From 69f61ebf8b0606be4c290ab75f4ace3fdd642233 Mon Sep 17 00:00:00 2001
From: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>
Date: Thu, 23 Oct 2025 10:49:27 +0100
Subject: [PATCH] gh-140474: Fix memory leak in `array.array` (GH-140478)
 (cherry picked from commit aa9d0a61d5c48717454f36351f0aabe4cc532de5)

Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>
---
 Lib/test/test_array.py                                    | 8 ++++++++
 .../2025-10-22-20-52-13.gh-issue-140474.xIWlip.rst        | 2 ++
 Modules/arraymodule.c                                     | 3 +++
 3 files changed, 13 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2025-10-22-20-52-13.gh-issue-140474.xIWlip.rst

diff --git a/Lib/test/test_array.py b/Lib/test/test_array.py
index 58ea89c4fac833..83b3c978da3581 100755
--- a/Lib/test/test_array.py
+++ b/Lib/test/test_array.py
@@ -1255,6 +1255,14 @@ def test_typecode_u_deprecation(self):
         with self.assertWarns(DeprecationWarning):
             array.array("u")
 
+    def test_empty_string_mem_leak_gh140474(self):
+        with warnings.catch_warnings():
+            warnings.simplefilter('ignore', DeprecationWarning)
+            for _ in range(1000):
+                a = array.array('u', '')
+                self.assertEqual(len(a), 0)
+                self.assertEqual(a.typecode, 'u')
+
 
 class UCS4Test(UnicodeTest):
     typecode = 'w'
diff --git a/Misc/NEWS.d/next/Library/2025-10-22-20-52-13.gh-issue-140474.xIWlip.rst b/Misc/NEWS.d/next/Library/2025-10-22-20-52-13.gh-issue-140474.xIWlip.rst
new file mode 100644
index 00000000000000..aca4e68b1e5e49
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-10-22-20-52-13.gh-issue-140474.xIWlip.rst
@@ -0,0 +1,2 @@
+Fix memory leak in :class:`array.array` when creating arrays from an empty
+:class:`str` and the ``u`` type code.
diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index 5d07de2fba9526..39d505c02596b8 100644
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -2838,6 +2838,9 @@ array_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
                         Py_SET_SIZE(self, n);
                         self->allocated = n;
                     }
+                    else {
+                        PyMem_Free(ustr);
+                    }
                 }
                 else { // c == 'w'
                     Py_ssize_t n = PyUnicode_GET_LENGTH(initial);