https://github.com/python/cpython/commit/d6c89a2df2c8b7603125883494e9058a88348f66
commit: d6c89a2df2c8b7603125883494e9058a88348f66
branch: main
author: Stan Ulbrych <[email protected]>
committer: kumaraditya303 <[email protected]>
date: 2025-11-06T11:20:57+05:30
summary:
gh-140939: Fix memory leak in `_PyBytes_FormatEx` error path (#140957)
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2025-11-03-17-21-38.gh-issue-140939.FVboAw.rst
M Lib/test/test_bytes.py
M Objects/bytesobject.c
diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index f10e4041937f4f..e012042159d223 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -802,6 +802,13 @@ def __int__(self):
with self.assertRaisesRegex(TypeError, msg):
operator.mod(format_bytes, value)
+ def test_memory_leak_gh_140939(self):
+ # gh-140939: MemoryError is raised without leaking
+ _testcapi = import_helper.import_module('_testcapi')
+ with self.assertRaises(MemoryError):
+ b = self.type2test(b'%*b')
+ b % (_testcapi.PY_SSIZE_T_MAX, b'abc')
+
def test_imod(self):
b = self.type2test(b'hello, %b!')
orig = b
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2025-11-03-17-21-38.gh-issue-140939.FVboAw.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2025-11-03-17-21-38.gh-issue-140939.FVboAw.rst
new file mode 100644
index 00000000000000..a2921761f75556
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2025-11-03-17-21-38.gh-issue-140939.FVboAw.rst
@@ -0,0 +1,2 @@
+Fix memory leak when :class:`bytearray` or :class:`bytes` is formated with the
+``%*b`` format with a large width that results in a :exc:`MemoryError`.
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index 9c807b3dd166ee..2b9513abe91956 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -985,6 +985,7 @@ _PyBytes_FormatEx(const char *format, Py_ssize_t format_len,
if (alloc > 2) {
res = PyBytesWriter_GrowAndUpdatePointer(writer, alloc - 2,
res);
if (res == NULL) {
+ Py_XDECREF(temp);
goto error;
}
}
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