> It would be possible to make ctime() be
>
>       tm = localtime(t);
>       if (tm == NULL)
>               return NULL;
>       return asctime(tm);
>
> and in theory that would be adequate, but I'm actually going to suggest moving the fix into asctime() (into asctime_r() really of course), and have
> asctime_r() start
>
>       if (timeptr == NULL)
>               return NULL;
>
> I think that's a safer fix.   Appended is the patch I suggest, made
> against the tzcode2009t sources (latest I believe.)

Any sentiment for (or against)...
       if (timeptr == NULL)
               return "?";
...or...
               return "??? ??? ?? ??:??:?? ????\n";
...or some variant?