From 142d4062df56aa3a6dd74b06e86700d95421b774 Mon Sep 17 00:00:00 2001
From: William S Fulton <wsf@fultondesigns.co.uk>
Date: Fri, 28 Sep 2018 07:08:12 +0100
Subject: [PATCH] Fix invalid free in SWIG_Python_AddErrMesg

Closes #1331
---
 Lib/python/pyrun.swg | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/Lib/python/pyrun.swg b/Lib/python/pyrun.swg
index 13738b668..53c3a32d1 100644
--- a/Lib/python/pyrun.swg
+++ b/Lib/python/pyrun.swg
@@ -1484,14 +1484,13 @@ SWIG_Python_AddErrMesg(const char* mesg, int infront)
     if (value) {
       PyObject *old_str = PyObject_Str(value);
       const char *tmp = SWIG_Python_str_AsChar(old_str);
-      if (!tmp)
-        tmp = "Invalid error message";
+      const char *errmesg = tmp ? tmp : "Invalid error message";
       Py_XINCREF(type);
       PyErr_Clear();
       if (infront) {
-	PyErr_Format(type, "%s %s", mesg, tmp);
+	PyErr_Format(type, "%s %s", mesg, errmesg);
       } else {
-	PyErr_Format(type, "%s %s", tmp, mesg);
+	PyErr_Format(type, "%s %s", errmesg, mesg);
       }
       SWIG_Python_str_DelForPy3(tmp);
       Py_DECREF(old_str);