gh-140474: Fix memory leak in array.array (GH-140478)

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'

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.

Modules/arraymodule.c

@@ -2833,6 +2833,9 @@ 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);