Unexpected things to know about working with Unicode in C++

It is rare to find a program that does not require string manipulation. If you are not limited to Latin ASCII, you have to deal with locales and national alphabets. Denis enjoyed digging through the source code of rantime libraries and discovered a lot of intricacies he wanted to talk about. Let's see what modern C++ has to offer for storing, comparing and processing Unicode strings. How productive are these operations and what assumptions might be wrong?