[3.13] gh-132171: Fix _interpreters.run_string crash on string subclass (GH-132173)

Lib/test/test__interpreters.py

@@ -745,6 +745,12 @@ def test_bytes_for_script(self):
         with self.assertRaises(TypeError):
             _interpreters.run_string(self.id, b'print("spam")')
 
+    def test_str_subclass_string(self):
+        class StrSubclass(str): pass
+
+        output = _run_output(self.id, StrSubclass('print(1 + 2)'))
+        self.assertEqual(output, '3\n')
+
     def test_with_shared(self):
         r, w = os.pipe()
 

Misc/NEWS.d/next/Library/2025-04-06-23-09-21.gh-issue-132171.zZqvfn.rst

@@ -0,0 +1 @@
+Fix crash of ``_interpreters.run_string`` on string subclasses.

Modules/_interpretersmodule.c

@@ -331,7 +331,7 @@ get_code_str(PyObject *arg, Py_ssize_t *len_p, PyObject **bytes_p, int *flags_p)
     int flags = 0;
 
     if (PyUnicode_Check(arg)) {
-        assert(PyUnicode_CheckExact(arg)
+        assert(PyUnicode_Check(arg)
                && (check_code_str((PyUnicodeObject *)arg) == NULL));
         codestr = PyUnicode_AsUTF8AndSize(arg, &len);
         if (codestr == NULL) {