MB_LEN_MAX - 사용할 수 있는 모든 로케일에서 문자의 최대 바이트 수
Standard C library (libc)
The MB_LEN_MAX macro is the maximum number of bytes needed to represent a single wide character, in any of the supported locales.
POSIX.1-2001, POSIX.1-2008, C99.
The entities MB_LEN_MAX and sizeof(wchar_t) are totally unrelated. In glibc, MB_LEN_MAX is typically 16 (6 in glibc versions earlier than 2.2), while sizeof(wchar_t) is 4.