Create ~/tmp/foo.cc with file contents:

  //

Start Emacs 24.5 by:

  emacs -Q ~/tmp/foo.cc

Type 42 in some other X11 window (eg Chrome), and select it. In the Emacs
window, paste it with the middle mouse button (mouse-yank-primary). The
number 4 is not fontified.

Try the same with Emacs 24.4 and all fontification is correct.



In GNU Emacs 25.0.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.23)
 of 2015-05-12 on REDACTED
Windowing system distributor `The X.Org Foundation', version 11.0.11501000
System Description: Ubuntu 14.04 LTS (upgraded from: Ubuntu 12.04.4 LTS)

Configured features:
XPM JPEG TIFF GIF PNG SOUND GSETTINGS NOTIFY FREETYPE XFT ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: C++/l

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  abbrev-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
foo.cc has auto save data; consider M-x recover-this-file

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message dired format-spec
rfc822 mml mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util help-fns mail-prsvr mail-utils cc-mode cc-fonts easymenu
cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs
mule-util time-date tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel x-win term/common-win x-dnd tool-bar dnd fontset
image regexp-opt fringe tabulated-list newcomment elisp-mode lisp-mode
prog-mode register page menu-bar rfn-eshadow timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core frame cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev
minibuffer cl-preloaded nadvice loaddefs button faces cus-face macroexp
files text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote gfilenotify
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 95173 6053)
 (symbols 48 20219 1)
 (miscs 40 298 85)
 (strings 32 17455 4710)
 (string-bytes 1 598651)
 (vectors 16 12120)
 (vector-slots 8 419820 4972)
 (floats 8 84 47)
 (intervals 56 186 0)
 (buffers 976 12)
 (heap 1024 27404 1005))