fprintf (stderr, format, ap);
int error = errno;  if (__progname) fprintf (stderr, "%s: ", __progname); if (format) { vfprintf (stderr, format, ap); fputs (": ", stderr); } fprintf (stderr, "%s\n", strerror (error));
vwarn (const char *format, __gnuc_va_list ap){  fprintf (stderr, format, ap);}