Are UTF16 (as used by for example wide-winapi functions) characters always 2 byte long?

Question

Please clarify for me, how does UTF16 work? I am a little confused, considering these points:

• There is a static type in C++, WCHAR, which is 2 bytes long. (alway

Answer 1

All characters in the Basic Multilingual Plane will be 2 bytes long.

Characters in other planes will be encoded into 4 bytes each, in the form of a surrogate pair.

Obviously, if a function does not try to detect surrogate pairs and blindly treats each pair of bytes as a character, it will bug out on strings that contain such pairs.