#error if min or max is defined

Eigen/Core

diff --git a/Eigen/Core b/Eigen/Core
index 7f42a6c..211e0f9 100644
--- a/Eigen/Core
+++ b/Eigen/Core
@@ -69,6 +69,13 @@
   #include <new>
 #endif
 
+// this needs to be done after all possible windows C header includes and before any Eigen source includes
+// (system C++ includes are supposed to be able to deal with this already):
+// windows.h defines min and max macros which would make Eigen fail to compile.
+#if defined(min) || defined(max)
+#error The preprocessor symbols 'min' or 'max' are defined. If you are compiling on Windows, do #define NOMINMAX to prevent windows.h from defining these symbols.
+#endif
+
 namespace Eigen {
 
 /** \defgroup Core_Module Core module