GCC 6 and polymake

[Jerry James]

Would one of you C++ experts help me out with a polymake build failure with
gcc 6?  Polymake defines a Vector class in lib/core/include/Vector.h (also
see lib/core/include/GenericVector.h).  Unlike with gcc 5 and earlier,
everywhere in the code that something like this is done:

Vector<int> x = ...;
Vector<int> y = ..;
const Vector<int> z = x + y;

where + can be one of several operators defined for the Vector class, gcc
errors like this:

error: invalid initialization of non-const reference of type
'pm::Vector<int>&' from an rvalue of type
'pm::Vector<int>'

I assume the error refers to the temporary created by the operator.  I've
added -std=gnu++98 to CXXFLAGS, but that doesn't help.  I guess that the
Vector class is missing something needed by gcc 6, but I don't know what
that something might be.  Any hints are much appreciated.

See http://koji.fedoraproject.org/koji/taskinfo?taskID=12969245 for an
example build showing the error.

Thank you,
-- 
Jerry James
http://www.jamezone.org/