MB_LEN_MAX - maximum multibyte length of a character across all locales
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.
A constant integer greater than zero.
C11, POSIX.1-2008.
C99, POSIX.1-2001.
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.
MB_CUR_MAX(3)