...and that is why you use QString if you are using the Qt framework. QString is a string class that actually does what you want when used in the obvious way. It probably helps that it was mostly created by people with "ASCII+" native languages. Or with customers that expect not exceedingly dumb behavior. The methods are called QString::toUpper() and QString::toLower() and take only the implicit "this" argument, unlike Win32 LCMapStringEx() which takes 5-8 arguments...
Qt does have a locale-aware equivalent (QLocale::toUpper/toLower) which calls out to ICU if available. Otherwise it falls back to the QString functions, so you have to be confident about how your build is configured. Whether it works or not has very little to do with the design of QString.
I don't see a problem with that. You can have it done locale-aware or not and "not" seems like a sane default. QString will uppercase 'ü' to 'Ü' just fine without locale-awareness whereas std::string doesn't handle non-ASCII according to the article. The cases where locale matters are probably very rare and the result will probably be reasonable anyway.
