According to the reference for wcstombs, wcstombs will translate wide-characters "until a wide character translates into a null character."
So what wide-characters are translated into a null multibyte? Is it a specific character? Or any character outside a given range?
The
wcstombs
function will translate until theL'\0'
character (the wide character NUL) is encountered in the wide string (or until the destination multibyte string is filled). That documentation describes what it does when it encounters an error.