VFPRINTF_LEN
char buf[VFPRINTF_LEN + 80];
written = vsnprintf(buf, VFPRINTF_LEN + 1, fmt, args);
if (expected_len > VFPRINTF_LEN) {
cmp_len = VFPRINTF_LEN;
llen += printf(" should be \"%.*s\"", VFPRINTF_LEN, expected);