GH-145247: Use _PyTuple_FromPair[Steal] in Objects by sergey-miryanov · Pull Request #145884 · python/cpython

sergey-miryanov · 2026-03-12T21:02:02Z

It is a second PR for usage of _PyTuple_FromPair[Steal] in the codebase.

Issue: Add PyTuple_FromPair #145247

methane · 2026-03-23T06:41:02Z

Objects/stringlib/unicode_format.h

+        result = _PyTuple_FromPairSteal(is_attr_obj, obj);
+        return result;

    done:


change done to error.

methane · 2026-03-23T06:41:18Z

Objects/stringlib/unicode_format.h

+    result = _PyTuple_FromPairSteal(first_obj, (PyObject *)it);
+    return result;

 done:


methane · 2026-03-23T06:51:08Z

Objects/dictobject.c

            to_delete = PyObject_RichCompareBool(val1, val2, Py_EQ);
+            Py_DECREF(val1);
            if (to_delete < 0) {
                goto error;


Is this safe? If goto error happens, won't it decref twice?

You are right, it is not safe. I don't understand why I did this (blame on me).

methane · 2026-03-23T06:59:05Z

Objects/listobject.c

@@ -1439,7 +1439,7 @@ list_extend_dictitems(PyListObject *self, PyDictObject *dict)
    Py_ssize_t i = 0;
    PyObject *key_value[2];


change this to key, value.

sergey-miryanov

Address review

sergey-miryanov · 2026-03-23T19:24:10Z

Objects/stringlib/unicode_format.h

+        result = _PyTuple_FromPairSteal(is_attr_obj, obj);
+        return result;

    done:


sergey-miryanov · 2026-03-23T19:24:20Z

Objects/stringlib/unicode_format.h

+    result = _PyTuple_FromPairSteal(first_obj, (PyObject *)it);
+    return result;

 done:


sergey-miryanov · 2026-03-23T19:24:34Z

Objects/listobject.c

@@ -1439,7 +1439,7 @@ list_extend_dictitems(PyListObject *self, PyDictObject *dict)
    Py_ssize_t i = 0;
    PyObject *key_value[2];


…ey-miryanov/cpython into feat/145247-pytuple-from-pair-use-2

vstinner

This change introduces a leak in the dict type (see my comment below about a leak).

vstinner · 2026-03-27T16:48:36Z

Objects/stringlib/unicode_format.h

+        result = _PyTuple_FromPairSteal(is_attr_obj, obj);
+        return result;


Please remove the result variable in this scope and replace return result with return NULL in the error path. By the way, previously this function had two result variables!

Suggested change

result = _PyTuple_FromPairSteal(is_attr_obj, obj);

return result;

return _PyTuple_FromPairSteal(is_attr_obj, obj);

vstinner · 2026-03-27T16:49:32Z

Objects/stringlib/unicode_format.h

+    result = _PyTuple_FromPairSteal(first_obj, (PyObject *)it);
+    return result;


Same remark, you can now remove the result variable to simplify the code.

Suggested change

result = _PyTuple_FromPairSteal(first_obj, (PyObject *)it);

return result;

return _PyTuple_FromPairSteal(first_obj, (PyObject *)it);

vstinner · 2026-03-27T17:03:22Z

Objects/dictobject.c

            Py_DECREF(pair);
        }
-        Py_DECREF(key);
-        Py_XDECREF(val1);


This removal is suspicious, since there is still Py_INCREF(val1); above.

The problem is that test_dict uses many immortal objects, so they can fail to detect refleaks.

With this patch, I can trigger a leak using ./python -m test -v test_dict -m test_dictview_set_operations_on_items -R 3:3:

diff --git a/Lib/test/test_dict.py b/Lib/test/test_dict.py index b2f4363b23e..4f2b6e1dc14 100644 --- a/Lib/test/test_dict.py +++ b/Lib/test/test_dict.py @@ -804,6 +804,11 @@ def test_dictview_set_operations_on_items(self): self.assertEqual(k1 ^ k2, {(3,3)}) self.assertEqual(k1 ^ k3, {(1,1), (2,2), (4,4)}) + obj = object() + d = {obj: b'abc'.decode()}.items() + d2 = {obj: b'def'.decode()}.items() + d ^ d2 + def test_items_symmetric_difference(self): rr = random.randrange for _ in range(100):

vstinner · 2026-03-27T17:03:56Z

Objects/enumobject.c

+    result = _PyTuple_FromPairSteal(next_index, next_item);
    return result;


Suggested change

result = _PyTuple_FromPairSteal(next_index, next_item);

return result;

return _PyTuple_FromPairSteal(next_index, next_item);

vstinner · 2026-03-27T17:04:12Z

Objects/enumobject.c

+    result = _PyTuple_FromPairSteal(next_index, next_item);
    return result;


