Currently we do it by throwing a UTFException. This has problems:
1. about anything that deals with UTF cannot be made nothrow 2. turns innocuous errors into major problems, such as DOS attack vectors http://en.wikipedia.org/wiki/UTF-8#Invalid_byte_sequences One option to fix this is to treat invalid sequences as: 1. the .init value (0xFF for UTF8, 0xFFFF for UTF16 and UTF32) 2. U+FFFD I kinda like option 1. What do you think?
