vwarnc
void vwarnc (int, const char *, __va_list) __printf0like(2, 0);
vwarnc(errno, fmt, ap);
vwarnc(errno, fmt, ap);
vwarnc(code, fmt, ap);
vwarnc(errno, fmt, ap);
static void vwarnc(int code, const char *fmt, va_list ap);