Check whether a string resize is necessary at the end

of PyString_DecodeEscape(). This prevents a call to
_PyString_Resize() for the empty string, which would
result in a PyErr_BadInternalCall(), because the
empty string has more than one reference.

This closes SF bug http://www.python.org/sf/603937

1 files changed, 4 insertions, 3 deletions

diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index 31f188a..dd38ee3 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -533,8 +533,8 @@ PyObject *PyString_DecodeEscape(const char *s,
 	char *p, *buf;
 	const char *end;
 	PyObject *v;
-	v = PyString_FromStringAndSize((char *)NULL, 
-				       recode_encoding ? 4*len:len);
+	int newlen = recode_encoding ? 4*len:len;
+	v = PyString_FromStringAndSize((char *)NULL, newlen);
 	if (v == NULL)
 		return NULL;
 	p = buf = PyString_AsString(v);
@@ -660,7 +660,8 @@ PyObject *PyString_DecodeEscape(const char *s,
 			break;
 		}
 	}
-	_PyString_Resize(&v, (int)(p - buf));
+	if (p-buf < newlen)
+		_PyString_Resize(&v, (int)(p - buf));
 	return v;
   failed:
 	Py_DECREF(v);