From 2d4fb51ae614df454b2458263dc0c80892b11c71 Mon Sep 17 00:00:00 2001
From: Tim Edwards <tim@opencircuitdesign.com>
Date: Fri, 26 Aug 2022 20:59:50 -0400
Subject: [PATCH] Corrected a failure to check for an invalid layer in the
 routine that queries a default layer width.  Otherwise this can cause a
 segfault, especially when a technology file has not been specified and the
 minimum tech is in effect.

---
 drc/DRCtech.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drc/DRCtech.c b/drc/DRCtech.c
index 13b7c603..74efbd27 100644
--- a/drc/DRCtech.c
+++ b/drc/DRCtech.c
@@ -4153,6 +4153,12 @@ DRCGetDefaultLayerWidth(ttype)
     DRCCookie *cptr;
     TileTypeBitMask *set;
 
+    if (ttype < 0)
+    {
+	TxError("Error:  Attempt to get default width of invalid layer!\n");
+	return 0;
+    }
+
     for (cptr = DRCCurStyle->DRCRulesTbl[TT_SPACE][ttype]; cptr != (DRCCookie *) NULL;
 	cptr = cptr->drcc_next)
     {