towupper(3) on macOS
The text af01d79e41f1, as Mac OS X 10.6.8, Mac OS X 10.6.7, Mac OS X 10.6.6, Mac OS X 10.6.5, Mac OS X 10.6.4, Mac OS X 10.6.3, Mac OS X 10.6.2, Mac OS X 10.6.1, Mac OS X 10.6, Mac OS X 10.5.8, Mac OS X 10.5.7, Mac OS X 10.5.6, Mac OS X 10.5.5, Mac OS X 10.5.4, Mac OS X 10.5.3, Mac OS X 10.5.2, Mac OS X 10.5.1, Mac OS X 10.5 shipped it.
lower case to upper case letter conversion (wide character version)