cc-mode in emacs 24.4 uses the cl compatibility package at compile-time
but does not require it when used like this:

  (require 'cc-mode)

  (eval-when-compile
    (require 'cc-langs))

  ; Symbol's function definition is void: set-difference
  (c-lang-const c-matchers-2 c)

  ; Symbol's function definition is void: cl-macroexpand-all
  (c-lang-defconst c-other-kwds t nil)

I observed breakage of php-mode and csharp-mode, but this affects any
derived mode that does not require cl or requires cl-lib instead of cl.

This seems to be recently fixed in trunk (revno 118032) so maybe no
further action is required and this bug report can be closed.

What would be the most appropriate way for affected derived modes to
work around this issue? Suppose I add:

  (eval-when-compile
    (if (and (= emacs-major-version 24) (= emacs-minor-version 4))
      (require 'cl)))

would that be fine and won't there be a future 24.4 release that fixes
this issue?



In GNU Emacs 24.4.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.14.3)
 of 2014-10-21 on bitzer.hoetzel.info
Windowing system distributor `The X.Org Foundation', version 11.0.11601000
System Description:    Arch Linux

Configured using:
 `configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/var --with-x-toolkit=gtk3 --with-xft
 'CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong
 --param=ssp-buffer-size=4' CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro'

Important settings:
  value of $LANG: C
  locale-coding-system: nil

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-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
  transient-mark-mode: t

Recent input:
M-x r e p o <tab> r <tab> <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Making completion list...

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message 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 help-mode easymenu time-date tooltip
electric uniquify ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list newcomment
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 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 make-network-process
dbusbind gfilenotify dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 72116 7225)
 (symbols 48 17651 0)
 (miscs 40 37 96)
 (strings 32 9247 4331)
 (string-bytes 1 253012)
 (vectors 16 8990)
 (vector-slots 8 383789 17145)
 (floats 8 64 304)
 (intervals 56 210 111)
 (buffers 960 12)
 (heap 1024 26191 1090))