globalconf | Persist flag values into an ini file | Access Management library

The error itself comes from the definition of std::deque states. Until C+11 the element types of std::deque had to be CopyAssignable and CopyConstructible (thus can't be const qualified as in you code) - see std::deque.

After C+11 the constraints are actually imposed by the operations done on the deque:

The requirements that are imposed on the elements depend on the actual operations performed on the container. Generally, it is required that element type is a complete type and meets the requirements of Erasable, but many member functions impose stricter requirements.

So without seeing the code that manipulates states it is hard to see what exactly triggers this. A trivial workaround (if the context allows it) is to remove the const there. Of course, both compilers should behave the same (if they both honor c++17 and there actually is an operation on the variable which violates the constness), but if you just need a quick fix this could do.