From 76a87f62eb34db9e95d6079a389e496a6d55078e Mon Sep 17 00:00:00 2001
From: Jim Wilcoxson <prirun@gmail.com>
Date: Sun, 12 Apr 2020 22:42:09 -0400
Subject: [PATCH] devpnc.h: check fd before FD_SET

If there is no socket connection, fd will be -1.  On Ubuntu 18.04, gcc doesn't like adding -1 with FD_SET, and gives a buffer overflow abort.
---
 devpnc.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/devpnc.h b/devpnc.h
index 1028f62..db3afc5 100644
--- a/devpnc.h
+++ b/devpnc.h
@@ -757,7 +757,8 @@ void pncrecv() {
   for (nodeid=0; nodeid<=MAXNODEID; nodeid++)
     if (ni[nodeid].cstate == PNCCSAUTH) {
       fd = ni[nodeid].fd;
-      FD_SET(fd, &fds);
+      if (fd != -1)
+        FD_SET(fd, &fds);
       if (fd > n)
 	n = fd;
     }