Tested in emac -Q:

Open any buffer.

Insert "force_default[]".

Enable subword-mode.

Go to the beginning of inserted line.

Do C-u 2 M-d. (kill-word 2)

The result should be:

"[]"

but in fact is:

"efault[]".

Changing the number in command deletes additional chars.

So for C-u 3 M-d the result will be:

"fault[]".

Here's test for it:

(ert-deftest subword-mode-breaks-kill-word ()

(with-temp-buffer

(insert "force_default[]")

(goto-char (point-min))

(subword-mode)

(kill-word 2)

(should (string= "[]" (buffer-string)))))

In GNU Emacs 24.4.50.2 (x86_64-pc-linux-gnu, GTK+ Version 3.10.8)

of 2014-05-20 on charichuelo

Windowing system distributor `The X.Org Foundation', version 11.0.11501000

System Description: Ubuntu 14.04 LTS

Configured using:

`configure --build=x86_64-linux-gnu --prefix=/usr

'--includedir=${prefix}/include' '--mandir=${prefix}/share/man'

'--infodir=${prefix}/share/info' --sysconfdir=/etc --localstatedir=/var

'--libdir=${prefix}/lib/x86_64-linux-gnu'

'--libexecdir=${prefix}/lib/x86_64-linux-gnu' --disable-maintainer-mode

--disable-dependency-tracking --prefix=/usr --sharedstatedir=/var/lib

--program-suffix=-snapshot --with-x=yes --with-x-toolkit=gtk3

'CFLAGS=-g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat

-Werror=format-security' CPPFLAGS=-D_FORTIFY_SOURCE=2

'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro''

Configured features:

XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS

NOTIFY LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB

Important settings:

value of $LANG: pl_PL.UTF-8

value of $XMODIFIERS: @im=ibus

locale-coding-system: utf-8-unix

Major mode: Help

Minor modes in effect:

shell-dirtrack-mode: t

diff-auto-refine-mode: t

projectile-global-mode: t

projectile-mode: t

yas-global-mode: t

yas-minor-mode: t

global-company-mode: t

company-mode: t

global-eclim-mode: t

global-flycheck-mode: t

global-undo-tree-mode: t

undo-tree-mode: t

flx-ido-mode: t

ido-vertical-mode: t

ido-ubiquitous-mode: t

ido-everywhere: t

which-function-mode: t

delete-selection-mode: t

global-subword-mode: t

subword-mode: t

winner-mode: t

show-paren-mode: t

savehist-mode: t

recentf-mode: t

global-auto-revert-mode: t

tooltip-mode: t

electric-indent-mode: t

mouse-wheel-mode: t

file-name-shadow-mode: t

global-font-lock-mode: t

font-lock-mode: t

auto-composition-mode: t

auto-encryption-mode: t

auto-compression-mode: t

buffer-read-only: t

line-number-mode: t

transient-mark-mode: 1

Recent input:

