bug#34123: A patch to fix reading EOF characters in non-interactive mode

[Noam Postavsky]

Shawn Presser <shawnpresser@gmail.com> writes:

> Notice that it’s currently impossible for non-interactive scripts to
> recover from EOF when reading from tty. After the user sends an EOF
> character by pressing C-d, calling read-from-minibuffer will always result
> in an error.

This isn't quite true, see the attached script which catches the error
and only exits after two EOFs.

bug-34123-read-script.el
Description: script demoing eof handling

A sample usage:

    $ emacs -Q --script ../bug-34123-read-script.el 
    > one
    line0: "one"
    > 
    EOF1
    > two
    line2: "two"
    > 
    EOF2

>        xfree (line);
> -      error ("Error reading from stdin");
> +      clearerr(stdin);
> +      return Qnil;

I think it would make sense to change that error to be an end-of-file
error, to make it easier to catch (having to examine the error message,
as I did in my script is not so nice).