gh-101892: Fix SystemError when a callable iterator call exhausts the iterator #101896

workingpayload · 2023-02-14T09:04:44Z

Updated Cython/objects/iterobject.c Line 217

Issue: Callable iterator can SystemError if call exhausts the iterator #101892

Updated Cython/objects/iterobject.c Line 217

Eclips4 · 2023-02-14T09:14:30Z

It's good to coverage this case in tests.

arhadthedev · 2023-02-14T19:21:53Z

Added a test copied from the issue with readability changes.

OTheDev · 2023-02-15T04:59:49Z

Objects/iterobject.c

@@ -214,7 +214,7 @@ calliter_iternext(calliterobject *it)
    }

    result = _PyObject_CallNoArgs(it->it_callable);
-    if (result != NULL) {
+    if (result != NULL && it->it_callable != NULL) {


Sorry, but this won't fix it. Notice the first if statement in the function. If it->it_callable == NULL is true, NULL is returned. So it->it_callable != NULL is already guaranteed at this point.

What if we check it->it_sentinel != NULL ?

OTheDev

It looks like NULL is being passed to PyObject_RichCompareBool() through it->it_sentinel when it expects an object?

If we add the check

if (result != NULL && it->it_sentinel != NULL) {

and get rid of that Py_DECREF(result) and place a new

Py_XDECREF(result);

just before return NULL;

Then the code in the issue will raise a StopIteration (no longer SystemError) and tests pass.

I'm not entirely sure if this is correct, TBH, but this is my guess.

OTheDev · 2023-02-15T06:03:48Z

Lib/test/test_iter.py

+            return NO_MORE
+        spam.need_reentrance = True
+        spam.iterator = iter(spam, NO_MORE)
+        next(spam.iterator)


What's the expected behaviour here? StopIteration?

Thank you for noticing the oversight! Fixed.

OTheDev · 2023-02-15T07:12:56Z

@workingpayload What do you think? Worth a try?

workingpayload · 2023-02-15T07:15:41Z

@workingpayload What do you think? Worth a try?

Yeah! Why not?

arhadthedev · 2023-02-15T08:04:35Z

Lib/test/test_iter.py

+        def spam():
+            if spam.need_reentrance:
+                spam.need_reentrance = False
+                list(spam.iterator) # Implicitly call ourselves


This evening (after getting access to my dev machine) I'll check whether the inner list() is required to throw StopIteration to trigger the bug. If no, I will simplify the test:

Suggested change

list(spam.iterator) # Implicitly call ourselves

try:

list(spam.iterator) # Implicitly call ourselves.

except StopIteration:

pass

I got it wrong. list() cannot throw an exception because it returns a ready-to-use list (possibly empty) processing StopIteration by itself.

furkanonder · 2023-02-15T22:23:46Z

LGTM. By the way PR title can be more meaningful. Ex: Fix SystemError when a callable iterator call exhausts the iterator.

Lib/test/test_iter.py

arhadthedev · 2023-03-04T11:34:23Z

@kumaraditya303 Thank you, addressed.

miss-islington · 2023-03-04T14:21:33Z

Thanks @workingpayload for the PR, and @kumaraditya303 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.10, 3.11.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

miss-islington · 2023-03-04T14:21:59Z

Sorry, @workingpayload and @kumaraditya303, I could not cleanly backport this to 3.10 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 705487c6557c3d8866622b4d32528bf7fc2e4204 3.10

bedevere-bot · 2023-03-04T14:22:01Z

GH-102418 is a backport of this pull request to the 3.11 branch.

…usts the iterator (pythonGH-101896) (cherry picked from commit 705487c) Co-authored-by: Raj <[email protected]> Co-authored-by: Oleg Iarygin <[email protected]>

…he iterator (GH-101896) (cherry picked from commit 705487c) Co-authored-by: Raj <[email protected]> Co-authored-by: Oleg Iarygin <[email protected]>

…usts the iterator (python#101896) Co-authored-by: Oleg Iarygin <[email protected]> (cherry picked from commit 705487c)

bedevere-bot · 2023-03-04T14:49:37Z

GH-102422 is a backport of this pull request to the 3.10 branch.

…austs the iterator (GH-101896) (#102422) gh-101892: Fix `SystemError` when a callable iterator call exhausts the iterator (#101896) Co-authored-by: Oleg Iarygin <[email protected]> (cherry picked from commit 705487c) Co-authored-by: Raj <[email protected]>

OTheDev · 2023-03-04T15:40:20Z

@arhadthedev Thanks for the continued work on this!