<triple-mouse-5> <down-mouse-5> <mouse-5> <double-down-mouse-5>

<double-mouse-5> <triple-down-mouse-5> <triple-mouse-5>

<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5>

<triple-mouse-5> <down-mouse-4> <mouse-4> <double-down-mouse-4>

<double-mouse-4> <triple-down-mouse-4> <triple-mouse-4>

<triple-down-mouse-4> <triple-mouse-4> <triple-down-mouse-4>

<triple-mouse-4> <triple-down-mouse-4> <triple-mouse-4>

<triple-down-mouse-4> <triple-mouse-4> <triple-down-mouse-4>

<triple-mouse-4> <triple-down-mouse-4> <triple-mouse-4>

<triple-down-mouse-4> <triple-mouse-4> <triple-down-mouse-4>

<triple-mouse-4> <help-echo> <help-echo> <down-mouse-1>

<mouse-movement> <mouse-1> C-x b C-g C-g C-g <help-echo>

<help-echo> <down-mouse-2> <help-echo> <mouse-1> <help-echo>

<help-echo> <help-echo> <down-mouse-1> <mouse-1> M-x

d e l e t e C-SPC s e l e c C-n <return> M-x <return>

M-x <return> M-x <return> <help-echo> <down-mouse-1>

<mouse-1> C-x b s c r a <return> ( w i t h - c u r

r e n t - b u f f e r SPC " <help-echo> <down-mouse-1>

<mouse-movement> <mouse-1> C-x b C-g C-x o d e f a

u l t . r b <right> <return> ( p r i n t SPC m i n

o r - <return> <right> C-x C-s C-g <right> C-x C-e

<help-echo> <help-echo> <down-mouse-1> <drag-mouse-1>

C-x o C-x b m e s s a C-n <return> M-> <down-mouse-4>

<mouse-4> <double-down-mouse-4> <double-mouse-4> <triple-down-mouse-4>

<triple-mouse-4> <down-mouse-5> <mouse-5> <double-down-mouse-5>

<double-mouse-5> <down-mouse-1> <mouse-movement> <mouse-1>

<down-mouse-5> <mouse-5> <down-mouse-5> <mouse-5> <down-mouse-1>

<mouse-movement> <drag-mouse-1> C-x b C-g <help-echo>

<down-mouse-1> <mouse-1> C-x b r u b y <backspace>

<backspace> <backspace> d <backspace> <backspace> d

e f a <return> M-x n o r m a <return> M-x s u b w o

r d - w <backspace> m o d e <return> <down> C-u 2 M-d

<down-mouse-1> <mouse-movement> <mouse-1> C-_ M-x p

a c k a C-SPC d e s c r <return> s u b w o <return>

<down-mouse-1> <mouse-1> M-x f i l e - b u <backspace>

<backspace> <backspace> <backspace> <backspace> C-SPC

e a <backspace> m a c s C-n C-n <return>

Recent messages:

((magit-blame-mode " blame") (edebug-mode " *Debugging*") (flyspell-mode flyspell-mode-line-string) (ispell-minor-mode " Spell") (magit-auto-revert-mode magit-auto-revert-mode-lighter) (view-mode " View") (diff-minor-mode " Diff") (mml-mode " MML") (ert--current-run-stats (:eval (ert--tests-running-mode-line-indicator))) (paredit-mode " Paredit") (ensime-popup-buffer-mode (:eval (ensime-modeline-string))) (ensime-mode (:eval (ensime-modeline-string))) (auto-complete-mode " AC") (flymake-mode flymake-mode-line) (hs-minor-mode " hs") (projectile-mode projectile-mode-line) (yas-minor-mode " yas") (company-search-mode company-search-lighter) (company-mode company-lighter) (compilation-minor-mode " Compilation") (compilation-shell-minor-mode " Shell-Compile") (compilation-in-progress " Compiling") (eclim-mode " Eclim") (global-whitespace-newline-mode " NL") (global-whitespace-mode " WS") (whitespace-newline-mode " nl") (whitespace-mode " ws") (flycheck-mode flycheck-mode-line) (smartparens-mode (" SP" (:eval (if smartparens-strict-mode "/s" "")))) (undo-tree-visualizer-selection-mode "Select") (undo-tree-mode undo-tree-mode-lighter) (rainbow-delimiters-mode "") (flx-ido-mode "") (server-buffer-clients " Server") (superword-mode " ²") (subword-mode " ,") (global-auto-revert-mode global-auto-revert-mode-text) (auto-revert-tail-mode auto-revert-tail-mode-text) (auto-revert-mode auto-revert-mode-text) (visible-mode " Vis") (visual-line-mode " Wrap") (next-error-follow-minor-mode " Fol") (abbrev-mode " Abbrev") (overwrite-mode overwrite-mode) (auto-fill-function " Fill") (defining-kbd-macro " Def") (isearch-mode isearch-mode))

user-error: Minibuffer window is not active

Mark set [2 times]

Quit

Subword mode disabled

Undo branch point!

Type "q" in help window to restore its previous buffer.

