bug#32414: 27.0.50; backtrace.el fails to require cl-print

[Pip Cet]

--text follows this line--

Evaluate

(throw 'a (make-string 4096 ?a))

in the *scratch* buffer.  I expected a backtrace, but got an error
message instead:

backtrace--print-to-string: Symbol’s function definition is void:
cl-print-to-string-with-limit

Upon investigation, it turns out backtrace.el is using code provided by
cl-print, but never requires it.

The obvious fix:

diff --git a/lisp/emacs-lisp/backtrace.el b/lisp/emacs-lisp/backtrace.el
index f13b43b465c..7180b58d1e4 100644
--- a/lisp/emacs-lisp/backtrace.el
+++ b/lisp/emacs-lisp/backtrace.el
@@ -36,6 +36,7 @@
 (eval-when-compile (require 'subr-x))        ; if-let
 (require 'help-mode)     ; Define `help-function-def' button type.
 (require 'lisp-mode)
+(require 'cl-print)

 ;;; Options


works.


In GNU Emacs 27.0.50 (build 19, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2018-08-10 built on amygdala
Repository revision: 243b68f73ff7cbb4d89a3f4a15a1cd38cfc14fae
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description: Debian GNU/Linux buster/sid

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Entering debugger...
backtrace--print-to-string: Symbol’s function definition is void:
cl-print-to-string-with-limit
Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND DBUS GSETTINGS NOTIFY ACL
GNUTLS LIBXML2 FREETYPE XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 THREADS
LCMS2

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

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

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny seq byte-opt gv
bytecomp byte-compile cconv dired dired-loaddefs format-spec rfc822 mml
mml-sec password-cache epa derived epg epg-config gnus-util rmail
rmail-loaddefs mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils debug backtrace help-mode easymenu
cl-loaddefs cl-lib elec-pair time-date mule-util tooltip eldoc electric
uniquify ediff-hook vc-hooks lisp-float-type mwheel term/x-win x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode elisp-mode lisp-mode
prog-mode register page menu-bar rfn-eshadow isearch timer select
scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame cl-generic cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932
hebrew greek romanian slovak czech european ethiopic indian cyrillic
chinese composite charscript charprop case-table epa-hook jka-cmpr-hook
help simple abbrev obarray 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 threads dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty make-network-process emacs)

Memory information:
((conses 16 98732 9659)
 (symbols 48 20420 1)
 (miscs 40 33 92)
 (strings 32 29574 1922)
 (string-bytes 1 780325)
 (vectors 16 15409)
 (vector-slots 8 513129 12196)
 (floats 8 49 110)
 (intervals 56 209 0)
 (buffers 992 12))