…usts the iterator (python#101896) Co-authored-by: Oleg Iarygin <[email protected]>

* main: (21 commits) pythongh-102192: Replace PyErr_Fetch/Restore etc by more efficient alternatives in sub interpreters module (python#102472) pythongh-95672: Fix versionadded indentation of get_pagesize in test.rst (pythongh-102455) pythongh-102416: Do not memoize incorrectly loop rules in the parser (python#102467) pythonGH-101362: Optimise PurePath(PurePath(...)) (pythonGH-101667) pythonGH-101362: Check pathlib.Path flavour compatibility at import time (pythonGH-101664) pythonGH-101362: Call join() only when >1 argument supplied to pathlib.PurePath() (python#101665) pythongh-102444: Fix minor bugs in `test_typing` highlighted by pyflakes (python#102445) pythonGH-102341: Improve the test function for pow (python#102342) Fix unused classes in a typing test (pythonGH-102437) pythongh-101979: argparse: fix a bug where parentheses in metavar argument of add_argument() were dropped (python#102318) pythongh-102356: Add thrashcan macros to filter object dealloc (python#102426) Move around example in to_bytes() to avoid confusion (python#101595) pythonGH-97546: fix flaky asyncio `test_wait_for_race_condition` test (python#102421) pythongh-96821: Add config option `--with-strict-overflow` (python#96823) pythongh-101992: update pstlib module documentation (python#102133) pythongh-63301: Set exit code when tabnanny CLI exits on error (python#7699) pythongh-101863: Fix wrong comments in EUC-KR codec (pythongh-102417) pythongh-102302 Micro-optimize `inspect.Parameter.__hash__` (python#102303) pythongh-102179: Fix `os.dup2` error reporting for negative fds (python#102180) pythongh-101892: Fix `SystemError` when a callable iterator call exhausts the iterator (python#101896) ...

* main: (37 commits) pythongh-102192: Replace PyErr_Fetch/Restore etc by more efficient alternatives in sub interpreters module (python#102472) pythongh-95672: Fix versionadded indentation of get_pagesize in test.rst (pythongh-102455) pythongh-102416: Do not memoize incorrectly loop rules in the parser (python#102467) pythonGH-101362: Optimise PurePath(PurePath(...)) (pythonGH-101667) pythonGH-101362: Check pathlib.Path flavour compatibility at import time (pythonGH-101664) pythonGH-101362: Call join() only when >1 argument supplied to pathlib.PurePath() (python#101665) pythongh-102444: Fix minor bugs in `test_typing` highlighted by pyflakes (python#102445) pythonGH-102341: Improve the test function for pow (python#102342) Fix unused classes in a typing test (pythonGH-102437) pythongh-101979: argparse: fix a bug where parentheses in metavar argument of add_argument() were dropped (python#102318) pythongh-102356: Add thrashcan macros to filter object dealloc (python#102426) Move around example in to_bytes() to avoid confusion (python#101595) pythonGH-97546: fix flaky asyncio `test_wait_for_race_condition` test (python#102421) pythongh-96821: Add config option `--with-strict-overflow` (python#96823) pythongh-101992: update pstlib module documentation (python#102133) pythongh-63301: Set exit code when tabnanny CLI exits on error (python#7699) pythongh-101863: Fix wrong comments in EUC-KR codec (pythongh-102417) pythongh-102302 Micro-optimize `inspect.Parameter.__hash__` (python#102303) pythongh-102179: Fix `os.dup2` error reporting for negative fds (python#102180) pythongh-101892: Fix `SystemError` when a callable iterator call exhausts the iterator (python#101896) ...

pythongh-101892 : Updated Cython/objects/iterobject.c Line 217

de17a82

Updated Cython/objects/iterobject.c Line 217

bedevere-bot added the awaiting review label Feb 14, 2023

bedevere-bot mentioned this pull request Feb 14, 2023

Callable iterator can SystemError if call exhausts the iterator #101892

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📜🤖 Added by blurb_it.

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arhadthedev added the interpreter-core (Objects, Python, Grammar, and Parser dirs) label Feb 14, 2023

Clarify the news entry

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workingpayload and others added 2 commits February 14, 2023 16:17

Merge branch 'main' into workingpayload/issue101892

25f4c06

Add a test

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Amend wording

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OTheDev reviewed Feb 15, 2023

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pythongh-101892 : Updated Cython/objects/iterobject.c Line 217

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workingpayload and others added 3 commits February 15, 2023 13:14

Merge branch 'main' into workingpayload/issue101892

6abb09a

Update test_iter.py

c8b6bad

Remove an unnecessary abstraction of reentrance

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arhadthedev reviewed Feb 15, 2023

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arhadthedev added 3 commits February 15, 2023 22:47

Clarify comments once more

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Update 2023-02-14-09-08-48.gh-issue-101892.FMos8l.rst

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Fix issues reported by patchcheck

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kumaraditya303 added needs backport to 3.10 only security fixes needs backport to 3.11 only security fixes labels Mar 4, 2023

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workingpayload deleted the workingpayload/issue101892 branch March 5, 2023 07:42

hugovk pushed a commit to hugovk/cpython that referenced this pull request Mar 6, 2023

pythongh-101892: Fix SystemError when a callable iterator call exha…

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…usts the iterator (python#101896) Co-authored-by: Oleg Iarygin <[email protected]>

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gh-101892: Fix SystemError when a callable iterator call exhausts the iterator #101896

gh-101892: Fix SystemError when a callable iterator call exhausts the iterator #101896

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OTheDev commented Mar 4, 2023

-                list(spam.iterator) # Implicitly call ourselves
+                try:
+                    list(spam.iterator) # Implicitly call ourselves.
+                except StopIteration:
+                    pass

gh-101892: Fix SystemError when a callable iterator call exhausts the iterator #101896

gh-101892: Fix SystemError when a callable iterator call exhausts the iterator #101896

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