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gh-139951: Tests on tuple GC tracking (#140575)
  • Loading branch information
efimov-mikhail committed Oct 28, 2025
commit 4583d27a4ee7093a45cf720b373c9bc8a57fa651
41 changes: 41 additions & 0 deletions Lib/test/test_capi/test_tuple.py
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,12 @@ class TupleSubclass(tuple):


class CAPITest(unittest.TestCase):
def _not_tracked(self, t):
self.assertFalse(gc.is_tracked(t), t)

def _tracked(self, t):
self.assertTrue(gc.is_tracked(t), t)

def test_check(self):
# Test PyTuple_Check()
check = _testlimitedcapi.tuple_check
Expand Down Expand Up @@ -52,16 +58,47 @@ def test_tuple_new(self):
self.assertEqual(tup1, ())
self.assertEqual(size(tup1), 0)
self.assertIs(type(tup1), tuple)
self._not_tracked(tup1)

tup2 = tuple_new(1)
self.assertIs(type(tup2), tuple)
self.assertEqual(size(tup2), 1)
self.assertIsNot(tup2, tup1)
self.assertTrue(checknull(tup2, 0))
self._tracked(tup2)

self.assertRaises(SystemError, tuple_new, -1)
self.assertRaises(SystemError, tuple_new, PY_SSIZE_T_MIN)
self.assertRaises(MemoryError, tuple_new, PY_SSIZE_T_MAX)

def test_tuple_fromarray(self):
# Test PyTuple_FromArray()
tuple_fromarray = _testcapi.tuple_fromarray

tup = tuple([i] for i in range(5))
copy = tuple_fromarray(tup)
self.assertEqual(copy, tup)
self._tracked(copy)

tup = tuple(42**i for i in range(5))
copy = tuple_fromarray(tup)
self.assertEqual(copy, tup)
self._not_tracked(copy)

tup = ()
copy = tuple_fromarray(tup)
self.assertIs(copy, tup)

copy = tuple_fromarray(NULL, 0)
self.assertIs(copy, ())

with self.assertRaises(SystemError):
tuple_fromarray(NULL, -1)
with self.assertRaises(SystemError):
tuple_fromarray(NULL, PY_SSIZE_T_MIN)
with self.assertRaises(MemoryError):
tuple_fromarray(NULL, PY_SSIZE_T_MAX)

def test_tuple_pack(self):
# Test PyTuple_Pack()
pack = _testlimitedcapi.tuple_pack
Expand All @@ -70,6 +107,10 @@ def test_tuple_pack(self):
self.assertEqual(pack(1, [1]), ([1],))
self.assertEqual(pack(2, [1], [2]), ([1], [2]))

self._tracked(pack(1, [1]))
self._tracked(pack(2, [1], b'abc'))
self._not_tracked(pack(2, 42, b'abc'))

self.assertRaises(SystemError, pack, PY_SSIZE_T_MIN)
self.assertRaises(SystemError, pack, -1)
self.assertRaises(MemoryError, pack, PY_SSIZE_T_MAX)
Expand Down
30 changes: 24 additions & 6 deletions Lib/test/test_tuple.py
Original file line number Diff line number Diff line change
Expand Up @@ -290,12 +290,18 @@ def test_repr(self):
self.assertEqual(repr(a0), "()")
self.assertEqual(repr(a2), "(0, 1, 2)")

# Checks that t is not tracked without any GC collections.
def _not_tracked_instantly(self, t):
self.assertFalse(gc.is_tracked(t), t)

# Checks that t is not tracked after GC collection.
def _not_tracked(self, t):
# Nested tuples can take several collections to untrack
gc.collect()
gc.collect()
self.assertFalse(gc.is_tracked(t), t)

# Checks that t continues to be tracked even after GC collection.
def _tracked(self, t):
self.assertTrue(gc.is_tracked(t), t)
gc.collect()
Expand All @@ -307,13 +313,19 @@ def test_track_literals(self):
# Test GC-optimization of tuple literals
x, y, z = 1.5, "a", []

self._not_tracked(())
self._not_tracked((1,))
self._not_tracked((1, 2))
self._not_tracked((1, 2, "a"))
self._not_tracked((1, 2, (None, True, False, ()), int))
self._not_tracked((object(),))
# We check that those objects aren't tracked at all.
# It's essential for the GC performance, see gh-139951.
self._not_tracked_instantly(())
self._not_tracked_instantly((1,))
self._not_tracked_instantly((1, 2))
self._not_tracked_instantly((1, 2, "a"))
self._not_tracked_instantly((1, 2) * 5)
self._not_tracked_instantly((12, 10**10, 'a_' * 100))
self._not_tracked_instantly((object(),))

self._not_tracked(((1, x), y, (2, 3)))
self._not_tracked((1, 2, (None, True, False, ()), int))
self._not_tracked((object(), ()))

# Tuples with mutable elements are always tracked, even if those
# elements are not tracked right now.
Expand Down Expand Up @@ -343,6 +355,12 @@ def check_track_dynamic(self, tp, always_track):
self._tracked(tp(tuple([obj]) for obj in [x, y, z]))
self._tracked(tuple(tp([obj]) for obj in [x, y, z]))

t = tp([1, x, y, z])
self.assertEqual(type(t), tp)
self._tracked(t)
self.assertEqual(type(t[:]), tuple)
self._tracked(t[:])

@support.cpython_only
def test_track_dynamic(self):
# Test GC-optimization of dynamically constructed tuples.
Expand Down