From e51d9e473aa1f882d3b3106ec2427a44d2a76ceb Mon Sep 17 00:00:00 2001
From: Rasmus Munk Larsen <rmlarsen@google.com>
Date: Thu, 23 Aug 2018 11:42:05 -0700
Subject: [PATCH] Protect #undef max with #ifdef max.

---
 unsupported/Eigen/CXX11/ThreadPool | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/unsupported/Eigen/CXX11/ThreadPool b/unsupported/Eigen/CXX11/ThreadPool
index 12aa07c7f..64ea83b7e 100644
--- a/unsupported/Eigen/CXX11/ThreadPool
+++ b/unsupported/Eigen/CXX11/ThreadPool
@@ -49,7 +49,9 @@
 // which trigger a check in test/main.h causing compilation to fail.
 // We work around the check here by removing the check for max in
 // the case where we have to emulate thread_local.
+#ifdef max
 #undef max
+#endif
 #include <unordered_map>
 #endif