From 28d8301b5fd871a216c7cbea3d7f18609f9ce408 Mon Sep 17 00:00:00 2001
From: Holger Vogt <holger.vogt@uni-due.de>
Date: Fri, 28 Jun 2024 15:05:28 +0200
Subject: [PATCH] Prevent crash upon buggy user input

---
 src/spicelib/parser/inpptree.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/spicelib/parser/inpptree.c b/src/spicelib/parser/inpptree.c
index 2301dd979..66c88768b 100644
--- a/src/spicelib/parser/inpptree.c
+++ b/src/spicelib/parser/inpptree.c
@@ -753,7 +753,7 @@ static INPparseNode *PTdifferentiate(INPparseNode * p, int varnum)
         break;
 
     default:
-        fprintf(stderr, "Internal error: bad node type %d\n", p->type);
+        fprintf(stderr, "Error: bad node type %d\n", p->type);
         newp = NULL;
         break;
     }
@@ -778,6 +778,10 @@ static INPparseNode *mkb(int type, INPparseNode * left,
     INPparseNode *p;
     int i;
 
+    if (!right || !left) {
+        return (NULL);
+    }
+
     if ((right->type == PT_CONSTANT) && (left->type == PT_CONSTANT)) {
         double value;
         switch (type) {
@@ -890,6 +894,9 @@ static INPparseNode *mkf(int type, INPparseNode * arg)
     INPparseNode *p;
     int i;
 
+    if (!arg)
+        return NULL;
+
     for (i = 0; i < NUM_FUNCS; i++)
         if (funcs[i].number == type)
             break;