Passing a non-copyable closure object to std::function parameter [duplicate]

Answer 1

If lifetime of the closure object isn't an issue, you could pass it in a reference wrapper:

int main()
{
    std::unique_ptr p(new int(5));
    auto f = [p = std::move(p)]{
        std::cout << *p << std::endl;
    };
    doit(std::cref(f));
}

This obviously doesn't apply to every scenario, but it's fine for your example program.

EDIT: Taking a glance at N3797 (C++14 working draft) § 20.9.11.2.1 [func.wrap.func.con] p7, the CopyConstructible requirement is still there. I wonder if there's a technical reason that can't be loosened to MoveConstructible, or if the committee just didn't get around to it?

EDIT: Answering my own question: std::function is CopyConstructible, so the wrapped functor needs to be CopyConstructible as well.