bug#47122: 27.1.91; Quitting GNU Emacs lets 'ccccc' appear in another X client

[Peter Dyballa]

Hello!

I made this observation first in macOS 11.2.2, Big Sur, on intel hardware, 
while testing the release candidates of XQuartz, an application bundle of the 
X.org server 'xorg-server 1.19.7' with X11 libraries and clients. During these 
tests I launched the X server very often and made it launch XTerm(s) + GNU 
Emacsen 27.1.91 and 28.0.50 (Repository revision: 
80e26472206cc44837521ba594cd50e724d9af5c, Repository branch: HEAD) via 
~/.xinitrc. Of course I quit quite as many times, for which I had to type C-x 
C-c in the Emacsen.

It seems that both Emacsen share a certain behaviour: They can make the next 
available X client receive an infinite times the last character I typed in the 
GNU Emacs I just quit. (To end appearing the series of characters I regularly 
just press RET.) And when this X client is GNU Emacs, the C-x starting the quit 
action is swallowed and mini buffer shows C-c and waits for some more input.

The next X client receives a lot of 'c' when I could quit GNU Emacs directly 
with C-x C-c. When I had a changed file open I had to input y (or n) before 
Emacs quit. In this case the next X client received lots of 'y' (or, untested 
yet, presumingly 'n').

A test from this morning showed the same behaviour with xorg-server-devel 
1.20.99.1.



In GNU Emacs 27.1.91 (build 1, x86_64-apple-darwin20.2.0, X toolkit, Xaw3d 
scroll bars)
 of 2021-01-30 built on Kleines.fritz.box
Windowing system distributor 'The X.Org Foundation', version 11.0.11907000
System Description:  macOS 11.2.2

Configured using:
 'configure --without-libsystemd --without-pop --without-sound
 --without-gpm --without-dbus --without-selinux --without-imagemagick
 --without-ns --disable-ns-self-contained --with-x
 --with-x-toolkit=athena --x-libraries=/opt/local/lib
 --x-includes=/opt/local/include
 '--enable-locallisppath=/Library/Application
 Support/Emacs/calendar27:/Library/Application Support/Emacs'
 --with-file-notification=yes CPPFLAGS=-I/opt/local/include 'CFLAGS=-g
 -H -pipe -fPIC -fno-common -Os -arch x86_64 -fomit-frame-pointer'
 'LDFLAGS=-v -arch x86_64 -Wl,-bind_at_load -Wl,-t -L /opt/local/lib'
 
PKG_CONFIG_PATH=/usr/lib/pkgconfig:/opt/local/lib/pkgconfig:/opt/local/share/pkgconfig:/usr/local/lib/pkgconfig
 CC=clang CXX=clang++'

Configured features:
XAW3D XPM JPEG TIFF GIF PNG RSVG GSETTINGS GLIB NOTIFY KQUEUE ACL GNUTLS
LIBXML2 FREETYPE HARFBUZZ LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS LUCID X11
XDBE XIM MODULES THREADS JSON PDUMPER LCMS2 GMP


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