From 46c5a8d375fdf6e3b878ad75a2857f371d7c153b Mon Sep 17 00:00:00 2001
From: Giles Atkinson <“gatk555@gmail.com”>
Date: Sat, 29 Mar 2025 14:20:52 +0000
Subject: [PATCH] Fix for an error message seen when testing the shx
 shared-library program: do not allow a negative timestep.

---
 src/sharedspice.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/sharedspice.c b/src/sharedspice.c
index 059e4a3e2..5049fd12a 100644
--- a/src/sharedspice.c
+++ b/src/sharedspice.c
@@ -2471,8 +2471,14 @@ sharedsync(double *pckttime, double *pcktdelta, double olddelta, double finalt,
                step if return value from getsync is 1. */
             int retval = getsync(*pckttime, pcktdelta, olddelta, redostep, ng_ident, loc, userptr);
             /* never move beyond final time */
-            if (*pckttime + *pcktdelta > finalt)
-                *pcktdelta = finalt - *pckttime - 1.1 * delmin;
+            if (*pckttime + *pcktdelta > finalt) {
+                double newdelta;
+
+                newdelta = finalt - *pckttime - 1.1 * delmin;
+                if (newdelta <= 0.0)
+                    newdelta = finalt - *pckttime;
+                *pcktdelta = newdelta;
+            }
 
             /* user has decided to redo the step, ignoring redostep being set to 0
             by ngspice. */