# HG changeset patch
# User Rubidium <rubidium@openttd.org>
# Date 2023-08-20 20:58:49
# Node ID 5c98d0beef709611ad9d9bcf8394c415bdb265a5
# Parent  8332df6ef79fcd4b18758cd9a7af18c65f2ffcbe

Fix #11181: attempting to read string as int triggers assertion

diff --git a/src/strings.cpp b/src/strings.cpp
--- a/src/strings.cpp
+++ b/src/strings.cpp
@@ -196,8 +196,11 @@ bool HaveDParamChanged(const std::vector
 {
 	bool changed = false;
 	for (size_t i = 0; !changed && i < backup.size(); i++) {
-		if (backup[i].string.has_value()) {
-			changed = backup[i].string.value() != (const char *)(size_t)_global_string_params.GetParam(i);
+		bool global_has_string = _global_string_params.GetParamStr(i) != nullptr;
+		if (global_has_string != backup[i].string.has_value()) return true;
+
+		if (global_has_string) {
+			changed = backup[i].string.value() != _global_string_params.GetParamStr(i);
 		} else {
 			changed = backup[i].data != _global_string_params.GetParam(i);
 		}
diff --git a/src/tests/CMakeLists.txt b/src/tests/CMakeLists.txt
--- a/src/tests/CMakeLists.txt
+++ b/src/tests/CMakeLists.txt
@@ -2,5 +2,6 @@ add_test_files(
     landscape_partial_pixel_z.cpp
     math_func.cpp
     string_func.cpp
+    strings_func.cpp
     test_main.cpp
 )
diff --git a/src/tests/strings_func.cpp b/src/tests/strings_func.cpp
new file mode 100644
--- /dev/null
+++ b/src/tests/strings_func.cpp
@@ -0,0 +1,52 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file strings_func.cpp Test functionality from strings_func. */
+
+#include "../stdafx.h"
+
+#include "../3rdparty/catch2/catch.hpp"
+
+#include "../strings_func.h"
+
+TEST_CASE("HaveDParamChanged")
+{
+	SetDParam(0, 0);
+	SetDParamStr(1, "some string");
+
+	std::vector<StringParameterBackup> backup;
+	CopyOutDParam(backup, 2);
+
+	CHECK(HaveDParamChanged(backup) == false);
+
+	/* A different parameter 0 (both string and numeric). */
+	SetDParam(0, 1);
+	CHECK(HaveDParamChanged(backup) == true);
+
+	SetDParamStr(0, "some other string");
+	CHECK(HaveDParamChanged(backup) == true);
+
+	/* Back to the original state, nothing should have changed. */
+	SetDParam(0, 0);
+	CHECK(HaveDParamChanged(backup) == false);
+
+	/* A different parameter 1 (both string and numeric). */
+	SetDParamStr(1, "some other string");
+	CHECK(HaveDParamChanged(backup) == true);
+
+	SetDParam(1, 0);
+	CHECK(HaveDParamChanged(backup) == true);
+
+	/* Back to the original state, nothing should have changed. */
+	SetDParamStr(1, "some string");
+	CHECK(HaveDParamChanged(backup) == false);
+
+	/* Changing paramter 2 should not have any effect, as the backup is only 2 long. */
+	SetDParam(2, 3);
+	CHECK(HaveDParamChanged(backup) == false);
+
+}