From 9d82a670f136b669d318581903469640a4be6fe2 Mon Sep 17 00:00:00 2001
From: DexFinder <63297382+shuimu5418@users.noreply.github.com>
Date: Wed, 11 Jun 2025 21:12:47 +0800
Subject: [PATCH 1/2] gh-135385: Fix memory regression for classes with both
 __slots__ and __dict__

---
 .../2025-06-11-21-40-21.gh-issue-135385.e2TFON.rst |  2 ++
 Objects/typeobject.c                               | 14 +++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2025-06-11-21-40-21.gh-issue-135385.e2TFON.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-06-11-21-40-21.gh-issue-135385.e2TFON.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-06-11-21-40-21.gh-issue-135385.e2TFON.rst
new file mode 100644
index 00000000000000..50cbe8f9091432
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-06-11-21-40-21.gh-issue-135385.e2TFON.rst
@@ -0,0 +1,2 @@
+Fixed a memory regression for classes that have both ``__slots__`` and
+``__dict__``.
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index db923c164774b7..1e974669ba20a7 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -4621,7 +4621,19 @@ type_new_descriptors(const type_new_ctx *ctx, PyTypeObject *type)
     }
 
     type->tp_basicsize = slotoffset;
-    type->tp_itemsize = ctx->base->tp_itemsize;
+
+    // Only inherit tp_itemsize if this type defines its own __slots__
+    // Classes that don't define __slots__ but inherit from __slots__ classes
+    // should not inherit tp_itemsize as they don't use variable-size items
+    if (et->ht_slots != NULL && PyTuple_GET_SIZE(et->ht_slots) > 0) {
+        // This type defines its own __slots__, inherit tp_itemsize
+        type->tp_itemsize = ctx->base->tp_itemsize;
+    }
+    else {
+        // This type doesn't define __slots__, don't inherit tp_itemsize
+        type->tp_itemsize = 0;
+    }
+
     type->tp_members = _PyHeapType_GET_MEMBERS(et);
     return 0;
 }

From 7ed3c02bb48fa2274f4c8903f3f853dda396997c Mon Sep 17 00:00:00 2001
From: BinFinder <63297382+shuimu5418@users.noreply.github.com>
Date: Thu, 12 Jun 2025 00:21:47 +0800
Subject: [PATCH 2/2] Update
 Misc/NEWS.d/next/Core_and_Builtins/2025-06-11-21-40-21.gh-issue-135385.e2TFON.rst

Co-authored-by: Peter Bierma <zintensitydev@gmail.com>
---
 .../2025-06-11-21-40-21.gh-issue-135385.e2TFON.rst            | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-06-11-21-40-21.gh-issue-135385.e2TFON.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-06-11-21-40-21.gh-issue-135385.e2TFON.rst
index 50cbe8f9091432..99824404dfd7f4 100644
--- a/Misc/NEWS.d/next/Core_and_Builtins/2025-06-11-21-40-21.gh-issue-135385.e2TFON.rst
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-06-11-21-40-21.gh-issue-135385.e2TFON.rst
@@ -1,2 +1,2 @@
-Fixed a memory regression for classes that have both ``__slots__`` and
-``__dict__``.
+Fix a memory regression for classes that have both :attr:`~object.__slots__` and
+:attr:`~object.__dict__`.