Question

I want to design an API, which internally uses EIGEN.

Based on http://eigen.tuxfamily.org/dox/TopicPassingByValue.html, if a class have a Eigen object as member, it can not be passed by value.

Is there any straight forward way to tell compiler (e.g. g++) the my object can not be passed by value?

Answer 1

You can simply make the copy constructor unavailable. You can achieve this by using Boost and inheriting from boost::noncopyable, or by making the copy constructor private:

struct Foo
{
private:
    Foo(Foo const &) { }
};

Or in the new C++ by explicitly deleting it:

struct Foo
{
    Foo(Foo const &) = delete;
    Foo(Foo &&)      = delete;
};

You should probably also make your class unassignable by doing the same to the assignment operator (and boost::noncopyable takes care of this for you).