Andrzej writes in his recent blog about an issue library writers have to take care of.

A conditional copy constructor

by Andrzej Krzemieński

From the article:

In this post we will try to define a ‘wrapper’ class template that does or does not have a copy constructor depending on whether the wrapped class has it. This will be a good opportunity to explore in depth a couple of advanced C++ features. Note that this is a rather advanced topic and, unless you are writing or maintaining a generic library, you will probably never need this knowledge.