Trying to Copy a std::ostream

I bumped into a particularly cryptic compiler error today...

undefined reference to `std::ios_base::ios_base(std::ios_base const&)'|

After some interesting debugging I came across the problem in my code.

The Problem

void print(std::ostream zout = std::cout) { /* Some Code */ }

Can you spot what the problem is?

Hopefully you noticed that I'm passing zout by value, and std::ostream doesn't have a copy constructor.

The Solution

void print(std::ostream &zout = std::cout) { /* Some Code */ }

If I pass zout as a reference the compiler accepts it without a word and the desired behavior is achieved.