bug#19175: 24.4; make-frame-on-display fails if emacs started with -nw

[Stefan Monnier]

>> How old is this bug?  IIUC it's pretty old, so there's no hurry to
>> fix it in 24.5 rather than in Emacs-25.  It's not fixing a regression.
> It is still a bad problem, and could very well raise its ugly head in
> other, more important situations.

It could, but it hasn't in the last many years that we've lived with it
without anyone noticing, so we can live with it a few more I think.
And the effect of the bug seems rather minor.
IOW the urgency is very low.

>> > Fixing the ChangeLog is easy, if
>> > that's the only problem: just swap the entries.
>> No, the problem is delaying the release by having another RC candidate.
> There's no need: we are making a simple change that doesn't require
> another RC, IMO.

I don't find it simple at all.  E.g. it doesn't seem obviously safe
(e.g. what if the X call ends up making a longjmp and hence skipping the
unblocking of sigio?  Seems highly unlikely, but we do make longjmps in
not-completely-different circumstances (e.g. to avoid killing Emacs when
an X connection dies), so I think that proving such a longjmp can't
happen would require a serious code analysis, i.e. pretty far from
"obviously safe").

Low urgency, non-zero risk, I'm surprised you'd even bother to lobby for
inclusion one day before the actual release.


        Stefan