вывод символов (character output)
Возвращаемое значение (Return value)
Upon successful completion, these functions shall return the
number of wide characters transmitted, excluding the terminating
null wide character in the case of swprintf(), or a negative
value if an output error was encountered, and set errno to
indicate the error.
If n or more wide characters were requested to be written,
swprintf() shall return a negative value, and set errno to
indicate the error.