Suggested change

result = _PyTuple_FromPairSteal(next_index, next_item);

return result;

return _PyTuple_FromPairSteal(next_index, next_item);

vstinner · 2026-03-27T17:08:29Z

Objects/longobject.c

+    z = _PyTuple_FromPairSteal((PyObject *)div, (PyObject *)mod);
    return z;


Suggested change

z = _PyTuple_FromPairSteal((PyObject *)div, (PyObject *)mod);

return z;

return _PyTuple_FromPairSteal((PyObject *)div, (PyObject *)mod);

The z variable is no longer needed.

vstinner · 2026-03-27T17:08:46Z

Objects/longobject.c

+    result = _PyTuple_FromPairSteal((PyObject *)quo, (PyObject *)rem);
    return result;


Suggested change

result = _PyTuple_FromPairSteal((PyObject *)quo, (PyObject *)rem);

return result;

return _PyTuple_FromPairSteal((PyObject *)quo, (PyObject *)rem);

vstinner · 2026-03-27T17:09:07Z

Objects/longobject.c

+    ratio_tuple = _PyTuple_FromPairSteal(numerator, _PyLong_GetOne());
    return ratio_tuple;


Suggested change

ratio_tuple = _PyTuple_FromPairSteal(numerator, _PyLong_GetOne());

return ratio_tuple;

return _PyTuple_FromPairSteal(numerator, _PyLong_GetOne());

vstinner · 2026-03-27T17:09:30Z

Objects/odictobject.c

+    item = _PyTuple_FromPairSteal(key, value);
    return item;


Suggested change

item = _PyTuple_FromPairSteal(key, value);

return item;

return _PyTuple_FromPairSteal(key, value);

vstinner · 2026-03-27T17:12:25Z

Objects/odictobject.c

        if (result == NULL) {
-            Py_DECREF(key);
-            Py_DECREF(value);
            goto done;


It's strange to call this label "done" whereas it's only used for error path. It should be called "error".

Use _PyTuple_FromPair[Steal] in Objects

eb71cca

sergey-miryanov requested review from JelleZijlstra, markshannon and methane as code owners March 12, 2026 21:02

bedevere-app bot mentioned this pull request Mar 12, 2026

Add PyTuple_FromPair #145247

Open

bedevere-app bot added the awaiting review label Mar 12, 2026

sergey-miryanov added the skip news label Mar 12, 2026

methane reviewed Mar 23, 2026

View reviewed changes

Address review

8a189d8

sergey-miryanov commented Mar 23, 2026

View reviewed changes

sergey-miryanov added 3 commits March 24, 2026 00:25

Merge branch 'main' into feat/145247-pytuple-from-pair-use-2

db20d92

Remove wrong decref

5c295d3

Merge branch 'feat/145247-pytuple-from-pair-use-2' of github.com:serg…

7e45fc5

…ey-miryanov/cpython into feat/145247-pytuple-from-pair-use-2

vstinner reviewed Mar 27, 2026

View reviewed changes

		@@ -1439,7 +1439,7 @@ list_extend_dictitems(PyListObject self, PyDictObject dict)
		Py_ssize_t i = 0;
		PyObject *key_value[2];

		result = _PyTuple_FromPairSteal(is_attr_obj, obj);
		return result;

	result = _PyTuple_FromPairSteal(is_attr_obj, obj);
	return result;
	return _PyTuple_FromPairSteal(is_attr_obj, obj);

		result = _PyTuple_FromPairSteal(first_obj, (PyObject *)it);
		return result;

	result = _PyTuple_FromPairSteal(first_obj, (PyObject *)it);
	return result;
	return _PyTuple_FromPairSteal(first_obj, (PyObject *)it);

		result = _PyTuple_FromPairSteal(next_index, next_item);
		return result;

	result = _PyTuple_FromPairSteal(next_index, next_item);
	return result;
	return _PyTuple_FromPairSteal(next_index, next_item);

		z = _PyTuple_FromPairSteal((PyObject )div, (PyObject )mod);
		return z;

	z = _PyTuple_FromPairSteal((PyObject )div, (PyObject )mod);
	return z;
	return _PyTuple_FromPairSteal((PyObject )div, (PyObject )mod);

		result = _PyTuple_FromPairSteal((PyObject )quo, (PyObject )rem);
		return result;

		ratio_tuple = _PyTuple_FromPairSteal(numerator, _PyLong_GetOne());
		return ratio_tuple;

	ratio_tuple = _PyTuple_FromPairSteal(numerator, _PyLong_GetOne());
	return ratio_tuple;
	return _PyTuple_FromPairSteal(numerator, _PyLong_GetOne());

	item = _PyTuple_FromPairSteal(key, value);
	return item;
	return _PyTuple_FromPairSteal(key, value);

Uh oh!

Conversation

sergey-miryanov commented Mar 12, 2026 • edited by bedevere-app bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

sergey-miryanov left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

vstinner left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

sergey-miryanov commented Mar 12, 2026 •

edited by bedevere-app bot

Loading