The wcsncat function appends wide characters from the wide- character string wstr_2 to the end of wstr_1, up to a maximum of maxchar characters. A terminating null wide character is always appended to the result of the wcsncat function. Therefore, the maximum number of wide characters that can end up in wstr_1 is wcslen(wstr_1) + maxchar + 1). See also wcscat.