12.8 UTF-8 String Constants

Writing ‘u8’ immediately before a string constant, with no intervening space, means to represent that string in UTF-8 encoding as a sequence of bytes. UTF-8 represents ASCII characters with a single byte, and represents non-ASCII Unicode characters (codes 128 and up) as multibyte sequences. Here is an example of a UTF-8 constant:

u8"A cónstàñt"

This constant occupies 13 bytes plus the terminating null, because each of the accented letters is a two-byte sequence.

Concatenating an ordinary string with a UTF-8 string conceptually produces another UTF-8 string. However, if the ordinary string contains character codes 128 and up, the results cannot be relied on.