From 120a69d7db2c7ecc04f6a1688df493dc43124a56 Mon Sep 17 00:00:00 2001
From: Varun Agrawal <varagrawal@gmail.com>
Date: Mon, 29 Nov 2021 16:41:13 -0500
Subject: [PATCH] add workaround for Eigen serialization issue

---
 gtsam/base/serialization.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/gtsam/base/serialization.h b/gtsam/base/serialization.h
index f589ecc5e..98112b256 100644
--- a/gtsam/base/serialization.h
+++ b/gtsam/base/serialization.h
@@ -40,6 +40,17 @@
 #include <boost/archive/binary_oarchive.hpp>
 #include <boost/serialization/export.hpp>
 
+// Workaround a bug in GCC >= 7 and C++17
+// ref. https://gitlab.com/libeigen/eigen/-/issues/1676
+#ifdef __GNUC__
+#if __GNUC__ >= 7 && __cplusplus >= 201703L
+namespace boost { namespace serialization { struct U; } }
+namespace Eigen { namespace internal {
+template<> struct traits<boost::serialization::U> {enum {Flags=0};};
+} }
+#endif
+#endif
+
 namespace gtsam {
 
 /** @name Standard serialization