From 5e76e6fb07b4398ea21a7b41907f4ffa2bf2dca5 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Mon, 2 Jan 2023 18:58:53 +0000
Subject: [PATCH] MacOS: Add workaround for std::variant

---
 cmake/CompileFlags.cmake     |  5 +++++
 src/os/macosx/CMakeLists.txt |  1 +
 src/os/macosx/misc_osx.cpp   | 19 +++++++++++++++++++
 3 files changed, 25 insertions(+)
 create mode 100644 src/os/macosx/misc_osx.cpp

diff --git a/cmake/CompileFlags.cmake b/cmake/CompileFlags.cmake
index 5b7711a880..e147c36c2a 100644
--- a/cmake/CompileFlags.cmake
+++ b/cmake/CompileFlags.cmake
@@ -193,4 +193,9 @@ macro(compile_flags)
         # rdynamic is used to get useful stack traces from crash reports.
         set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -rdynamic")
     endif()
+
+    if (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+        # workaround for MacOS 10.13 and below which does not support std::variant, etc
+        add_definitions(-D_LIBCPP_DISABLE_AVAILABILITY)
+    endif()
 endmacro()
diff --git a/src/os/macosx/CMakeLists.txt b/src/os/macosx/CMakeLists.txt
index 645a057c7d..0b6264d294 100644
--- a/src/os/macosx/CMakeLists.txt
+++ b/src/os/macosx/CMakeLists.txt
@@ -4,6 +4,7 @@ add_files(
     font_osx.h
     macos.h
     macos.mm
+    misc_osx.cpp
     osx_stdafx.h
     string_osx.cpp
     string_osx.h
diff --git a/src/os/macosx/misc_osx.cpp b/src/os/macosx/misc_osx.cpp
new file mode 100644
index 0000000000..499c92b0e7
--- /dev/null
+++ b/src/os/macosx/misc_osx.cpp
@@ -0,0 +1,19 @@
+/*
+ * 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 misc_osx.cpp OS X misc functionality */
+
+#include "../../stdafx.h"
+
+#include "../../safeguards.h"
+
+#include <variant>
+
+/* See: https://stackoverflow.com/questions/52310835/xcode-10-call-to-unavailable-function-stdvisit/53868971#53868971 */
+const char* std::bad_variant_access::what() const noexcept {
+	return "bad_variant_access";
+}