Merge pull request #944 from borglab/eigen-update

Eigen Serialization Fix

gtsam/base/serialization.h

@@ -19,8 +19,9 @@
 
 #pragma once
 
-#include <sstream>
+#include <Eigen/Core>
 #include <fstream>
+#include <sstream>
 #include <string>
 
 // includes for standard serialization types
@@ -40,6 +41,17 @@
 #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