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gh-157176: Make time.struct_time type immutable #157179

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Merged
vstinner merged 6 commits into from
Oct 7, 2026
Merged

gh-157176: Make time.struct_time type immutable #157179

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ad2aa7b
fix(structseq): enable GC tracking in PyStructSequence_New
ashm-dev Sep 8, 2026
60b9a41
Merge branch 'main' into gh-157176
ashm-dev Sep 8, 2026
053f101
fix(structseq): track struct_time and asyncgen_hooks in GC
ashm-dev Oct 5, 2026
a5a15b2
fix(time): make struct_time type immutable
ashm-dev Oct 6, 2026
e996c40
test(structseq): use immutable type check
ashm-dev Oct 7, 2026
675e4ba
Merge branch 'main' into gh-157176
vstinner Oct 7, 2026
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fix(time): make struct_time type immutable
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@ashm-dev
ashm-dev committed Oct 6, 2026
commit a5a15b2755e08369b4e4a5b40330e63e2f561b91
4 changes: 0 additions & 4 deletions Doc/c-api/tuple.rst
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Expand Up @@ -232,10 +232,6 @@ type.
Creates an instance of *type*, which must have been created with
:c:func:`PyStructSequence_NewType`.

The returned instance is not tracked by the garbage collector. If the
instance can contain objects that participate in reference cycles, call
:c:func:`PyObject_GC_Track` after populating its fields.

Return ``NULL`` with an exception set on failure.


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16 changes: 7 additions & 9 deletions Lib/test/test_structseq.py
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Expand Up @@ -351,9 +351,9 @@ def test_reference_cycle(self):
# was cleared first, the structseq instance would crash in the
# destructor.
script_helper.assert_python_ok("-c", textwrap.dedent(r"""
import time
t = time.gmtime()
type(t).refcyle = t
import os
t = os.stat('.')
type(t).refcycle = t
"""))

def test_replace_gc_tracked(self):
Expand All @@ -365,12 +365,10 @@ def test_replace_gc_tracked(self):

self.assertTrue(gc.is_tracked(replaced_struct))

def test_gc_tracked(self):
# Instances created via Python or stdlib callers that may participate
# in cycles are GC-tracked; simple instances like os.stat_result are not.
self.assertTrue(gc.is_tracked(time.gmtime()))
self.assertTrue(gc.is_tracked(time.struct_time((2020, 1, 1, 0, 0, 0, 0, 1, 0))))
self.assertFalse(gc.is_tracked(os.stat(__file__)))
def test_struct_time_type_immutable(self):
t = time.gmtime()
with self.assertRaisesRegex(TypeError, "immutable type"):
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type(t).refcycle = t

if __name__ == "__main__":
unittest.main()
1 change: 0 additions & 1 deletion Lib/test/test_sys.py
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Expand Up @@ -1969,7 +1969,6 @@ def test_asyncgen_hooks(self):

sys.set_asyncgen_hooks(firstiter=firstiter)
hooks = sys.get_asyncgen_hooks()
self.assertTrue(gc.is_tracked(hooks))
self.assertIs(hooks.firstiter, firstiter)
self.assertIs(hooks[0], firstiter)
self.assertIs(hooks.finalizer, None)
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2 changes: 1 addition & 1 deletion Misc/NEWS.d/next/Core_and_Builtins/2026-09-08-15-55-00.gh-issue-157176.yZ8a1B.rst
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@StanFromIreland StanFromIreland Oct 7, 2026

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This should be in Library.

@vstinner vstinner Oct 7, 2026

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Oh! I didn't pay attention to the section of the Changelog entry. Sadly, I saw your comment after the PR was merged.

@StanFromIreland StanFromIreland Oct 7, 2026

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I wrote #158983 to move it.

Original file line number Diff line number Diff line change
@@ -1 +1 @@
Track :func:`time.struct_time` and :func:`sys.get_asyncgen_hooks` objects in the garbage collector to prevent reference cycle leaks. Patch by Shamil Abdulaev.
Make the :class:`time.struct_time` type immutable to prevent reference cycles between the type and its instances. Patch by Shamil Abdulaev.
5 changes: 3 additions & 2 deletions Modules/timemodule.c
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Expand Up @@ -5,6 +5,7 @@
#include "pycore_moduleobject.h" // _PyModule_GetState()
#include "pycore_namespace.h" // _PyNamespace_New()
#include "pycore_runtime.h" // _Py_ID()
#include "pycore_structseq.h" // _PyStructSequence_NewType()
#include "pycore_time.h" // _PyTimeFraction

#include <time.h> // clock()
Expand Down Expand Up @@ -497,7 +498,6 @@ tmtotuple(time_module_state *state, struct tm *p
#undef SET
#undef SET_ITEM

PyObject_GC_Track(v);
return v;
}

Expand Down Expand Up @@ -2111,7 +2111,8 @@ time_exec(PyObject *module)
}

// struct_time type
state->struct_time_type = PyStructSequence_NewType(&struct_time_type_desc);
state->struct_time_type = _PyStructSequence_NewType(
&struct_time_type_desc, Py_TPFLAGS_IMMUTABLETYPE);
if (state->struct_time_type == NULL) {
return -1;
}
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1 change: 0 additions & 1 deletion Python/sysmodule.c
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Expand Up @@ -1531,7 +1531,6 @@ sys_get_asyncgen_hooks_impl(PyObject *module)
PyStructSequence_SET_ITEM(res, 0, Py_NewRef(firstiter));
PyStructSequence_SET_ITEM(res, 1, Py_NewRef(finalizer));

PyObject_GC_Track(res);
return res;
}

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