From 2524d699f572c5839dcc5c6a7ce06533ac2ef0a6 Mon Sep 17 00:00:00 2001
From: Jeremy Hylton <jeremy@alum.mit.edu>
Date: Mon, 5 Feb 2001 17:23:16 +0000
Subject: [PATCH] SF patch 103596 by Nick Mathewson: rause UnboundLocalError
 for uninitialized free variables

---
 Python/ceval.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/Python/ceval.c b/Python/ceval.c
index 264ba30a759..9d6549572f5 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1646,6 +1646,22 @@ eval_code2(PyCodeObject *co, PyObject *globals, PyObject *locals,
 		case LOAD_DEREF:
 			x = freevars[oparg];
 			w = PyCell_Get(x);
+			if (w == NULL) {
+				if (oparg < f->f_ncells)
+					v = PyTuple_GetItem(co->co_cellvars,
+							       oparg);
+				else
+				       v = PyTuple_GetItem(
+						      co->co_freevars,
+						      oparg - f->f_ncells);
+
+				format_exc_check_arg(
+					PyExc_UnboundLocalError,
+					UNBOUNDLOCAL_ERROR_MSG,
+					v);
+				err = -1;
+				break;
+			}
 			Py_INCREF(w);
 			PUSH(w);
 			break;