bug#49723: 28.0.50; Test in coding.c for NUL bytes in filenames is not reliable

[Eli Zaretskii]

> From: Federico Tedin <federicotedin@gmail.com>
> Cc: phst@google.com,  49723@debbugs.gnu.org
> Date: Thu, 16 Sep 2021 18:58:02 +0200
> 
> >> +** 'expand-file-name' now checks for null bytes in filenames.
> >> +The function will now check for null bytes in both NAME and
> >> +DEFAULT-DIRECTORY arguments, as well as in the 'default-directory'
> >> +buffer-local variable, assuming its value is used.
> >
> > This should say that if null bytes are found, expand-file-name will
> > signal an error.
> 
> Makes sense! I'm attaching a revised version.

Thanks.  Did you run the test suite after applying the changes, and
did you see no regressions?  If you didn't yet run the test suite,
please be sure to run all of it, as the use of expand-file-name is
universal.