bug#20356: 25.0.50; Strange terminal glyphs in emacs -nw in recent master

[Jorgen Schaefer <contact@jorgenschaefer.de>]

Hello!
Since a few days (I recompiled Emacs the first time on Wed 15th or Thu
16th, not sure when this was introduced before that) I see terminal
glyph garbage on certain deletion operations in emacs -nw.

A reliable way to trigger this for me is M-DEL, though many deletion
operations cause spurious data to be displayed. C-l will remove said
glyphs, and neither scrolling, normal editing nor indeed
single-character deletion will trigger this bug.

This is in a Gnome Terminal with TERM=xterm, sshing to a server, and
Emacs started in a screen with TERM=screen.

The Emacs built from ref 0465c9dd (last Apr 7th commit) does not exhibit
this behavior.

I know from at least one other person that recent builds with emacs -nw
work fine for them, so this is likely going to be tricky to debug. I'm
happy to do any testing needed.

Thanks!
Jorgen


Configured using:
 `configure --without-x'

Configured features:
SOUND DBUS NOTIFY ACL GNUTLS LIBXML2 ZLIB

Important settings:
  value of $LC_ALL: 
  value of $LC_COLLATE: de_DE.UTF-8
  value of $LC_CTYPE: de_DE.UTF-8
  value of $LC_MESSAGES: POSIX
  value of $LC_MONETARY: POSIX
  value of $LC_NUMERIC: POSIX
  value of $LC_TIME: POSIX
  value of $LANG: POSIX
  locale-coding-system: utf-8-unix