From 6227bdf43872e6288dde6fe1f2ec0f2026b38678 Mon Sep 17 00:00:00 2001
From: Pasi Kallinen <paxed@alt.org>
Date: Fri, 20 Mar 2020 21:04:16 +0200
Subject: [PATCH] Prevent setting boulder symbol to a control character

---
 src/options.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/options.c b/src/options.c
index 4570bcf1f..63740330d 100644
--- a/src/options.c
+++ b/src/options.c
@@ -739,7 +739,10 @@ char *op UNUSED;
             clash = opts[0] ? 1 : 0;
         else if (opts[0] >= '1' && opts[0] < WARNCOUNT + '0')
             clash = 2;
-        if (clash) {
+        if (opts[0] < ' ') {
+            config_error_add("boulder symbol cannot be a control character");
+            return optn_ok;
+        } else if (clash) {
             /* symbol chosen matches a used monster or warning
                symbol which is not good - reject it */
             config_error_add("Badoption - boulder symbol '%s' would conflict "