bug#41853: 28.0.50; Peculiar "args out of range" error when using Edebug

[Philipp Stephani <p.stephani2@gmail.com>]

This error is somewhat common when using `edebug-all-defuns'.  It's not
easy to reproduce with a minimal example, but happens in real-world
code.  For example, the following recipe works for me consistently:

1. Clone the Flycheck repository at commit
   c02cd773dded0215f9417ec04dfe8dabda63ef43 (probably most other commits
   also work, this is just for reproducibility).

2. Clone the dash.el repository at commit
   ea4a4cc7cce7c3b93862a22df8bca8b83052ccbf (probably the exact commit
   doesn't matter here as well).

3. Visit flycheck.el like so:

   emacs -Q -L /src/dash.el/ -l edebug -f edebug-all-defuns \
     -f toggle-debug-on-error flycheck.el

4. M-x eval-buffer

5. Step through macro expansions using the `G' key.  Repeat until
   `eval-buffer' is complete or has signalled and error.

6. At some point, there will be an error

   edebug--display: Args out of range: [66 86 129 138 139], 5

   without invoking the debugger or backtrace.

This looks like a bug in Edebug.


In GNU Emacs 28.0.50 (build 25, x86_64-pc-linux-gnu, GTK+ Version 3.24.14, cairo version 1.16.0)
 of 2020-06-14
Repository revision: b3e7d046c3a94556fcaf6f9ce72aa2ecb20262a6
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12007000
System Description: Debian GNU/Linux rodete

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

Configured using:
 'configure --enable-gcc-warnings=warn-only
 --enable-gtk-deprecation-warnings --without-pop --with-mailutils
 --enable-checking --enable-check-lisp-object-type --with-modules
 'CFLAGS=-O0 -ggdb3''

Configured features:
XPM JPEG TIFF GIF PNG CAIRO SOUND DBUS GSETTINGS GLIB NOTIFY INOTIFY
LIBSELINUX GNUTLS FREETYPE HARFBUZZ ZLIB TOOLKIT_SCROLL_BARS GTK3 X11
XDBE XIM MODULES THREADS PDUMPER GMP

Important settings:
  value of $LANG: en_US.utf8
  value of $XMODIFIERS: @im=ibus
  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 dired dired-loaddefs
format-spec rfc822 mml easymenu mml-sec epa epg epg-config gnus-util
rmail rmail-loaddefs text-property-search time-date mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils phst skeleton
derived edmacro kmacro pcase ffap thingatpt url url-proxy url-privacy
url-expand url-methods url-history url-cookie url-domsuf url-util
url-parse auth-source cl-seq eieio eieio-core cl-macs eieio-loaddefs
password-cache json map url-vars mailcap subr-x rx gnutls puny seq
byte-opt gv bytecomp byte-compile cconv dbus xml compile comint
ansi-color ring cl-loaddefs cl-lib 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 tab-bar menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame minibuffer 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 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 dynamic-setting system-font-setting
font-render-setting cairo move-toolbar gtk x-toolkit x multi-tty
make-network-process emacs)

Memory information:
((conses 16 68581 6800)
 (symbols 48 8624 1)
 (strings 32 23721 1916)
 (string-bytes 1 764482)
 (vectors 16 13090)
 (vector-slots 8 166268 6503)
 (floats 8 25 36)
 (intervals 56 213 0)
 (buffers 992 11))

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