bug#12911: 24.3.50; let users decide where (& perhaps whether) `emacs_backtrace.txt' files are written

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: drew.adams@oracle.com, 12911@debbugs.gnu.org
> Date: Mon, 19 Nov 2012 13:35:15 -0500
> 
> >> >> >> No need to change anything on platforms where stderr works.
> >> >> > stderr works on Windows as well.  See the code I wrote.
> >> >> If stderr works, then why do we need emacs_backtrace.txt?
> >> > For when the stuff written to stderr ends up in the Great Void, or
> >> > scrolls off the screen, or whatever.
> >> Right.  That's what I meant by "stderr doesn't work" (IOW while it does
> >> work in some cases, it can't be relied upon).
> > But then your first sentence above applies not only to Windows,
> > because stderr "doesn't work" in this sense on Unix as well.
> 
> I don't know of any case under Unix where stderr is dumped into the
> great void

It can still scroll off the screen.  Or end up in some file that the
window-system developers or admins set up, and that is some random or
unknown place, as far as Emacs users and maintainers are concerned.  I
see no significant difference.

> >> So let me reword my suggestion:
> >> I suggested to change the code such that, in those cases where we need
> >> to use emacs_backtrace.txt, we use ~/.emacs.d/backtrace.txt instead.
> > I already agreed to this, provided that Emacs puts stderr output there
> > on all platforms.
> 
> Yes, on all platforms where emacs_backtrace.txt is needed (in practice,
> this does reduce to w32, AFAIK).

No, on _all_ platforms.

But I'm repeating myself.