You can run the command `describe-package' with C-h P

Type "q" in help window to restore its previous buffer.

Load-path shadows:

/usr/share/emacs/site-lisp/dictionaries-common/ispell hides /usr/share/emacs/24.4.50/lisp/textmodes/ispell

/usr/share/emacs/site-lisp/dictionaries-common/flyspell hides /usr/share/emacs/24.4.50/lisp/textmodes/flyspell

Features:

(finder-inf cus-start cus-load shadow sort mail-extr python emacsbug

sendmail magit-blame tabify network-stream starttls tls scala-mode2

scala-mode2-sbt scala-mode2-map scala-mode2-fontlock scala-mode2-indent

scala-mode2-paragraph scala-mode2-syntax scala-mode2-lib conf-mode

smartparens-ruby ruby-mode smie jka-compr eieio-opt speedbar sb-image

ezimage dframe misearch multi-isearch edebug flyspell ispell

magit-key-mode magit view tramp tramp-compat tramp-loaddefs trampver

shell pcomplete epa epg epg-config diff-mode git-rebase-mode

git-commit-mode log-edit message dired format-spec rfc822 mml mml-sec

mm-decode mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045

ietf-drums mailabbrev mail-utils gmm-utils mailheader pcvs-util add-log

ert ewoc debug chef-attributes vc-git paredit ensime easy-mmode

ensime-ui ensime-semantic-highlight ensime-doc ensime-scalex url

url-proxy url-privacy url-expand url-methods url-history url-cookie

url-domsuf url-util url-parse auth-source eieio byte-opt bytecomp

byte-compile cconv eieio-core gnus-util mm-util mail-prsvr

password-cache url-vars mailcap ensime-search ensime-undo

ensime-refactor ensime-builder ensime-debug derived ensime-inf

ensime-sbt ensime-comint-utils ensime-auto-complete ensime-config

auto-complete popup flymake hideshow pp ensime-connections ensime-core

ensime-macros smart-mode-line mule-util key-chord projectile pkg-info

lisp-mnt epl grep clojure-snippets java-snippets yasnippet company-files

company-oddmuse company-keywords company-etags company-gtags

company-dabbrev-code company-dabbrev company-capf company-cmake

company-ropemacs company-xcode company-clang company-template

company-semantic company-css company-bbdb company-emacs-eclim

eclim-completion company help-at-pt eclimd eclim eclim-problems

eclim-maven compile comint ansi-color eclim-ant eclim-java json

eclim-project etags whitespace flycheck find-func help-mode rx f s

smartparens-config smartparens thingatpt dash undo-tree diff

rainbow-delimiters smex flx-ido flx ido-vertical-mode ido-ubiquitous

advice ido saveplace ace-jump-mode-autoloads

annoying-arrows-mode-autoloads tex-site company-cider-autoloads

csharp-mode-autoloads flycheck-color-mode-line-autoloads f-autoloads

edmacro kmacro ido-hacks-autoloads ido-ubiquitous-autoloads

ido-vertical-mode-autoloads js2-mode-autoloads json-mode-autoloads

json-reformat-autoloads git-rebase-mode-autoloads

git-commit-mode-autoloads malabar-mode-autoloads fringe-helper-autoloads

multi-autoloads openwith-autoloads popup-autoloads pkg-info-autoloads

epl-autoloads info python-info-autoloads rainbow-delimiters-autoloads

s-autoloads slime-autoloads help-fns cl-macs cl gv package server

which-func imenu delsel cap-words superword subword winner ring paren

savehist recentf tree-widget wid-edit cl-loaddefs cl-lib easymenu

autorevert filenotify wombat-theme 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 583547 441771)

(symbols 48 44205 29)

(miscs 40 2920 6324)

(strings 32 98883 94092)

(string-bytes 1 2821585)

(vectors 16 91969)

(vector-slots 8 3235944 20211)

(floats 8 16135 308)

(intervals 56 16223 8822)

(buffers 960 74)

(heap 1024 92284 9505))