PyObject_SetAttr(PyStackRef_AsPyObjectBorrow(owner),
		name, PyStackRef_AsPyObjectSteal(v));
		name, PyStackRef_AsPyObjectBorrow(v));

Fidget-Spinner Jun 28, 2024 •

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PyObject_SetAttr actually takes borrowed refs too, so this shouldn't be stolen. This was caught when the DECREF_INPUTS tried to close an already stolen stackref.

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Fidget-Spinner requested a review from colesbury

June 28, 2024 14:26

Fidget-Spinner added the topic-free-threading label

Jun 28, 2024

Fidget-Spinner mentioned this pull request

Jun 28, 2024

gh-117139: A StackRef Debugging Mode #121134

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markshannon approved these changes

Jun 28, 2024

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bedevere-app Bot added awaiting merge and removed awaiting core review labels

Jun 28, 2024

Fidget-Spinner merged commit e6543da into python:main

Jun 28, 2024

bedevere-app Bot removed the awaiting merge label

Jun 28, 2024

bedevere-bot commented Jun 28, 2024

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⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Debian root 3.x has failed when building commit e6543da.

What do you need to do:

Don't panic.
Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/345/builds/8384) and take a look at the build logs.
Check if the failure is related to this commit (e6543da) or if it is a false positive.
If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/345/builds/8384

Failed tests:

test_repl

Failed subtests:

test_asyncio_repl_is_ok - test.test_repl.TestInteractiveInterpreter.test_asyncio_repl_is_ok

Summary of the results of the build (if available):

Click to see traceback logs

Traceback (most recent call last):
xiting asyncio REPL...
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/asyncio/__main__.py", line 109, in run
    raise OSError(errno.ENOTTY, "tty required", "stdin")
Fatal Python error: _enter_buffered_busy: could not acquire lock for <_io.BufferedWriter name='<stderr>'> at interpreter shutdown, possibly due to daemon threads
Python runtime state: finalizing (tstate=0x000055da69db5ad0)


Traceback (most recent call last):
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/test_repl.py", line 199, in test_asyncio_repl_is_ok
    assert_python_ok("-m", "asyncio")
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/support/script_helper.py", line 180, in assert_python_ok
    return _assert_python(True, *args, **env_vars)
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/support/script_helper.py", line 165, in _assert_python
    res.fail(cmd_line)
    ~~~~~~~~^^^^^^^^^^
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/test/support/script_helper.py", line 75, in fail
    raise AssertionError("Process return code is %d\n"
    ...<13 lines>...
                            err))
AssertionError: Process return code is -6
command line: ['/root/buildarea/3.x.angelico-debian-amd64/build/python', '-X', 'faulthandler', '-I', '-m', 'asyncio']


Traceback (most recent call last):
xiting asyncio REPL...
  File "/root/buildarea/3.x.angelico-debian-amd64/build/Lib/asyncio/__main__.py", line 109, in run
    raise OSError(errno.ENOTTY, "tty required", "stdin")
Fatal Python error: _enter_buffered_busy: could not acquire lock for <_io.BufferedWriter name='<stderr>'> at interpreter shutdown, possibly due to daemon threads
Python runtime state: finalizing (tstate=0x000055bec2fccad0)

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Fidget-Spinner commented Jun 28, 2024

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It looks unrelated and more like a buildbot problem.

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mrahtz pushed a commit to mrahtz/cpython that referenced this pull request

Jun 30, 2024


          pythongh-117139: Fix a few wrong steals in bytecodes.c (pythonGH-121127)

d2dc86f

Fix a few wrong steals in bytecodes.c

estyxx pushed a commit to estyxx/cpython that referenced this pull request

Jul 17, 2024


          pythongh-117139: Fix a few wrong steals in bytecodes.c (pythonGH-121127)

Fix a few wrong steals in bytecodes.c

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Fidget-Spinner commented Jun 28, 2024 • edited by bedevere-app Bot Loading Uh oh! There was an error while loading. Please reload this page.

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bedevere-bot commented Jun 28, 2024

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

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Fidget-Spinner commented Jun 28, 2024 •

edited by bedevere-app Bot

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Fidget-Spinner Jun 28, 2024 •

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