From df9a52de6cb8e8a1003c55cf8b9b947d82b442c4 Mon Sep 17 00:00:00 2001
From: Tim Edwards <tim@opencircuitdesign.com>
Date: Sat, 23 May 2020 21:33:42 -0400
Subject: [PATCH] Corrected potential crash condition that can happen if there
 is one or more repeated "equiv" lines in a .ext file.  This implies two ports
 with different names are connected, indicating probably a bad layout, but
 that's not a reason to have magic crash.

---
 extflat/EFbuild.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/extflat/EFbuild.c b/extflat/EFbuild.c
index 0eac0168..115a5b8c 100644
--- a/extflat/EFbuild.c
+++ b/extflat/EFbuild.c
@@ -457,10 +457,14 @@ efBuildEquiv(def, nodeName1, nodeName2)
 			EFStrToHN((HierName *) NULL, nodeName2));
 	return;
     }
+    else if (nn2->efnn_node == (EFNode *)NULL)
+	return;		/* Repeated "equiv" statement */
 
     /* If both names exist and are for different nodes, merge them */
     if (nn1)
     {
+	if (nn1->efnn_node == (EFNode *)NULL)
+	    return;		/* Repeated "equiv" statement */
 	if (nn1->efnn_node != nn2->efnn_node)
 	{
 	    if (efWarn)