typedef o-type mbstate_t;
The type is an object type o-type that can represent a conversion state for any of the functions mbrlen, mbrtowc,
mbsrtowcs, wcrtomb, or wcsrtombs. A definition of the form:
mbstate_t mbst = {0};
ensures that mbst represents the initial conversion state. Note, however, that other values stored in an object of type
mbstate_t can also represent this state. To test safely for this state, use the function mbsinit.