From 281ab5d9034c10b1a457eeb0db8cb180384cf7ca Mon Sep 17 00:00:00 2001
From: Martin Ridgers <martin.ridgers@epicgames.com>
Date: Wed, 17 Nov 2021 13:27:11 +0100
Subject: Enabled the use-of-undefined-preprocessor macro warning

---
 xmake.lua | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/xmake.lua b/xmake.lua
index 0e9468cc0..d93f73c4f 100644
--- a/xmake.lua
+++ b/xmake.lua
@@ -61,6 +61,13 @@ if is_os("linux") then
     add_cxxflags("-Wno-missing-field-initializers")
 end
 
+-- Turn use of undefined cpp macros into errors
+if is_os("windows") then
+    add_cxxflags("/we4668")
+else
+    add_cxxflags("-Wundef")
+end
+
 function add_define_by_config(define, config_name)
     local value = has_config(config_name) and 1 or 0
     add_defines(define.."="..value)
-- 
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