bug#55153: 29.0.50; Implement system_process_attributes on Cygwin

[Ken Brown]

On 4/27/2022 11:53 AM, Eli Zaretskii wrote:
> > Date: Wed, 27 Apr 2022 11:16:46 -0400
> > From: Ken Brown <kbrown@cornell.edu>
> >
> > +# ifdef CYGWIN
> > +  /* ttname */
> > +  strcpy (procfn_end, "/ctty");
> > +  fd = emacs_open (fn, O_RDONLY, 0);
> > +  if (fd < 0)
> > +    nread = 0;
> > +  else
> > +    {
> > +      record_unwind_protect_int (close_file_unwind, fd);
> > +      nread = emacs_read_quit (fd, procbuf, sizeof procbuf);
> > +    }
> > +  /* /proc/<pid>/ctty should always end in newline. */
> > +  if (0 < nread && procbuf[nread - 1] == '\n')
> > +    procbuf[nread - 1] = '\0';
> > +  else
> > +    procbuf[0] = '\0';
> > +  attrs = Fcons (Fcons (Qttname, build_string (procbuf)), attrs);
>
> Is what you read from /proc/<pid>/ctty guaranteed to be pure-ASCII
> string?

Yes.  It's typically something like "/dev/pty0".

> P.S. Doesn't this warrant a NEWS entry?

Revised patch attached, with a NEWS entry.

Ken

0001-Implement-system_process_attributes-on-Cygwin.patch
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