bug#47596: File descriptor error when exiting emacs on android 11

[Eli Zaretskii <eliz@gnu.org>]

> From: Henrik Grimler <henrik@grimler.se>
> Cc: 47596@debbugs.gnu.org
> Date: Mon, 05 Apr 2021 10:59:55 +0200
> 
> > #include <stdio.h>
> > int main()
> > {
> >   fdopen (2, "w");
> >   fclose (stderr);
> > }
> > ```
> 
> Changing to this:
> 
> ```
> 
> #include <stdio.h>
> int main()
> {
>   FILE *err = fdopen (2, "w");
>   fclose (err);
> }
> ```
> 
> makes it work.

Which again makes no sense, because the program that works is a no-op:
it creates a copy of stderr and immediately closes it.

> So I suppose the sanitizer does not like that stderr is
> closed with `fclose (stderr)` instead of by using the fd obtained from
> fdopen (which was thrown away in my minimal example). 
> 
> Still not sure if this is actually problematic, but at least now I
> understand how the sanitizer "thinks".

If that's what it thinks, it's a clear bug in the sanitizer, IMO.