From 664df71d6042b9c570df705a41a7a8e9a6664749 Mon Sep 17 00:00:00 2001
From: Piotr Sawicki <sawickipiotr@outlook.com>
Date: Tue, 20 Oct 2026 12:45:37 +0200
Subject: [PATCH 1/2] [mypyc] Release boxed integers on invalid byteorder
 errors

---
 mypyc/lib-rt/int_ops.c            |  1 +
 mypyc/test-data/run-integers.test | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/mypyc/lib-rt/int_ops.c b/mypyc/lib-rt/int_ops.c
index f5dfa98a595b0..b03095d04ba0a 100644
--- a/mypyc/lib-rt/int_ops.c
+++ b/mypyc/lib-rt/int_ops.c
@@ -641,6 +641,7 @@ PyObject *CPyTagged_ToBytes(CPyTagged self, Py_ssize_t length, PyObject *byteord
     } else if (strcmp(order, "little") == 0) {
         little_endian = 1;
     } else {
+        Py_DECREF(pyint);
         PyErr_SetString(PyExc_ValueError, "byteorder must be either 'little' or 'big'");
         return NULL;
     }
diff --git a/mypyc/test-data/run-integers.test b/mypyc/test-data/run-integers.test
index cbcb0d43fc9db..7a31f3cf5e3a3 100644
--- a/mypyc/test-data/run-integers.test
+++ b/mypyc/test-data/run-integers.test
@@ -574,6 +574,7 @@ class int:
     pass
 
 [case testIntToBytes]
+import sys
 from testutil import assertRaises
 def to_bytes(n: int, length: int, byteorder: str, signed: bool = False) -> bytes:
     return n.to_bytes(length, byteorder, signed=signed)
@@ -594,6 +595,17 @@ def test_to_bytes() -> None:
     with assertRaises(OverflowError):
         to_bytes(128, 1, "big", True)
 
+def test_invalid_byteorder_refcount() -> None:
+    n = int("123456789012345678901234567890")
+    before = sys.getrefcount(n)
+    for _ in range(10):
+        with assertRaises(ValueError):
+            to_bytes(n, 16, "invalid")
+    assert sys.getrefcount(n) == before
+
+[file sys/__init__.pyi]
+def getrefcount(n: object) -> int: ...
+
 [case testBitLength]
 def bit_length(n: int) -> int:
     return n.bit_length()

From 52223059cb67b12ee04228bb7a029e1926c2343a Mon Sep 17 00:00:00 2001
From: Piotr Sawicki <sawickipiotr@outlook.com>
Date: Tue, 20 Oct 2026 14:19:45 +0200
Subject: [PATCH 2/2] Fix test

---
 mypyc/test-data/run-integers.test | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mypyc/test-data/run-integers.test b/mypyc/test-data/run-integers.test
index 7a31f3cf5e3a3..3e4f29345250a 100644
--- a/mypyc/test-data/run-integers.test
+++ b/mypyc/test-data/run-integers.test
@@ -602,6 +602,8 @@ def test_invalid_byteorder_refcount() -> None:
         with assertRaises(ValueError):
             to_bytes(n, 16, "invalid")
     assert sys.getrefcount(n) == before
+    # Keep n alive across both refcount checks.
+    assert n == int("123456789012345678901234567890")
 
 [file sys/__init__.pyi]
 def getrefcount(n: object) -> int: ...