gh-130070: Fix exec(<string>, closure=<non-None>) unexpected path

Lib/test/test_builtin.py

@@ -984,6 +984,13 @@ def four_freevars():
             closure=my_closure)
         self.assertEqual(result, 2520)
 
+        # should fail: closure isn't allowed
+        # when source is a string
+        self.assertRaises(TypeError,
+            exec,
+            "pass",
+            closure=my_closure)
+
         # should fail: closure isn't allowed
         # for functions without free vars
         self.assertRaises(TypeError,

Misc/NEWS.d/next/Core_and_Builtins/2025-02-13-05-09-31.gh-issue-130070.C8c9gK.rst

@@ -0,0 +1,2 @@
+``exec()`` called with a string ``source`` argument and non-``None`` ``closure`` argument no longer fails with a segmentation
+fault. Patch by Bartosz Sławecki.

Python/bltinmodule.c

@@ -1175,6 +1175,7 @@ builtin_exec_impl(PyObject *module, PyObject *source, PyObject *globals,
         if (closure != NULL) {
             PyErr_SetString(PyExc_TypeError,
                 "closure can only be used when source is a code object");
+            goto error;
         }
         PyObject *source_copy;
         const char *str;