GUIs have these problems in spades. For example, all GUIs must display filenames (say in a file-picker), but how do you display the filenames if you don't know

GUIs have these problems in spades. For example, all GUIs must display filenames (say in a file-picker), but how do you display the filenames if you don't know what the encoding is, or if the filename disobeys the encoding? What should you show a user when "control-A" is one of the "characters"? How can you give line-at-a-time display when newline is in a filename? How do you process filename, since it may not be a legal string in the current encoding (a problem both Qt and Python have hit)? The Qt solution is to mandate that filenames must be in UTF-8. Period. So the nonsense that "filenames can be almost any sequence of bytes" is just that, nonsense. It's silly anyway; why allow ALMOST anything, but not anything? This also assumes that GUI programs never invoke other programs, which is also absurd. Every time a GUI does system(), exec(), and so on, it risks these filename problems (e.g., if it tries to pass a filename with a leading "-"). The problems are WORSE in shell, but they still occur in other languages.