From 70bca27c0a54accc637d7e23a8089126b00f2113 Mon Sep 17 00:00:00 2001
From: Max Horn <max@quendi.de>
Date: Mon, 23 Oct 2023 01:20:04 +0200
Subject: [PATCH] Fix infinite recursion in ReplacedString

... when <old> is empty
---
 lib/init.g                  | 6 ++++++
 tst/testinstall/strings.tst | 8 ++++++++
 2 files changed, 14 insertions(+)

diff --git a/lib/init.g b/lib/init.g
index cea842f139..40faba053b 100644
--- a/lib/init.g
+++ b/lib/init.g
@@ -104,7 +104,13 @@ infinity := "2b defined";
 ##
 ReplacedString := function ( str, old, new, arg... )
     local lss, all, p, s, pp;
+    if old = new then
+        return str;
+    fi;
     lss := LEN_LIST( old );
+    if lss = 0  then
+        Error("<old> must not be empty");
+    fi;
     if LEN_LIST( arg ) > 0  then
         all := arg[1] = "all";
     else
diff --git a/tst/testinstall/strings.tst b/tst/testinstall/strings.tst
index d0dd5388b7..84439e4d9a 100644
--- a/tst/testinstall/strings.tst
+++ b/tst/testinstall/strings.tst
@@ -209,5 +209,13 @@ gap> for len in [10,100,1000,10000,100000] do
 > Assert(0, Concatenation(str,"\n") = DisplayString(str));
 > od;;
 
+#
+gap> ReplacedString("Hello world", "Hello", "Goodbye");
+"Goodbye world"
+gap> ReplacedString("Hello world", "", "");
+"Hello world"
+gap> ReplacedString("Hello world", "", "*");
+Error, <old> must not be empty
+
 #
 gap> STOP_TEST( "strings.tst", 1);